skype and lync video capture specification · skype and lync video capture specification h100693...

Skype & Lync

Video Capture Specification

For devices using Skype/Lync’s video processing

Document Number: H100693

Release Date: August 2013

Disclaimer: This document is provided “as-is”. Information and views expressed in this document, including URL and

other Internet Web site references, may change without notice. You bear the risk of using it.

This document does not provide you with any legal rights to any intellectual property in any Microsoft product. You

may copy and use this document for your internal, reference purposes.

Feedback: You have no obligation to give Microsoft any suggestions, comments or other feedback ("Feedback")

relating to the materials herein (“Materials”). However, any Feedback you voluntarily provide may be used in Microsoft

products and related specifications or other documentation (collectively, "Microsoft Offerings") which in turn may be

relied upon by other third parties to develop their own products. Accordingly, if you do give Microsoft Feedback on any

version of these Materials or the Microsoft Offerings to which they apply, you agree: (a) Microsoft may freely use,

reproduce, license, distribute, and otherwise commercialize your Feedback in any Microsoft Offering; (b) you also grant

third parties, without charge, only those patent rights necessary to enable other products to use or interface with any

specific parts of a Microsoft product that incorporate your Feedback; and (c) you will not give Microsoft any Feedback

(i) that you have reason to believe is subject to any patent, copyright or other intellectual property claim or right of any

third party; or (ii) subject to license terms which seek to require any Microsoft Offering incorporating or derived from

such Feedback, or other Microsoft intellectual property, to be licensed to or otherwise shared with any third party.

© 2013 Microsoft Corporation. All rights reserved.

Skype and Lync Video Capture Specification

H100693 of 68

Table of Contents 1 Revision History ................................................................................................................................ 5

2 Introduction ...................................................................................................................................... 6

2.1 Overview ....................................................................................................................................... 6

2.2 Performance levels ....................................................................................................................... 7

2.3 Definitions ..................................................................................................................................... 8

2.4 Classification of the products........................................................................................................ 9

Default testing position ......................................................................................................... 9

3 Entry criteria for video testing ........................................................................................................ 10

3.1 Video prerequisite testing .......................................................................................................... 10

E2E Scenarios: Video Sanity Tests ....................................................................................... 11

3.2 Driver ........................................................................................................................................... 12

Support USB Video Class (UVC) Driver ................................................................................ 12

Support USB Audio Class (UAC) Driver ................................................................................ 12

CPU usage ........................................................................................................................... 13

3.3 Basic video attributes .................................................................................................................. 14

Windows HCK video test must be passed ........................................................................... 14

Image resolutions, frame rates, color spaces ..................................................................... 14

UVC 1.5 compatibility for H.264 hardware encoding webcams ......................................... 17

3.4 Pre-conditions to enable testing the video quality requirements .............................................. 18

Anti-flicker solution ............................................................................................................. 18

Automatic white balance, exposure and gain ..................................................................... 18

Pixel aspect ratio ................................................................................................................. 18

Autofocus performance ...................................................................................................... 19

Verify cameras correct use of luminance and color spaces ................................................ 20

3.5 Other ........................................................................................................................................... 22

Embedded camera shipping protection .............................................................................. 22

Usage indicator ................................................................................................................... 22

4 Video quality requirements ............................................................................................................ 23

4.1 Image detail quality..................................................................................................................... 23

MTF ..................................................................................................................................... 23


H100693 of 68

Oversharpening ................................................................................................................... 26

Edge roughness ................................................................................................................... 27

Depth of field ...................................................................................................................... 28

Texture acutance ................................................................................................................ 28

4.2 Noise ........................................................................................................................................... 30

Image spatial SNR ................................................................................................................ 30

Image temporal SNR ........................................................................................................... 31

4.3 Color quality ................................................................................................................................ 32

Gamma ................................................................................................................................ 32

Image dynamic range .......................................................................................................... 33

Relative illumination ........................................................................................................... 34

Color uniformity .................................................................................................................. 35

Veiling glare ......................................................................................................................... 36

Color accuracy ..................................................................................................................... 38

Color saturation .................................................................................................................. 39

Exposure accuracy ............................................................................................................... 39

White balance error ............................................................................................................ 40

4.4 Geometry .................................................................................................................................... 40

Field of view ........................................................................................................................ 40

Field of view consistency .................................................................................................... 42

Geometric distortion ........................................................................................................... 43

4.5 Timing .......................................................................................................................................... 44

System latency .................................................................................................................... 44

Jitter .................................................................................................................................... 45

Audio/video synchronization .............................................................................................. 45

Time to capture first image, change resolutions ................................................................ 46

Video latency during a call .................................................................................................. 46

Video frame rate during a call ............................................................................................. 47

5 Video test setup .............................................................................................................................. 48

Main video test setup ......................................................................................................... 48

Video latency test setup for system latency ....................................................................... 49

Video latency test setup – End to End ................................................................................ 49


H100693 of 68

End to End testing over Skype video call ............................................................................ 50

Light setup and conditions .................................................................................................. 52

Test charts ........................................................................................................................... 56

Latency measurement kit ................................................................................................... 62

Other inventory ................................................................................................................... 63

6 Appendix ......................................................................................................................................... 64

6.1 Camera location interface ........................................................................................................... 64

6.2 Conference room camera criteria ............................................................................................... 65


H100693 of 68

1 Revision History Revision Published Description

1.0

8/2013 First official release of the unified specification. Change list below refers to

changes from draft versions.

Modified ST-52 is not used. ST-52 may be used with shutters as in Skype

specification version 6.

Exposure accuracy test added back.

SNR improvement test is integrated into spatial noise requirements.

E27/A19 lights described.

Oversharpening requirement added in 200lux.

Geometric distortion requirement is revised.

New method to test 3.3.5.

Texture acuity algorithm revised and requirement relaxed.

Additional details provided in Sections 3.1, 3.3.4 and 5.

Based on Lync specification revision G and Skype specification version 6.


H100693 of 68

2 Introduction

2.1 Overview The family of documents supporting the Lync logo and Skype Certification program is shown below and

contains detailed requirements that candidate devices, being submitted to the Logo Program, must

meet. In this document, most items apply equally for products seeking the Lync Logo as well as Skype

certification. Use of the Logo Program will refer to both Skype and Lync.

The technical requirements listed in this document, the Skype & Lync Video Test Specification, have

been derived solely for the purpose of maximizing interoperability and optimizing the quality of

experience using the devices with Skype and Lync. Any use of this technical specification for purposes

other than optimizing the video quality for Skype and Lync is not authorized.

Partners who license, develop, market, and/or sell Skype and Lync devices that are qualified by

Microsoft, are required to adhere to the specifications outlined in this document. Partners seeking

changes, modifications and/or additions to this specification will be required to receive written approval

from Microsoft before certification of the device. Microsoft reserves the right to update the contents of

this technical specification at any time without prior notice. Purposes of such updates include the

Lync Logo Program OverviewDoc#: H100689

Skype & Devices SpecificationDoc#: H100689

Skype & Lync Audio SpecificationDoc#: H100691

Skype & Lync Offloaded Audio Specification

Doc #: H003302

Skype & Lync Video Capture SpecificationDoc#: H100693

Skype & Lync Call Display Specification

Doc#: H100690

Skype & Lync H.264 Video Encoder Specification

Doc#:H105958


H100693 of 68

capture of new capabilities in Skype and Lync platforms, new device categories, as well as performance

improvements in the hardware used in peripheral devices.

2.2 Performance levels This document provides performance requirements for Lync and Skype certified devices.

There are two levels of webcam performance defined by this specification:

Standard: Defines a good video quality level that, when achieved, allows use of both Skype and

Lync logos in association with the product.

Premium: Defines Skype and Lync’s preferred video quality level.


H100693 of 68

2.3 Definitions

Color accuracy The measurement of the deviation of colors captured by a camera and the expected colors using a test chart like the ColorChecker.

Color uniformity

The measurement of the variation of color throughout an image (not just the center compared to the edges).

Color space A color space is a mathematical model describing the way colors can be represented as tuples of numbers, typically as three or four values or color components. The standard PC color space for displays is sRGB, while webcams generally use YUV color spaces for capture.

Depth of field Depth of field is the distance between the nearest and farthest objects in a scene that appear acceptably sharp in an image.

DUT Device under testing.

Dynamic range Dynamic range is the ratio between the brightest object in the scene and the noise of the darkest non-saturated object in the scene.

Field of view The field of view is the angular extent of the observable world that is seen at any given moment from a camera.

Focus An image, or image point or region, is in focus if light from object points is converged almost as much as possible in the image, and out of focus if light is not well converged. The border between these is sometimes defined using a circle of confusion criterion.

Gamma Gamma correction is a nonlinear operation used to code and decode luminance or tristimulus values in video or still image system.

Geometric distortion

Geometric distortion is a deviation from rectilinear projection, a projection in which straight lines in a scene remain straight in an image.

HCK Windows Hardware Certification Kit. The Windows HCK provides the tools, processes, and tests to create and upload submission packages to the Windows Dev Center Hardware Dashboard to certify your devices and systems.

Jitter Jitter is the measure of time deviation from an expected periodic event. For example, a constant frame rate camera should ideally have a zero jitter, though in practice it is usually a few milliseconds.

Latency Latency is a measure of time delay experienced in a system. For video conferencing the most important latency measurement is end-to-end latency, which is the time from photons in to a camera to photons out of a display.

