[FFmpeg-trac] #431(undetermined:open): 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:  open
             Priority:  normal       |                Component:
              Version:  git-master   |  undetermined
             Keywords:  CBR          |               Resolution:
             Blocking:               |               Blocked By:
Analyzed by developer:  0            |  Reproduced by developer:  0
-------------------------------------+-------------------------------------

Comment (by schtorch):

 It seems it has worked before. Here is a comment I found on the ffmpeg
 user mailinglist:
 http://ffmpeg-users.933282.n4.nabble.com/mp3-bitrate-vlc-td3548853.html

 Another info, I tried to use lame directly and mediainfo reports a correct
 bit rate mode.

 {{{
 # lame --preset cbr 128k test_orig.mp3 test_lame_cbr.mp3
 ID3v2 found. Be aware that the ID3 tag is currently lost when transcoding.
 LAME 3.98.4 64bits (http://www.mp3dev.org/)
 Using polyphase lowpass filter, transition band: 16538 Hz - 17071 Hz
 Encoding test_orig.mp3 to test_lame_cbr.mp3
 Encoding as 44.1 kHz j-stereo MPEG-1 Layer III (11x) 128 kbps qval=3
     Frame          |  CPU time/estim | REAL time/estim | play/CPU |    ETA
   8102/8103  (100%)|    0:05/    0:05|    0:05/    0:05|   37.393x|
 0:00
 --------------------------------------------------------------------------------------------------------------------------------------------------------------------------
    kbps        LR    MS  %     long switch short %
   128.0        3.3  96.7        84.8   8.9   6.3
 Writing LAME Tag...done
 ReplayGain: -8.6dB
 }}}

 {{{
 # mediainfo test_lame_cbr.mp3
 General
 Complete name                    : test_lame_cbr.mp3
 Format                           : MPEG Audio
 File size                        : 3.23 MiB
 Duration                         : 3mn 31s
 Overall bit rate                 : 128 Kbps
 Writing library                  : LAME3.98r

 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                    : Constant
 Bit rate                         : 128 Kbps
 Channel(s)                       : 2 channels
 Sampling rate                    : 44.1 KHz
 Stream size                      : 3.23 MiB (100%)
 Writing library                  : LAME3.98r
 Encoding settings                : -m j -V 4 -q 3 -lowpass 17 -b 128
 }}}

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Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/431#comment:2>
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