Re: Surround via SPDIF with ALSA/emu10k1?

Lennart Sorensen
2005-08-29T12:52:40Z

On Sat, Aug 27, 2005 at 05:47:08PM -0400, Lee Revell wrote:
> For the best S/N ratio and dynamic range all mixer controls SHOULD be at
> 100%, assuming the volume control in your driver only attenuates
> signals. This is the case for the emu10k1 which implements all mixer
> controls via DSP programs that run on the soundcard anyway, and handles
> overflow itself.

Well I don't want them all at 100% since I do want to be able to have
even levels between the cd, midi and wave, which isn't always the case
at 100%. They sure sounded worse.

I certainly know some simpler sound cards would have more distrosion
when you ran the amplifiers on the card at 100%.

> Think about it, if you lower the mixer controls to 75%, you're not
> getting the full 16 bits of dynamic range, it's probably more like 14 or
> 15. 16 bits is barely enough headroom anyway, so you really don't want
> this.

Bit 16 is used as soon as the signal passes 50%. After all it is
required when the signal goes past 32767 and is on all the way to 65535.

So at 75% depending on how things are done internally I will be either
using the full range just not amplified to the same amount, or if truly
done entirely digitally, then I will be using 75% of the range, which is
still more than even 15bit could handle (since 15 bit has half the range
of 16bit).

> Anyway the problem here is a bug in the emu10k1 driver, see alsa-devel
> for the resolution.

Well that probably helps.

Len Sorensen