MTF Modulation Transfer Function is the magnitude of the Optical Transfer Function. MTF30 is the cycles/pixel where the MTF=30%, generally considered to be the lowest acceptable MTF for imaging.

Oversharpening Oversharpening or undersharpening is an Imatest measurement that characterizes the degree that the image is sharpened relative to a standard sharpening model. If it is negative, sharpening is applied to the original response; if it is positive, de-sharpening is applied.

Relative illumination

Relative illumination, or vignetting, is a measure of the diminishing of image brightness from the center towards the corners.

ROI Region of interest

RMS edge roughness

RMS edge roughness is an Imatest measurement of how rough an edge is. An edge can be rough due to demosaicing, image scaling, spatial denoising and excessive noise level.

SNR Signal to Noise Ratio is the ratio of the signal power to the noise power corrupting the signal. The SNR can be measured spatially using a single image or temporally using more than one image.

Table 1: Definitions

http://en.wikipedia.org/wiki/ColorChecker

http://en.wikipedia.org/wiki/Color_space

http://en.wikipedia.org/wiki/SRGB

http://en.wikipedia.org/wiki/YUV

http://en.wikipedia.org/wiki/Depth_of_field

http://en.wikipedia.org/wiki/Dynamic_range

http://en.wikipedia.org/wiki/Field_of_view

http://en.wikipedia.org/wiki/Focus_(optics)

http://en.wikipedia.org/wiki/Gamma_correction

http://en.wikipedia.org/wiki/Distortion_(optics)

http://en.wikipedia.org/wiki/Jitter

http://en.wikipedia.org/wiki/Latency_(engineering)

http://en.wikipedia.org/wiki/Optical_transfer_function

http://www.imatest.com/docs/sharpening.html

http://en.wikipedia.org/wiki/Vignetting

http://www.imatest.com/docs/sfrplus_instructions3.html#edgerough

http://en.wikipedia.org/wiki/Signal-to-noise_ratio


H100693 of 68

2.4 Classification of the products This document applies to all PCs with integrated webcam and video peripheral devices for the PCs. The

described requirements are the same, but the differences in usage scenarios are considered when

positioning the device under testing in video lab.

In this document the following categories are distinguished:

Portable devices (with built-in cameras): laptops, tablets and other mobile devices running

Windows.

Desktop cameras: All-in-one solutions, external USB webcams, large displays with built-in

webcam.

Living room cameras: TVs and peripherals for TVs.

Conferencing cameras: meeting room solutions.

Default testing position

Microsoft reserves the right to choose the distances for each solution separately based on the

intended use cases. The end user documentation (packaging and manual) will be considered also.

Typically used distances between the test target and camera are the following:

Section Category Nominal distance Minimum

distance

Maximum

distance

4.1 Image detail

quality

Portable

devices nomd = 0.50m

mind = 0.30m maxd = 1.5 m

Desktop

cameras nomd = 0.70m

mind = 0.40m maxd = 1.5m

Living room

cameras nomd = 2.0m


Conferencing

cameras nomd = 1.50m


4.2 Noise

0

Color quality

All

Test charts fits the VFOV

and active chart area fills

at least 70% of VFOV

N/A N/A

4.4 Geometry All Test chart fills the full FOV N/A N/A

Table 2: Testing distances


H100693 of 68

3 Entry criteria for video testing A solution submitted to testing must meet some essential requirements to enable the testing.

If any of the tested items in this chapter fails then the tester has the right to stop testing any further and

the test will be considered completed (and the test fees may not be refunded).

Battery powered devices are tested so that they are connected to external power supply.

3.1 Video prerequisite testing All devices shall be evaluated over Lync or Skype call at each engineering stage (e.g. by the OEM at

major internal milestones, and again by the test lab prior to beginning the quantitative testing). The goal

is to identify any obvious problems before beginning the quantitative testing.

The evaluation should be performed under well-lit office condition and simulated living room lighting

conditions. Lighting conditions for these sanity tests are intentionally less controlled (and slightly more

relaxed) than those for the formal quantitative tests because these are intended to be easy to execute,

with a focus on highlighting obvious issues that would be apparent to an average end user. All tests

below require two people. The term “near-end user” describes the person using the DUT and the term

“far-end user” describes the person in a remote room who is using a reference device to communicate

with the near-end user.

Well lit office environment:

Moderately sized room, with fluorescent overhead lights in the FOV behind the DUT user.

Lighting level is 125 lux plus or minus 50 lux using measured with the light meter sensor held at users face at face level of the DUT user facing the camera.

Examples of simulated living room conditions:

Reduced ambient light level is 40 lux plus or minus 20 lux using incandescent indirect lighting measured with the light meter at face level of the DUT user facing the camera. Incandescent indirect lighting example would be a floor standing Touchier lamp with either tungsten filament or halogen lamp with adjustable brightness. The lamp should be approximately 1.5 meters behind the user and visible in the field of view.

Far-end system requirements:

The far-end user is required to have a system capable of rendering the max resolution and supported by the camera (http://technet.microsoft.com/en-us/library/jj688132.aspx).

Good quality HD (1080p capable) monitor Test Score definitions scale

Test scoring will be done on a scale of 1 to 5, with a score of 1 being BAD and 5 being GOOD 5: No detectable flaws in the observed metric (Pass)

http://technet.microsoft.com/en-us/library/jj688132.aspx


H100693 of 68

4: Some minor flaws detectable by an observant user (Pass) 3: Flaws detectable to the casual user (Possible Fail further review required) 2: Serious flaws making the call difficult to continue (Fail) 1: Very serious flaws preventing the completion of the call (Fail)

E2E Scenarios: Video Sanity Tests

3.1.1.1 Video Render

1. With the DUT in well-light office environment, place an E2E Skype video call and later E2E Lync video call between the two users.

2. Begin the evaluation by opening video in both directions. Far end user will need to resize video image to achieve the maximum resolution of the DUT camera (720p or 1080p)

The far end user will observe and evaluate the video image for any image clarity flaws. i. Watch for texture based on natural features (e.g. ceiling tiles, user’s hair) and

test texture chart.

The far end user will observe and evaluate the video for encoding related artifacts. i. Watch for video jerkiness – stalling or skipping video frames.

ii. Watch for image blockiness. iii. Watch for other encoding artifacts like blurring, color bleeding, staircase effect,

ringing, false contouring, and mosquito effect.

The far end user will observe and evaluate the video image for any image color flaws. i. Watch for skin tone, walls, and light coming from light fixture.

ii. Watch for disturbing color noise levels. 3. Turn the lights off and on while creating as little physical movement on the scene as possible.

Check if the image is restored correctly (without artifacts, correct colors, no significant noise additions).

4. Repeat step 2 in living room simulated environment.

3.1.1.2 Image Motion

1. With the DUT in normal usage environment, place an E2E Skype video call and later E2E Lync video call between the two users.

2. Begin the evaluation by opening video in both directions. Near end user to waive hand as sanity check for Jitter. Near end user to Clap hands as sanity check for A/V sync.

Far-end user to watch for Jitter during hand wave.

Far-end user to watch for A/V sync during hand clap.

Far-end user to verify sufficient frame rate at various resolutions. 3. Repeat step 2 in low light stress environment.


H100693 of 68

3.2 Driver This section applies to external USB webcams.

Support USB Video Class (UVC) Driver

3.2.1.1 Purpose

Webcams should be fully functional with default Windows drivers. Note all tests in this specification

need to be run with the default Windows drivers as well as the OEM drivers (if supplied to the end user

with a product).

3.2.1.2 Requirements

If the webcam uses USB bus it must support the UVC standard 1.0 or later versions and work with

standard Windows UVC drivers.

3.2.1.3 Test procedure

Run Device Manager and check if the webcam is using the Windows UVC driver usbvideo.sys and that

the driver provider is Microsoft. If the driver is not the Windows UVC driver, roll back the driver to the

Windows UVC driver.

Support USB Audio Class (UAC) Driver

3.2.2.1 Purpose

USB webcams should be fully functional with default Windows drivers. If the webcam has a microphone

built-in then it must work with UAC driver.


If the USB webcam has built-in microphone then it must support the UAC standard 1.0 and later and

work with standard Windows drivers.


Run Device Manager and check if the webcam is using the Windows UAC driver usbaudio.sys and the

provider is Microsoft. If the driver is not the Windows UAC driver, roll back the driver to the Windows

UAC driver.


H100693 of 68

CPU usage

3.2.3.1 Purpose

Makes sure the webcam driver (not standard UVC/UAC drivers), which includes any video processing, do

not cause excessive CPU usage. Only the CPU usage of OEM drivers are measured, not the Windows in-

box UVC/UAC drivers.


The CPU usage requirements are given in Table 3.

* Skype and Lync test labs use Surface Pro with Intel HD Graphics 4000 for this test in case of

external webcam.

Table 3: CPU usage


Install the 3rd party webcam driver and verify the right driver is in use for the Camera from

Device Manager

Run AmCap and configure it to show video in 640x480 YUY2 or I420 mode

Run Performance Monitor (perfmon.exe). Configure it to show the % Processor Time for the

AmCap process

Repeat for 720p and if available then 1080p resolutions in MJPEG or YUY2 mode.

