[MPlayer-users] Standalone AAC file decoding not supported

[Jan Engelhardt]

On Thursday 2008-11-27 00:13, Nico Sabbi wrote:
>> >The man page says:
>> >> -dumpaudio (MPlayer only)
>> >>   Dumps  raw  compressed  audio stream to ./stream.dump (useful with MPEG/AC-3, in most other
>> >>   cases the resulting file will not be playable).
>> >
>> >Where "not playable" does really mean "No way _anything_ can play that.
>> >Really. Impossible."
>> 
>> Oh really? Then why can the standalone programs mpg123 and faad2
>> decode/play it without any problems?
>
>if the is in ADTS format then mplayer can play it, too, (eventually
>with -demuxer aac) but if the file is in raw format the configuration
>bits are missing, thus not even faad can decode it. Reimar is right:
>no one can.
>
>Run
>$ file file.aac
>
>what's the output?

Finding test cases where this triggers, here goes.
Two different ones: MP3 and AAC.

#
# certain imeem.com streams with MP3 audio and no video
# e.g.
# http://www.imeem.com/groups/evHYCbeE/music/ei3FP_r2/chi_chi_ching_ft_bling_dawg_popcorn_pop_summer_2k8/
#
$ mv /tmp/FlashDZK7MX t1.flv
$ mplayer t1.flv
Opening audio decoder: [mp3lib] MPEG layer-2, layer-3
AUDIO: 44100 Hz, 2 ch, s16le, 128.0 kbit/9.07% (ratio: 16000->176400)
Selected audio codec: [mp3] afm: mp3lib (mp3lib MPEG layer-2, layer-3)
(outputs sound)

$ file t1-stream.dump 
stream.dump: MPEG ADTS, layer III, v1, 128 kbps, 44.1 kHz, JntStereo

$ mplayer stream.dump
MPEG-PES file format detected.
MPEG: FATAL: EOF while searching for sequence header.
Video: Cannot read properties.
==========================================================================
Opening audio decoder: [mp3lib] MPEG layer-2, layer-3
ADecoder init failed :(
ADecoder init failed :(
Opening audio decoder: [ffmpeg] FFmpeg/libavcodec audio decoders
Unknown/missing audio format -> no sound
(more)

$ mpg123 stream.dump
(outputs sound)


#
# youtube files with AAC audio
# e.g. http://www.youtube.com/watch?v=T6KICpFueHg&feature=related&fmt=18
#
$ mplayer t2.flv
Opening audio decoder: [faad] AAC (MPEG2/4 Advanced Audio Coding)
FAAD: compressed input bitrate missing, assuming 128kbit/s!
AUDIO: 44100 Hz, 2 ch, s16le, 128.0 kbit/9.07% (ratio: 16000->176400)
Selected audio codec: [faad] afm: faad (FAAD AAC (MPEG-2/MPEG-4 Audio) decoder)
(outputs sound)

$ file t2-stream.dump
stream.dump: data

$ faad -f2 -o- t2-stream.dump | aplay -f cd
t2-stream.dump file info:
LC AAC  180.405 secs, 2 ch, 44100 Hz
(outputs sound)