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Newtec SATCOM HUB NAB 2019 - Damien Sterkers (Broadpeak)
1. The document discusses reducing latency in over-the-top (OTT) video streaming. It compares latency from unicast adaptive bitrate (ABR) delivery, which can have latency up to 30 seconds, to multicast ABR delivery, which can reduce latency to 5 seconds. 2. Multicast ABR delivery involves sending content to multiple users simultaneously over an operator's IP network using multicast technology, rather than unicast which sends content individually. This allows for steadier traffic and minimum buffering. 3. The document also describes how chunk transfer encoding (CTE) and CMAF chunking within video segments can further reduce latency to around 5 seconds by starting playback before an entire segment
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Newtec SATCOM HUB NAB 2019 - Damien Sterkers (Broadpeak)
- 1. www.broadpeak.tv CM|IP NAB 2019 Howto erase OTT latency with Multicast ABR contact@broadpeak.tv
- 2. 2 What we wantto avoid… 22:42:06 GOOOOOOAL! « Hey guys, there will be a goal in 48s (says Twitter) »
- 3. 3 Where does latencycome 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 toMulticast 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-ABRdelivery 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 playerbuffer 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 Realtime: 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 Lowlatency 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 Lowlatency packager Low latency player Unicast network Multicast network Quality* Latency *Service continuity, video layer reached
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