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This is an attempt of breaking up the documentation, currently spread across several pages. We're left with a few high-level topics with various things grouped underneath those. Further refinement is necessary, but this can now be done in incremental steps over massive reworks.
73 lines
1.9 KiB
Plaintext
73 lines
1.9 KiB
Plaintext
/** \page page_pulseaudio PulseAudio compatibility
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# Internals - Mapping between ALSA and streams
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This explains the mapping between alsa cards and streams and session manager
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objects.
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## ALSA Cards
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An ALSA card is exposed as a PipeWire device
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## Streams
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Each alsa PCM is opened and a Node is created for each PCM stream.
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# Session Manager
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## ALSA UCM
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The mapping of the PipeWire object hierarchy to the ALSA object hierarchy is the following:
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One PipeWire device is created for every ALSA card.
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For each UCM verb, a Node is created for the associated PCM devices.
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For each UCM verb, an Endpoint is created.
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In a first step: For each available combination of UCM device and modifier,
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a stream is created. Streams are marked with compatible other streams.
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Streams with the same modifier and mutually exclusive devices are grouped
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into one stream and the UCM devices are exposed on the endpoint as destinations.
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## ALSA fallback
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Each PCM stream (node) becomes an endpoint. The endpoint references the
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alsa device id
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Each endpoint has 1 stream (for now) called HiFi Playback / HiFi Capture.
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More streams can be created depending on the format of the node.
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## ALSA pulse UCM
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Using the alsa backend of pulseaudio we can create the following streams
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## ALSA pulse fallback
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The pulse alsa backend will use the mixer controls and some probing to
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create the following nodes and endpoints
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# PulseAudio
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PulseAudio uses the session manager API to construct cards with profiles
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and sink/source with ports.
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If an Endpoint references a Device, a card object is created for the device.
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Each Endpoint becomes a sink/source.
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Each Stream in the endpoint becomes a profile on the PulseAudio card. Because
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only one profile is selected on the device, only 1 stream is visible on
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the endpoint. This clashes with the notion that multiple streams can be
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active at the same time but is a pulseaudio limitation.
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Each Endpoint destination becomes a port on the sink/source.
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*/
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