Wrong Bitrate after ffmpeg WAV to MP3 Conversion

Question

I converted a WAV file to MP3. ffmpeg's output states that it's being converted into 128k bitrate, but it ends up with only 32k bitrate.

# ffmpeg -i 3.28.09.WAV -acodec libmp3lame -ab 128k 3.28.09.mp3
ffmpeg version 0.8.6-6:0.8.6-1, Copyright (c) 2000-2013 the Libav developers
  built on Mar 24 2013 07:20:17 with gcc 4.7.2
*** THIS PROGRAM IS DEPRECATED ***
This program is only provided for compatibility and will be removed in a future release. Please use avconv instead.
[wav @ 0x954f800] max_analyze_duration reached
Input #0, wav, from '3.28.09.WAV':
  Duration: 00:27:07.47, bitrate: 2304 kb/s
    Stream #0.0: Audio: pcm_s24le, 48000 Hz, 2 channels, s32, 2304 kb/s
Incompatible sample format 's32' for codec 'libmp3lame', auto-selecting format 's16'
Output #0, mp3, to '3.28.09.mp3':
  Metadata:
    TSSE            : Lavf53.21.1
    Stream #0.0: Audio: libmp3lame, 48000 Hz, 2 channels, s16, 128 kb/s
Stream mapping:
  Stream #0.0 -> #0.0
Press ctrl-c to stop encoding
size=   25430kB time=1627.51 bitrate= 128.0kbits/s    
video:0kB audio:25430kB global headers:0kB muxing overhead 0.000495%

The original WAV file is RIFF (little-endian) data, WAVE audio, Microsoft PCM, 24 bit, stereo 48000 Hz.

The output MP3 file is an audio file with ID3 version 2.4.0, contains: MPEG ADTS, layer III, v1, 32 kbps, 48 kHz, Stereo when inspected with the file utility. My PHP library getID3 also state.

# ffmpeg -i 3.28.09.mp3
ffmpeg version 0.8.6-6:0.8.6-1, Copyright (c) 2000-2013 the Libav developers
  built on Mar 24 2013 07:20:17 with gcc 4.7.2
*** THIS PROGRAM IS DEPRECATED ***
This program is only provided for compatibility and will be removed in a future release. Please use avconv instead.
[mp3 @ 0x8f56800] max_analyze_duration reached
Input #0, mp3, from '3.28.09.mp3':
  Metadata:
    encoder         : Lavf53.21.1
  Duration: 00:27:07.51, start: 0.000000, bitrate: 128 kb/s
    Stream #0.0: Audio: mp3, 48000 Hz, stereo, s16, 128 kb/s
At least one output file must be specified

Any ideas what I might be missing here?

I installed ffmpeg via brew on OS X, so maybe that's the problem. — Nick Weisser
what does ffmpeg -i 3.28.09.mp3 says? 32k? Really weird if so. — Vladimir Kunschikov
How did you end up with Libav stuff if you used brew? Instructions to install FFmpeg via brew. — llogan

Nick Weisser Nick Weisser · Accepted Answer · 2015-02-26T22:15:59

It turned out that the ffmpeg version I was using, installed via Debian packet manager:

version 0.8.6-6:0.8.6-1
Copyright (c) 2000-2013 the Libav developers
built on Mar 24 2013 07:20:17 with gcc 4.7.2

Locally I just upgraded to the latest version via Homebrew:

version 2.5.4
Copyright (c) 2000-2015 the FFmpeg developers
built on Feb 15 2015 20:17:10 with Apple LLVM version 6.0 (clang-600.0.56) (based on LLVM 3.5svn)

Wrong Bitrate after ffmpeg WAV to MP3 Conversion

1 Answers