[pulseaudio-discuss] [PATCH] Fix: Distorted audio during Bluetooth SCO HFP/HSP playback

[Georg Chini]

On 27.01.2017 21:40, Georg Chini wrote:
> On 03.01.2017 18:17, Tanu Kaskinen wrote:
>> On Thu, 2016-12-15 at 12:34 +0530, Renjith Thomas wrote:
>>> Issue: When HFP/HSP profile is used with certain BT chipsets, the
>>> audio sounds heavily distorted, with very slow playback full of noise.
>>> During recording, the samples are dropped and it distorts the recorded
>>> audio samples.
>>>
>>> The root cause of both the issues are related to the fixed MTU sizes
>>> in the PA stack, which is 48 bytes. Here, the BT chipset CC256x had
>>> 180 bytes MTU and it was being under-utilized and the rate at which
>>> the samples were being accepted where not matching the expected rate,
>>> and hence the distortion.
>>>
>>> Solution: The appropriate solution to this problem is by reading the
>>> MTU size of the SCO socket using getsockopts dynamically.
>>>
>>> BugLink: http://bit.ly/2gDpGPv
>>> BugLink: http://bit.ly/2hQsARK
>>> ---
>>>   src/modules/bluetooth/backend-native.c | 28 
>>> ++++++++++++++++++----------
>>>   1 file changed, 18 insertions(+), 10 deletions(-)
>> Thanks! Applied to the "next" branch.
>>
> Hi,
>
> this patch breaks HSP for me. My headset (Plantonics Backbeat Pro)
> returns an MTU of 64, but it looks like this is only working for 
> recording.
> When I try to play back something, I cannot hear any sound and the
> headset disconnects after a few seconds.
>
> When I set omtu to 48, everything is working again.
Tested a second headset - same result. The headset returns 64 as MTU
but only works if I set omtu to 48. Should the patch be reverted or modified
to change only imtu? Can anyone else confirm my problem?

Regards
              Georg