Resolution CPU usage for AMCap process on Windows 8 64bit (CPU load limit is defined for single core)

VGA 30 FPS <10% on Core [email protected]

720p 30 FPS <40% on Core [email protected]

1080p 30 FPS <95% on Core [email protected]


H100693 of 68

3.3 Basic video attributes

Windows HCK video test must be passed

3.3.1.1 Purpose

The Windows Hardware Certification Kit (HCK) video test is verifying several essential video attributes

that are necessary for conducting the video tests in this document. It also covers certain areas that are

left out of this specification.


Solution that are sold with Windows pre-installed or have Windows OS marked as a supported operating

system must pass the testcases in Windows HCK video test. The passed test report must be provided

before the testing is started.

3.3.1.3 Test process

Verify that the HCK video test report is submitted.

Make sure that the report is matching with the product. In case of any doubt about the HCK video report

the tester must rerun the HCK test to verify.

Image resolutions, frame rates, color spaces

3.3.2.1 Purpose

This test ensures that required (priority 1) and recommended (priority 2) image resolutions, native frame

rates, and color spaces are supported.


3.3.2.2.1 Image resolutions for USB cameras

Resolution Nominal frame rate in 80 lux

Minimum frame rate in 20 lux

Encoding Priority

640x480 30 15 YUY2 1

30 15 I420 2

320x240 30 15 YUY2 1

30 15 I420 2 Table 4: 4:3 aspect ratio video for USB 2.0 and 3.0 webcams


H100693 of 68



Encoding Priority

1920x1080 30 15 MJPEG or YUY2 1

1280x720 30 15 MJPEG or YUY2 1

30 15 I420 2

960x540 30 15 MJPEG or YUY2 1

30 15 I420 2

848x480 30 15 MJPEG or YUY2 1

30 15 I420 2

640x360 30 15 YUY2 1

30 15 I420 2

424x240 30 15 YUY2 1

30 15 I420 2

320x180 30 15 YUY2 1

30 15 I420 2 Table 5: 16:9 aspect ratio video for USB 2.0 HD webcams



Encoding Priority

1920x1080 30 15 YUY2 1

30 15 I420 2

1280x720 30 15 YUY2 1

30 15 I420 2

960x540 30 15 YUY2 1

30 15 I420 2

848x480 30 15 YUY2 1

30 15 I420 2

640x360 30 15 YUY2 1

30 15 I420 2

424x240 30 15 YUY2 1

30 15 I420 2

320x180 30 15 YUY2 1

30 15 I420 2 Table 6: 16:9 aspect ratio video for USB 3.0 HD webcams

3.3.2.2.2 Image resolutions for MIPI cameras

Resolution Nominal frame rate

in 80 lux

Minimum frame rate

in 20 lux

Encoding Priority

640x480 30 15 NV12 or I420 1

320x240 30 15 NV12 or I420 1 Table 7: 4:3 aspect ratio video for MIPI webcams


H100693 of 68


in 80 lux

Minimum frame rate

in 20 lux

Encoding Priority

1920x1080 30 15 NV12 or I420 1

1280x720 30 15 NV12 or I420 1

960x540 30 15 NV12 or I420 1

848x480 30 15 NV12 or I420 1

640x360 30 15 NV12 or I420 1

424x240 30 15 NV12 or I420 1

320x180 30 15 NV12 or I420 1 Table 8: 16:9 aspect ratio video for HD MIPI webcams

3.3.2.2.3 Image resolutions for H.264 cameras


in 80 lux

Minimum frame rate

in 20 lux

Encoding Priority

1920x1080 30 15 H.264 1

1280x720 30 15 H.264 1

960x540 30 15 H.264 1

848x480 30 15 H.264 1

640x360 30 15 H.264 1

480x270 30 15 H.264 1

424x240 30 15 H.264 1

320x180 30 15 H.264 1 Table 9: Encoded resolutions for H.264 HD webcams

3.3.2.2.4 UVC Color Matching Descriptor

A UVC webcam must set the UVC Color Matching Descriptor to the following values:

UVC Color Matching Descripting Uncompressed, MJPEG frame type

bColorPrimaries 1 (BT.709, sRGB)

bTransferCharacteristics 1 (BT.709)

bMatrixCoefficients 4 (BT.601) Table 10: UVC Color Matching Descriptor

3.3.2.2.5 Media Foundation color properties for MIPI cameras

A MIPI webcam must set the following Media Foundation parameters:

Media Foundation properties Uncompressed, MJPEG frame type

MF_MT_VIDEO_PRIMARIES MFVideoPrimaries_BT709

MF_MT_TRANSFER_FUNCTION MFVideoTransFunc_709

MF_MT_YUV_MATRIX MFVideoTransferMatrix_BT601 Table 11: Media Foundation color properties for MIPI cameras

http://msdn.microsoft.com/en-us/library/windows/desktop/ms697241(v=vs.85).aspx




H100693 of 68

3.3.2.2.6 Luminance and chrominance ranges

The luminance and chrominance ranges for supported color spaces are given in Table 12.

For Windows 8.1 devices with embedded cameras the MF_MT_VIDEO_NOMINAL_RANGE property is

used and validated using the Modified ST-52 chart (Figure 35). The MF_MT_VIDEO_NOMINAL_RANGE

values for the in-box UVC drivers is given in Table 13. Devices that wish to use other color ranges can do

so in their own custom driver.

Color space Luminance Chrominance

YUY2 16-235 16-240

NV12 16-235 16-240

I420 16-235 16-240

MJPEG 0-255 0-255 Table 12: Luminance and chrominance ranges

Image type MF_MT_VIDEO_NOMINAL_RANGE

MJPEG MFNominalRange_0_255

Uncompressed MFNominalRange_16_235

Table 13: MF_MT_VIDEO_NOMINAL_RANGE for Windows 8.1 in-box UVC drivers

3.3.2.2.7 Notes

It is critical that webcams do not expose 1280x720 or 1920x1080 modes if 15 FPS can’t be met.

1080p is only required if webcam supports it. In this document’s context HD webcams are 1080p

or 720p. Higher resolutions can be supported, but not used in a video call.

MJPEG streams should be exposed rather than having custom drivers that decompress MJPEG.

UVC 1.5 compatibility for H.264 hardware encoding webcams

3.3.3.1 Purpose

H.264 hardware encoded cameras will need to use a specific interface to be compatible with Microsoft

Lync and Skype. H.264 hardware encoded cameras can be either USB tethered, integrated USB, or using

MIPI bus connected to a SOC. The H.264 webcams need to support the Version 1.5 of the USB Video

Class (UVC) Definition for Video Devices standard.


If the device supports H.264 hardware encoding then the solution submitted to testing must be fully

compatible with the Microsoft Lync & Skype H.264 Encoder Specification. The passed report must be

provided before the testing is started.

3.3.3.3 Test process

Verify that the required video test report is submitted.

Make sure that the report is matching with the product under testing.


H100693 of 68

3.4 Pre-conditions to enable testing the video quality requirements The requirements in this chapter are to ensure the feasibility and reliability of automated tests

described in Section 4. The automatically adjusted image parameters (such as gain and white balance)

must stabilize within 5 seconds after change of scene or light conditions. If the camera has auto focus,

the focus should also stabilize to focused image in less than 5 seconds.

Anti-flicker solution

3.4.1.1 Purpose

Imaging in lighting powered by 50 or 60 Hz mains frequency can result in flicker that significantly

degrades SNR (> 8 dB). The camera has to be able to suppress this effect in captured video. This is

especially important for notebook computers that may travel between 50 and 60 Hz countries.


The camera must include one of the following solutions to remove flickers due to 50 and 60 Hz lighting.

Standard Premium

Anti-flicker Support 50 Hz and 60 Hz

AEC modes Automatically selects 50 Hz or 60

Hz AEC mode Table 14: Anti-flicker solution

Automatic white balance, exposure and gain

3.4.2.1 Purpose

Automatic white balance, exposure and gain control are needed to ensure the image has sufficient

contrast and isn't over-saturated or under-saturated in typical light conditions.

The image must be stabilized within 5 seconds after the target change to provide reasonable video call

experience. This is also important from test automation perspective – the stabilization time between

changing the test target or light conditions is typically set to 5-6 seconds in the test automation scripts

used.


Requirement

Supports automatic white balance Enabled by default

Supports automatic gain and exposure Enabled by default

Stabilization time < 5s Table 15: Video AEC and AGC

Pixel aspect ratio

3.4.3.1 Purpose

The correct pixel aspect ratio is important so that the captured images look normal and not stretched

out horizontally or vertically.

If the pixel aspect ratio is incorrect then it is also likely to cause issues with automatic detection of the

test charts and the Video quality requirements cannot be tested using the Video Analyzer.

3.4.3.2 Requirement

Requirement

All resolutions 0.98 ≤ R ≤ 1.02 Table 16: Pixel aspect ratio


H100693 of 68

Autofocus performance

3.4.4.1 Purpose

This requirement specifies autofocus performance and manual focus API support (for cameras with

autofocus). Most webcams with autofocus experience “focus swimming” and sometimes get stuck in an

unfocused state. The typical desktop scenario doesn’t need autofocus, as the camera’s depth of field at

the nominal distance is sufficient. To minimize focus swimming, the autofocus performance is specified

in a real-world test. To allow Microsoft Lync and Skype to programmatically specify manual focus, the

application must be able to switch off autofocus through api and set it to default focal distance.


1. Autofocus performance: Images must be focused 99% of the time over 5 minutes in a typical

use-case scenario.

