aligning streams in st 2110 or how to manage lip sync · curated by ip showcase theater at nab –...
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C U R A T E D B Y
IP SHOWCASE THEATER AT NAB – APRIL 8-11, 2019
Aligning Streams in ST 2110 or How to Manage Lip Sync
Leigh Whitcomb, SMPTE Fellow, Architect
Imagine Communications
What Problem Are We Solving?
2
With ST 2110, Did the Problem Magically Go Away?
No
3
With ST 2110, Did the Problem Get Worse?
Yes
4
ST 2110 Has Separate Essence Flows
5
SDI
21
10
GW
2110-20 video
2110-30 audio
2110-40 ancillary
Network
2110-20 video
2110-30 audio
2110-40 ancillary 21
10
GW
SDI
6
t=0
Processing delay
Processing delay
spatial delay
RX@41ms
TX@12ms
NET
NET Processing delay
TX@50ms
Processing delay
RX@13ms TX@20ms
TX@40ms
Receiver
NET
(aud) RX@21ms
(vid) RX@51ms
13 in/ms
Receiver has to re-align the
A/V
6 slides of Doom and Gloom, Will It Get Better?
Yes
Time Stamps
7
8
t=0
Processing delay
Processing delay
spatial delay
TS=0 RX@41ms
TS=0 TX@12ms
NET
NET Processing delay
TS=0 TX@50ms
Processing delay
TS=0 RX@13ms
TS=0 TX@20ms
TS=0 TX@40ms
Receiver
NET
(aud) TS=0 RX@21ms
(vid) TS=0 RX@51ms
13 in/ms
Receiver has to re-align the
A/V
All Devices Locked Together
Network Time and
Clock
2059 Grandmaster #1
Network Time and
Clock
2059 Grandmaster #2
Ethernet Switch
Local version of
Network Time and
Clock
Media Node #1
GPS #1 GPS #2
Local version of
Network Time and
Clock
Media Node #2
Local version of
Network Time and
Clock
Media Node #3
RTP Time Stamp
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | V |P|X| CC |M| PT | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Time Stamp | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SSRC | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
RTP Header
Link Offset -> Presentation Delay -> Reconstruction Delay
11 Source: VSF TR-03
Reconstruction Delay
• Process each stream separately
• Indirectly align
SDI
21
10
GW
2110-20 video
2110-30 audio
2110-40 ancillary
Network
2110-20 video
2110-30 audio
2110-40 ancillary 21
10
GW
SDI
RTP Timestamps
• Metadata that describes when the essence was created ‒ Can be changed independently of the essence
• Initially created from PTP/2059 time
• 32-bit rollover
• Units ‒ -20 Video: 90 KHz ticks
‒ -30 Audio: 48 KHz ticks
‒ -40 ANC: 90 KHz ticks
RTP Timestamps
0
1E+09
2E+09
3E+09
4E+09
5E+09
6E+09
7E+09
8E+09
9E+09
1E+10
0
30
00
60
00
90
00
12
00
0
15
00
0
18
00
0
21
00
0
24
00
0
27
00
0
30
00
0
33
00
0
36
00
0
39
00
0
42
00
0
45
00
0
48
00
0
51
00
0
54
00
0
57
00
0
60
00
0
63
00
0
66
00
0
69
00
0
72
00
0
75
00
0
78
00
0
81
00
0
84
00
0
87
00
0
90
00
0
93
00
0
96
00
0
99
00
0
RTP
VA
lue
PTP Time (s)
RTP Count value
Audio RTP TS Video RTP TS PTP Time
Testing
• “Dirty Hands” Workshop ‒ Feb. 18 – 22, 2019
‒ Testing newer parts of the standard and parts that were not well tested
Open Work
16
• What is the minimum Reconstruction Delay a product should support?
• Re-timestamping
Key Take Aways
• Separate essence flows requires alignment
• All devices locked together
• RTP Timestamps from PTP/2059 time
• Change RTP Timestamp without changing the Essence
• Reconstruction Delay ‒ Indirectly aligns the streams
• Open work ‒ Re-timestamping and Reconstruction Delay
C U R A T E D B Y
IP SHOWCASE THEATER AT NAB – APRIL 8-11, 2019
Thank You
Leigh Whitcomb, Imagine Communications