[FFmpeg-trac] #431(FFmpeg:new): When converting audio to an MP3 using CBR, result is reported VBR

[FFmpeg]

#431: When converting audio to an MP3 using CBR, result is reported VBR
--------------------------------------+---------------------------------
               Reporter:  schtorch    |                  Owner:  michael
                   Type:  defect      |                 Status:  new
               Priority:  normal      |              Component:  FFmpeg
                Version:  git-master  |               Keywords:  CBR
             Blocked By:              |               Blocking:
Reproduced by developer:  0           |  Analyzed by developer:  0
--------------------------------------+---------------------------------
 When I try to convert a file to MP3 with CBR using the latest GIT, I get a
 file which is reported by various players (mediainfo, VLC) to be a
 variable bitrate (VBR) file.


 {{{
 ffmpeg -i test_orig.mp3 -ab 128k test_ffmpeg_cbr.mp3
 ffmpeg version N-32327-g27bf599, Copyright (c) 2000-2011 the FFmpeg
 developers
   built on Sep  5 2011 21:57:49 with gcc 4.5.1 20101208 [gcc-4_5-branch
 revision 167585]
   configuration: --shlibdir=/usr/lib64 --prefix=/usr
 --mandir=/usr/share/man --libdir=/usr/lib64 --enable-shared --enable-
 libmp3lame --enable-libvorbis --enable-libtheora --enable-libspeex
 --enable-libxvid --enable-postproc --enable-gpl --disable-network --extra-
 cflags='-fmessage-length=0 -O2 -Wall -D_FORTIFY_SOURCE=2 -fstack-protector
 -funwind-tables -fasynchronous-unwind-tables -fPIC -I/usr/include/gsm'
 --disable-stripping --enable-libschroedinger --enable-libdirac --enable-
 libgsm --enable-avfilter --enable-libvpx --enable-version3 --enable-
 libopencore-amrnb --enable-libopencore-amrwb --enable-libx264 --enable-
 pthreads --enable-libfaac --enable-nonfree --disable-doc --disable-ffplay
 --disable-ffserver
   libavutil    51. 16. 0 / 51. 16. 0
   libavcodec   53. 13. 0 / 53. 13. 0
   libavformat  53. 11. 0 / 53. 11. 0
   libavdevice  53.  3. 0 / 53.  3. 0
   libavfilter   2. 37. 0 /  2. 37. 0
   libswscale    2.  1. 0 /  2.  1. 0
   libpostproc  51.  2. 0 / 51.  2. 0
 [mp3 @ 0x6319e0] max_analyze_duration 5000000 reached at 5015510
 Input #0, mp3, from 'test_orig.mp3':
   Duration: 00:03:31.61, start: 0.000000, bitrate: 128 kb/s
     Stream #0.0: Audio: mp3, 44100 Hz, stereo, s16, 128 kb/s
 File 'test_ffmpeg_cbr.mp3' already exists. Overwrite ? [y/N] y
 Output #0, mp3, to 'test_ffmpeg_cbr.mp3':
   Metadata:
     TSSE            : Lavf53.11.0
     Stream #0.0: Audio: mp3, 44100 Hz, stereo, s16, 128 kb/s
 Stream mapping:
   Stream #0.0 -> #0.0 (mp3 -> libmp3lame)
 Press [q] to stop, [?] for help
 size=    3307kB time=00:03:31.64 bitrate= 128.0kbits/s
 video:0kB audio:3307kB global headers:0kB muxing overhead 0.005581%
 }}}


 {{{
 mediainfo test_ffmpeg_cbr.mp3
 General
 Complete name                    : test_ffmpeg_cbr.mp3
 Format                           : MPEG Audio
 File size                        : 3.23 MiB
 Duration                         : 3mn 31s
 Overall bit rate                 : 128 Kbps
 Encoding settings                : Lavf53.11.0

 Audio
 Format                           : MPEG Audio
 Format version                   : Version 1
 Format profile                   : Layer 3
 Mode                             : Joint stereo
 Mode extension                   : MS Stereo
 Duration                         : 3mn 31s
 Bit rate mode                    : Variable
 Bit rate                         : 128 Kbps
 Channel(s)                       : 2 channels
 Sampling rate                    : 44.1 KHz
 Stream size                      : 3.23 MiB (100%)
 }}}

-- 
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/431>
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