Re: [hatari-devel] Cracks in the sound (YM+DMA)

[Nicolas Pomarède <npomarede@xxxxxxxxxxxx>]

Le 24/02/2013 05:56, David Savinkoff a écrit :
> Hi,
>
> dma @ atari-forum noted sound distortion in Hatari:
> http://www.atari-forum.com/viewtopic.php?f=51&t=24669&sid=f08b16bc7408e46efabdcc0459add885#p226677
>
> I found and solved the problem. YM + DMA sound samples
> exceeded 16 bits at line 549 in dmaSnd.c (see code):
>
> /* DMA and (YM2149 0 dB) mixing */
> MixBuffer[nBufIdx][0] = MixBuffer[nBufIdx][0] + dma.FrameLeft * -((256*3/4)/2)/4;
>
> A solution is to center the YM sound table with sound.c.overflow.diff
> A side effect of centering the sound table is an audible click when
> cold-starting hatari (power cycling on a real Atari).
>
> I also made a patch to do efficient clipping instead of overflow for
> LMC1992 distortion.
>
> David

Hello

I tried the patch, and it's true the click on the start is not very nice.

Instead of centering the ym sound, can't we just found a maximum value 
for YM_OUTPUT_LEVEL that doesn't create the observed overflow ? Sound 
level will be lower, but the user can still adjust the output volume on 
his PC (ratio between dma and ym would also need to be adjusted when 
mixing both if we lower YM_OUTPUT_LEVEL)

Nicolas