[pulseaudio-discuss] Problems with Pulseaudio and Bluetooth Headset

[James Bottomley]

On Sun, 2008-06-08 at 23:07 +0200, Lennart Poettering wrote:
> On Wed, 04.06.08 20:07, James Bottomley (James.Bottomley at HansenPartnership.com) wrote:
> 
> > I suspect this is some type of resampler problem rather than an actual
> > connection problem.  The headset is a GN6210H (which is a phone headset,
> > so mono earpiece and mono mic).  The only other oddity is that apart
> > from having only one channel, its sample rate is 8000Hz.
> > 
> > I have it all correctly plumbed into alsa using bluez and if I just use
> > alsa, I can send sound to it with mplayer using
> > 
> > mplayer -ao alsa:device=headset
> > 
> > Since mplayer sees the device directly, it sends the sound stream as
> > 
> > AO: [alsa] 800Hz 1ch s16le (2 bytes per sample)
> 
> 800? Uh? 

Transcription error; should be 8000Hz

> > And everything sounds fine.
> > 
> > When I plug it into pulseaudio with
> > 
> > pactl load-module module-alsa-sink device=headset
> > 
> > It correctly picks up the sample rate and channels.  However, trying to
> > switch an application to it results in dramatic speed increases and the
> > output being chopped to pieces.  If I set up pulseaudio only to have
> > this device and nothing else, mplayer plays the sound file at at least
> > 2x the usual speed.
> > 
> > Since the output has this:
> > 
> > AO: [pulse] 44100Hz 2ch s16le (2 bytes per sample)
> > 
> > I suspect the problem is somewhere in the pulseaudio resampling down
> > from 2 channels at 44100Hz to a single channel at 8000Hz.  I've tried
> > forcing different resampling methods with slightly different sounding
> > results but still playing at at least 2x the speed.
> 
> The current BT for ALSA code is not really that good for doing
> timing. Which is mostly BT's fault, not ALSAs or the driver's
> code. We're working on some better way to directly hook up BT with PA,
> which will hopefully also allows us to do fancier timing/latency estimation:
> 
> See
> https://tango.0pointer.de/pipermail/pulseaudio-discuss/2008-June/001909.html
> for more details.
> 
> I don't have no SCO device, so my priority right now is to get PA/BT
> to play together directly, instead of trying to fix the
> PA-on-ALSA-on-BT mess working. 

Hmm, OK ... it is strange that alsa by itself works fine ... it just
doesn't work with pulsaudio -> alsa.

James