Re: bandwidth limits
Re: bandwidth limits
- Subject: Re: bandwidth limits
- From: "Roman Thilenius" <email@hidden>
- Date: Wed, 24 Sep 2003 23:18:01 +0200 (MEST)
>
Roman, et al,
>
>
On Tuesday, September 23, 2003, at 09:12 AM, Roman Thilenius wrote:
>
> you will not use any compression for realtime streaming of audio or
>
> video,
>
> that would need a bit too much CPU.
>
>
Not at all sure what you mean here.
>
>
QT's Broadcaster is able to broadcast using AAC (and other audio
>
codecs), speech based codecs like CELP, etc, also do not consume that
>
much CPU either and all of these are entirely usable in a real-time
>
situation. (For instance, AAC on an 800MHz iMac is somewhere in the
>
vicinity of 10% or "real" time for encoding. Decoding AAC on a similar
>
machine is now around 1-2% CPU usage).
>
>
You should do some research on the time these processes take as they
>
are in *very* common use (in fact far more use than doing NO
>
compression because the data rates are typically far more crucial and
>
limiting a factor than the CPU needed to compress the data within
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real-time constraints) - this applies to video even more so than for
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audio
>
>
Bill
>
>
QT's Broadcaster is able to broadcast using AAC
yes, but quicktime server is not sending to coreaudio it is a TCP IP server
application. and one does not listen to 48 radios at once.
what i meant is, that 1-2% CPU is already far too much in the given case:
if austin needs to play 48 mono channels from disk that would mean its
already around 24-48% (on an 800Mhz G4 imac !) - while playing the files
from disk would really only need 3% or so.
now i know that austin makes system utilities, and not sounddesign
enviroments, i would not not consider stuff like .aac for things music
or speech because it is not even a lossless codec.
>
this applies to video even more so than for audio
yeah i know; again, i am thinking too much DSP here maybe.
but i must disagree that compression is very common, you will normally
never compress things which you plan to put effects on it later.
in practice of TV and movie production you use "DV 30" and "DV 50",
these are nearly the only formats used in industry. not mpeg. mpeg is
what you give the end user :)
where it should be common for audio, i dont know. well.. ok, games.
but most existing _audio apps cannot play compressed audio file
multichannel.
logic , nuendo, and audacity might be doing that in the future.
sorry, i cant escape my thinking structures where quality is all, if i had
to
decide that ( you will smile now and say "what a luck, he doesnt !" ) ,
coreaudio would be 32 bit INTEGER anyway ... i cant wait for the day when
that will be available (= affordable) for hardware IOs.
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