Re: 5.1 AC-3 WAVs recognized as 2 channels?
Re: 5.1 AC-3 WAVs recognized as 2 channels?
- Subject: Re: 5.1 AC-3 WAVs recognized as 2 channels?
- From: Brad Ford <email@hidden>
- Date: Thu, 15 Jun 2006 11:45:01 -0700
On Jun 15, 2006, at 11:21 AM, Stephen F. Booth wrote:
Hello all,
I recently downloaded a 5.1 AC-3 sample WAV from http://
www.kellyindustries.com/sounds.html
Background: Opening the file with QuickTime Player results in
static- the file is shown as stereo. However, VLC correctly opens
and plays the file.
Apple does not currently ship an AC-3 'adec' component. VLC is able
to play it correctly because they BTOAC3D (Bring Their Own AC-3
Decoder). You're welcome to file an enhancement request at
bugreport.apple.com.
-Brad Ford
QuickTime Engineering
If I open the file with ExtAudioFileOpen(), and then get
information using ExtAudioFileGetProperty(), the resulting
AudioStreamBasicDescription is filled in with 44.1 kHz, 2-channel
audio at 16 bits per sample. Obviously any operations performed on
the 5.1 file treating it as 2 channels result in audio garbage (I
primarily want to convert to FLAC).
The WAVE header looks like (starting at the 'fmt ' chunk): 66 6D 74
20 10 00 00 00 01 00 02 00 44 AC 00 00 10 B1 02 00 04 00 10 00.
With this header, the Core Audio interpretation seems to be
correct- the header implies 2-channel audio (I referred to the WAVE
header info at http://ccrma.stanford.edu/courses/422/projects/
WaveFormat/).
I couldn't find any information on 5.1 WAVE format, but assuming
the same as regular WAVE, I am stumped how this file plays
correctly in VLC but generates static in QuickTime Plyaer. Have I
done something wrong or does Core Audio not support this type of WAV?
Thanks,
Stephen
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