Re: External PCM plugin SDK

[Marcel Holtmann <marcel@holtmann.org>]

Hi Takashi,

> > it is putting the PCM data into the SBC encoder and then sending it to
> > the RFCOMM socket. This is not the standard for high quality audio over
> > Bluetooth, but my Aiptek headphone supports this stuff. For now this is
> > easier than dealing with A2DP and AVDTP.
> > 
> > The SCO support for the headsets is another story.
> 
> ... and we'll need control plugin for mixers, too.

and I need full duplex IO and volume control inside the same plugin for
the headset/handsfree support.

> > The XMMS is version 1.2.10 and BMP is version 0.9.7. In what versions
> > are the ALSA plugins fixed. I will build it from source.
> 
> The patch isn't in the released version.  IIRC, they were applied to
> CVS, though.

I checked the latest XMMS CVS and even it segfaults or I get an error:

xmms: pcm_params.c:2294: sndrv_pcm_hw_params: Assertion `err >= 0' failed.

Looks like a problem on my side.

> > > Do you have buffer or period size constraints?
> > 
> > Oh yes, that is the point where I am not sure what I am doing. The SBC
> > is a codec like MP3 and actually I have no idea what are the best values
> > here. These are software soundcards.
> 
> You don't have to set them if the hardware has no restriction.
> Usually, the period size defines the interrupt period.  In the case of
> user-space driver, it corresponds to the expected poll period, etc.

I can skip IOPLUG_HW_PERIOD_BYTES and IOPLUG_HW_PERIODS, but I must set
IOPLUG_HW_BUFFER_BYTES, because otherwise it segfaults even with aplay.

> > > > We also talked about making these IO plugins visible when ALSA is
> > > > listing its hardware devices. Is this possible now?
> > > 
> > > No, it's still in planning.
> > > We'll need to define a usable API first...
> > 
> > What about a flags variable in snd_pcm_ioplug for activating it. This is
> > generic and for me this is enough, because both Bluetooth IO plugins are
> > virtual soundcards and they should always be listed. Or maybe list IO
> > plugins in general.
> 
> This sounds good.  I'll add like the following:

Let's take an unsigned long to handle more than 32 flags ;)

Regards

Marcel




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