JPEG 2000

Image Compression Standard

Enrique Nava, University of Málaga (Spain) Brasov, July 2006

Grupo de Investigación:Tratamiento Digital de Imágenes Radiológicas

GTDIR

Standard organization

Standard organization

How a standard is made? Exploration (6-12 months)

The search for new technology Seek Industry experts Open seminars

Requirements (6-12 months) Establish the scope of work Call for Proposals

Competitive phase (3-6 months) Do Homework Response to CfP Initial technology selection

Collaborative phase (1 year) Core Experiments Working Drafts

Standard phases

3 months 2 months publishDocumenttype

Specification CD FCD FDIS IS

Amendment PDAM FPDAM FDAM AMD

Corrigenda X DCOR X COR

TechnicalReport PDTR X DTR TR

All documents start out in life as working drafts (WD)

4 months

Nomenclature WD - Working Draft

CD - Committee Draft FCD - Final Committee Draft FDIS© - Final Draft International Standard IS © - International Standard © indicates ISO copyright

PDAM - Proposed Draft Amendment FPDAM - Final Proposed Draft Amendment FDAM © - Final Draft Amendment AMD © - Amendment

DCOR - Draft Corrigenda COR © - Corrigenda

PDTR - Proposed Draft Technical Report DTR © - Draft Technical Report TR © - Technical Report

DoC - Disposition of Comments

Why JPEG 2000?

To improve quality-performance ratio: Low bit-rate compression (<0.25 bpp) Lossy and lossless compression (both high performace) Computer graphics, bi-level and raster images Transmission in noise channels Random access to data and progressive transmission Open architecture (different application can be

optimized)

Low-rate transmission rate

0.125bpp (192:1) 0.25bpp (96:1) 0.5bpp (48:1)

Progressive transmission

Applications

Internet Cellular phone imaging Printers and scanners Digital photography Medical imaging Digital libraries E-commerce Facsimile transmission

JPEG 2000: a big standard Core standard was proposed to finish in Dec

2000. It replaces JPEG standard (ISO 10918) It has been proposed 12 parts

Part 1 is the core standard Part 2 is extensions to the core system Part 3 is motion Jpeg 2000 Parts 4-5 are conformance and reference software Parts 6 and 12 are File Format issues Parts 8-11 are applied extensions

JPEG 2000 parts (ISO/IEC 15444)

Part Name IS Year

1 Core Coding system 2000

2 Extensions

3 Motion JPEG 2000 2002

4 Conformance 2002

5 Reference software 2003

6 Compound image file format 2003

7

8 JPSEC: Secure JPEG 2000 2005

9 JPIP: Interactivity tools, APIs and protocols 2004

10 JP3D: Extensions for 3D data 2006

11 JPWL: Wireless 2005

12 ISO Base Media File Format 2004

13 Entry level JPEG 2000 encoder

Building blocks

Color coding

Irreversible Color Transform (ICT) Used for conventional YCbCr transform for image and

video signals. Not valid for lossless coding

BGR

CCY

r

b

081.0419.0500.0500.0331.0169.0114.0587.0299.0

r

b

CCY

BGR

0.07718.10.17142.03441.00.14021.10000.00.1

Color coding

Reversible color codingOnly integer operations

Forward RCT:

Y= (R+2G+B)/4

Cb=B-G

Cr=R-G

Inverse RCT:

G= Y-(Cb+Cr)/4

B=Cb+G

R=Cr+G

Discrete Wavelet Transform

Multirresolution image representation: DWT. The full-frame nature of the transform decorrelates the image across

a larger scale and eliminates blocking artifacts at high compression. Use of integer DWT filters allows for both lossless and lossy

compression within a single compressed bit-stream. DWT provides a frequency band decomposition of the image where

each subband can be quantized according to its visual importance. Two filters in Part 1: irreversible Daubechies (9,7) and reversible

(5,3) Part 2 allows arbitrary filters

2-D Wavelet Decomposition

•Most wavelet based image compression systems use a class of analysis/synthesis filters known as bi-orthogonal filters:

•– The basis functions of h0(n) and g1(n) are orthogonal as the basis functions for h1(n) and g0(n) are orthogonal.•– Linear-phase (symmetrical) and perfect reconstruction.•– Unequal length; odd-length filters differ by an odd multiple of two (e.g., 7/9), while even-length filters differ by an even multiple of two (e.g., 6/10).•– Symmetric boundary extension.

