Music Player Multizone Audio

[danry25]

Multiple different radio stations and songs should be able to be played concurrently when you have multiple audio output devices.

This enhancement awaits completion of issue #3, once that issue is complete, this issue can be worked on.

[mk-fg]

Implemented via JACK audio options, such as:

• jack-output-ports
• jack-music-client-name
• jack-music-links

ALSA usually provides many output devices with pretty much any modern sound card, e.g. (for crappy internal HDA):

% aplay -L
null
    Discard all samples (playback) or generate zero samples (capture)
pulse
    PulseAudio Sound Server
default
    Default ALSA Output (currently PulseAudio Sound Server)
sysdefault:CARD=SB
    HDA ATI SB, ID 440 Analog
    Default Audio Device
front:CARD=SB,DEV=0
    HDA ATI SB, ID 440 Analog
    Front speakers
surround21:CARD=SB,DEV=0
    HDA ATI SB, ID 440 Analog
    2.1 Surround output to Front and Subwoofer speakers
surround40:CARD=SB,DEV=0
    HDA ATI SB, ID 440 Analog
    4.0 Surround output to Front and Rear speakers
surround41:CARD=SB,DEV=0
    HDA ATI SB, ID 440 Analog
    4.1 Surround output to Front, Rear and Subwoofer speakers
surround50:CARD=SB,DEV=0
    HDA ATI SB, ID 440 Analog
    5.0 Surround output to Front, Center and Rear speakers
surround51:CARD=SB,DEV=0
    HDA ATI SB, ID 440 Analog
    5.1 Surround output to Front, Center, Rear and Subwoofer speakers
surround71:CARD=SB,DEV=0
    HDA ATI SB, ID 440 Analog
    7.1 Surround output to Front, Center, Side, Rear and Woofer speakers
hdmi:CARD=SB,DEV=0
    HDA ATI SB, ID 440 Digital
    HDMI Audio Output
hdmi:CARD=HDMI,DEV=0
    HDA ATI HDMI, HDMI 0
    HDMI Audio Output

Each can be plugged into jack via something like alsa_in -d hdmi:CARD=HDMI,DEV=0 (alsa_in is a binary that comes with jack-1, at least, iirc jack-2 has some different way of connecting extra hw).

Default "jack-output-ports" matches everything, so it'll match whatever that alsa_in creates and pjsua audio will be routed there, as well as audio from all players matched by "jack-music-client-name".

---

Can also be controlled which players get connected to which outputs.

For example, with mpd-1 output config like this:

audio_output {
  type "jack"
  name "jack"
  client_name "mpd.paging:player-1"
}

mpd-2 having "mpd.paging:player-2" there.

./paging.py --dump-jack-ports should list something like this (among other stuff):

  mpd.paging:player-1:right
    type: input (player or other sound source)
    uuid: ...
  mpd.paging:player-1:left
    type: input (player or other sound source)
    uuid: ...
  mpd.paging:player-2:right
    type: input (player or other sound source)
    uuid: ...
  mpd.paging:player-2:left
    type: input (player or other sound source)
    uuid: ...
  system:playback_1:left
    type: output (speakers, audio card or such)
... (you get the idea)

Default jack-music-client-name = ^mpd\.paging:(.*)$ will match all ports above as "player-{1,2}:{left,right}".

Then "jack-music-links" can be set to jack-music-links = player-1:left---playback_1:left player-1:right---playback_1:right player-2:left---playback_2:left player-2:right---playback_2:right to connect all these left-to-right.
paging.example.conf and README have more details on these.

A bit verbose in "jack-music-links", probably can be improved somehow.
For one player, default of jack-music-links = left---left right---right should connect all players to all speakers, left-to-left and right-to-right channel-wise, as thes thing on both sides of "---" are actually regexps, not exact matches.

[mk-fg]

jack-music-links is probably not that pretty, but I think this one should be done as well.

Anything on top should be glitter (such as less ugly config spec) and bugfixes (if stuff doesn't work).