kAudioFilePropertyChannelLayout vs. kExtAudioFileProperty_FileChannelLayout
kAudioFilePropertyChannelLayout vs. kExtAudioFileProperty_FileChannelLayout
- Subject: kAudioFilePropertyChannelLayout vs. kExtAudioFileProperty_FileChannelLayout
- From: "Stephen F. Booth" <email@hidden>
- Date: Thu, 27 Jan 2011 09:39:36 -0800
I seem to have run into conflicting behavior between AudioFile and ExtAudioFile when reading a file's channel layout- in particular for WAVE files. I believe that according to the WAVE specification, channels in a WAVE file are in the "standard" order: FL FR FC LF BL BR etc. When I attempt to retrieve a stereo WAVE file's channel layout using AudioFile, I get kAudioFileInvalidChunkError. However, when I retrieve the channel layout for the same file using ExtAudioFile I get a 12-byte AudioChannelLayout struct filled with all zeroes. Obviously this isn't a valid channel layout, and I expect to get a layout with kAudioChannelLayoutTag_Stereo set (or an error). I suspect this is a bug in ExtAudioFile as the default ctor for CAAudioChannelLayout creates an empty struct, but I'm not sure.
For 6 channel WAVE files both AudioFile and ExtAudioFile return kAudioChannelLayoutTag_MPEG_5_1_A and for 8 channel files they return kAudioChannelLayoutTag_MPEG_5_1_A. For stereo AAC and ALAC I get kAudioChannelLayoutTag_Stereo.
Is this an ExtAudioFile bug or have I done something wrong?
Stephen
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