[pulseaudio-discuss] RME Babyface Pro: How do I get pulseaudio to see output 3/4?

[Tanu Kaskinen]

On Mon, 2016-10-24 at 10:09 -0400, Allan Wind wrote:
> I frequently switch between monitors (output 1/2) and headphones (output 3/4),
> and doing so on hardware is a 2 or 3 step process, so I was hoping there is a
> way to get pulseaudio to see output 3/4.
> 
> Here is what the relevant sink from pactl:
> 
> Sink #29
>         State: RUNNING
>         Name: alsa_output.usb-RME_Babyface_Pro__70793162__926E13156329DC8-00.analog-stereo
>         Description: Babyface Pro (70793162) Analog Stereo
>         Driver: module-alsa-card.c
>         Sample Specification: s24le 2ch 44100Hz
>         Channel Map: front-left,front-right
>         Owner Module: 48
>         Mute: no
>         Volume: front-left: 65807 / 100% / 0.11 dB,   front-right: 65807 / 100% / 0.11 dB
>                 balance 0.00
>         Base Volume: 65536 / 100% / 0.00 dB
>         Monitor Source: alsa_output.usb-RME_Babyface_Pro__70793162__926E13156329DC8-00.analog-stereo.monitor
>         Latency: 9333 usec, configured 8000 usec
>         Flags: HARDWARE DECIBEL_VOLUME LATENCY 
>         Properties:
>                 alsa.resolution_bits = "24"
>                 device.api = "alsa"
>                 device.class = "sound"
>                 alsa.class = "generic"
>                 alsa.subclass = "generic-mix"
>                 alsa.name = "USB Audio"
>                 alsa.id = "USB Audio"
>                 alsa.subdevice = "0"
>                 alsa.subdevice_name = "subdevice #0"
>                 alsa.device = "0"
>                 alsa.card = "1"
>                 alsa.card_name = "Babyface Pro (70793162)"
>                 alsa.long_card_name = "RME Babyface Pro (70793162) at usb-0000:00:14.0-6, high speed"
>                 alsa.driver_name = "snd_usb_audio"
>                 device.bus_path = "pci-0000:00:14.0-usb-0:6:1.0"
>                 sysfs.path = "/devices/pci0000:00/0000:00:14.0/usb1/1-6/1-6:1.0/sound/card1"
>                 udev.id = "usb-RME_Babyface_Pro__70793162__926E13156329DC8-00"
>                 device.bus = "usb"
>                 device.vendor.id = "2a39"
>                 device.vendor.name = "RME"
>                 device.product.id = "3fb0"
>                 device.product.name = "Babyface Pro (70793162)"
>                 device.serial = "RME_Babyface_Pro__70793162__926E13156329DC8"
>                 device.string = "front:1"
>                 device.buffering.buffer_size = "529200"
>                 device.buffering.fragment_size = "264600"
>                 device.access_mode = "mmap+timer"
>                 device.profile.name = "analog-stereo"
>                 device.profile.description = "Analog Stereo"
>                 device.description = "Babyface Pro (70793162) Analog Stereo"
>                 alsa.mixer_name = "USB Mixer"
>                 alsa.components = "USB2a39:3fb0"
>                 module-udev-detect.discovered = "1"
>                 device.icon_name = "audio-card-usb"
>         Ports:
>                 analog-output: Analog Output (priority: 9900)
>         Active Port: analog-output
>         Formats:
>                 pcm
> 
> I was able to see all 12 inputs in ardour.  `aplay -L` looks... well, not quite
> right, this is multi-channel and not a surround card:

Does the card have any profiles that would have more channels than just
two? You can see the available profiles with "pactl list cards" or in
pavucontrol's "Configuration" tab.

If there are profiles with more channels, they will anyway be surround
oriented, but that's still better than having just a 2-channel sink
available. If such profiles aren't available, you'll have to write the
profile configuration yourself.

Once you have a 4-channel sink available, you'll need to use module-
remap-sink to create virtual stereo sinks on top of the 4-channel sink.
There's an example for doing that in the module-remap-sink
documentation:

https://wiki.freedesktop.org/www/Software/PulseAudio/Documentation/User/Modules/#index12h3

It would be nice to be able to split multichannel sinks into multiple
stereo sinks in some more straightforward way, but currently such
feature doesn't exist.

-- 
Tanu