[FFmpeg-user] HE-AAC: mono not recognized
Christian Ebert
blacktrash at gmx.net
Fri Jan 24 11:02:26 CET 2014
Hi,
HE-AAC is seen as stereo by ffprobe and also ffmpeg:
$ ffmpeg -i in.aiff -c:a libfdk_aac -profile:a aac_he -b:a 32k -ac 1 fdk-he-mono.m4a
ffmpeg version N-60118-g4d888a0 Copyright (c) 2000-2014 the FFmpeg developers
built on Jan 23 2014 21:13:13 with Apple LLVM version 5.0 (clang-500.2.79) (based on LLVM 3.3svn)
configuration: --enable-gpl --enable-version3 --enable-nonfree --disable-network --disable-ffserver --enable-shared --enable-libfdk-aac --enable-libx264 --enable-libxvid --enable-libfaac --enable-libmp3lame --enable-libtheora --enable-libvorbis --enable-libvpx --enable-librtmp --extra-cflags=-I/sw/include --extra-libs=-L/sw/lib
libavutil 52. 63.100 / 52. 63.100
libavcodec 55. 49.100 / 55. 49.100
libavformat 55. 25.101 / 55. 25.101
libavdevice 55. 5.102 / 55. 5.102
libavfilter 4. 1.100 / 4. 1.100
libswscale 2. 5.101 / 2. 5.101
libswresample 0. 17.104 / 0. 17.104
libpostproc 52. 3.100 / 52. 3.100
Guessed Channel Layout for Input Stream #0.0 : stereo
Input #0, aiff, from 'in.aiff':
Duration: 00:00:30.43, start: 0.000000, bitrate: 1411 kb/s
Stream #0:0: Audio: pcm_s16le (sowt / 0x74776F73), 44100 Hz, stereo, s16, 1411 kb/s
Output #0, ipod, to 'fdk-he-mono.m4a':
Metadata:
encoder : Lavf55.25.101
Stream #0:0: Audio: aac (libfdk_aac) (HE-AAC) (mp4a / 0x6134706D), 44100 Hz, mono, s16, 32 kb/s
Stream mapping:
Stream #0:0 -> #0:0 (pcm_s16le -> libfdk_aac)
Press [q] to stop, [?] for help
size= 123kB time=00:00:30.44 bitrate= 33.0kbits/s
video:0kB audio:119kB subtitle:0 global headers:0kB muxing overhead 2.760628%
$ ffprobe -show_streams fdk-he-mono.m4a 2>/dev/null | fgrep chan
channels=2
channel_layout=stereo
Omitting HE leads to correct diagnosis:
$ ffmpeg -i in.aiff -c:a libfdk_aac -b:a 32k -ac 1 fdk-mono.m4a
ffmpeg version N-60118-g4d888a0 Copyright (c) 2000-2014 the FFmpeg developers
built on Jan 23 2014 21:13:13 with Apple LLVM version 5.0 (clang-500.2.79) (based on LLVM 3.3svn)
configuration: --enable-gpl --enable-version3 --enable-nonfree --disable-network --disable-ffserver --enable-shared --enable-libfdk-aac --enable-libx264 --enable-libxvid --enable-libfaac --enable-libmp3lame --enable-libtheora --enable-libvorbis --enable-libvpx --enable-librtmp --extra-cflags=-I/sw/include --extra-libs=-L/sw/lib
libavutil 52. 63.100 / 52. 63.100
libavcodec 55. 49.100 / 55. 49.100
libavformat 55. 25.101 / 55. 25.101
libavdevice 55. 5.102 / 55. 5.102
libavfilter 4. 1.100 / 4. 1.100
libswscale 2. 5.101 / 2. 5.101
libswresample 0. 17.104 / 0. 17.104
libpostproc 52. 3.100 / 52. 3.100
Guessed Channel Layout for Input Stream #0.0 : stereo
Input #0, aiff, from 'in.aiff':
Duration: 00:00:30.43, start: 0.000000, bitrate: 1411 kb/s
Stream #0:0: Audio: pcm_s16le (sowt / 0x74776F73), 44100 Hz, stereo, s16, 1411 kb/s
Output #0, ipod, to 'fdk-mono.m4a':
Metadata:
encoder : Lavf55.25.101
Stream #0:0: Audio: aac (libfdk_aac) (mp4a / 0x6134706D), 44100 Hz, mono, s16, 32 kb/s
Stream mapping:
Stream #0:0 -> #0:0 (pcm_s16le -> libfdk_aac)
Press [q] to stop, [?] for help
size= 125kB time=00:00:30.44 bitrate= 33.7kbits/s
video:0kB audio:119kB subtitle:0 global headers:0kB muxing overhead 4.902738%
$ ffprobe -show_streams fdk-mono.m4a 2>/dev/null | fgrep chan
channels=1
channel_layout=mono
I first believed this was a problem with fdk-aac, but a HE-AAC by
iTunes yields the same:
$ ffprobe -show_streams itunes-he-mono.m4a 2>/dev/null | fgrep chan
channels=2
channel_layout=stereo
See also:
http://sourceforge.net/p/opencore-amr/mailman/message/31874638/
ff.
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