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Posted by dpierce on 12/03/07 23:00
On Dec 3, 3:33 pm, "Richard Crowley" <rcrow...@xp7rt.net> wrote:
> Most modern programming languages ("C" for example)
> only treat input/output data as a stream, there is no "block"
> notion of data. It doesn't matter whether the data is coming
> from a 10-year old disk file or from a real-time ADC. It is
> just a data stream to most software. And that is the way all
> data is processed, even on 64-bit wide CPUs.
And what the sorry lot of you are missing is that MPEG audio
is processed as BLOCKS, not as a continuous stream. The
algorithms take a pile of samples until it has a block,
processes the block applying the psychoacoustic
criteria as needed, then produces a block a psychoacoustically
reduced data.
And then, lo and behold, it takes that block and runs it through
a nice, old everyday Lempel-Ziv data compressor, and out
spits a block of data that has been compressed both
psychoacoustically AND compressed data wise to remove
redundant data patterns.
At the other end, the first thing that happens is that it
takes one of these compressed blocks and uncompresses
it, and then applies minimal reconstruction to get the final
data in the block out, and then parcels out the data, sample
by sample.
The ONLY thing that makes this whole process "real-time" is
NOT whether the data is a stream (it is) or a blocked (it is), but
that it can happen at least as fast as the data is arriving or needs
to be delivered.
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