Re: [linux-audio-dev] using SB Live (emu 10K1) for realtime sample rate conversion?

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Subject: Re: [linux-audio-dev] using SB Live (emu 10K1) for realtime sample rate conversion?
From: Martijn Sipkema (msipkema_AT_sipkema-digital.com)
Date: Tue Aug 06 2002 - 15:33:41 EEST


> Right now we're looking at the smartest way to do realtime sample rate
> conversion (ie change playing speed) on 2 mp3 audio files at once, which
> should be good quality (ie good anti aliasing filters), low latency
(beneath
> 12ms), stable, fast and the output should be send to 2 independent
analogue
> stereo outputs. (yes yes, *another* DJ'ing device ;)

Should both streams' pitch be changed independantly?
Perhaps there is hardware that can do this, but you can do it in software
also.

Some hardware supports changing the DAC pitch, but most does not. Also
most hardware probably uses the same clock for all inputs/outputs. Note
that changing the DAC pitch this changes I/O latency since it is constant in
samples.

> For our proof-of-concept prototype we were looking at using a simple
> Creative SB Live 1024 card with the emu 10K1 chipset on it. The specs of
> this chip show us 2 independent stereo outs and on-chip sample rate
> conversion including anti aliasing filters. Does any of you know if it's
> possible under Linux/FreeBSD to do this? Ie use 2 stereo outputs
> independently, and/or do sample rate conversion on the chip in steps of
0,1%
> (base rate will be 44.1 KHz i think, so the sample rate should be able to
> increment or decrement around this 44.1KHz)

I'm not familiar with this hardware, but although it may be capable of doing
what you
want I doubt that is what it was designed for.

I'd say changing the pitch in software is the better approach for this
application.

--martijn


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