[FFmpeg-user] To convert or not to convert

Cecil Westerhof Cecil at decebal.nl
Sat Dec 15 18:54:34 CET 2012

I already send this email, but with the wrong title. I was composing
my email and found out that the problem was that my (old) system could
not keep up with the high def video. So I went a resolution lower and
there was no problem with the audio, but saw the warning. I rewrote
the message, but not the title. :-(

I just bought a Canon SX240 HS. I made a short video for testing
purposes. When looking at the input file with:
    ffmpeg -i MVI_0019.MOV 

I get:
    ffmpeg version 0.9.1, Copyright (c) 2000-2012 the FFmpeg developers
      built on Jan  6 2012 11:01:08 with gcc 4.6.2
      configuration: --shlibdir=/usr/lib --prefix=/usr --mandir=/usr/share/man --libdir=/usr/lib --enable-shared --disable-static --enable-libmp3lame --enable-libvorbis --enable-libtheora --enable-libspeex --enable-libxvid --enable-postproc --enable-gpl --enable-x11grab --extra-cflags='-fomit-frame-pointer -fmessage-length=0 -O2 -Wall -D_FORTIFY_SOURCE=2 -fstack-protector -funwind-tables -fasynchronous-unwind-tables -g -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -I/usr/include/gsm' --enable-debug --disable-stripping --enable-libgsm --enable-libschroedinger --enable-libdirac --enable-avfilter --enable-libvpx --enable-version3 --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libx264 --enable-libdc1394 --enable-pthreads --enable-librtmp
      libavutil    51. 32. 0 / 51. 32. 0
      libavcodec   53. 42. 4 / 53. 42. 4
      libavformat  53. 24. 2 / 53. 24. 2
      libavdevice  53.  4. 0 / 53.  4. 0
      libavfilter   2. 53. 0 /  2. 53. 0
      libswscale    2.  1. 0 /  2.  1. 0
      libpostproc  51.  2. 0 / 51.  2. 0

    Seems stream 0 codec frame rate differs from container frame rate: 60000.00 (60000/1) -> 29.97 (30000/1001)
    Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'MVI_0019.MOV':
        major_brand     : qt  
        minor_version   : 537331968
        compatible_brands: qt  CAEP
        creation_time   : 2012-12-15 14:16:51
      Duration: 00:01:11.80, start: 0.000000, bitrate: 25145 kb/s
        Stream #0:0(eng): Video: h264 (Constrained Baseline) (avc1 / 0x31637661), yuvj420p, 1280x720, 23599 kb/s, 29.97 fps, 29.97 tbr, 30k tbn, 60k tbc
          creation_time   : 2012-12-15 14:16:51
          handler_name    : 
        Stream #0:1(eng): Audio: pcm_s16le (sowt / 0x74776F73), 48000 Hz, stereo, s16, 1536 kb/s
          creation_time   : 2012-12-15 14:16:51
          handler_name    : 
    At least one output file must be specified

Why do I get the frame rate differs message?

I need to cut the start and the end from the video. That is not a
problem. I was just wondering: should I do just a copy, or convert it
to another format? I now have a warning, so something is not quite
right. I also want to make sure it will play on as much
systems/players as possible. (For example default Kaffeine does not
play h264.) And if I can make the file smaller, without degrading the
quality to much, then that would not hurt also.

So when I cut the video to the needed part, which (if any) conversion
should I do? (I properly should at least go from stereo to mono I
think, because it is just speaking what is recorded.)

Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof

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