Re: [PATCH 10/11] alsaaudio: change default playback settings

[Volker Rümelin]

> > > diff --git a/audio/alsaaudio.c b/audio/alsaaudio.c
> > > index 5f50dfa0bf..0cc982e61f 100644
> > > --- a/audio/alsaaudio.c
> > > +++ b/audio/alsaaudio.c
> > > @@ -913,17 +913,14 @@ static void *alsa_audio_init(Audiodev *dev)
> > >       alsa_init_per_direction(aopts->in);
> > >       alsa_init_per_direction(aopts->out);
> > >   -    /*
> > > -     * need to define them, as otherwise alsa produces no sound
> > > -     * doesn't set has_* so alsa_open can identify it wasn't set by 
> > > the user
> > > -     */
> > > +    /* don't set has_* so alsa_open can identify it wasn't set by 
> > > the user */
> > >       if (!dev->u.alsa.out->has_period_length) {
> > > -        /* 1024 frames assuming 44100Hz */
> > > -        dev->u.alsa.out->period_length = 1024 * 1000000 / 44100;
> > > +        /* 256 frames assuming 44100Hz */
> > > +        dev->u.alsa.out->period_length = 5805;
> > >       }
> > >       if (!dev->u.alsa.out->has_buffer_length) {
> > >           /* 4096 frames assuming 44100Hz */
> > > -        dev->u.alsa.out->buffer_length = 4096ll * 1000000 / 44100;
> > > +        dev->u.alsa.out->buffer_length = 92880;
> > Not a big fan of magic numbers, as it makes code less readable.
>
> I can't see how this can be improved. The buffer length is unchanged. 
> I just evaluated the constant expression to have a time in 
> microseconds like the rest of the audio backends. And libasound tells 
> me to use 5804us for the period length which I rounded up to 5805us. I 
> would prefer a period length of 5000us.
>
> ./qemu-system-x86_64 -device ich9-intel-hda -device 
> hda-duplex,audiodev=audio0 -audiodev 
> alsa,id=audio0,out.period-length=5000,out.dev=PCH,,0
> alsa: Requested period time 5000 was rejected, using 5804

The correct command line is:
./qemu-system-x86_64 -device ich9-intel-hda -device 
hda-duplex,audiodev=audio0 -audiodev 
alsa,id=audio0,out.period-length=5000,out.dev=hw:PCH,,0
alsa: Requested period time 5000 was rejected, using 5804

> > >       }
> > >         /*