2. Manual-focus performance: The default distance for manual focus must be equal to the nominal

distance for the matching category as described in Section 2.4.1. This allows manual focus to be

used to eliminate focus swimming and ensures that users are in focus in most desktop and

notebook scenarios. The default manual focus MTF30 must be with 15% relative error to the

autofocus MTF30.

3. If the auto-focus cannot be manually disabled, it must adapt to changes of the test target or

lighting within 5 seconds.


1. Choose the testing area the following way:

Only overhead lighting without any sunlight – on the table in front of the tester it should be

around 300 lux.

The background should be neutral colors. The tester should avoid wearing clothing with high

frequencies (i.e. no stripes thinner than 25mm / 1 inch.

Use two tilted edge printouts on either side of the persons head (above shoulders). These will

be used to determine if the image in respective frame is in focus. Having the edges on either

side should help make sure that there is at least one visible on all frames. The tilted edges are

no farther than 30cm (1 feet) behind the tester.

2. Set up the camera at nominal distance from the tester.

3. Record a simulated 5 minute video call.

4. Measure the time while autofocus was automatically being adjusted. If there was a period when the

autofocus was set incorrectly then this time should be added to the measured time.

Also, take a note in case the autofocus was not adapting within 5 seconds in any occurrence.

1. Set up the solution at nominal distance from the SFRplus chart.

2. Find manually the best focus setting for the center of the chart. Calculate the average MTF30 of the

4 edges in the center of the chart with the Video Analyzer.

3. Manually offset the focus to an extreme and enable autofocus.

4. Once the autofocus is stabilized calculate the MTF30 values again and compare the average with

previously found average.


H100693 of 68

Verify cameras correct use of luminance and color spaces

3.4.5.1 Purpose

The luminance range of video render for Skype and Lync is 0 to 255.

As listed in sections 3.3.2.2.4 and 3.3.2.2.5 a camera should represent 0..255 luminance and

chrominance levels in MJPEG mode, but Luminance 16-235 and Chrominance 16-240 in case of a raw

video mode (YUY2, NV12, I420). For raw video modes the Skype or Lync client does the stretching to full

RGB range during the video render.


Requirement

Average luminance pixel value for “patch 36 (black)” when YUY transform is turned off in Remote Capture Tool

16 ≤ avg pixel value

Average luminance pixel value for “ patch 1 (white)” when YUY transform in Remote Capture Tool is turned off

avg pixel value ≤ 235

Table 17: min/max luminance level requirements


Test target ITDR-36 chart

ROI Patch 1 (white reference) / patch 36 (black reference)

Analysis Skype Certification Video Analyzer: automatic detection of the ROI and calculation of value

Table 18: min/max luminance level test details

Figure 1: Transmissive dynamic range test chart


H100693 of 68

Use Remote capture tool – make snapshots for all raw video mode resolutions (YUY2, NV12,

I420) of ITDR-36 chart without the YUV transform enabled

Figure 2: YUV transform setting in RCT

Analyze the patch 1 and 36 for the average luminance level. The white level shall not exceed

pixel value 235

The black level shall not be below pixel value 16

If the values are above or below these thresholds it means the camera does not follow the

luminance and chrominance values correctly as listed in sections 3.3.2.2.4 and 3.3.2.2.5

Below are two samples where the camera poses a correct behavior. The left picture is

without the YUV transform and right picture has the YUV transform enabled during render

(as Skype and Lync clients will do for the raw video camera modes on render side).

Figure 3: Sample image - YUV transform off (left) and on (right)

With correct behavior the white and black will go close to pixel values of 255 and 0 only when YUV

transform is enabled. Also the color saturation increase is visible on the image on right.


H100693 of 68

3.5 Other

Embedded camera shipping protection

3.5.1.1 Purpose

Most notebook and desktop embedded cameras ship with a protective plastic cover. Some of these

covers are not noticeable by the user as they are clear and well aligned over the camera cover glass.

Since the user only sees a preview image they might not detect the degraded image quality.


If the product ships with a protective lens cover then

o It is recommended that the shipping cover is colored (for example blue, to make it easy

to detect)

o Has a small lobe to allow easy removal with fingers

o Could have a written instruction such as “remove”


Examine the DUT’s protective plastic cover. It must not be clear and should include a “Remove” label or

icon.

Usage indicator

3.5.2.1 Purpose

This requirement lets the user know when the camera is on and imaging the user or off and not imaging

the user.

It is advised to either use a low power diffuse LED or add a diffusing glass/plastic in front of the LED. Too

bright indicator LED could disturb the user when he or she is looking direct at the camera in dark room.


Requirement

Usage indicator Light on when capturing video

Light can be on when capturing audio (optional) Usage light off otherwise

Table 19: Usage indicator


For each P1 resolution and max frame rate:

Open and render the capture source. DUT usage indicator should be on.


H100693 of 68

4 Video quality requirements This section defines video metrics that help ensure good-quality Windows video capture for UC.

In case a standalone webcam has a custom driver then it will tested two times – with UVC driver and

with the custom driver. All requirements must be met in both cases.

Webcams will be tested under all available P1 resolutions and color spaces unless specified otherwise. IF

the webcam has autofocus then this will be disabled for all tests except for the depth of field test.

The DUT is positioned as described Section 2.4.1 Default testing position.

4.1 Image detail quality These tests ensure that images provide a desired level of image acuity; for example, the lens is sharp

enough for the sensor, and the sensor has enough pixels to capture the desired resolution after

demosaicing and image processing.

MTF

4.1.1.1 Purpose

MTF30 is a measure of the spatial frequency response of a camera system. Poor MTF30 is typically due

to a poor quality lens or lens/sensor fit, or poor image signal processing. For example, Figure 5 shows a

synthetic example of an image with good and poor MTF. Figure 4 shows the MTF of a typical Premium

webcam and the criteria for Standard and Premium.

Related standard: ISO 12233-2000.

Standard

Premium

Figure 4: MTF30 criteria shown in a typical Premium webcam

http://webstore.ansi.org/RecordDetail.aspx?sku=ISO+12233:2000


H100693 of 68

Figure 5: Left: MTF30=0.20; Middle: MTF=0.53; Right: MTF30=0.88

Figure 6: Sample of 80% center circle area for cameras with different FOV


H100693 of 68


MTF30 Standard Premium

MTF30 (20lux 3000K LED, center) [0.3,0.8] [0.4,0.7]

MTF30 (80lux 3000K LED, center) [0.3,0.8] [0.4,0.7]

MTF30 (80lux 3000K LED, 80% center circle) N/A [0.3,0.7] Table 20: MTF requirements


Test target Default: SFR Plus (small) Alternate: SFR Plus (large) in case all corners fit into the wider ROI on SFR Plus (small)

ROI Center: 2 horizontal and 2 vertical edges in the middle of the SFR Plus chart Average: all complete edges within the wider ROI (circle with diameter equal to 80% of the width of the frame)


Table 21: MTF test details


H100693 of 68

Oversharpening

4.1.2.1 Purpose

Oversharpening (and undersharpening) is a measure used to ensure that cameras are not using too

much sharpening (or not enough), which induces image artifacts like ringing around edges or fuzzy

images. Most cameras will need a certain amount of image sharpening. It is possible to sharpen images

captured with soft focus arbitrarily, enough to pass the MTF requirements. However, images obtained

this way would still have significant loss of detail and high probability of artifacts appearing. This metric

limits the amount of oversharpening or undersharpening allowed. Figure 7 shows an example

oversharpening and undersharpening.

Figure 7: Left: undersharpening 24.6%; Middle: undersharpening=0.3%;

Right: oversharpening=33%


Oversharpening Standard Premium

Oversharpening(20lux 3000K LED, center square) |≤ 20%| |≤ 15%|

Oversharpening(80lux 3000K LED, center square) |≤ 20%| |≤ 15%|

Oversharpening(200lux 3000K LED, center square) |≤ 20%| |≤ 15%| Table 22: Oversharpening requirements


Test target Refer to Table 21: MTF test details

ROI 2 horizontal and 2 vertical edges in the middle of the test target

Analysis Skype Certification Video Analyzer: automatic detection of the ROI and analysis Table 23: Oversharpening test details

http://www.imatest.com/docs/sharpening.html


H100693 of 68

Edge roughness

4.1.3.1 Purpose

Edge roughness is a measure of image downscaling quality (for example, bilinear scaling method is

greatly preferred over nearest neighbor scaling, and bicubic is preferred over bilinear).

Figure 8: Left: bicubic scaling, edge roughness=0.039; Middle: bilinear scaling,

edge roughness=0.052; Right: nearest neighbor scaling, edge roughness=0.309


Edge roughness Standard Premium

ER(80lux 3000K LED, center square) ≤ 0.1 ≤ 0.05 Table 24: Edge roughness requirements


Test target Refer to Table 21: MTF test details


Analysis Skype Certification Video Analyzer: automatic detection of the ROI and calculation of value Table 25: Edge roughness test details


H100693 of 68

Depth of field

4.1.4.1 Purpose

Defines the range where a camera with fixed focus, manual focus, or automatic focus should be able to

focus.



Depth of field Standard Premium

MTF30 min distance (80lux 3000K LED, center square / all edges)

[0.3,0.8] [0.4,0.7]

MTF30 max distance (80lux 3000K LED, center square / all edges)

[0.3,0.8] [0.4,0.7]

Table 26: Depth of field requirements


Test target Default: SFR Plus (small) Alternate: SFR Plus (large) Use the SFRPlus (small) test chart, capture the image. Make sure that the full chart fills at least 75% of pixel area. If the camera FOV is very wide or test distance causes the chart to appear smaller than the above recommendation then use the alternate test chart instead.



