Re: Timing Information MPEG-2 TS

From: <Clift>, Graham <Graham.Clift@am.sony.com<mailto:Graham.Clift@am.sony.com>>
Date: Monday, March 3, 2014 at 5:29 PM
To: "public-inbandtracks@w3.org<mailto:public-inbandtracks@w3.org>" <public-inbandtracks@w3.org<mailto:public-inbandtracks@w3.org>>
Subject: Timing Information MPEG-2 TS
Resent-From: <public-inbandtracks@w3.org<mailto:public-inbandtracks@w3.org>>
Resent-Date: Monday, March 3, 2014 at 5:29 PM

This question is specific to MPEG-2 TS and this:
·         startTime is set to the time in the media resource timeline when the first private data packet in the DataCue was received.
http://www.w3.org/community/inbandtracks/wiki/Main_Page#MPEG-2_TS
In current proposal, textTracks with cues of type metadata are expected to have startTime’s populated .For PES packets the PTS may be available (although not guaranteed) however for private payloads the PTS might only be available from, say, a video frame. However, the transport stream may have many video/audio streams that may not be directly associated with this metadata track.

 I don’t know of any instances where MPEG-2 TS has multiple video streams. Even if it did, only one can be selected in HTML.

So the question is, which PTS would be used to timestamp this cue data? Or is another clock expected to be used (which BTW might have similar issue)?

startTime is the time in the media resource timeline, as determined by the UA. How this is determined is not specified.


Regards
Graham Clift
Sony Corporation