[Ffmpeg-devel] Possible bug in reading PTS/DTS

Måns Rullgård mans
Mon Apr 23 16:27:31 CEST 2007

Michael Niedermayer wrote:
> Hi
> On Mon, Apr 23, 2007 at 12:20:17PM +0200, Michel Bardiaux wrote:
>> Luca Abeni wrote:
>> > Hi Michel,
>> >
>> > Michel Bardiaux wrote:
>> > [...]
>> >>> (If the problem really is in the user application, I can prepare and
>> >>> send a patch fixing ffmpeg.c and ffserver.c)
>> >>>
>> >>> Or maybe the problem is in my (mis)understanding of this issue?
>> >> I'm not sure the problem is in decoding. I find it rather strange that
>> >> the first frame, which is a keyframe, does not have PTS=DTS.
>> > I do not know... I see that for containers that store both PTS and DTS,
>> > ffmpeg generally generates
>> > DTS = PTS - frame period
>> > for video (I am not using B frames, to simplify the testing). Is this
>> > wrong? If yes, then I think there is something to fix in the encoding /
>> > muxing side.
>> I think so too. My reading of the spec is that in the absence of
>> B-frames, the DTS are not even necessary; I'm afraid there is something
>> very wrong in the MPEG muxer.
> nonsense, dts==pts for mpeg1/2/4 b frames _always_ and pts>dts for i/p frames
> unless the stream is low delay but this is rare

No coded DTS means DTS = PTS, so I don't think he's talking complete nonsense
even if he could have use a clearer phrasing.

M?ns Rullg?rd
mans at mansr.com

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