Re: AudioConverterFillComplexBuffer for transcoding streamed audio [iMac OSX10.5.6]
Re: AudioConverterFillComplexBuffer for transcoding streamed audio [iMac OSX10.5.6]
- Subject: Re: AudioConverterFillComplexBuffer for transcoding streamed audio [iMac OSX10.5.6]
- From: Richard Dobson <email@hidden>
- Date: Thu, 10 Jun 2010 08:02:46 +0100
On 10/06/2010 00:38, Brian Willoughby wrote:
On Jun 9, 2010, at 14:59, Abhinav Tyagi wrote:
1) I have noticed that the header is 4096 bytes if we use
AudioFileWritePackets. I remember the header for RIFF wave file is
only 44 bytes. Why is the header 4096 bytes.
RIFF/WAVE does not have a header. RIFF is a sequence of chunks which can
come in any order, and have varying sizes. The term 'header' usually
refers to a fixed length of data that always comes at the beginning of a
file, but since WAVE does not work this way, I avoid using the term
header.
I think this is a little misleading. The order of chunks does not come
in any order (that privilege is reserved for AIFF files). In a RIFF
WAVE file, the fmt chunk ~must~ precede the data chunk. This makes the
file technically speaking streamable, as all the required format
information is supplied prior to the data to be rendered. It is true
that one can never say WAVE has a fixed-size header - the best one can
say is that there is a minimum header size corresponding to the
RIFF<WAVE> fixed opening chunk header, minimum 16byte fmt chunk, the
data chunk and nothing else. It is really a variable-sized header, which
~necessarily~ precedes the audio data itself. Some systems insist on
placing data after the audio data chunk, something which I have always
thought a very bad idea!
Richard Dobson
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