Hi!
On Thu, Mar 30, 2006 at 10:33:58PM +0200, torbenh@email-addr-hidden wrote:
> i cant use a 2 times upsampler....
> i want to use an unsynced soundcard with clockdrift as a recording
> source. and i really dont want to make any quality compromises.
>
> i need all features of libsrc (slowly changing samplerate, and resample
> factors of 1.00001 or so)
Ok, I thought a bit in this case. You probably can get better quality
than the libsrc linear interpolation while still being quite a bit
faster than libsrc sinc interpolation.
First algorithm: upsample by factor 2 (you can use my code as it is),
then use linear interpolation. Why this is better than plain linear
interpolation? Because low frequency signals can be better approximated
by lines than high frequency signals, and after upsampling by factor 2
your signals will tend to be low frequency signals.
Second algorithm: perform factor N upsampling (for instance factor 16
upsampling), then use linear interpolation. The quality should become
even better. The performance will not suck as badly as "factor 16
upsampling" sounds, because you only need to compute those sample values
that you need to do linear interpolation.
As performance estimate, I think the first algorithm should outperform
libsrc with a factor between 10 and 30, the second algorithm should
outperform libsrc with a factor between 3 and 15 (given that both are
implemented in an SSE accelerated way, like I did).
As for quality, I'd really like to know what quality can be attained by
this approach at what speed. Could it even outperform libsrc on both,
quality and performance, under some circumstances?
Cu... Stefan
-- Stefan Westerfeld, Hamburg/Germany, http://space.twc.de/~stefanReceived on Sat Apr 1 16:15:04 2006
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