From: Stainless Steel Rat <[EMAIL PROTECTED]>
To: MD-L <[EMAIL PROTECTED]>
Sent: Thursday, March 16, 2000 1:11 AM
Subject: Re: MD: Sony's new Internet Audio Recording Interface
> USB 1.1 maxes out at 12Mb/s (bit vs. Byte), or 90MB/minute. A 74 minute
CD
> is 640MB, or ~8MB/minute. Kick the math around and, after you figure in
> something like a 5% loss due to overhead, you can dump raw, 16-bit PCM
down
> the USB pipe about 10 times faster than real-time playback. Encoding on
> the host machine saves you nothing.
5% loss due to overhead?!? What I wouldn't give for only 5% loss even on a
modern PC! In real terms it's more like 15% even on a well specified system.
16 bit PCM stereo is 10.09MB/min without any error correction which it would
probably need, although I'll assume for the moment that this is a perfect
world and it doesn't. Ripping from a CD (IDE interface) would invoke about
30-40% CPU utilisation and this would have a bad effect on the USB system -
buffering would really be needed as it is when burning a CD-R. Assuming the
system wasn't too upset about this I would expect a massive 7.5x max
transfer rate over USB. Of course not many systems actually manage the
12Mb/s that USB1.1 specifies, they often only make about 8 or 9Mb/s, but
fair enough it is quite fast. With all that going on it makes ATRAC encoding
at the PC end sound easy!
> The entire point of USB is to move hardware *outside* of the host machine.
> If you put the encoder inside, then there is no reason for a USB device.
*Looks at his USB keyboard and mouse* ..... odd.... I never usually have my
keyboard and mouse inside my PC, but then maybe you're a closet Amiga
fan.......
The point of USB was to introduce a better serial port system - the current
UART devices etc. are too slow to cope with today's applications. USB was
invented to be a small, simple and high-spec interface for transferring data
between devices, not necessarily to put them outside the PC.
Magic
--
"Creativity is more a birthright than an acquisition, and the power of sound
is wisdom and understanding applied to the power of vibration."
Location : Portsmouth, England, UK
Homepage : http://www.mattnet.freeserve.co.uk
EMail : [EMAIL PROTECTED]
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