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d2046adcd1
Although it's a valid UCM configuration to have multiple devices using
the same PlaybackPCM or CapturePCM, it's unclear how PulseAudio should
handle the cases where multiple of these devices are enabled. Some
options I can think of are:
- Merge all devices sharing the same PCM into the same mapping, open
only one PCM substream for this mapping, and add 'combination ports'
that enable combinations of the devices. This has been the case until
recently, although the combination port logic was broken. A problem
with this is that we can't independently control device volumes. We
most likely cannot use hardware volumes either.
- Have one mapping for each device in the same profile, and open one PCM
substream for each mapping. This is the current state, and it fails
when there are fewer substreams than devices. Otherwise it works, but
it's still confusing, as sound directed to a device-specific mapping
might end up playing at multiple devices.
- Make multiple profiles each with combinations of upto-substream-count
devices, and have one mapping/substream per device. This still causes
the confusion mentioned above. And it's likely that the substream
count will almost always be one, where this case degenerates into the
last one.
- Have one mapping for each device in the same profile, but open only
one PCM substream. I assume this is possible with software mixing, but
it is still confusing like the above, and probably less performant.
- Generate multiple profiles each with one of the shared-PCM devices,
again with one mapping/substream for that one device. The trade-off
with this is that we can't use multiple of these devices at the same
time. However, this doesn't have the output device confusion,
combination port's volume problems, or the substream count limitation.
This patch takes a short-cut to achieve the last option, by considering
shared-PCM devices implicitly conflicting with each other.
Link:
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|---|---|---|
| .. | ||
| acp | ||
| mixer | ||
| 90-pipewire-alsa.rules | ||
| acp-tool.c | ||
| alsa-acp-device.c | ||
| alsa-compress-offload-device.c | ||
| alsa-compress-offload-sink.c | ||
| alsa-pcm-device.c | ||
| alsa-pcm-sink.c | ||
| alsa-pcm-source.c | ||
| alsa-pcm.c | ||
| alsa-pcm.h | ||
| alsa-seq-bridge.c | ||
| alsa-seq.c | ||
| alsa-seq.h | ||
| alsa-udev.c | ||
| alsa.c | ||
| alsa.h | ||
| compress-offload-api-util.c | ||
| compress-offload-api-util.h | ||
| compress-offload-api.c | ||
| compress-offload-api.h | ||
| meson.build | ||
| test-hw-params.c | ||
| test-timer.c | ||