[pulseaudio-discuss] PA resampler issue with BT headset?

Zhang, Xing Z xing.z.zhang at intel.com
Tue Nov 4 01:19:05 PST 2008

Hi, I found below letter and met same problem with new BT module "module-bluetooth-device".
Mplayer play stream as
AO: [alsa] 44100HZ 2ch s16le (2 bytes per sample)
And BT headset works fine in ALSA.

When I choose to PA by
Load-module module-bluetooth-device sink_name=bt address=xx.xx.xx.xx.xx.xx profile=a2dp
the stream played at least 2x the speed as the letter said. The module picks up configure correctly as
    monitor source: 2
    sample spec: s16le 2ch 44100Hz
channel map: front-left,front-right

so I want to know is it a blueZ bug or PA bug due to Lennart said it's a BT bug

in reply to below letter.

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)

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.


Zhang Xin(Wing)
Intel, OTC ShangHai

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