Sound - Simultaneous Output - Nearly Working - HELP

redger · November 30, 2016 at 2:38 PM

I have a Pi 2 with an attached USB sound card. I'd like sound through both of them at the same time.
I can make it work by creating a new Alsa definition and then adding that definition to Pulseaudio.
The problem is that I can only use the newly defined Pulse device when (a) I manually define it via pactl (b) restart kodi using "pkill -9 kodi.bin"

/storage/.config/asound.conf is as follows

Code

# Define pihdmi as a destination (for our duplication)
pcm.pihdmi {
   type hw
   card 0
   device 1
}
ctl.pihdmi {
   type hw
   card 0
   device 1
}


#
# Define usbcm106 as a destination (for our duplication)
pcm.usbcm106 {
   type hw
   card 1
   device 0
}
ctl.usbcm106 {
   type hw
   card 1
   device 0
}


#
pcm.usbmulti {
   type multi
   slaves.a.pcm "pihdmi"
   slaves.b.pcm "usbcm106"
   slaves.a.channels 2
   slaves.b.channels 2


   bindings.0.slave a
   bindings.0.channel 0     # bind alsa channel 0 to front left
   bindings.1.slave a
   bindings.1.channel 1     # bind alsa channel 1 to front right


   bindings.2.slave b
   bindings.2.channel 0     # bind alsa channel 2 to front left
   bindings.3.slave b
   bindings.3.channel 1     # bind alsa channel 3 to front right
}
#
pcm.usbcopy {
 type route
 slave.pcm "usbmulti"
 slave.channels 4


 # syntax for ttable is "ttable.inputchannel.outputchannel volume"


 # First send info to Slave A (HDMI = 2 channel)
 ttable.0.0 1                 # Copy input channel 0 to output channel 0 ie. Slave A channel 0 at 100% volume
 ttable.1.1 1


 # Now send info to Slave B (usbcm106 = 6 channel)
 ttable.0.2 1                 # Copy input channel 0 (front left) to output channel 2 ie. Slave B channel 0 (front left) at 100% volume
 ttable.1.3 1                 # Copy input channel 1 (front left) to output channel 3 ie. Slave B channel 1 (front right) at 100% volume


}


#
pcm.usbboth {
 type plug
 slave.pcm "usbcopy"
 hint {
     show on
     description "Multichannel output to both usb device and hdmi"
   }
}

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Then I define the Pulseaudio elements in /storage/.conf/autostart.sh

Code

# Set devices for Pulseaudio
pactl load-module module-alsa-sink device=hw:0,1 channels=2
pactl load-module module-alsa-sink device=hw:1,0 channels=2


pactl load-module module-combine-sink slaves=alsa_output.hw_0_1,alsa_output.hw_1_0


pactl load-module module-alsa-sink device=plug:usbboth

Sadly the final load of "usbboth" doesn't do anything.

On the other hand if I log in via ssh and then issue

Code

pactl load-module module-alsa-sink device=plug:usbboth
pkill -9 kodi.bin

When kodi restarts (auto-magically) I can now select a new audio device. The ALSA:bcm2836 ALSA, bcm2835 IEC958/HDMI device actually sends sound to both the PI built in HDMI and the USB card (furthermore passthrough to both seems to work too, an unexpected bonus)

PROBLEM: How can I automate this so the Pulseaudio device is loaded/created at boot time ???
Is this a sequencing problem, or is there something else occurring ?

Note that combine-sink is created successfully at boot time and can be used by Kodi. The problem with the combined sink is that it induces so much audio delay that it's basically unuseable (unpleasant anyway

Any help gratefully appreciated

**lrusak** · November 30, 2016 at 5:51 PM Official Post

you don't need the asound.conf at all

use

Code

dtparam=audio=on

in you config.txt, this will load the rpi alsa module.

Then you can just use pulseaudio to load the 'udev-detect' module, then make the combined sink

redger · November 30, 2016 at 9:49 PM

Thanks for the response.
Yes, I have set dtparam=audio=on. Alsa is loaded at boot and the new plugin appears immediately after boot in the list generated by aplay -L ie.

Code

OE-Pi3:~ # aplay -L
null
   Discard all samples (playback) or generate zero samples (capture)
usbboth
   Multichannel output to both usb device and hdmi
default:CARD=ALSA
   bcm2835 ALSA, bcm2835 ALSA
   Default Audio Device
sysdefault:CARD=ALSA
   bcm2835 ALSA, bcm2835 ALSA
   Default Audio Device
default:CARD=Device
   USB Sound Device, USB Audio
   Default Audio Device
sysdefault:CARD=Device
   USB Sound Device, USB Audio
   Default Audio Device
front:CARD=Device,DEV=0
   USB Sound Device, USB Audio
   Front speakers
surround21:CARD=Device,DEV=0
   USB Sound Device, USB Audio
   2.1 Surround output to Front and Subwoofer speakers
surround40:CARD=Device,DEV=0
   USB Sound Device, USB Audio
   4.0 Surround output to Front and Rear speakers
surround41:CARD=Device,DEV=0
   USB Sound Device, USB Audio
   4.1 Surround output to Front, Rear and Subwoofer speakers
surround50:CARD=Device,DEV=0
   USB Sound Device, USB Audio
   5.0 Surround output to Front, Center and Rear speakers
surround51:CARD=Device,DEV=0
   USB Sound Device, USB Audio
   5.1 Surround output to Front, Center, Rear and Subwoofer speakers
surround71:CARD=Device,DEV=0
   USB Sound Device, USB Audio
   7.1 Surround output to Front, Center, Side, Rear and Woofer speakers
iec958:CARD=Device,DEV=0
   USB Sound Device, USB Audio
   IEC958 (S/PDIF) Digital Audio Output

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The challenge is that the key pulse sink can only be created manually after boot. All the others are created successfully during boot as shown by pactl list sinks short ie.

