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I am doing a conversion of mp4 to flv on a GUI less server where I have only SSH access.( I tried winff and X forwarding that had hanged while doing this conversion so winff is not possible for me)

I do not have any idea of the codecs,bitrate of this mp4 video. Some one had converted from an m4v to mp4 and then uploaded this on the server.

When I tried converting on command line as follows

ffmpeg -i stats_estimation.mp4 out.flv
FFmpeg version SVN-r0.5.1-4:0.5.1-1ubuntu1, Copyright (c) 2000-2009 Fabrice Bellard, et al.
  configuration: --extra-version=4:0.5.1-1ubuntu1 --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-pthreads --enable-zlib --disable-stripping --disable-vhook --enable-runtime-cpudetect --enable-gpl --enable-postproc --enable-swscale --enable-x11grab --enable-libdc1394 --enable-shared --disable-static
  libavutil     49.15. 0 / 49.15. 0
  libavcodec    52.20. 1 / 52.20. 1
  libavformat   52.31. 0 / 52.31. 0
  libavdevice   52. 1. 0 / 52. 1. 0
  libavfilter    0. 4. 0 /  0. 4. 0
  libswscale     0. 7. 1 /  0. 7. 1
  libpostproc   51. 2. 0 / 51. 2. 0
  built on Mar  4 2010 12:41:55, gcc: 4.4.3

Seems stream 0 codec frame rate differs from container frame rate: 29.94 (5000/167) -> 44.92 (539/12)
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'stats_estimation.mp4':
  Duration: 02:47:05.56, start: 0.000000, bitrate: 237 kb/s
    Stream #0.0(eng): Video: h264, yuv420p, 320x240, 44.92 tbr, 14.97 tbn, 29.94 tbc
    Stream #0.1(eng): Audio: aac, 32000 Hz, stereo, s16
Output #0, flv, to 'out.flv':
    Stream #0.0(eng): Video: flv, yuv420p, 320x240, q=2-31, 200 kb/s, 90k tbn, 44.92 tbc
    Stream #0.1(eng): Audio: adpcm_swf, 32000 Hz, stereo, s16, 64 kb/s
Stream mapping:
  Stream #0.0 -> #0.0
  Stream #0.1 -> #0.1
[adpcm_swf @ 0xa4ef60]Sample rate must be 11025, 22050 or 44100
Error while opening codec for output stream #0.1 - maybe incorrect parameters such as bit_rate, rate, width or height

I have above error. I checked this page but I could not understand much. Can some one help to figure out what should I be doing to get this video to flv in this case? The OS is Ubuntu 10.04 64 bit server edition and aptitude install winff was what I had used to get ffmpeg or any thing else.

share|improve this question

Try to start FFmpeg with "-ar 44100" to correct audio rate, and if quality matters, with a "-sameq". like the line below.

ffmpeg -i stats_estimation.mp4 -sameq -ar 44100 out.flv
share|improve this answer
Ok and is there a way on command line so that I preserve the aspect ratio of video. – Bond Nov 8 '10 at 7:48
Normally it should not change resolution or aspect ratio, unless you force ffmpeg to resize source. here is a full guide to see all parameters of ffmpeg. – risyasin Nov 11 '10 at 20:32

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