[FFmpeg-user] How can I eliminate audio distortion when converting fly to mp4?

John Almberg jalmberg at identry.com
Sat Dec 15 15:18:32 CET 2012

My client has a large library of FLV videos (public access tv) that he now wishes to convert to MP4. I am a ffmpeg newbie, so I tried the most obvious conversion first. I am running on Ubuntu:

ubuntu at domU-12-31-39-09-48-A5:~/test$ uname -a
Linux domU-12-31-39-09-48-A5 2.6.35-24-virtual #42-Ubuntu SMP Thu Dec 2 05:01:52 UTC 2010 i686 GNU/Linux

With the following version of ffmpeg:

ubuntu at domU-12-31-39-09-48-A5:~/test$ ffmpeg -v
FFmpeg version 0.6-4:0.6-2ubuntu6.1, Copyright (c) 2000-2010 the FFmpeg developers
 built on Mar 31 2011 18:42:12 with gcc 4.4.5

When I run a simple conversion, the output is as shown below.

Result: the video looks fine and the audio is pretty good, but there is a distinct distortion -- almost like an echo -- on the audio track. The input and output files are in this tar file:


Question: is there anything I can do to remove this audio distortion? Any help, much appreciate.

-- John

ubuntu at domU-12-31-39-09-48-A5:~/test$ ffmpeg -i input.flv output.mp4
FFmpeg version 0.6-4:0.6-2ubuntu6.1, Copyright (c) 2000-2010 the FFmpeg developers
 built on Mar 31 2011 18:42:12 with gcc 4.4.5
 configuration: --extra-version=4:0.6-2ubuntu6.1 --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-vaapi --enable-pthreads --enable-zlib --enable-libvpx --disable-stripping --enable-runtime-cpudetect --enable-gpl --enable-postproc --enable-x11grab --enable-libdc1394 --enable-shared --disable-static
 WARNING: library configuration mismatch
 libavutil   configuration: --extra-version=4:0.6-2ubuntu6.1 --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-vaapi --enable-pthreads --enable-zlib --enable-libvpx --disable-stripping --enable-runtime-cpudetect --enable-gpl --enable-postproc --enable-x11grab --enable-libdc1394 --shlibdir=/usr/lib/i686/cmov --cpu=i686 --enable-shared --disable-static --disable-ffmpeg --disable-ffplay
 libavcodec  configuration: --extra-version=4:0.6-2ubuntu6.1 --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-vaapi --enable-pthreads --enable-zlib --enable-libvpx --disable-stripping --enable-runtime-cpudetect --enable-gpl --enable-postproc --enable-x11grab --enable-libdc1394 --shlibdir=/usr/lib/i686/cmov --cpu=i686 --enable-shared --disable-static --disable-ffmpeg --disable-ffplay
 libavformat configuration: --extra-version=4:0.6-2ubuntu6.1 --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-vaapi --enable-pthreads --enable-zlib --enable-libvpx --disable-stripping --enable-runtime-cpudetect --enable-gpl --enable-postproc --enable-x11grab --enable-libdc1394 --shlibdir=/usr/lib/i686/cmov --cpu=i686 --enable-shared --disable-static --disable-ffmpeg --disable-ffplay
 libavdevice configuration: --extra-version=4:0.6-2ubuntu6.1 --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-vaapi --enable-pthreads --enable-zlib --enable-libvpx --disable-stripping --enable-runtime-cpudetect --enable-gpl --enable-postproc --enable-x11grab --enable-libdc1394 --shlibdir=/usr/lib/i686/cmov --cpu=i686 --enable-shared --disable-static --disable-ffmpeg --disable-ffplay
 libavfilter configuration: --extra-version=4:0.6-2ubuntu6.1 --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-vaapi --enable-pthreads --enable-zlib --enable-libvpx --disable-stripping --enable-runtime-cpudetect --enable-gpl --enable-postproc --enable-x11grab --enable-libdc1394 --shlibdir=/usr/lib/i686/cmov --cpu=i686 --enable-shared --disable-static --disable-ffmpeg --disable-ffplay
 libswscale  configuration: --extra-version=4:0.6-2ubuntu6.1 --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-vaapi --enable-pthreads --enable-zlib --enable-libvpx --disable-stripping --enable-runtime-cpudetect --enable-gpl --enable-postproc --enable-x11grab --enable-libdc1394 --shlibdir=/usr/lib/i686/cmov --cpu=i686 --enable-shared --disable-static --disable-ffmpeg --disable-ffplay
 libpostproc configuration: --extra-version=4:0.6-2ubuntu6.1 --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-vaapi --enable-pthreads --enable-zlib --enable-libvpx --disable-stripping --enable-runtime-cpudetect --enable-gpl --enable-postproc --enable-x11grab --enable-libdc1394 --shlibdir=/usr/lib/i686/cmov --cpu=i686 --enable-shared --disable-static --disable-ffmpeg --disable-ffplay
 libavutil     50.15. 1 / 50.15. 1
 libavcodec    52.72. 2 / 52.72. 2
 libavformat   52.64. 2 / 52.64. 2
 libavdevice   52. 2. 0 / 52. 2. 0
 libavfilter    1.19. 0 /  1.19. 0
 libswscale     0.11. 0 /  0.11. 0
 libpostproc   51. 2. 0 / 51. 2. 0
[flv @ 0x9e46420]Estimating duration from bitrate, this may be inaccurate

Seems stream 0 codec frame rate differs from container frame rate: 1000.00 (1000/1) -> 15.00 (15/1)
Input #0, flv, from 'input.flv':
   metadatacreator : Yet Another Metadata Injector for FLV - Version 1.4
   hasKeyframes    : true
   hasVideo        : true
   hasAudio        : true
   hasMetadata     : true
   canSeekToEnd    : false
   duration        : 51
   datasize        : 5397204
   videosize       : 4813773
   videocodecid    : 2
   width           : 640
   height          : 480
   framerate       : 15
   videodatarate   : 740
   audiosize       : 576011
   audiocodecid    : 1
   audiosamplerate : 22000
   audiosamplesize : 16
   stereo          : false
   audiodatarate   : 87
   filesize        : 5399221
   lasttimestamp   : 51
   lastkeyframetimestamp: 51
   lastkeyframelocation: 5356974
 Duration: 00:00:50.73, start: 0.000000, bitrate: 846 kb/s
   Stream #0.0: Video: flv, yuv420p, 640x480, 757 kb/s, 15 tbr, 1k tbn, 1k tbc
   Stream #0.1: Audio: adpcm_swf, 22050 Hz, 1 channels, s16, 88 kb/s
Output #0, mp4, to 'output.mp4':
   encoder         : Lavf52.64.2
   Stream #0.0: Video: mpeg4, yuv420p, 640x480, q=2-31, 200 kb/s, 15 tbn, 15 tbc
   Stream #0.1: Audio: aac, 22050 Hz, 1 channels, s16, 64 kb/s
Stream mapping:
 Stream #0.0 -> #0.0
 Stream #0.1 -> #0.1
Press [q] to stop encoding
frame=  762 fps= 14 q=11.7 Lsize=    2008kB time=50.80 bitrate= 323.8kbits/s    
video:1585kB audio:407kB global headers:0kB muxing overhead 0.799008%

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