[vlc-devel] vlc wmv start playing time control and key frame position do not tally

zhu shi song zhushisongzhu at yahoo.com
Sun Jan 15 11:20:19 CET 2012

I have hzvideo.wmv video file, first I use asfbin to see its key frames.

C:\videotools\asfbin1.8.2.903>asfbin -infokf -i hzvideo.wmv


Parsing file C:\videotools\hzvideo.wmv:
File C:\videotools\hzvideo.wmv key samples:
                         Video Stream Numbers
Time    [ms] HH.MM.SS.MMM  1
           0 00:00:00.000  X
       10000 00:00:10.000  X
       20000 00:00:20.000  X
       30000 00:00:30.000  X
From asfbin output info, there is one keyframe for every 10s.
Then I test the video using ffplay, when I set to play from 11s,  we can see that it starts playing from 10s(key frame point).  Seeking of ffplay is correct.  See the following output:

[root at bogon ~]# ffplay -ss 11 hzvideo.wmv
ffplay version N-34849-g07c7ffc, Copyright (c) 2003-2011 the FFmpeg developers
input #0, asf, from 'hzvideo.wmv':
    WM/Writer       : 
    WMFSDKVersion   :
    WMFSDKNeeded    :
    IsVBR           : 0
  Duration: 00:00:37.99, start: 0.000000, bitrate: 755 kb/s
    Stream #0:0(chi): Video: wmv2 (WMV2 / 0x32564D57), yuv420p, 704x576, 700 kb/s, 25 tbr, 1k tbn, 1k tbc
[asf @ 0xb2101320] freeing incomplete packet size 3598, new 3421
[wmv2 @ 0xb21079c0] warning: first frame is no keyframe
  10.80 A-V:  0.000 fd=   0 aq=    0KB vq=   14KB sq=    0B f=0/0   0/0   

I  try hard to play the video using every version of vlc(vlc-1.1.11, vlc-1.2.0-rc1, vlc-1.3.0-git), every of  them  has the same problem.  They all can't seek to correct keyframe point. For example, I seek to 13s, player should play from 10s, but vlc starts playing from 0s.  When I seek to 16s, vlc then seeks to 10s.  VLC does start-time control  wrongly.   The error causes that the length of partially transcoded video is not correct.
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