Table 27: Depth of field test details

Texture acutance

4.1.5.1 Purpose

Many new webcams use very small pixels that are less sensitive than larger pixels and therefore have

higher noise (lower SNR). To improve the SNR, noise suppression methods can be used; however, even if

it improves SNR, excessive noise suppression will often lose small details from the image, degrading the

Texture acutance and MTF. For example, Figure 9 (left) shows a camera image with a low Texture

acutance due to excessive noise suppression, even in >200 lux of light. In the same scene, Figure 9 (right)

shows a camera image with high Texture acutance. Both cameras pass Premium levels for MTF30 and

SNR, but obviously the left camera has inferior quality for video conferencing.

Standard: CPIQ Texture Acutance, Phase 3.

http://webstore.ansi.org/RecordDetail.aspx?sku=ISO+12233:2000

http://www.i3a.org/resources/


H100693 of 68

Figure 9: Left: Cropped image from a 720p camera with low Texture acutance;

Right: cropped image from another 720p camera (different than the left one) with

high Texture acutance


Texture acutance Standard Premium

Acutance (20lux 3000K LED) ≥ 0.70 ≥ 0.80

Acutance (80lux 3000K LED) ≥ 0.70 ≥ 0.83 Table 28: Texture acutance requirements

Resolutions to be tested for texture acutance are the following:

640x360

640x480

1280x720

1920x1080(if supported)


Test target Default: 8”x8” Spilled coins test chart Alternate: 12”x12” Spilled coins test chart Use the 8’’x8’’ test chart, capture the image Make sure that the chart active analysis area is at least 256 pixels high vertically. If the camera FOV is very wide or the test 1m test distance causes the chart to appear smaller than the above recommendation, then use the 12’’x12’’ test chart instead.


Table 29: Texture acutance test details


H100693 of 68

4.2 Noise

Image spatial SNR

4.2.1.1 Purpose

Spatial noise is the measure of image noise in a single image. Spatial noise indicates a pixel level

variation of each pixel compared to neighboring pixels on single captured image. Figure 10 is an example

of a high and low noise image.

Figure 10: Left: SNR=29.2 dB; Right: SNR=44.2 dB

4.2.1.2 Requirement

Spatial SNR Standard Premium

SNR(20lux 3000K LED) ≥ 32 dB ≥ 35 dB

SNR(80lux 3000K LED) ≥ 35 dB ≥ 38 dB

SNR(20lux 6000K LED) ≥ 32 dB ≥ 35 dB

SNR(80lux 6000K LED) ≥ 35 dB ≥ 38 dB Table 30: Image spatial SNR requirements for resolutions upto and including 360p

Spatial SNR Standard Premium

SNR(20lux 3000K LED) ≥ 30 dB ≥ 33 dB

SNR(80lux 3000K LED) ≥ 33 dB ≥ 36 dB

SNR(20lux 6000K LED) ≥ 30 dB ≥ 33 dB

SNR(80lux 6000K LED) ≥ 33 dB ≥ 36 dB Table 31: Image spatial SNR requirements for resolutions higher than 360p


Test target ST-52 (LED brightness determined in Section 3.4.5)

ROI Patch number 7


Table 32: Image spatial SNR test details


H100693 of 68

Image temporal SNR

4.2.2.1 Purpose

Temporal noise is the measure of noise as difference of pixel values in consecutive frames. As opposed

to spatial noise that indicates a pixel level variation of each pixel within a single captured frame,

compared to neighboring pixels, the temporal noise measurement compares the pixel value difference

of the same pixel on two consecutive images. Temporal noise becomes visible to human eye when

looking at a live video image instead of a single snapshot.

4.2.2.1.1 Requirement

Temporal SNR Standard Premium

TSNR(20lux 3000K LED) ≥ 30 dB ≥ 33 dB



TSNR(80lux 6000K LED) ≥ 33 dB ≥ 36 dB Table 33: Image temporal SNR requirements

4.2.2.1.2 Test procedure

Test target ST-52

ROI Patch number 7

Analysis Skype Certification Video Analyzer: automatic detection of the ROI and calculation of value Select 2 captures in the Video Analyzer and run the test. The captures have to be unique frames with the same resolution and captured in minimal interval between them without moving the camera.

Table 34: Image temporal SNR test details


H100693 of 68

4.3 Color quality

Gamma

4.3.1.1 Purpose

Windows monitors and projectors are standardized to have a gamma of 2.2 (via sRGB), so a camera

gamma of 0.45 ensures a linear response of the total capture-to-render system. Gamma >> 0.45 can give

images that have excessive contrast and look unnatural due to the non-linear color mapping.


Figure 11: Upper-Left: gamma=0.3, Upper-Right: gamma=0.5,

Bottom-Left: gamma=0.7, Bottom-Right: gamma=0.9


Gamma Standard Premium

Gamma(20lux 3000K LED) [0.4, 0.75] [0.4, 0.65]

Gamma(80lux 3000K LED) [0.4, 0.75] [0.4, 0.65] Table 35: Gamma requirements


Test target ST-52

ROI All patches


Table 36: Gamma test details

http://en.wikipedia.org/wiki/SRGB


H100693 of 68

Image dynamic range

4.3.2.1 Purpose

Sufficient dynamic range is required to capture the user and background without driving significant

amount of the dark or bright tones to the limits.

Figure 12: Left: dynamic range=33dB, Right: dynamic range=36 dB


Dynamic range Standard Premium

DR(20lux 3000K LED) ≥ 33 dB ≥ 36 dB

DR(80lux 3000K LED) ≥ 33 dB ≥ 36 dB Table 37: Image dynamic range requirements


Test target ST-52

ROI All patches


Table 38: Image dynamic range test details


H100693 of 68

Relative illumination

4.3.3.1 Purpose

This test checks that a relatively uniform image of the user and the background is captured. Relative

illumination ensures that the luminance is uniform across the image.

Figure 13: Left: Relative illumination=65%; Right: Relative illumination=86%


Relative illumination Standard Premium

RI (80lux 3000K LED) ≥ 70% ≥80% Table 39: Relative illumination requirements


Test target Gray board

ROI Whole frame

Analysis Skype Certification Video Analyzer Table 40: Relative illumination test details


H100693 of 68

Color uniformity

4.3.4.1 Purpose

This test checks that a relatively uniform image of the user and the background is captured.. Color

uniformity ensures that the color is uniform across the image.

Related standards: CPIQ Phase 2 – Color Uniformity.

Figure 14: Left: Max C=12.3; Right: Max C=3.2


Color uniformity Standard Premium

Max C (80lux 3000K LED) ≤ 10 ≤ 5

Table 41: Color uniformity requirements



ROI Whole frame

Analysis Skype Certification Video Analyzer Table 42: Color uniformity test details


H100693 of 68

Veiling glare

4.3.5.1 Purpose

Due to internal reflections, light sources targeted to a camera may cause light scattering to extensive

areas of its sensor. This stray light mostly affects the darker parts of a frame, in effect lowering the

dynamic range of the camera. For cameras without anti-reflective coating and/or without lens hoods,

even common overhead lighting can cause significant fidelity problems. The Veiling glare test measures

the amount of stray light, to avoid its impact on image quality and the loss of dynamic range and acuity.

Figure 15: Left: Notebook webcam image with typical room lighting; Right: same

camera with simple lens hood added, which improves the veiling glare from Basic

to Premium; good anti-reflective coatings can have the same improvement


Veiling glare Standard Premium

Veiling glare (avg pixel value) ≤ 10 ≤ 5 Table 43: Veiling glare requirements


Adjust the veiling glare light for a reading of 80Lux at a horizontal surface at the camera

position, as described in Section 0

o Make sure to use exactly the same type of light bulb for the veiling glare light as for the

two auxiliary test target illumination lights.

o Verify that the veiling glare light does not increase the illuminance of the test target by

more than 5 Lux

Adjust the main auxiliary lights for 80Lux on test target

Capture an image of the uniform gray board with only the two main auxiliary lights turned on

Capture an image of the uniform gray board with both the two main auxiliary lights turned on

and the glare light also turned on


H100693 of 68

Analyze the two images by making the images monochrome and then subtracting the second

image from the first image. Calculate the average pixel value difference between the two

images.


ROI Whole frame

Analysis Skype Certification Video Analyzer Table 44: Veiling glare test details

Figure 16: Veiling glare algorithm explanation


H100693 of 68

Color accuracy

4.3.6.1 Purpose

Accurate colors are required to make images look natural under various lighting temperatures. Note the

criteria for A (2856K) lighting is relaxed compared to 3500 K CFL and 5000K LED to allow A lighting to still

have a yellow tint. Figure 17 gives an example of good and bad color accuracy.