Code

OE-Pi3:~ # pactl list sinks short
1       alsa_output.hw_0_1      module-alsa-sink.c      s16le 2ch 44100Hz       SUSPENDED
2       alsa_output.hw_1_0      module-alsa-sink.c      s16le 2ch 44100Hz       SUSPENDED
3       combined        module-combine-sink.c   s16le 2ch 44100Hz       SUSPENDED
OE-Pi3:~ #

This is even after (a) the autostart.sh entries above AND (b) creating similar entries in /storage/.config/pulse-daemon.conf.d/99-default.conf ie.

Code

load-module module-alsa-sink device=hw:0,1 channels=2
load-module module-alsa-sink device=hw:1,0 channels=2
load-module module-combine-sink slaves=alsa_output.hw_0_1,alsa_output.hw_1_0
load-module module-alsa-sink device=plug:usbboth

Once the machine is booted I can successfully manually add the usbboth plugin to Pulse ...

Problem How do I ensure Pulseaudio recognises and creates the usbboth sink during the boot procedure ?

Thanks for your advice

**lrusak** · November 30, 2016 at 10:57 PM Official Post

I'm saying you don't need any of the asound.conf

simply

Code

pactl load-module module-udev-detect
pactl load-module module-compine-sink slaves=alsa_output.platform-soc_audio.analog-stereo,<some-other-alsa-device>

redger · December 1, 2016 at 3:22 AM

yes, thanks. I still need the asound.conf for channel mapping because the 2 device display a different number of channels and I couldn't make that work directly with Pulse combin-sink

It's working now

here's the final asound.conf

Code

# Define pihdmi as a destination (for our duplication)
pcm.pihdmi {
    type hw
    card 0
    device 1
}
ctl.pihdmi {
    type hw
    card 0
    device 1
}


#
# Define usbcm106 as a destination (for our duplication)
pcm.usbcm106 {
    type hw
    card 1
    device 0
}
ctl.usbcm106 {
    type hw
    card 1
    device 0
}


#
pcm.usbmulti {
    type multi
    slaves.a.pcm "pihdmi"
    slaves.b.pcm "usbcm106"
    slaves.a.channels 2
    slaves.b.channels 2


    bindings.0.slave a
    bindings.0.channel 0     # bind alsa channel 0 to front left
    bindings.1.slave a
    bindings.1.channel 1     # bind alsa channel 1 to front right


    bindings.2.slave b
    bindings.2.channel 0     # bind alsa channel 2 to front left
    bindings.3.slave b
    bindings.3.channel 1     # bind alsa channel 3 to front right
}
#
pcm.usbcopy {
  type route
  slave.pcm "usbmulti"


  # syntax for ttable is "ttable.inputchannel.outputchannel volume"


  # First send info to Slave A (HDMI = 2 channel)
  ttable.0.0 1                 # Copy input channel 0 to output channel 0 ie. Slave A channel 0 at 100% volume
  ttable.1.1 1


  # Now send info to Slave B (usbcm106 = 6 channel)
  ttable.0.2 1                 # Copy input channel 0 (front left) to output channel 2 ie. Slave B channel 0 (front left) at 100% volume
  ttable.1.3 1                 # Copy input channel 1 (front left) to output channel 3 ie. Slave B channel 1 (front right) at 100% volume
}
#
pcm.usbboth {
  type plug
  slave.pcm "usbcopy"
  hint {
      show on
      description "Multichannel output to both usb device and hdmi"
    }
}

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here's the final autostart.sh

Bash

#!/bin/bash
# ...... other "stuff" in here (mostly lirc)
# Set devices for Pulseaudio
pulseaudio -k
pkill -9 kodi.bin
pulseaudio --system
sleep 2
#
pactl load-module module-udev-detect
pactl load-module module-alsa-sink device=hw:0,1 channels=2
pactl load-module module-alsa-sink device=hw:1,0 channels=2
pactl load-module module-combine-sink slaves=alsa_output.hw_0_1,alsa_output.hw_1_0
pactl load-module module-alsa-sink device=plug:usbboth
#
sleep 10

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I needed to

Stop pulse and restart it before doing anything else. For whatever reason this makes the process consistent. Then restart pulse manually. Actually not sure I needed to stop it first
Stop Kodi just in case. Probably not necessary, but didn't seem to do any harm so I've kept it
"sleep" statements to slow the process down before Kodi starts. For some reason it takes Pulse a while to create the combined sink and kodi had been starting in the meantime so it didn't read & recognise the new sink

Additionally, in Kodi we then set the following in system settings/audio output/ -
Audio Output Device = "ALSA: bcm2835, bcm2835 IEC958/HDMI"
Number of Channels = 2
Enable Passthrough = true
Passthrough Output Device = "ALSA: USB Sound Device, S/PDIF"
AC3 Capable = true
DTS Capable = true

Try some AC3 and DTS files, plus some stereo.
Stereo will play through both the TV and the Amp, but AC3 and DTS will only play through the amp (tv limitation)
We could make everything always play through both by setting Passthrough OFF ... this compromises quality BUT provides greater consistency of experience (WAF ?)

I've tried a few reboots and the setup seems to consistently provide the same result (not necessarily a given due to timing issues)