Re: [Qemu-devel] [PATCH 21/25] audio: common rate control code for timer based outputs

[Kővágó Zoltán]

Hi,

2015-08-21 00:37 keltezéssel, Marc-André Lureau írta:
> Hi
>
> On Thu, Aug 6, 2015 at 8:28 PM, Kővágó, Zoltán <address@hidden> wrote:
> > -    decr = rate_get_samples(&hw->info, &out->rate);
> > -    decr = audio_MIN(out->fsize - out->fpos, decr);
> > -
> > -    *size = decr << 2;
> > +    *size = audio_rate_get_bytes(&hw->info, &out->rate,
> > +                                 (out->fsize - out->fpos) << 2);
> >       return out->frame + out->fpos;
> >   }
>
> I am not familiar with this "rate" thing, but you are changing the way
> it works for Spice without explaining why, and that worries me a
> little.
>
> The rate->bytes_sent is not updated the same way, the result is not
> always << 2..
>
> I really don't get what this is really doing tbh, some kind of clever
> buffer limit :)

The old code pretty much ignored if the buffer overflow (which shouldn't 
happen normally), while the new one doesn't.  The problem is that with 
this new get_buffer/put_buffer thing if we reach the end of the circular 
buffer, it will produce have the same effect as a buffer overflow, but 
we need to handle it more gracefully as it will now happen every now and 
then.

But probably I'll change << 2 to info.shift, to handle more gracefully 
if the spice stream format changes.

Zoltan