[pulseaudio-discuss] HDMI support

[pl bossart]

If I use HDMI to connect to a receiver, the number of supported channels
depends on the number of speakers and the capabilities of the receiver. The
HDMI protocol provides a means for the receiver to let the transmitter know
its speaker configuration, but so far you cannot query it from ALSA, there's
just no interface for this. Your best bet is to try to open the device with
an increasing number of channels and see when it stops working.

When I look at the PulseAudio code in alsa-utils.c , it looks like the HDMI
profile is set to two channels, if more channels are requested the device
selected will be the first surroundxx profile that is a superset of the
channel map.
Now I have the following questions:
- First is my understanding correct?
- Does this solution entail any configuration of  /etc/asound.conf to link
surroundxx with the HDMI device number? And if this is the case, how
compatible is this with hot-plug (depending on the order in which I plug all
the audio devices the number could be different).
- last, if the number of speakers on the receiver side is smaller than the
number of channels requested, who does the required downmix?

Thanks for your help.
- Pierre
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