[vlc-devel] WMV2 timestamp positioning problem in vlc-1.2.0-pre4

Kaarlo Räihä kaarlo.raiha at gmail.com
Fri Jan 13 07:27:41 CET 2012

2012/1/13 zhu shi song <zhushisongzhu at yahoo.com>

>     I use vlc-1.2.0-pre4 to test some WMV2 videos, I find that vlc 1.2
> can't position timestamp correctly when I seek the video.
>     The defect causes two unpleasant consequences of user experience:
>     1、From user's view, he will be confused by the player because it can't
> reach the presicely correct position he has specified.
>     2、The video can't be partially transcoded correctly because
> -start-time has been changed inside vlc when user passes the value to it.
>     I doubt the problem is from ffmpeg.  I test the video using ffplay.
> It has the same problem.  I report it to ffmpeg bug track.  Cehoyos
> responsed the problem with the following words:
> ' For most videos, media players can only seek to keyframes ("I-frames"),
> they cannot seek to non-keyframes (all other frames), if they seem to allow
> to seek to non-keyframes, they do it by seeking further back and not
> displaying the frames in-between (this can be different for H264, but your
> sample is WMV2)' .
> I wonder whether  TS has the same mechnanism with WMV2.  If  vlc 1.2  can
> now control timestamp of TS video correctly, it  should  fix the problem in
> WMV2 seeking problem.

Most decoders only support fast I frame seeking. But usually long I frame
distances (like 250 frames) are only used in H.264 videos, so most other
videos should have fast seeking accuracy of ±2 seconds.

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