edit lists

[jpiesing]

This issue is for discussion about what we should do about edit lists, what we should put in the DPCTF spec and what we should test.

Note that the MSE byte stream spec for ISOBMFF only requires support for a very limited subset of edit list functionality.

"The user agent MUST support setting the offset from media composition time to movie presentation time by handling an Edit Box (edts) containing a single Edit List Box (elst) that contains a single edit with media rate one. This edit MAY have a duration of 0 (indicating that it spans all subsequent media) or MAY have a non-zero duration (indicating the total duration of the movie including fragments)."

See also the following DASH-IF IOP issues on edit lists.

• Edit Lists with Bitstream Switching Dash-Industry-Forum/DASH-IF-IOP#168
• When, if ever, are edit lists okay to use and how to they affect timing calculations? Dash-Industry-Forum/Guidelines-TimingModel#27

[haudiobe]

Discussion with Romain:

• we would be interested to know if you provide representative test content with the following options:
  • With edit lists for video and audio.
  • Without edit lists uses negative offsets for video and avoiding audio priming.
  • In the CTA WAVE context, do we have these different options?

Romain Bouqueau: No. I did take care of video. Audio was handled by Resillion.
I'm pretty sure the Resillion streams use edit lists. For video we have no edit list.

[haudiobe]

Actions from f2f IBC

• Generate Questions about edit lists in deployments
  • We need to make sure that the manifest generation takes into account the edit lists
• Create a tests in DPCTF for edit list playback (functional, audio, video, sync, random access)
• We add content validation for edit lists or make sure that it is correctly implemented

[haudiobe]

Draft questions are generated here: https://docs.google.com/document/d/10Nw9MtJprr8qFzN7uERU9Ql7q3KPOLNaP1kM3xScXRs/edit?tab=t.0

[haudiobe]

A survey has been launched, we are collecting responses.

Dear colleagues,

In MPEG and CTA WAVE we have identified that Edit Lists in CMAF content may be a source of problems in playback.
Reason is that edit lists shift the timeline on a global basis and have been used in early deployments to address for example audio priming or in video to address backward-predicted pictures.
CMAF includes options for edit lists, but at this stage we are unsure whether they are deployed.

For this purpose, we have created a survey around edit list in order to develop tests in CTA WAVE together with the Device Playback Suite.

We would appreciate your feedback on this matter by February 5, 2025. You may also forward this survey to your colleagues and possibly vendors.
If you have questions, please feel free to reach out to me.

Some recent details on the test suite are here
• Get started: https://www.cta.tech/Resources/Standards/WAVE-Project/WAVE-Streaming-Media-Test-Suite-Devices
• W3C presentation https://www.w3.org/2024/09/03-me-minutes.html with full presentation here: https://www.w3.org/2011/webtv/wiki/images/0/0b/2024-09-03-WAVE-Streaming-Media-Test-Suite-Devices.pdf
• SVTA DASH-IF special session: October 25, 2024 with slides 2024-10-25-WAVE-Streaming-Media-Test-Suite-Devices.pdf and Recording mp4

We wish you happy holiday.

Thanks for your collaboration.

Thomas (as CTA WAVE DPCTF Interim Chair)