Re: AudioConverter MP3 decode questions
Re: AudioConverter MP3 decode questions
- Subject: Re: AudioConverter MP3 decode questions
- From: William Stewart <email@hidden>
- Date: Tue, 14 Mar 2006 12:29:20 -0800
Vince,
Thought I'd also forward this to the list...
On 14/03/2006, at 12:18 PM, Vince Shumaker wrote:
Thanks everyone for the quick replies!
So following up on my original post...
What does a packet represent to the AudioConverter?
For any format its basically a slice of time. So, for linear PCM, a
packet is all of the time-adjacent samples... That is, for a stereo
lpcm stream, it would be the left and right sample for any given time
(we call this left/right sample pair a frame). For a compressed bit
stream, it is a discreet "blob" of data that can't be broken down
without a decoder.
How time a given packet represents is described by the ASBD - most
formats specify a frames per packet (for linear pcm this is 1, for
compressed its generally > 1). For instance, AAC typically represents
its data as 1024 frames/packet - apple lossless as 4096, etc...
A parser can tell the difference between these two by examining the
bitsPerSample field - if this is non-zero then you can go into the
packet further (linear pcm, pwm), it is is zero, then as a generic
parser you can't - you then deal with these blobs of data which is
the packet.
Bill
Is it frames per
packet... samples per frame... or does it dependend on the data data
format?
--
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