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Re: FLLR (compression ?) in AIFF file
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Re: FLLR (compression ?) in AIFF file



The FLLR chunk is added by the AudioFile code to align the data chunk on a 4K page boundary for optimized I/O during playback.

The AIFF specification says to ignore chunks you don't recognize and skip over them. This is such a chunk. :-)

As for the NONE chunk, it is not a separate chunk but is found in the "compressionType" field of the COMM chunk.

hth,
stephen

On Aug 5, 2008, at 10:27 PM, Francois Baronnet wrote:

Hi,

using some code provided by Apple to record audio
(http://developer.apple.com/documentation/MusicAudio/Conceptual/AudioQueueProgrammingGuide/AQRecord/chapter_3_section_6.html ),
I'm able to create AIFF files.
Now I want to read thoses files using some code found on this mailing
list (http://lists.apple.com/archives/coreaudio-api/2003/Feb/msg00244.html ).
It doesn't work for me :)


When I open my file using hexadecimal editor, I can see the "FORM",
"AIFF" and "COMM" headers. But I can't find the "NONE" one saying
there is no compression. That's why above objective-C routine can't
work. Instead of "NONE", there is "FLLR". And there is no such header
in AIFF format specification...

If I record my file as AIFC, the begining of the file is different but
still with "FLLR".

Here are my settings for AIFF file:

aqData.mDataFormat.mFormatID = kAudioFormatLinearPCM;
aqData.mDataFormat.mSampleRate = 44100.0;
aqData.mDataFormat.mChannelsPerFrame = 2;
aqData.mDataFormat.mBitsPerChannel = 16;
aqData.mDataFormat.mBytesPerPacket =
aqData.mDataFormat.mBytesPerFrame =
aqData.mDataFormat.mChannelsPerFrame * sizeof (SInt16);

aqData.mDataFormat.mFramesPerPacket = 1;
AudioFileTypeID fileType = kAudioFileAIFFType;

aqData.mDataFormat.mFormatFlags =
	kLinearPCMFormatFlagIsBigEndian
	| kLinearPCMFormatFlagIsSignedInteger
	| kLinearPCMFormatFlagIsPacked;

Thanks for reading me.



--
François Baronnet
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References: 
 >FLLR (compression ?) in AIFF file (From: "Francois Baronnet" <email@hidden>)



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