[FFmpeg-trac] #3990(ffmpeg:new): Video duration increases when reducing frame rate

FFmpeg trac at avcodec.org
Tue Sep 30 09:52:28 CEST 2014


#3990: Video duration increases when reducing frame rate
--------------------------------+--------------------------------------
             Reporter:  t.rapp  |                     Type:  defect
               Status:  new     |                 Priority:  normal
            Component:  ffmpeg  |                  Version:  git-master
             Keywords:          |               Blocked By:
             Blocking:          |  Reproduced by developer:  0
Analyzed by developer:  0       |
--------------------------------+--------------------------------------
 When reducing the frame rate of a 25Hz/20sec AVI/HuffYUV video test file
 to 1Hz the duration increases to 22sec.

 Comparing the framemd5 output of input file and output file (see
 attachments) it seems that the first two frames of the input file are
 passed through, then each frame at the middle of the output interval is
 passed (frame 13 for the first 1sec interval, frame 38 for the second 1sec
 interval, ...).

 How to reproduce:
 {{{
 # create 25Hz test input file
 % ffmpeg -f lavfi -graph "testsrc=size=pal:rate=25 [out0]" -i dummy \
   -f avi  -codec:v huffyuv -pix_fmt yuv422p -t 20 /tmp/test-25hz.avi

 # create 1Hz test output file
 % ffmpeg -i /tmp/test-25hz.avi -f avi -codec:v huffyuv -r 1 /tmp/test-
 1hz.avi

 ffmpeg version N-66544-g61c0683 Copyright (c) 2000-2014 the FFmpeg
 developers
   built on Sep 30 2014 09:02:33 with gcc 4.8 (Ubuntu 4.8.2-19ubuntu1)
   configuration: --cc='ccache gcc' --enable-debug --enable-version3
   libavutil      54.  7.101 / 54.  7.101
   libavcodec     56.  1.101 / 56.  1.101
   libavformat    56.  7.101 / 56.  7.101
   libavdevice    56.  1.100 / 56.  1.100
   libavfilter     5.  1.102 /  5.  1.102
   libswscale      3.  1.100 /  3.  1.100
   libswresample   1.  1.100 /  1.  1.100
 Input #0, avi, from '/tmp/test-25hz.avi':
   Metadata:
     encoder         : Lavf56.7.101
   Duration: 00:00:20.00, start: 0.000000, bitrate: 46859 kb/s
     Stream #0:0: Video: huffyuv (HFYU / 0x55594648), yuv422p, 720x576,
 46945 kb/s, SAR 1:1 DAR 5:4, 25 fps, 25 tbr, 25 tbn, 25 tbc
 [huffyuv @ 0x1be5a20] using huffyuv 2.2.0 or newer interlacing flag
 Output #0, avi, to '/tmp/test02-1hz.avi':
   Metadata:
     ISFT            : Lavf56.7.101
     Stream #0:0: Video: huffyuv (HFYU / 0x55594648), yuv422p, 720x576 [SAR
 1:1 DAR 5:4], q=2-31, 200 kb/s, 1 fps, 1 tbn, 1 tbc
     Metadata:
       encoder         : Lavc56.1.101 huffyuv
 Stream mapping:
   Stream #0:0 -> #0:0 (huffyuv (native) -> huffyuv (native))
 Press [q] to stop, [?] for help
 frame=   22 fps= 13 q=0.0 Lsize=    5040kB time=00:00:22.00
 bitrate=1876.8kbits/s dup=0 drop=478
 video:5034kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB
 muxing overhead: 0.124002%
 }}}

--
Ticket URL: <https://trac.ffmpeg.org/ticket/3990>
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