[FFmpeg-trac] #2348(undetermined:new): Slowmotion when reencoding mpeg stream

[FFmpeg]

#2348: Slowmotion when reencoding mpeg stream
-------------------------------------+-------------------------------------
               Reporter:  cehoyos    |                  Owner:
                   Type:  defect     |                 Status:  new
               Priority:  normal     |              Component:
                Version:  git-       |  undetermined
  master                             |               Keywords:  dts
             Blocked By:             |  mpeg2video mpegps
Reproduced by developer:  0          |               Blocking:
                                     |  Analyzed by developer:  0
-------------------------------------+-------------------------------------
 http://thread.gmane.org/gmane.comp.video.ffmpeg.user/44508
 A user uploaded a mpeg sample file that plays for approximately 11 seconds
 with current ffplay, mplayer (both -demuxer mpegps and -demuxer lavf, both
 -vc ffmpeg12 and -vc mpeg12), vlc and WMP.
 If the sample gets re-encoded with ffmpeg, the output file plays at half
 speed (for 22 seconds).
 {{{
 $ ffmpeg -i rob-test.mpg -qscale 2 out.avi
 ffmpeg version N-50651-g1123080 Copyright (c) 2000-2013 the FFmpeg
 developers
   built on Mar 11 2013 12:49:54 with gcc 4.7 (SUSE Linux)
   configuration: --enable-gpl --disable-indev=jack --enable-libopenjpeg
   libavutil      52. 19.100 / 52. 19.100
   libavcodec     54. 92.100 / 54. 92.100
   libavformat    54. 63.104 / 54. 63.104
   libavdevice    54.  3.103 / 54.  3.103
   libavfilter     3. 44.101 /  3. 44.101
   libswscale      2.  2.100 /  2.  2.100
   libswresample   0. 17.102 /  0. 17.102
   libpostproc    52.  2.100 / 52.  2.100
 [mpeg @ 0x1be0f40] max_analyze_duration 5000000 reached at 5005000
 microseconds
 Input #0, mpeg, from 'rob-test.mpg':
   Duration: 00:00:11.34, start: 0.360000, bitrate: 7140 kb/s
     Stream #0:0[0x1e0]: Video: mpeg2video (Main), yuv420p, 720x480 [SAR
 32:27 DAR 16:9], 29.97 fps, 29.97 tbr, 90k tbn, 59.94 tbc
 Please use -q:a or -q:v, -qscale is ambiguous
 Output #0, avi, to 'out.avi':
   Metadata:
     ISFT            : Lavf54.63.104
     Stream #0:0: Video: mpeg4 (FMP4 / 0x34504D46), yuv420p, 720x480 [SAR
 32:27 DAR 16:9], q=2-31, 200 kb/s, 29.97 tbn, 29.97 tbc
 Stream mapping:
   Stream #0:0 -> #0:0 (mpeg2video -> mpeg4)
 Press [q] to stop, [?] for help
 frame=  341 fps=0.0 q=2.0 Lsize=   11255kB time=00:00:22.68
 bitrate=4063.5kbits/s
 video:11233kB audio:0kB subtitle:0 global headers:0kB muxing overhead
 0.193383%
 }}}
 Workaround is to specify an input frame rate:
 $ ffmpeg -r 30 -i rob-test.mpg -qscale 2 out.avi

-- 
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/2348>
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