Début du message réexpédié :
> De : Lucas Soltic <[email protected]>
> Objet : Rép : [Libav-user] Why is av_seek_frame() inaccurate in some cases ?
> Date : 14 avril 2012 19:24:01 HAEC
> À : "This list is about using libavcodec, libavformat, libavutil, libavdevice
> and libavfilter." <[email protected]>
>
>
> Le 14 avr. 2012 à 18:49, Michael Bradshaw a écrit :
>
>> On Sat, Apr 14, 2012 at 10:40 AM, Lucas Soltic <[email protected]>
>> wrote:
>> So I don't think I did anything fancy, but I still can't find out why the
>> video seeking is inaccurate. I would be really grateful if someone had ideas
>> about this issue.
>>
>> There's two reasons I can see why you would be getting this result: 1) It
>> could be seeking to the closest keyframe in the video, and 2) some demuxers
>> seek by DTS and not PTS.
>>
>> You say it works fine for H.264 videos though, so I'm not entirely sure what
>> could be causing it.
>
> Hello!
>
> I tried to use AVSEEK_FLAG_ANY for the av_seek_frame() parameter, so that it
> does not only seek to keyframes, but it still gives important gaps.
> As for the DTS, in the movie I read, they are equal to the PTS (for any of
> the ~10 seeking I did). These results concern the MPEG4v2 video.
> I'm going to investigate further with other codecs but I wanted to tell these
> points.
>
> Lucas SOLTIC
Actually I noticed than when seeking (even with AVSEEK_FLAG_ANY), the real
sought position is 0 to 10s before the position I wanted. Then, if the video
PTS is 9.90s before the position I wanted, and I seek a little bit further (say
0.1s), the video PTS becomes the exact position I wanted. So it looks like it's
just seeking to keyframes, whatever seek flag I use.
Considering this, are there more accurate ways to directly reach the expected
position or should I just do avcodec_decode_video2() until the PTS becomes the
one I wanted ? Decoding 10s of video could take some time on high resolution
movies...
Regards,
Lucas SOLTIC
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