[FFmpeg-trac] #1925(undetermined:new): Transcoding mjpeg video results in a very short frame

[FFmpeg]

#1925: Transcoding mjpeg video results in a very short frame
-------------------------------------+-------------------------------------
               Reporter:  mbradshaw  |                  Owner:
                   Type:  defect     |                 Status:  new
               Priority:  normal     |              Component:
                Version:  git-       |  undetermined
  master                             |               Keywords:
             Blocked By:             |               Blocking:
Reproduced by developer:  0          |  Analyzed by developer:  0
-------------------------------------+-------------------------------------
 '''Summary of the bug:'''
 I have a mjpeg video I've created using libav*. The video plays fine in
 QuickTime, VLC, ffplay, etc. However, when I transcode the mjpeg video
 using FFmpeg, the first frame goes from a duration of 1.315918 seconds to
 just a fraction of a second. This happens on every mjpeg file I've tested
 that I create using libav*.

 I've tried FFmpeg 1.0 and current git head; results are the same.

 I suppose it's possible I'm generating the mjpeg wrong, but it plays fine
 in everything I've tried (QuickTime, VLC, ffplay, etc.) with no warnings
 or errors, FFmpeg gives no errors or warnings when transcoding, and I've
 inspected the frames with ffprobe and I can't see anything wrong with the
 mjpeg.

 '''How to reproduce:'''
 Using the following command, the output file (mpg.mpg) has a short first
 frame and doesn't match the source mjpeg (mjpeg.mov). I have attached both
 files.
 {{{
 $ ffmpeg -i mjpeg.mov -vcodec mpeg2video -acodec mp2 -r 24 -bufsize
 4000000 -maxrate 5000000 mpg.mpg
 ffmpeg version 1.0 Copyright (c) 2000-2012 the FFmpeg developers
   built on Nov 16 2012 15:00:58 with llvm-gcc 4.2.1 (LLVM build
 2336.11.00)
   configuration:
   libavutil      51. 73.101 / 51. 73.101
   libavcodec     54. 59.100 / 54. 59.100
   libavformat    54. 29.104 / 54. 29.104
   libavdevice    54.  2.101 / 54.  2.101
   libavfilter     3. 17.100 /  3. 17.100
   libswscale      2.  1.101 /  2.  1.101
   libswresample   0. 15.100 /  0. 15.100
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x7fb25b00f200] max_analyze_duration 5000000
 reached at 5000272
 Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'mjpeg.mov':
   Metadata:
     major_brand     : qt
     minor_version   : 512
     compatible_brands: qt
     encoder         : Lavf54.29.104
   Duration: 00:00:05.27, start: 0.000000, bitrate: 631 kb/s
     Stream #0:0(eng): Video: mjpeg (jpeg / 0x6765706A), yuvj420p,
 1024x768, 536 kb/s, 1.02 fps, 4.58 tbr, 44100 tbn, 44100 tbc
     Metadata:
       handler_name    : DataHandler
     Stream #0:1(eng): Audio: aac (mp4a / 0x6134706D), 44100 Hz, stereo,
 s16, 227 kb/s
     Metadata:
       handler_name    : DataHandler
 Output #0, mpeg, to 'mpg.mpg':
   Metadata:
     major_brand     : qt
     minor_version   : 512
     compatible_brands: qt
     encoder         : Lavf54.29.104
     Stream #0:0(eng): Video: mpeg2video, yuv420p, 1024x768, q=2-31, 200
 kb/s, 90k tbn, 24 tbc
     Metadata:
       handler_name    : DataHandler
     Stream #0:1(eng): Audio: mp2, 44100 Hz, stereo, s16, 128 kb/s
     Metadata:
       handler_name    : DataHandler
 Stream mapping:
   Stream #0:0 -> #0:0 (mjpeg -> mpeg2video)
   Stream #0:1 -> #0:1 (aac -> mp2)
 Press [q] to stop, [?] for help
 frame=   95 fps=0.0 q=31.0 Lsize=     766kB time=00:00:05.27
 bitrate=1189.9kbits/s dup=91 drop=0
 video:678kB audio:82kB subtitle:0 global headers:0kB muxing overhead
 0.751412%
 }}}

 In the files, the symbol clash should match with the start of each frame.

-- 
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/1925>
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