[FFmpeg-user] When encoding mp3 at low bitrate FFmpeg gives error report.

[bat guano]

Hi
When encoding to mp3 at low bitrate FFmpeg gives a (red) error report.
[mp3 @ 0x9777d40] Unsupported sample rate.

lame --longhelp shows:-
MPEG-2   layer III sample frequencies (kHz):  16  24  22.05
bitrates (kbps):  8 16 24 32 40 48 56 64 80 96 112 128 144 160

So 16Kbps, 22.05Khz is valid.

Although it is "MPEG-2" layer III, this is still mp3.

FFmpeg does the conversion OK, but why does it say "Unsupported sample rate"?

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@ubuntu:~$ ffmpeg -i foo.flac -c:a libmp3lame -b:a 16k -ar 22050 -ac 1 foo.mp3
ffmpeg version N-37961-gf649247 Copyright (c) 2000-2012 the FFmpeg developers
  built on Feb 18 2012 00:14:51 with gcc 4.5.2
  configuration: --enable-gpl --enable-version3 --enable-nonfree --enable-postproc --enable-libfaac --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxvid --enable-x11grab --disable-encoder=vorbis --enable-libvo-amrwbenc --enable-libvo-aacenc --enable-libspeex
  libavutil      51. 39.100 / 51. 39.100
  libavcodec     54.  3.100 / 54.  3.100
  libavformat    54.  1.100 / 54.  1.100
  libavdevice    53.  4.100 / 53.  4.100
  libavfilter     2. 62.101 /  2. 62.101
  libswscale      2.  1.100 /  2.  1.100
  libswresample   0.  6.100 /  0.  6.100
  libpostproc    52.  0.100 / 52.  0.100
[flac @ 0x9723ac0] max_analyze_duration 5000000 reached at 5015510
[flac @ 0x9723ac0] Estimating duration from bitrate, this may be inaccurate
Input #0, flac, from 'foo.flac':
  Duration: N/A, bitrate: N/A
    Stream #0:0: Audio: flac, 44100 Hz, stereo, s16
[mp3 @ 0x9777d40] Unsupported sample rate.
Output #0, mp3, to 'foo.mp3':
  Metadata:
    TSSE            : Lavf54.1.100
    Stream #0:0: Audio: mp3, 22050 Hz, 1 channels, s16, 16 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (flac -> libmp3lame)
Press [q] to stop, [?] for help
size=     201kB time=00:01:42.81 bitrate=  16.0kbits/s    
video:0kB audio:201kB global headers:0kB muxing overhead 0.016534%
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