Figure 17: Left: Image with poor color accuracy (Mean ∆𝑪𝟎𝟎 = 𝟗. 𝟒𝟎, Max ∆𝑪𝟎𝟎 = 𝟏𝟓. 𝟗);

Right: good color accuracy (Mean ∆𝑪𝟎𝟎 = 𝟒. 𝟏, Max ∆𝑪𝟎𝟎 = 𝟔. 𝟔𝟕);


Color accuracy Standard Premium

Max ∆𝐶00 (80lux 2700K E27 Warm LED) ≤ 20 ≤ 15

Mean ∆𝐶00 (80lux 2700K E27 Warm LED) ≤ 15 ≤ 10

Max ∆𝐶00 (80lux A-light: 2856 K) ≤ 20 ≤ 15

Mean ∆𝐶00 (80lux A-light: 2856 K) ≤ 15 ≤ 10

Max ∆𝐶00 (20lux 3000K LED) ≤ 15 ≤ 10

Mean ∆𝐶00 (20lux 3000K LED) ≤ 10 ≤ 5

Max ∆𝐶00 (80lux 3000K LED) ≤ 15 ≤ 10

Mean ∆𝐶00 (80lux 3000K LED) ≤ 10 ≤ 5

Max ∆𝐶00 (80lux 6000K LED) ≤ 15 ≤ 10

Mean ∆𝐶00 (80lux 6000K LED) ≤ 10 ≤ 5

Max ∆𝐶00 (80lux 5000K E27 Cool LED) ≤ 15 ≤ 10

Mean ∆𝐶00 (80lux 5000K E27 Cool LED) ≤ 10 ≤ 5

Max ∆𝐶00 (80lux CFL 3500K) ≤ 15 ≤ 10

Mean ∆𝐶00 (80lux CFL 3500K) ≤ 10 ≤ 5 Table 45: Color accuracy requirements


Test target ColorChecker

ROI Patches 1-18


Table 46: Color accuracy test details


H100693 of 68

Color saturation

4.3.7.1 Purpose

Accurate color saturation are required to make images look natural under various lighting temperatures.


Saturation Standard Premium

Sat (80lux 2700K E27 Warm LED) [75%, 130%] [85%, 120%]

Sat (80lux A-light: 2856 K) [90%, 140%] [100%, 130%]

Sat (20lux 3000K LED) [75%, 130%] [85%, 120%]

Sat (80lux 3000K LED) [75%, 130%] [85%, 120%]

Sat (80lux 6000K LED) [75%, 130%] [85%, 120%]

Sat (80lux 5000K E27 Cool LED) [75%, 130%] [85%, 120%]

Sat (80lux CFL 3500K) [75%, 130%] [85%, 120%] Table 47: Color saturation requirements



ROI Patches 1-18


Table 48: Color saturation test details

Exposure accuracy

4.3.8.1 Purpose

Automatic exposure is needed to ensure the image has sufficient contrast and isn't saturated or under-

saturated in typical light conditions.


Mean value of Y channel on patch 22 on ColorChecker

Standard Premium

Y(20lux 3000K LED) [88, 168] [108, 148]

Y(80lux 3000K LED) [88, 168] [108, 148]

Y(200lux 3000K LED) [88, 168] [108, 148]

Y(1000lux 5000K LED) [88, 168] [98, 158] Table 49: Image exposure accuracy requirements



ROI Patch 22


Table 50: Image exposure accuracy test details


H100693 of 68

White balance error

4.3.9.1 Purpose

Accurate color representation is required to make images look natural under various types of lighting

with different color temperatures. In addition to color accuracy also gray world should keep neutral gray

tone instead of pink or magenta toning for example.


White balance error Standard Premium

WB error P.21 (80lux 2700K E27 Warm LED) N/A ∆𝐶00 ≤ 10

WB error P.21 (80lux A-light: 2856 K) N/A ∆𝐶00 ≤ 10

WB error P.21 (20lux 3000K LED) N/A ∆𝐶00 ≤ 10



WB error P.21 (80lux 5000K E27 Cool LED) N/A ∆𝐶00 ≤ 5

WB error P.21 (80lux CFL 3500K) N/A ∆𝐶00 ≤ 5 Table 51: White balance error requirements



ROI Patch 21


Table 52: White balance error test details

4.4 Geometry

Field of view

4.4.1.1 Purpose

This test ensures that the camera has sufficient field of view (FOV) to capture the “talking head”

scenario (a person in front of a PC). See Figure 18 for typical notebook user scenarios and their

corresponding Vertical FOV (VFOV) values. Note that notebook webcams are typically pointed

orthogonal with the screen and the screen needs to be pointed down at a non-optimal viewing angle in

order for the camera FOV to image the head and upper torso. An ideal integrated notebook webcam

would have an adjustable tilt angle so that the display angle and camera angle can be optimized

independently. While a VFOV=40⁰ captures the head and shoulders for this scenario, a VFOV=60⁰ with a

10⁰ down look angle is required to capture the body gestures, which are an important part of non-verbal

communication.


H100693 of 68

60°40°

90°

Figure 18: Vertical FOV for a notebook conferencing scenario

Figure 19: Left: 40⁰ VFOV; Right: 60⁰ VFOV


Vertical field of view Standard Premium Recommended

VFOV ≥ 35 ≥ 40 60 Table 53: Vertical field of view requirements

4.4.1.3 Notes

A typical user’s head must be fully visible (not partially cropped) in a normal sitting position as

shown in Figure 18. For some systems this may involve angling the camera angle down or

providing a camera angle adjustment.



ROI Whole chart


Table 54: Vertical field of view test details


H100693 of 68

Field of view consistency

4.4.2.1 Purpose

In addition to a minimal or target VFOV the FOV should also be consistent within different resolutions

and image aspect ratios (16:9 or 4:3). The camera may be reopened at various resolutions due to

bandwidth limitation or lighting changes, and to keep a smooth user experience, the center of FOV

should not move when switching between the resolutions.

Figure 20: Sample of poor FOV consistency


Field of view consistency Standard Premium

FOV(consistency) ≤ 3% ≤ 1% Table 55: Field of view consistency requirements



ROI Whole chart


Table 56: Vertical field of view test details


H100693 of 68

Geometric distortion

4.4.3.1 Purpose

Low geometric distortion guarantees that straight lines in a scene remain straight on the captured

image. Large geometric distortion makes it difficult to accurately perceive the shape and size of objects

in the captured scene.

Figure 21: Left: Distortion=6.2%; Right: Distortion=0%


Geometric distortion Standard Premium

Camera FOV measured in 4.4.3 is 35 to 45deg Distortion (80lux 3000K LED, max resolution)

|≤ 6%| |≤ 3%|

Camera FOV measured in 4.4.3 is 46 to 65deg Distortion (80lux 3000K LED, max resolution)

|≤ 10%| |≤ 6%|

Camera FOV measured in 4.4.3 is > 65deg Distortion (80lux 3000K LED, max resolution)

|≤ 14%| |≤ 10%|

Table 57: Geometric distortion requirements


Test target Default: Dot Pattern test chart (small) Alternate: Dot Pattern test chart (large)

ROI Whole chart Make sure the chart fills full field of view. If needed, move the camera closer, or use a bigger test chart size. Camera must be aligned very carefully to avoid trapezoidal distortions due to camera position.


Table 58: Geometric distortion test details


H100693 of 68

4.5 Timing

System latency

4.5.1.1 Purpose

This requirement makes sure the webcam or its driver does not induce excessive latency, which would

degrade the overall video end-to-end experience. The latency is measured over the complete system -

from the photons entering the webcam to the photons emitted by the display.


Local video latency (VL) (from capture of photons to render on screen)

Standard Premium

VL(200+ lux, YUY2, I420, NV12) ≤ 110 ms ≤ 90 ms

VL(200+ lux, MJPEG) ≤ 120 ms ≤ 110 ms

* Skype and Lync test labs use Surface Pro (1st generation)with Intel HD Graphics 4000 for this

test in case of external webcam.

Table 59: Video latency (system) requirements


Test target Blinking LED

Analysis Latency measurement kit Can be used together with Skype Certification Video Analyzer

Table 60: Video latency (system) test details

4.5.1.4 Notes

The DUT has to be positioned so that the blinking LED is on the center row of the video frames.

The rendered video on DUT (or test PC) screen should reach the cameras maximum 30FPS.

If the camera supports adjusting gain and exposure separately then this is allowed to manually set the

exposure to low and the gain to high value, in case it helps to reduce the latency by shortening the

exposure time.


H100693 of 68

Jitter

4.5.2.1 Purpose

Ensure the webcam and its drivers provide frames at a consistent rate without excessive jitter in frame

timing.


The jitter at all P1 resolutions and at 30 fps must be ≤ 7 ms.

Jitter Standard

Jitter(80lux 3000K LED) ≤ 7 ms Table 61: Jitter requirement


Analysis Skype Certification Video Analyzer peered with Remote Capture Tool

Table 62: Jitter test details

Audio/video synchronization

4.5.3.1 Purpose

Audio video synchronization is required for lip synchronization. ITU-R BT.1359-1 gives recommended

limits on audio video synchronization. Audio video synchronization can fail if the webcam uses excessive

frame buffers for processing video with low latency audio, or has significant delay with audio processing

with low latency video.

Related standards: ITUR BT.1359-1, ITU-T J.100.


The requirements are given in Table 63. This is a capture only specification and is adjusted to account for

that.

AV synchronization Standard Premium

AVoffsync(200+lux) |≤ 45 ms| |≤ 35 ms| Table 63: Audio/video synchronization requirements




Table 64: Audio/video synchronization test details


H100693 of 68

Time to capture first image, change resolutions

4.5.4.1 Purpose

The time to capture the first image is important to minimize the latency seen by the user, to facilitate

dynamic changing of resolutions and to avoid excessive AV offsync from appearing right from the

beginning of a video transmission.


