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alsa pcm plugin: minor man page additions
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borine committed Dec 19, 2024
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23 changes: 13 additions & 10 deletions doc/bluealsa-plugins.7.rst
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Expand Up @@ -105,10 +105,10 @@ PCM Parameters
softvol value. The default value is **unchanged**.

HWCOMPAT
Modifies the behaviour of the plugin on ``a2dp-sink``, ``hfp-hf`` and
Modifies the behavior of the plugin on ``a2dp-sink``, ``hfp-hf`` and
``hsp-hs`` nodes in order to align better with the behaviour of the ALSA
``hw`` plugin. This is a string option which takes the values **"none"**,
**"busy"** or **silence**.
``hw`` plugin. This is a string option which takes the values **none**,
**busy** or **silence**.
See `Transport acquisition`_ in the **NOTES** section below for more
information.

Expand Down Expand Up @@ -580,12 +580,12 @@ transfer when the plugin starts the PCM.
When used on an A2DP sink or HFP/HSP HF/HS node then **bluealsad(8)** must wait
for the remote device to acquire the transport. The ALSA PCM plugin state model
does not define any state that can be directly mapped to this situation, so
the BlueALSA PCM plugin offers a choice of behaviours to suit various
the BlueALSA PCM plugin offers a choice of behaviors to suit various
application requirements. The choice is selected using the parameter
**hwcompat** (**HWCOMPAT** argument to the pre-defined `bluealsa` PCM) which
takes the following values:
takes one of the following values:

- "none"
- none

By default during this waiting time the PCM plugin behaves as if the device
timer is stopped; it does not generate any poll() events, and the
Expand All @@ -597,19 +597,22 @@ takes the following values:
ones which attempt to manage latency such as ``alsaloop(1)``, may become
unstable in this situation.

- "busy"
- busy

Causes snd_pcm_open() to return immediately with error code **-EBUSY**
("Device or resource busy") on A2DP sink, HFP-HF and HSP-HS nodes if the
transport is not yet acquired. With this option the plugin also stops the
PCM stream and enters the **SND_PCM_STATE_DISCONNECTED** state if the
remote device releases the transport while in use.

- "silence"
- silence

Inserts silence for capture streams, or simply drops frames for playback
streams, whenever the transport is not acquired, thus maintaining a
continuous stream as far as the application is concerned.
streams, whenever the transport is not acquired. Short intervals of silence
may also be inserted into capture streams if there is a break in the
incoming stream (for example as a result Bluetooth link instability). By
this means a continuous stream is maintained as far as the application is
concerned, which matches the behavior of a hardware DAC.

PCM drain and non-blocking operation
------------------------------------
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