[alsa-devel] Fwd: ALSA queries

[Takashi Iwai]

On Tue, 07 Aug 2018 15:36:22 +0200,
Chakravarthi Pradeep wrote:
> 
> >In the case above it's in frames.  But it can be defined in bytes
> >depending on the hardware spec.  Some hardware defines in the time
> >unit (like msec), too.
> 
> Can you please tell me how to define in bytes ?

Read the source before asking like this.  If not found, read the
source again.  If still it's not fulfilled, ask more specific
questions.

The driver doesn't define it.  Rather the driver lets ALSA PCM core
choose the parameters given from user-space.  But some parameters
might not fit with the requirement of your hardware.  For satisfying
it, the driver may give hw constraints to PCM core beforehand,
typically set in the open callback.

> >Now you know it.  And remember that PA is often die-hard.
> So it means that I can not do rmmod until pulseaudio is removed , is
> it correct ?

Yes.  You cannot rmmod during any program is accessing to the sound
device, not only PA.


Takashi

> Regards,
> Chakravarthi
> On Tue, Aug 7, 2018 at 6:45 PM Takashi Iwai <tiwai at suse.de> wrote:
> >
> > On Tue, 07 Aug 2018 15:12:08 +0200,
> > Chakravarthi Pradeep wrote:
> > >
> > > Dear Takashi,
> > >
> > > Thanks for your reply.
> > >
> > > > The "period" in ALSA PCM definition represents the interval time (or
> > > > frames) of the periodical interrupts on the ring buffer.  If the irq
> > > > is issued for each 256 frames while the ring buffer size is 1024
> > > > frames, periods = 1024/256 = 4.  The periods_min defines the minimal
> > > > number of periods the hardware may accept.
> > >
> > > Is it  256 frames or  256 bytes ?
> >
> > In the case above it's in frames.  But it can be defined in bytes
> > depending on the hardware spec.  Some hardware defines in the time
> > unit (like msec), too.
> >
> > > fuser -v /dev/snd/* output is
> > >                                          USER
> > >   PID   ACCESS    COMMAND
> > > /dev/snd/controlC0         Dell                                   1815
> > > F.....           pulseaudio
> >
> > Now you know it.  And remember that PA is often die-hard.
> >
> >
> > Takashi
> 
> 
> 
> -- 
> Thanks and Regards
> Chakravarthi Pradeep.K
> Ph: 91 9980434900
>