Hi,
(Sorry I can't address you by name).
Stainless Steel Rat <[EMAIL PROTECTED]> writes:
> * Eric Woudenberg <[EMAIL PROTECTED]> on Mon, 06 Mar 2000
> | On what do you base this statement? My understanding of ATRAC (based
> | upon looking at an ATRAC decoder) is that the computational demands of
> | encoding ATRAC are similar to those for MP3. I would expect a software
> | ATRAC encoder to run about as fast as an MP3 encoder.
>
> If that were the case, then you would be able to encode MP3 streams that
> sound as good as ATRAC 4 (which they do not) in real time on your desktop
> (which you cannot at this time). As I mentioned previously, a Pentium II
> running at 400MHz is capable of turning SPDIF into 128Kbps MP3 in real
> time, if it is not doing anything else. The particular machine in question
> is a 64Mb system with fast/wide SCSI (so, no bottleneck there), using LAME.
> 128Kbps MP3s do not sound nearly as good as ATRAC 4, so I have to say that
> the computational loads are not comparable.
Somehow my encoding times are quite different than yours, running
LAME/Linux on a 500MHZ PIII, I get these times for encoding a 1 minute
44.1khz stereo signal:
Output Bitrate (kbps): 32 64 128 256 320
User time (secs): 15 16 21 21 19
At worst, this is 3 times faster than realtime. The ATRAC encoder is
not significantly different in structure from MPEG 1 Layer I (a
simpler encoder than MP3), so it is reasonable to expect that an ATRAC
encoder would offer similar encoding times.
Also, regarding the ATRAC ASIC, AFAIK (and please correct me if I'm
wrong), these are microcontrollers with a DSP core for doing the ATRAC
calculation. Please don't imagine that the ATRAC encoder operates as
one huge logic operation of an ASIC. ATRAC encoding is still
programmed in discrete, sequential steps, with lots of multiplies and
adds. I would imagine the computing power (for performing ATRAC
encoding) of the CXD-2652AR inside the MZ-R55 to be substantially less
than a 500MHZ PIII (and it certainly runs a lot cooler!).
Regards,
Rick
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