Quantization

Uniform quantization with deadzone is used to quantize all the wavelet coefficients.

For each subband b, a basic quantizer step size b is selected by the user and is used to quantize all the coefficients in that subband.

The choice of the quantizer step size for each subband can be based on visual models, such as the contrast sensitivity function (CSF). This gives higher compression ratio for same visual quality.

Quantization

Where: y is the input to the quantizer, b is the quantizer step size, q is the resulting quantizer index.

Dequantization

Where: z is the reconstructed signal value r is the reconstruction bias

R = 0.5 -> midpoint reconstruction (no bias) R < 0.5 reconstruction is biased to zero (typical is r=3/8) In JPEG 2000 (Part 1), parameter r is arbitrarily selected by

the decoder

Quantization Unlike JPEG Baseline, where the resulting quantizer

index q is encoded as a single symbol, in JPEG2000 it is encoded one bit at a time, starting from the MSB and proceeding to the LSB.

During this progressive encoding, the quantized wavelet coefficient is called insignificant if the quantizer index q is still zero. Once the first nonzero bit is encoded, the coefficient becomes significant and its sign is encoded.

If the p least significant bits of the quantizer index still remain to be encoded, the reconstructed sample at that stage is identical to the one obtained by using a USQ with deadzone with a step size of b 2p

Bit-plane coding quantization

Bit-plane coding quantization example Wavelet coefficient: 83. Quantizer step size: 3

Quantizer index: 83/3=27 (00011011)

Dequantized value full: (27+0.5) 3 = 82.5 Dequantized value 6BP:

000110=6 Step size = 3x4=12 Dequantized value = (6+0.5) 12 = 78

Dequantized value 4BP: 0001=1 Step size = 3x16=48 Dequantized value = (1+0.5) 48 = 72

Entropy coding

Context-based adaptive binary arithmetic coding is used in JPEG2000 to efficiently compress each individual bit plane.

The binary value of a sample in a block of a bit plane of a subband is coded as a binary symbol with the JBIG2 MQ-Coder.

Bit coding example

Bit coding example

Bit coding example

Bit coding example

Bit coding example

Bit coding example

Bit coding example

Bit coding example

Visual quality

SNR quality

Full image

Resolution

SNR progressive examplelayer

resolution

Rate allocation Rate allocation is the process that allows to target a

specific compression ratio with the best possible quality (MSE, visual or other) for each layer and/or entire codestream. Possible types are: None: compression ratio is determined solely by the quantization

step sizes and image content. Iterative: quantization step sizes are adjusted according to

obtained compression ratio and operation is repeated. Post-compression: rate allocation is performed after the image

data has been coded, in one step. Others (Lagrangian, scan-based, etc.)

Not standardized by JPEG 2000 -> encoder choice.

ROI coding Region of Interest (ROI) coding allows a non-uniform

distribution of quality. The ROI is coded with a higher quality than the background (BG). A higher compression ratio can be achieved with same or higher quality inside ROIs.

Static ROIs are defined at encoding time and are suitable for storage, fixed transmission, remote sensing, etc. Commonly referred to as ROI coding.

Dynamic ROIs are defined interactively by a user in a client/server situation during a progressive transmission. Suitable for telemedicine, PDAs, mobile communications, etc. They can be achieved by the dynamic generation of layers matching the user’s request.

ROI coding

Error Transmission When delivering compressed images across error-prone

channels any transmission error can severely affect the decoded image quality. This is specially true since variable length coding is used in the code-block entropy coding and packet heads.

Error types can be random errors, burst error and missing bytes (i.e. network packet loss).

Since each code-block is independently coded an error in a code-block’s bitstream will be contained within that code-block. Nevertheless severe distortion can occur in the case of an error.

Packet heads are interdependent and thus fragile.

