Re: Re: dmix plugin

[Jaroslaw Sobierski <fycio@gucio.com>]

Quoting Abramo Bagnara <abramo.bagnara@libero.it>:
> 
> The results are amazing and I'd say Jaroslav has done some mistakes in
> his handmade asm.
> 

This may be true, but I think you're trying to be a little too quick yourself.
Did you *test* your code? I only had time to take a short glance at it, but
too me it seems that this is not the correct check for overflow on signed
numbers:

>                       if (unlikely(sample & 0xffff0000))
>                                s = sample > 0 ? 0x7fff : -0x8000;
>                        else
>                                s = sample;

I noticed it because this is the first thought I had, but it only works
for unsgined. Notice that -1 will be 0xffffffff in a 32 bit sample. So
your code will "saturate" all negative samples to -8000 effectively
killing half of the wave, the way a diode does. I'm pretty sure this
would not sound good ;-). Still, even if you change this to two normal
ifs I assume the speed will not be affected by an order of magnitude.

Secondly, the test code is hardly a good representation of our "working"
environment because we're expecting multiple processes to write
concurrently to the buffer. I think you sholud have a "verification"
procedure which carefully mixes the waves one by one and then the 
n test mixes should be run in m processes concurrently. And the result
compared to the "verification" table.

--------------
Fycio (J.Sobierski)
 fycio@gucio.com


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