[pulseaudio-discuss] Timing interval for Bluetooth Wideband speech

Tanu Kaskinen tanuk at iki.fi
Fri Mar 16 19:56:02 UTC 2018

On Thu, 2018-03-15 at 14:49 +0530, Sathish Narasimman wrote:
> Hi,
> I would like to know the PulseAudio module that is responsible for pushing
> the audio for every 1 millisecond.
> For NBS the packets are pushed with 48bytes and 1milli sec interval.

Where does this 1 ms interval come from? The audio that pulseaudio
writes with SCO is mono, 16-bit, 8000 Hz. With that specification 48
bytes means 3 ms packets, not 1 ms.

> But for WBS the timing between 2 SCO packets needs to be *7.5 Milli Sec.*
> *May I know how to change the packet interval between the 2 SCO packets.*

The write_block_size variable in src/modules/bluetooth/module-bluez5-
device.c controls how big packets pulseaudio writes. That in turn is
calculated based on write_link_mtu, and that comes from the transport
acquire() callback. The ofono backend always returns 48 bytes. The
native backend returns 48 bytes by default, but it can also be
configured to ask the kernel what the real MTU is.



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