[FFmpeg-trac] #431(undetermined:closed): When converting audio to an MP3 using CBR, result is reported VBR
FFmpeg
trac at avcodec.org
Wed Sep 21 12:29:39 EEST 2016
#431: When converting audio to an MP3 using CBR, result is reported VBR
-------------------------------------+-------------------------------------
Reporter: schtorch | Owner: michael
Type: defect | Status: closed
Priority: normal | Component:
Version: git-master | undetermined
Keywords: CBR mp3 | Resolution: fixed
Blocking: | Blocked By:
Analyzed by developer: 0 | Reproduced by developer: 0
-------------------------------------+-------------------------------------
Comment (by volker):
Seems that the problem is back (or has not been fixed completely). This is
the offending command line:
{{{ffmpeg.exe -i infile.mp4 -loglevel error -stats -y -c:v libxvid -b:v
1750k -c:a libmp3lame -b:a 128k -async 1 outfile.avi}}}
Here's what ffprobe has to say:
{{{ffprobe -v error infile.mp4}}}
ffprobe version N-78197-g5893e87 Copyright (c) 2007-2016 the FFmpeg
developers
built with gcc 5.2.0 (GCC)
configuration: --enable-gpl --enable-version3 --disable-w32threads
--enable-av
isynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls
--enab
le-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-
libcaca --
enable-libdcadec --enable-libfreetype --enable-libgme --enable-libgsm
--enable-l
ibilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb
--enab
le-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-
librtmp --en
able-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora
--ena
ble-libtwolame --enable-libvidstab --enable-libvo-aacenc --enable-libvo-
amrwbenc
--enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp
--enabl
e-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-
libzimg --
enable-lzma --enable-decklink --enable-zlib
libavutil 55. 16.101 / 55. 16.101
libavcodec 57. 22.102 / 57. 22.102
libavformat 57. 23.101 / 57. 23.101
libavdevice 57. 0.101 / 57. 0.101
libavfilter 6. 27.100 / 6. 27.100
libswscale 4. 0.100 / 4. 0.100
libswresample 2. 0.101 / 2. 0.101
libpostproc 54. 0.100 / 54. 0.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'infile.mp4':
Metadata:
major_brand : mp42
minor_version : 0
compatible_brands: isommp42
creation_time : 2016-03-17 10:20:35
Duration: 00:03:48.74, start: 0.000000, bitrate: 3027 kb/s
Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p,
1280x720
[SAR 1:1 DAR 16:9], 2833 kb/s, 25 fps, 25 tbr, 25 tbn, 50 tbc (default)
Metadata:
handler_name : VideoHandler
Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz,
stereo, flt
p, 191 kb/s (default)
Metadata:
creation_time : 2016-03-17 10:20:37
handler_name : IsoMedia File Produced by Google, 5-11-2011
{{{ffprobe outfile.avi}}}
ffprobe version N-78197-g5893e87 Copyright (c) 2007-2016 the FFmpeg
developers
built with gcc 5.2.0 (GCC)
configuration: --enable-gpl --enable-version3 --disable-w32threads
--enable-av
isynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls
--enab
le-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-
libcaca --
enable-libdcadec --enable-libfreetype --enable-libgme --enable-libgsm
--enable-l
ibilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb
--enab
le-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-
librtmp --en
able-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora
--ena
ble-libtwolame --enable-libvidstab --enable-libvo-aacenc --enable-libvo-
amrwbenc
--enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp
--enabl
e-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-
libzimg --
enable-lzma --enable-decklink --enable-zlib
libavutil 55. 16.101 / 55. 16.101
libavcodec 57. 22.102 / 57. 22.102
libavformat 57. 23.101 / 57. 23.101
libavdevice 57. 0.101 / 57. 0.101
libavfilter 6. 27.100 / 6. 27.100
libswscale 4. 0.100 / 4. 0.100
libswresample 2. 0.101 / 2. 0.101
libpostproc 54. 0.100 / 54. 0.100
Input #0, avi, from 'outfile.avi':
Metadata:
encoder : Lavf57.23.101
Duration: 00:02:35.09, start: 0.000000, bitrate: 1922 kb/s
Stream #0:0: Video: mpeg4 (Simple Profile) (xvid / 0x64697678),
yuv420p, 128
0x720 [SAR 1:1 DAR 16:9], 1788 kb/s, 25 fps, 25 tbr, 25 tbn, 25 tbc
Stream #0:1: Audio: mp3 (U[0][0][0] / 0x0055), 44100 Hz, stereo, s16p,
128 k
b/s
{{{ffmpeg.exe -version}}}
ffmpeg version N-78197-g5893e87 Copyright (c) 2000-2016 the FFmpeg
developers
built with gcc 5.2.0 (GCC)
configuration: --enable-gpl --enable-version3 --disable-w32threads
--enable-avis
ynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls
--enable
-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-
libcaca --en
able-libdcadec --enable-libfreetype --enable-libgme --enable-libgsm
--enable-lib
ilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb
--enable
-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp
--enab
le-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora
--enabl
e-libtwolame --enable-libvidstab --enable-libvo-aacenc --enable-libvo-
amrwbenc -
-enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp
--enable-
libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-
libzimg --en
able-lzma --enable-decklink --enable-zlib
libavutil 55. 16.101 / 55. 16.101
libavcodec 57. 22.102 / 57. 22.102
libavformat 57. 23.101 / 57. 23.101
libavdevice 57. 0.101 / 57. 0.101
libavfilter 6. 27.100 / 6. 27.100
libswscale 4. 0.100 / 4. 0.100
libswresample 2. 0.101 / 2. 0.101
libpostproc 54. 0.100 / 54. 0.100
Screenshot from VirtualDub attached, it seems that is sees the MP3 stream
encoded as "VBR" with a bitrate of exactly 128k. Unfortunately, this
breaks compatibility with some hardware players and contradicts what -c:a
libmp3lame -b:a 128k is advertised to do.
Thanks for having a look.
--
Ticket URL: <https://trac.ffmpeg.org/ticket/431#comment:18>
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