Example of error resilience

Error management

Coded image data Code-block partition Regular termination of arithmetic coder Segmentation symbols

Packet heads Start of packet markers Packet heads in main / tile codestream header Partition of packets into precincts

JP2 file format JP2 is the optional JPEG 2000 file format to encapsulate

JPEG 2000 codestreams. Extension: jp2 Allows to embed XML information (e.g., metadata) Alpha channel (e.g., transparency) Accurate color interpretation “True color” and “palette color” supported Intellectual property information Capture and default display resolution File “magic number” File transfer errors (ASCII ftp, 7 bit e-mail, etc.)

Software for JPEG 2000

C (University of Arizona/HP)Verification model (VM) used in the standard

phase of JPEG 2000 Java (EPFL, Ericsson, Canon)

Part 5 (Reference Software) of JPEG2000 standard (http://jpeg2000.epfl.ch)

Also a C implementation is publicly accessible

More…

http://www.jpeg.org (JPEG official web page) D.S. Taubman; M.W. Marcellin: “JPEG2000:

image compression fundamentals, standards and practice”. Kluwer 2002.

Signal Processing: Image Communication, vol 17(1), pp. 1-144, Jan 2002 (special issue)

Touradj Ebrahimi web page at epfl.ch

MPEG Moving Picture Experts Group (MPEG) Coding of Moving Pictures and Audio Five Standards:

MPEG-1 - Error free environments MPEG-2 - Broadcast TV (SD and HD) MPEG-4 - Object based coding MPEG-7 - Multimedia description MPEG-21 - Seven element initiative for multimedia

deployment

MPEG 1:1992 (ISO/IEC 11172) Coding of moving pictures and associated audio for digital storage media at up to about 1,5 Mbit/s

Part 1 - MPEG-1 Systems - Program Stream Part 2 - MPEG-1 Video for CD -I Part 3 - MPEG-1 audio

including Layers I, II, and III(a.k.a. mp3) Part 4 - Conformance Part 5 - Technical Report

Directed primarily at error free environments

Part -1 Systems - joint with ITU - 2 ed Dec 2000 Part -2 Video - joint with ITU – 2 ed Dec 2000 Part -3 Audio- forward/backward compatible to MPEG-1(1998) Part -4 Conformance (1998) Part -5 Technical Report (1998) Part -6 DSM CC - Digital Storage Media Cmd and Cntl (1998) Part -7 AAC - Advanced Audio Coding (1997) Part -9 RTI - Real Time Interface (1996) Part -10 Conformance Extensions for DSM-CC (1999) Part -11 IPMP on MPEG-2 Systems

1996 Emmy for technical excellence

MPEG 2:1994 (ISO/IEC 13818) Generic coding of moving pictures and associate audio information

Part 1 Systems (2001) Part 2 Visual (2001) Part 3 Audio (2001) Part 4 Conformance (2002) Part 5 Reference Software (2002) Part 6 DMIF - Delivery Multimedia Integration Framework (2000) Part 7 Optimized Software (2002) Part 8 MPEG 4 on IP (2002) Part 9 Reference Hardware (2003) Part 10 Advanced Video Coding (AVC) joint with ITU-T (2003) Part 11 Scene Description and Application Engine Part 12 ISO Base Media File Format Part 13 IPMP Extensions Part 14 MP4 File Format Part 15 Advanced Video Coding File Format Part 16 Animation Framework eXtension (AFX) Part 17 Streaming Text Format Part 18 Font Compression and Streaming

MPEG 4:1998 (ISO/IEC 14496) Coding of audio-visual objects

Part 1 Systems Part 2 DDL - Description definition language Part 3 Visual Part 4 Audio Part 5 Multimedia description schemes Part 6 Reference software Part 7 Conformance testing Part 8 Extraction and use of description Part 9 MPEG-7 Profiles Part 10 Schema Definition

MPEG 7:2001 (ISO/IEC 15938) Multimedia content description interface

Part -1 Technical Report (2001) Part -2 Digital item declaration (2002) Part -3 Digital item identification(2002) Part -4 IPMP Part -5 Rights Expression Language Part -6 Rights Data Dictionary Part -7 Digital Item Adaptation Part -8 Reference Software Part -9 File Format Part -10Digital Item Processing Part -11Evaluation Methods for Persistent Association Part -12Test Bed for MPEG-21 Resource Delivery Part -14Conformance Testing

MPEG 21:2005 (ISO/IEC 21000) Multimedia framework