[pulseaudio-discuss] Problems with Pulseaudio and Bluetooth Headset

[Lennart Poettering]

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? 

> 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. 

Stay tuned.

Lennart

-- 
Lennart Poettering                        Red Hat, Inc.
lennart [at] poettering [dot] net         ICQ# 11060553
http://0pointer.net/lennart/           GnuPG 0x1A015CC4