Extensions for Hybrid Delivery using MPEG-2 TS and DASH
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The document discusses enhancements for hybrid delivery systems using MPEG-2 TS and DASH, primarily focusing on improving the broadcast infrastructure to accommodate new services like 3D and UHD without disrupting existing operations. It identifies challenges related to finding the MPD, describing it, managing timing, and addressing latencies in live broadcasts. Proposed solutions include using MPD URLs in PMT, implementing a new URL scheme for PIDs, and better synchronization of media timelines.
Extensions for Hybrid Delivery using MPEG-2 TS and DASH
- 1. m26903 Extensions for Hybrid Delivery using MPEG-2 TS and DASH Jean Le Feuvre Cyril Concolato {lefeuvre, concolato} @ telecom-paristech.fr
- 2. Context ■ Connected TVs and STBs • But dedicated services: broadcast or broadband ■ Existing broadcast Infrastructure • MPEG-2 TS based ■ New services • 3DHD, UD, UHD, FVP, … • Need more bandwidth • May not target 100% of the deployed TVs/STBs − Broadcasting all data too costly 1 1/15/2013
- 3. Goals ■ Enhance existing broadcast • Media replacements − Audio, subtitles, … • Scalable enhancements − AVC 1080p broadcast + HEVC Scalable 4K − 3D: AVC 1080p broadcast + MVC or other AVC right view ■ Without impacting existing broadcast infrastructure • StatMux or other equipments ■ Use DASH for delivery of enhancements • MPD covers most of the use cases − Alternative, scalability, BR adaptation, … • But misses − Description of broadcast TS in MPD − Description of TS « MPD timing » – Need frame-accurate timing for scalable-based services 2 1/15/2013
- 4. Problem #1: Find the MPD ■ Out-of-band (out of TS) signaling • How does a STB locate the MPD? − Likely complex & out of scope: less interoperable • Need identifier for − TS program − Potentially TS Mux ID, tuner params (T or S) … ■ In-band signaling • Send MPD Location (URL) − Lighter than sending the MPD … • OPT1: MPD associated with a mux − Needs program identifier • OPT1: MPD associated with a program − DONE ! 3 1/15/2013
- 5. Problem #2: Describe in MPD ■ Existing Tools • DVB triplets and co − Hard to use in non-DVB world ■ Define new scheme • pid:// or similar to identify a PID in a program − Scheme pid:// already used in 4on2 • Use scheme in MPD URL describing the TS representation(s) • Maybe not elegant but PIDs are usually static ■ Brodacasted TS not « segmentable » • Can’t use SegmentList or SegmentTemplate • Single segment running « forever » − Use SegmentBase 4 1/15/2013
- 6. Problem #3: Find the TS « MPD Timing » ■ Using PCR & PTS • How to handle discontinuities? • PCR can be modified by network equipements ■ Fingerprinting & co • Complex • Accuracy ~10ms − Not for scalable-based services… ■ Recovery from UTC info in TS • TDT, … − From other SBOs … • Table insertions not accurate enough − Up to 2s drift on french DVB-T networks ■ Send the media time • PES data streaming • Associate media timeline to PES PTS 5 1/15/2013
- 7. Problem #4: Latencies ■ Classic Hybrid Delivery issues • Broadcast is real-time live − Pausing live for buffering not desired • Broadband is onDemand − Latency in delivery ■ Provide some hints • Enable prefetching of broadband media for each new event − Period anouncements 6 1/15/2013
- 8. Proposal Overview 7 1/15/2013
- 9. Proposal ■ MPD URL in PMT through Descriptor ■ URL scheme PID:// to identify PIDs in MPD ■ TS « MPD Timeline » PES data streaming • Presentation time: media timeline associated to PES MPT (in seconds) = (PTS - PTS0 )/90000 + (MPT0 - @presentationTimeOffset)/SegmentBase.timescale • PeriodID: indicate the ID of the current period or the following period • Period_switch_time: indicate time when this periodID becomes the current one − Allows prefetch 8 1/15/2013
- 10. Example <Period> <AdaptationSet …> <Representation id="R1" codecs="avc1.4D401F" mimeType="video/mp2t" > <SegmentBase media="pid://110" timescale=”25000”/> </Representation> <Representation id="R11" dependencyId="R1" > </Representation> </AdaptationSet> <AdaptationSet mimeType="video/mp2t" codecs="mp4a" …> <Representation id="R2"> <SegmentBase media="pid://120" timescale=”25000”/> </Representation> </AdaptationSet> </Period> 9 1/15/2013
- 11. Questions ?