Standard Premium

Time to capture first image ≤ 1500 ms ≤ 500 ms

Time to change resolutions ≤ 250 ms ≤ 250 ms Table 65: Time to capture first image requirements


Analysis Skype Certification Video Analyzer peered with Remote Capture Tool

Table 66: Time to capture first image test details

Video latency during a call

4.5.5.1 Purpose

To ensure that the video would not have too high latency in lossless network condition and using a

maximum frame rate.


Video delays during call Standard Premium

Send video latency (max resolution) < 170ms < 150ms

Preview video latency (max resolution) < 130ms < 110ms

Receive video latency (max resolution)1 < 180ms < 150ms

Table 67: Video latency during call requirements




Table 68: Video latency (system) test details

1 Applicable only for devices that have receive video capability as part of the solution


H100693 of 68

Video frame rate during a call

4.5.6.1 Purpose

To ensure that the video stream is transmitted without significant degradation.


Video framerate during a call Standard

Send video frame rate (20lux 3000K LED) >14 fps




Receive video frame rate (30fps, max resolution)2 >29 fps

Table 69: Video frame rate during a call requirements


1. Set up a Skype video call to reference PC. The reference PC should have 1080p webcam to enable

sending maximum resolution the DUT can receive.

2. Set the DUT camera and reference camera so that the blinking appears the center height of both

video frames.

3. Ensure the lights are set to >200lux to maximize the camera frame rate.

4. Capture the video from the reference PC using DVI capture card and measure the frame rate using

Video Analyzer.

5. Optionally in case of questions or doubts a rotating object can be used to manually check the unique

frame rate and visualize any issues (300RPM speed is recommended as it is easier to calculate the

frame rate and also an exposure time)

Test target Timing test chart

Analysis Skype Certification Video Analyzer with Datapath DVI capture card Table 70: Video frame rate during a call test details

2 Applicable only for devices that have receive video capability as part of the solution.


H100693 of 68

5 Video test setup

Main video test setup

DUT camera is connected to a test PC unless it is an embedded camera in Laptop or All In One type of

computer.

The Remote Capture Tool is used to capture the images and transport the images to the Video TMT

machine for analysis.

Figure 22: Main video test setup


H100693 of 68

Video latency test setup for system latency

Figure 23: System latency test setup

Video latency test setup – End to End

Figure 24: End to end latency measurement setup


H100693 of 68

End to End testing over Skype video call

Figure 25: End to End test setup over Skype call

End to End test is conducted over a Skype to Skype two way video call. Skype call is made in the ideal

network conditions.

If the DUT is a laptop or All In One computer that allows both the LAN and Wi-Fi connection, then LAN

connection is used as the first preference, and Wi-Fi is verified as a secondary option. If only Wi-Fi is

supported, then Wi-Fi connection will be used.

Video resolutions (send and receive) and frame rates are the highest which the device enables in ideal

conditions, unless otherwise stated in the test case.

A call is made between the DUT and the Reference Skype PC. The Reference PC is configured for

1280x720 or 1920x1080 resolution and one of the two video output cables is connected to the DVI

capture card in Test Management PC.

The tests are conducted by using the DVI capture card to capture the DUT camera send video and

extracting the frames for image processing/analysis. The DVI video is captured at constant frame rate

50 or 60 frames per second.


H100693 of 68

On the reference Skype PC it is possible to open the call technical information window to verify the

DUT send video parameters and network parameters. Go to Skype -> Call menu -> Technical Call Info

(visible only if a call is ongoing).

Verify the following parameters from Call Technical Info prior to testing

The call is UDP – UDP

Relays = 0

Video receive - resolution, frame rate, bit rate - make sure these parameters have reached the

maximum supported before starting the testing (these are the DUT camera send video

parameters!)

5.1.4.1 Call Technical Info during Skype calls

Figure 26: Snapshot of the call technical info displayed in Skype UI

on reference PC.

Much more detailed description about the various info presented in the Call Technical Info window,

please refer to http://developer.skype.com/skypekit/development-guide/audio-video-

integration/technical-call-info

http://developer.skype.com/skypekit/development-guide/audio-video-integration/technical-call-info

http://developer.skype.com/skypekit/development-guide/audio-video-integration/technical-call-info


H100693 of 68

Light setup and conditions

In order to control the lighting conditions a dedicated test room that is isolated from outside light

sources. The walls and objects in the room should be matt black or dark gray. The wall behind the test

chart could be painted mid gray. Any light fixtures, poles etc, should not produce light reflections on

test target or camera.

The lights for objective testing enable us to independently alter the color temperature and illuminance

on the test target in given boundaries.

to

Figure 27: Light sources in video lab

A19/E27

alternate

lights

A19/E27

alternate

lights

iW Blast

Powercore

iW Blast

Powercore

iW Blast

Powercore

iW Blast

Powercore

Glare

light


H100693 of 68

Figure 28: E27/A19 light fixture

Lighting intensity and color temperature are calibrated at the test targets center position with three-

channel photometer Gigahertz-Optik HCT-99D (or alternatively with spectroradiometer JETI Specbos

1211).

Light source Lux levels on target

2700K A19 Warm LED Philips A19 replacement LED 80Lux

A-light: 2856 K Halogen type A-light (reflector must not be part of the light bulb)

80Lux

3000K LED Philips iW Blast Powercore 10Lux ….. 1000Lux USB/DMX control

6000K LED Philips iW Blast Powercore 10Lux ….. 1000Lux USB/DMX control

5000K A19 Cool LED Philips A19 replacement LED 80Lux

CFL 3500K Philips Warm White (3500K) Compact Fluorescent

80Lux

Table 71: Light sources used in video tests

Alternate light source light bulbs are

installed in a vertical row. Left and right side

bulbs are in reverse order (upper bulb on

left side and lower bulb in right side are of

same type).

A mirror is used to direct the light energy to

test target. This helps to achieve the

required Lux level on test target with 2 light

bulbs and also helps to improve the light

uniformity achieving the 10% tolerance over

Colorcheck chart.

http://www.amazon.com/Philips-424382-11-Watt-Household-Dimmable/dp/B00APTS03K

http://www.amazon.com/Philips-410480-EcoVantage-100-Watt-Equivalent/dp/B006Q2617W/ref=sr_1_9?s=hi&ie=UTF8&qid=1370344807&sr=1-9&keywords=A19+halogen

http://www.amazon.com/Philips-425264-Household-Daylight-Dimmable/dp/B00APTS030/ref=sr_1_6?s=hi&ie=UTF8&qid=1368824483&sr=1-6&keywords=philips+led+5000K

http://www.homedepot.com/p/Philips-23-Watt-100-Watt-Energy-Saver-Warm-White-3500K-Compact-Fluorescent-Light-Bulb-E-414052/203349669?N=1z0wptw#.Ub7AHvkwd8E


H100693 of 68

The USB controlled variable Lux/temperature light setup is built using 4 iWBlast Powercore lights in X

shape configuration. This setup gives the best and largest area of light uniformity. The 10% uniformity

criteria can be achieved for 90% area on the 1mx1m test chart. Thus also the SFRPlus and Dot chart

can be lit uniformly.

Figure 29: Distances between the centers of the lamps

The centers of iWBlast Powercore lamps are on a plane that is 70..75cm from test target surface.

The initial alignment of the 4 lamps are made experimentally by photographing the full test chart area

and running the uniformity measurement on the chart are on resulting image as shown on example

below.

Figure 30: Uniformity of main lamps

170cm

75

cm

75

cm


H100693 of 68

The E27 socket alternate lights cannot achieve equally big good uniformity area, thus the optimization

is done to make sure the 10% uniformity is achieved at center of the test target area in equal size to

the X-Rite Color check

Figure 31: Uniformity of A19/E27 socket lights

Below drawings give guidelines for veiling glare test setup. Important note here is that the main lights

used for the test and the veiling glare light are of the same exact type. For example the same type of

A19/E27 socket 2700K Philips Warm LED-s are used for all three.

Figure 32: Veiling glare test setup


H100693 of 68

Test charts

List of all test charts used to measure objective image and video quality parameters:

5.1.6.1 Gray Board – for light falloff, color uniformity and framerate tests

Figure 33: Gray board

The board is made of aluminum composite, surrounded with aluminum profile and covered with

Hama neutral gray background paper.

It is possible to order the boards from Reklaamikompanii (http://www.reklaamikompanii.ee/).

NB! The same dimensions apply also to the gray background test baffles of the other charts.

http://www.reklaamikompanii.ee/


H100693 of 68

5.1.6.2 X-Rite ColorChecker Classic

Figure 34: X-Rite ColorCheker

5.1.6.3 ST-52 / 12 patch 160:1 contrast ratio OECF chart

Figure 35: ST-52 with shutters

Typically the ST-52 is used without the shutters.

Note !

The chart used by Skype is

from Applied Image Inc.

Chart model nr ST-52-RM


H100693 of 68

The shutters are used only in case the automatic exposure is fails due to dark scene.

1) Put on the 80Lux 3000K light condition

2) Capture the ST-52 chart, if the two upmost white patches or the two lowest dark patches

appear same light and are impossible to discern from each other, the camera needs the

shutters to optimize the exposure and gamma for testing.

