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CAF file anomalies
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CAF file anomalies


  • Subject: CAF file anomalies
  • From: William Bates <email@hidden>
  • Date: Tue, 18 Nov 2008 19:27:08 -0600


I've been parsing CAF files that I created with ExtAudioFile, and some Apple-distributed in various sample code.


I'm doing this on an Intel machine. Everything works well as long as you are very careful about Endian-ness.

However, I note the following anomalies and would like opinions on whether the following are me, known bugs, or worth filing bug reports on:

(1) Missing channels per frame in Audio Description Chunk.

An Audio Description Chunk Data is 32 bytes, whereas the fields described should take 36 bytes:
Size of Float64 = 8
Size of UInt32 = 4
8 + 7*4 = should be size = 36
sizeof(CAFAudioDescription) = 32
ChunkSize in file = 32


In practice, it seems that mChannelsPerFrame field is simply missing.

The Float64 does indeed seem to be a Float64.

(2) As a possibly related aside, I note that QuickTime Player (current version, Pro)
on a newly-created CAF file
appears to play
but fails to produce any sound
the _first_ time the file is opened.
It seems to work the second time; or if the file has been previewed in the Finder.


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