[Bug 22120] Variable Frame Rate

https://www.w3.org/Bugs/Public/show_bug.cgi?id=22120

--- Comment #4 from Cyril Concolato <cyril.concolato@telecom-paristech.fr> ---
I was probably a bit too quick when I filed the bug. What I meant was that the
Coded Frame Processing algorithm assumes that the frame duration is known. But
when you have variable frame rate streams, the duration of a frame may not be
available and cannot be assumed to be the duration of the previous frame. In
some cases, the duration of a frame may span over more than one segment.

In MPEG-2 TS, where duration is not coded, you have to wait for the next frame
to arrive to compute the PTS difference. That frame may arrive a long time
after (e.g. in video surveillance application), that may cause the previous
video frame to be dropped because not processed on time or the playback to
stall. This raises also the question of the last frame in an MPEG-2 TS segment,
for which no duration can be computed.

As I explained in my original comment, for the MP4 case, it is possible to
update the duration of the previous sample. You would create a segment whose
last sample does not have the entire duration, and then send an update in the
next sample (in the next segment) to extend the duration.

For these cases, I think the MSE spec as is cannot be used.

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Received on Tuesday, 11 June 2013 14:49:32 UTC