3) Use the shutters in case the light patches appear clipped as on the image:

Figure 36: Clipped white patches

4) Start closing the shutters from both sides (3:2, 4:3 and 1:1 markers can be used as guidelines)

5) Continue capture -> check -> adjust, until both lightest and darkest patches are clearly

discernible as on the image:

Figure 37: Scene with shutters


H100693 of 68

5.1.6.4 36-Patch Dynamic Range Test Chart (transmissive)

Figure 38: Transmissive dynamic range test chart (ITDR-36 chart)

5.1.6.5 Dead Leaves / Spilled Coins - texture acuity test chart

Figure 39: Spilled Coins test chart

Imatest order information - Spilled Coins (Dead Leaves) Test Chart, Size – 8’’x 8’’ active area, matte

Alternate size - Imatest order information - Spilled Coins (Dead Leaves) Test Chart, Size – 12’’x 12’’

active area, matte.

Note!

For very wide FOV cameras,

Conferencing cameras or

Living Room cameras the

12’’x12’’ version of the chart

will be used for test

reliability.

Note !

This chart needs an uniform

light emitting surface below

the chart, such as a dedicated

light box. See suggestions

under test equipment

section.


H100693 of 68

5.1.6.6 Small Imatest SFR Plus 5x7 chart for Acuity test

Figure 40: SFRplus test chart (small)

Imatest order information - SFRplus test chart, 24X40", 5X7, matte, black&white, 2-tone.

5.1.6.7 Imatest Dot Pattern Test Chart

Figure 41: Dot Pattern test chart (small)

Imatest order information - Dot Pattern Test Chart, Size - Medium, 15 dot.

Note!

This chart is used for

distortion measurement, but

in future it will be also used

for chromatic aberration

test.


H100693 of 68

5.1.6.8 Timing test chart

Figure 42: Timing test chart

Blinking LED is part of the Latency measurement kit described in Section 5.1.7.

Fix rotation motor is optional – it is not needed for any automated tests.

5.1.6.9 Large Imatest SFR Plus 5x7 chart – for >1.5m depth of field test

Figure 43: SFRplus test chart (large)

Imatest order information - SFRplus test chart, 40X60", 5X7, matte, black&white, 2-tone

Note!

Blinking LED is part of the

latency measurement kit.

Rotating wheel is optional.

Frame rate test can be also

conducted using an empty

gray board


H100693 of 68

5.1.6.10 Large Imatest Dot Pattern Test Chart

Figure 44: Dot Pattern test chart (large)

Imatest order information - Dot Pattern Test Chart, Size – X-Large, 15 dot.

Latency measurement kit

ScienceMosaic™ (http://sciencemosaic.com/) video and audio latency measurement system is intended

to provide an accurate way to measure latencies between different video and audio signals. It is designed

as an on-the-field tool for video and audio equipment designers and QA specialists to get a fast

understanding of what are the latency parameters in the audio/video system they are working with.

Latency measurement system generates visible (LED with different blinking patterns) and audible (speaker

with different beeping patterns) reference signal and it has 3 optical inputs (with TOSLINK connectors) for

different video signals and 2 RCA audio inputs for different audio signals.

Figure 45: Latency measurement kit

http://sciencemosaic.com/


H100693 of 68

Other inventory

Besides the charts, Skype uses the following equipment when performing the certification tests:

Lights with power supply and controller

o AC -> DC -> AC 50/60Hz conversion for lights

RSP-1000-48 – AC to 48V/21A DC

TS-700-248 - DC to 50/60Hz 110/230V AC converter

o USB to DMX controller - Enttec DMX USB Pro controller

o Two / four Color Kinetics iW Blast 12 Powercore lights (83° Beam Angle)

four lights achieve a better uniformity over the full 0.9 x 1m test chart area

color temperature adjustable in the region of – K9002 – K6500

luminous intensity controllable

average power consumption is 200W

AC/DC converter built into the lights (accepts 110V … 230V AC)

light controlling data path: PC → DMX USB Pro → Data Enabler → Lights

o Color Kinetics iW Data Enabler- power supply and data repeater (DMX version)

o DMX controlled AC dimmer.

Camera holder mechanism

Laser distance meter

o Bosch DLE 50 Professional

o minimum measuring distance: 5 cm

Video test managemant PC

o Operating system: Microsoft Windows 7 / Windows 8 64bit

o CPU Type: 4 Core or more, ≥3GHz

o system memory: ≥6Gb

o SSD hard drive with sequential transfer read/write speed of 360Mb/s

o Must be able to fit full size PCI Express x4 plug in capture card

o ≥ 6 USB sockets, including USB 3.0 support

Datapath VisionRGB-E2 / VisionRGB-E2s Dual DVI capture card

Reference Skype PC / DUT PC for USB webcams

o Operating system: Microsoft Windows 8 / 64bit

o CPU Type: Core 2 Duo or more , ≥3GHz

o System memory: ≥6Gb

Color and lux-meter

o Gigahertz Optik HCT-99D (measures both – color temperature and illuminance)

o JETI specbos 1211 broadband spectroradiometer (measures incident and reflected light spectra, color temperature, illuminance, and luminance)

http://www.meanwell.com/search/rsp-1000/default.htm

http://www.meanwell.com/search/TS-700/default.htm

http://www.enttec.com/index.php?main_menu=Products&prod=70304&show=description

http://www.colorkinetics.com/support/datasheets/iW_Blast_Powercore_ProductGuide.pdf

http://www.colorkinetics.com/oem/pds/dataenablerpro/

http://www.datapath.co.uk/products/video-capture-cards/visionrgb-e2s

http://www.gigahertz-optik.de/13-1-Measurement+of+Light.html#HCT-99D

http://www.jeti.com/cms/index.php/instruments-55/radiometer


H100693 of 68

6 Appendix

6.1 Camera location interface The following interface allows Lync to query the webcam location and orientation with respect to the

monitor. The IKsPropertySet::CAMERA_LOCATION GUID is defined below:

// {E2F79997-A8AB-4A65-B824-C01CF3740A5F}

DEFINE_GUID(CAMERA_LOCATION,

0xe2f79997, 0xa8ab, 0x4a65, 0xb8, 0x24, 0xc0, 0x1c, 0xf3, 0x74, 0xa, 0x5f);

The IKsPropertySet::CAMERA_LOCATION property is used in the following ways. See Figure 46 for the

coordinate system used in the camera locations.

#define MAX_CAMERAS 16

#define CAMERA_DIRECTION_FRONT_FACING 1

#define CAMERA_DIRECTION_REAR_FACING 2

#define CAMERA_ORIENTATION_PORTRAIT 1

#define CAMERA_ORIENTATION_LANDSCAPE 2

struct CAMERA_LOCATION_S {

USHORT num_webcams;

USHORT monitor_width; // in mm

USHORT monitor_height; // in mm

SHORT camera_x[MAX_CAMERAS]; // in mm

SHORT camera_y[MAX_CAMERAS]; // in mm

USHORT camera_direction[MAX_CAMERAS]; // front or rear facing

USHORT camera_orientation[MAX_CAMERAS]; // portrait or landscape

};

To query if the display supports camera location:

IKsPropertySet *propertySet = …

HRESULT hresult;

ULONG supported;

hresult = propertySet ->QuerySupported(CAMERA_LOCATION, 0, &supported);

To query the camera locations:

IKsPropertySet *propertySet = …

HRESULT hresult;

CAMERA_LOCATION_S camera_location;

hresult = propertySet -> Get(CAMERA_LOCATION, 0, 0, 0, & camera_location,

sizeof(camera_location));

http://msdn.microsoft.com/en-us/library/ms810531.aspx

http://msdn.microsoft.com/en-us/library/ms810531.aspx


H100693 of 68

Data

RemoteVideo

IM

454mm.

552mm.

34

3m

m.

275mm.

(0,0) X

Y

Figure 46: Coordinate system for defining camera locations and example for 2

camera desktop monitor

6.2 Conference room camera criteria This section gives the criteria for webcams used in conference rooms for room system scenarios (as

opposed to personal desktop scenarios). Figure 47 shows a typical small sized conference room with a

10x5’ table. Table 72 gives the resolution for imaging with a 720p and 1080p camera for 6’ and 10’

tables. Figure 48 to Figure 51 show facial resolutions from 20 to 50 pixels across the face. About 40

pixels across the face are required to give good facial expression recognition.

Table 73 gives the criteria for conference room cameras which differ from the desktop scenario criteria.

These criteria will be enforced for devices that are intended to be used in conference rooms for room

system scenarios.


H100693 of 68

Whiteboard

Vid

eo10x5' tableD

ata

Camera 100°

3'-6" 3'-6"

Figure 47: Small conference room

HFOV (deg) 100 100

Horizontal resolution (pixels) 1280 1920

Horizontal resolution (pixels/deg) 12.8 19.2

Head width (feet) 0.5 0.5

Table length (feet) 6.0 10.0

Head distance (feet) 10.0 14.0

Head width (deg) 2.9 2.0

Pixels across head 36.6 39.3 Table 72: Pixels across the head for different conference room sizes and 720p,

1080p cameras

Horizontal FOV >= 100⁰

Table length <= 6’ 720p required

Table length <= 10’ 1080p required

Depth of field 0.5m to 4m Table 73: Conference room camera criteria


H100693 of 68

Figure 48: 20 pixels across the head (anger, fear, surprise, sadness, joy, disgust)



H100693 of 68



skype and lync video capture specification · skype and lync video capture specification h100693...

Documents