Damien Sterkers' (Broadpeak) presentation at the Newtec SATCOM HUB at NAB 2019.

1. www.broadpeak.tv
CM|IP NAB 2019
How to erase OTT latency
with Multicast ABR
contact@broadpeak.tv

2. 2
What we want to avoid…
22:42:06
GOOOOOOAL!
« Hey guys, there will be
a goal in 48s
(says Twitter) »

3. 3
Where does latency come from?
*6s chunk **3 chunks buffering
Unicast ABR delivery
HLS + TS
Packaging
6 000 ms
Player Buffering
18 000 ms
Decoding
50 – 500 ms
Unicast
Transmission
0 – 600 ms Total delay:
26 050 – 30 100 ms
28s
Unicast ABR delivery
DASH, HLS/mp4
Decoding
50 – 500 ms
Unicast
Transmission
0 – 600 ms Total delay:
10 050 – 14 100 ms
12 s
Packaging
2 000 ms
Player Buffering
6 000 ms
Typical: 6s segments
Typical: 2s segments
Video encoding
2000 – 5000 ms
Video encoding
2000 – 5000 ms
IPTV delivery (TS)
Video encoding
2000 – 5000 ms
Multicast
Transmission
0 – 600 ms
Player
Buffering
500 ms
Decoding
50 – 500 ms
Total delay:
2 550– 6 600 ms
5 s

4. 4
Unicast ABR
OTT
Origin
Transcaster
Unicast to Multicast
Gateway
or STB
Standard
OTT players
Unicast
Agent
Multicast to
Unicast
Home Network
What is multicast ABR?
Content delivered only once to all users
Operator’s IP
network
Applicable for xDSL, HFC/DOCSIS, FTTH
OTT Standards: HLS, DASH, Smooth
Multicast ABR

5. 5
HTTP vs Multicast-ABR delivery
Irregular & best effort traffic
 Large buffering (~3 segments)
HTTP Multicast ABR
Steady & prioritized traffic
 minimum buffering
M-ABR uses the same transport technology as IPTV -> same buffering (~0.5s)

6. 6
Reducing the player buffer
Multicast ABR delivery
(HLS, DASH)
Player Buffering
2 000 ms
Decoding
50 – 500 ms
Total delay:
6 050 – 10 100 ms
8 sMulticast
Transmission
0 – 600 ms
Unicast ABR delivery
DASH, HLS/mp4
Decoding
50 – 500 ms
Unicast
Transmission
0 – 600 ms Total delay:
10 050 – 14 100 ms
12 s
Packaging
2 000 ms
Player Buffering
6 000 ms
Typical: 2s segments
Video encoding
2000 – 5000 ms
Packaging
2 000 ms
Video encoding
2000 – 5000 ms
IPTV delivery (TS)
Video encoding
2000 – 5000 ms
Multicast
Transmission
0 – 600 ms
Player
Buffering
500 ms
Decoding
50 – 500 ms
Total delay:
2 550– 6 600 ms
5 s
Only possible if the
source is guaranteed

7. Segments download latency
Real time:
2s to receive the whole segment
Packaging
• OTT “streaming” is based on segments “progressive download”
– Constraint: download the entire segment before process
Download
manager
Player
Media
decoder
usually RT
(else higher quality selected)
2s
Example with segment = 2s
Encoding
4s latency added

8. CTE and Low latency in CMAF
• CAUTION: CMAF does NOT imply low latency
– CMAF proposes an optional media segment structure that allows reducing it
– The secret: create a sub-structure within the segment, at the video structure level, called CMAF chunks,
IDR IDR
Chunk
#1
Chunk
#2
Chunk
#3
Chunk
#4
Chunk
#5
Chunk
#6
Chunk
#7
Chunk
#8
…
Segment
• CTE = Chunked Transfer Encoding
– Standard http 1.1 transfer mechanism
– Files can start being transferred even if not yet entirely available, pieces by pieces called HTTP chunks
• Both concepts are combined
CMAF chunk
HTTP
chunk
CMAF
chunk
…
HTTP
chunk
CMAF
chunk
…
HTTP
chunk
CMAF
chunk
…

9. Latency with CTE & CMAF chunking
Chunk immediately
transfered to the CDN
0.2s
Packaging
• Network latency proportional to the chunk size
Download
manager
Player
Media
decoder
Starts decoding before the whole
segment is present
0.2s
Encoding
Example with segment = 2s & chunk = 0.2s
0.4s latency added

10. 10
Latency with CTE & CMAF chunking
Decoding
50 – 500 ms
Total delay:
2 750 – 6 700ms
5 sMulticast
Transmission
0 – 600 ms
Packng
200 ms
Video encoding
2000 – 5000 ms
Buffering
500 ms
Multicast ABR delivery
(HLS, DASH)
Player Buffering
2 000 ms
Decoding
50 – 500 ms
Total delay:
6 050 – 10 100 ms
8 sMulticast
Transmission
0 – 600 ms
Packaging
2 000 ms
Video encoding
2000 – 5000 ms
Multicast ABR with CTE/CMAF
(DASH only)
IPTV delivery (TS)
Video encoding
2000 – 5000 ms
Multicast
Transmission
0 – 600 ms
Player
Buffering
500 ms
Decoding
50 – 500 ms
Total delay:
2 550– 6 600 ms
5 s

11. 11
Summary
Low latency
packager
Standard
packager
Unicast
network
Standard
player
Low latency
player
Low latency
packager
Low latency
player
Unicast
network
Multicast
network
Quality* Latency
*Service continuity, video layer reached

12. @broadpeak
broadpeak
www.broadpeak.tv
@broadpeak
broadpeak
www.broadpeak.tv
Thank you