[MPlayer-users] AAC LC 5.1 audio not recognized by mplayer

[Justin Randall]

Hi all,

I can't seem to get mplayer to give me 6 channel audio playback on my
AAC encodes.  Here are the steps I take and some debug info...

I converted a valid AC3 5.1 surround audio file to a 6 channel wave using:
> mplayer $infile -af channels=6:6:0:0:1:1:2:4:3:5:4:2:5:3 -ao pcm:fast: -channels 6 -novideo
and then I converted that 6 channel wave to AAC LC 5.1 using nero
> neroAacEnc -ignorelength -q 0.38 -if $wav_file -of $aac_file
but the resulting supposed 5.1 channel audio file is not recognized by
mplayer.  It says that FAAD cannot find the compressed input bitrate
of the aac stream.  I'm asking because while mplayer falls back to two
channels for audio, both my PS3 and QuickTime (if you believe it)
recognize the audio as 5.1.  I can confirm that the PS3 does in fact
put out all 6 channels over my surround system.  I can only confirm
that QuickTime recognizes the stream in it's info settings since I
don't have surround set up on my PC (maybe that is why mplayer
defaults to stereo?).

Here is the printout of mplayer:

>>mplayer test.mp4
MPlayer Sherpya-SVN-r26446-4.2.3 (C) 2000-2008 MPlayer Team
CPU: AMD Athlon(tm) 64 X2 Dual Core Processor 4200+ (Family: 15, Model: 43, Step
ping: 1)
CPUflags:  MMX: 1 MMX2: 1 3DNow: 1 3DNow2: 1 SSE: 1 SSE2: 1
Compiled with runtime CPU detection.

Playing test.mp4.
libavformat file format detected.
[lavf] Video stream found, -vid 0
[lavf] Audio stream found, -aid 1
VIDEO:  [avc1]  1280x720  24bpp  23.976 fps    0.0 kbps ( 0.0 kbyte/s)
==========================================================================
Opening video decoder: [ffmpeg] FFmpeg's libavcodec codec family
Selected video codec: [ffh264] vfm: ffmpeg (FFmpeg H.264)
==========================================================================
==========================================================================
Opening audio decoder: [faad] AAC (MPEG2/4 Advanced Audio Coding)
FAAD: compressed input bitrate missing, assuming 128kbit/s!
AUDIO: 48000 Hz, 2 ch, s16le, 128.0 kbit/8.33% (ratio: 16000->192000)
Selected audio codec: [faad] afm: faad (FAAD AAC (MPEG-2/MPEG-4 Audio) decoder)
==========================================================================
AO: [dsound] 48000Hz 2ch s16le (2 bytes per sample)
Starting playback...
VDec: vo config request - 1280 x 720 (preferred colorspace: Planar YV12)
VDec: using Planar YV12 as output csp (no 0)
Movie-Aspect is 1.78:1 - prescaling to correct movie aspect.
VO: [directx] 1280x720 => 1280x720 Planar YV12


The output of mp4box -info for the same file results in the audio
stream being reported correctly as 6 channels on track 2.

>>mp4box -info test.mp4
* Movie Info *
        Timescale 600 - Duration 00:21:17.161
        Fragmented File no - 2 track(s)
        File Brand isom - version 1
        Created: GMT Sat May 03 04:53:57 2008

File has root IOD
Scene PL 0xff - Graphics PL 0xff - OD PL 0xff
Visual PL: AVC/H264 Profile (0x15)
Audio PL: AAC Profile @ Level 4 (0x2a)
No streams included in root OD

Track # 1 Info - TrackID 1 - TimeScale 24000 - Duration 00:21:17.067
Media Info: Language "English" - Type "vide:avc1" - 30619 samples
MPEG-4 Config: Visual Stream - ObjectTypeIndication 0x21
AVC/H264 Video - Visual Size 1280 x 720 - Profile High @ Level 4.1
NAL Unit length bits: 32
Pixel Aspect Ratio 1:1 - Indicated track size 1280 x 720
Self-synchronized

Track # 2 Info - TrackID 2 - TimeScale 48000 - Duration 00:21:17.162
Media Info: Language "English" - Type "soun:mp4a" - 59867 samples
MPEG-4 Config: Audio Stream - ObjectTypeIndication 0x40
MPEG-4 Audio AAC LC - 6 Channel(s) - SampleRate 48000
Synchronized on stream 1


Does anybody have any thoughts on this or have you seen this behavior
before?  Does mplayer need to have the audio in the first stream to
properly detect all channels?  I am fairly confident I did all the
right steps, but mplayer refuses to acknowledge 6 channel audio.  Any
advice would be appreciated on this problem.

Thanks,
Justin