[alsa-devel] dmix does not mix small files??

[Prabhu Sivaraja]

Thanks for your suggestion. I do agree with you. But when I change my
period_size to 4KB and set number of periods to 16, my hw_ptr or appl_ptr
never move from their initial value of 0. So you think this a driver
problem? But the hw_ptr is not something the driver controls? Would
appreciate if you could explain more on this.

Thanks.
Prabhu.


 On 5/3/07, Jaroslav Kysela <perex at suse.cz> wrote:

> On Thu, 3 May 2007, Prabhu Sivaraja wrote:
>
> > Hi,
> >
> > I've been stuck on this dmix problem for the past week and have tried
> > everything under the sun. Please any help or comment is much
> appreciated.
> > Thanks a lot.
>
> For nice dmix support, it's better to have more periods than 2 and small
> ones. Your allowed configuration 2 x 32KB is not very good.
>
> But judging from the current dmix code, this code may cause to skip large
> count of samples or your driver behaves badly:
>
> /* If we have too litte periods, better to align the start  position
> * to the period boundary so that the interrupt can be handled  properly
> * at the right time.
> */
> dmix->slave_appl_ptr = ((dmix->slave_appl_ptr + dmix->slave_period_size -
> 1)
>                       / dmix->slave_period_size) *
> dmix->slave_period_size;
>
>
> It's from changeset:
>
> hangeset:   2109:349c0b0018b9
> user:        tiwai
> date:        Fri Mar 24 14:53:41 2006 +0000
> files:       src/pcm/pcm_direct.c src/pcm/pcm_dmix.c
> description:
> Fix noisy output of dmix with two periods
>
> Fixed the noisy output of dmix with two (or less) periods.
> The dmix tends to give noise or XRUN when running with two periods
> because of its implementation nature.  To avoid this, the start
> position is aligned to the period size, so that the updates are synced
> with interrupts of slave PCM.
>
> > So in order to debug this I tried to decrease my period_size = 4KB but
> when
> > I do this my hw_ptr never moves.
>
> Driver problem?
>
>                                        Jaroslav
>
> -----
> Jaroslav Kysela <perex at suse.cz>
> Linux Kernel Sound Maintainer
> ALSA Project, SUSE Labs
>