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GradedJestRisk edited this page Nov 11, 2020 · 25 revisions

Table of Contents

General

Test sound: espeak hello

Overview

Layers:

  • sound card device drivers API
    • Advanced Linux Sound Architecture - ALSA
    • Open Sound System - OSS
  • sound devices API (sound server), allowing mixing
    • Pulse
    • JACK: real-time, low-latency connections (you'll neeed a real-tipe kernel)

Hardware

To listed sound devices, including: - embeded soundcard (here Intel) - USB microphone (here, Yeti) - external soundcard (here, AudioEngine)

sudo lshw -class multimedia 

[sudo] password for topi: 
  *-usb:0                   
       description: Audio device
       product: Yeti Stereo Microphone
       physical id: 3
  *-usb:0
       description: Audio device
       product: Audioengine HD3
       physical id: 2
  *-multimedia
       description: Audio device
       product: Sunrise Point-LP HD Audio
       physical id: 1f.3

ALSA

ALSA: Advanced Linux Sound Architecture, API for sound card device drivers The sound servers PulseAudio work on top of ALSA and implements sound card device drivers.

overview here

General:

  • restart: sudo alsa force-reload
  • play file: aplay <FILE>
  • sound level control: alsamixer
  • get driver vi /proc/asound/oss/sndstat

Pulse

Deep dive

General:

  • GUI
    • control levels: pavucontrol (Playback tab: mute a window, change sink..)
  • config file are:
    • system-wide: /etc/pulse/default.pa
    • user: ~/.config/pulse/default.pa

No sound ?

General:

  • check if running: pulseaudio --check
  • show logs: pulseaudio --verbose (-v)
  • stop : pulseaudio --kill (-k)
  • restart:
    • as service: systemctl --user restart pulseaudio.service
    • as dameon: pulseaudio --daemon (-D)
  • if problem persists, consider ALSA

Sinks, sources, streams

Glossary:

  • input hardware device (eg. microphone) is called a source
  • output hardware device (eg. loudspeaker) is called a sink
  • actual data exchange between application throught Pulse is called a stream
List:
  • sink:
    • pacmd list-sink-inputs
    • pactl list short sinks
  • sources:
    • pacmd list-sink-sources
    • pactl list short sources
  • ingoing (sink) streams
    • list-sink-inputs
Sample of pactl list short sinks output 
1	alsa_output.usb-Audioengine_Audioengine_HD3_B40020170802-00.iec958-stereo	module-alsa-card.c	s16le 2ch 48000Hz	IDLE
2	alsa_output.usb-Blue_Microphones_Yeti_Stereo_Microphone_797_2019_09_27_71466-00.iec958-stereo	module-alsa-card.c	s16le 2ch 48000Hz	IDLE
3	alsa_output.pci-0000_00_1f.3.analog-stereo	module-alsa-card.c	s16le 2ch 48000Hz	IDLE

Sample of pactl list short sources 

1	alsa_output.usb-Audioengine_Audioengine_HD3_B40020170802-00.iec958-stereo.monitor	module-alsa-card.c	s16le 2ch 48000Hz	RUNNING
2	alsa_output.usb-Blue_Microphones_Yeti_Stereo_Microphone_797_2019_09_27_71466-00.iec958-stereo.monitor	module-alsa-card.c	s16le 2ch 48000Hz	RUNNING

Set device

From here

Input (source)

List:

  • get: pactl list short source
  • set default for current session (lost at reboot): pactl set-default-source'<SOURCE_NAME>'

Output (sink)

List:

  • set default for current session (lost at reboot): pactl set-default-sink '<SINK_NUMBER>'

Default sinks and sources

Get

List:

  • default sink: pacmd info | grep 'Default sink'
  • default source: pacmd info | grep 'Default source'

Set

Session level

Set default for current session (lost at reboot):

  • source: pactl set-default-source <SOURCE_NUMBER>
  • sink: pactl set-default-sink '<SINK_NUMBER>'
See here to change this while playing

System level

Edit system-wide pulse configuration sudo vi /etc/pulse/default.pa

Uncomment the following lines 

### Make some devices default
#set-default-sink output
#set-default-source input

Replace output/input by their values 

### Make some devices default
set-default-sink 1
set-default-source 2

Delete user pulse config rm -rf ~/.config/pulse

Reboot

Modules

General:

  • list modules: pactl list short modules
  • load module: pactl load-module <MODULE_NAME>
  • unload module: pactl unload-module <MODULE_NAME>
Modules:
  • loopback (hear your voice): pactl load-module module-loopback latency_msec=1

GNOME

List:

Multiple soundcard

Identify soundcards

Use aplay --list-devices (Alsa play) 

aplay --list-devices
**** List of PLAYBACK Hardware Devices ****
card 0: HD3 [Audioengine HD3], device 0: USB Audio [USB Audio]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: Microphone [Yeti Stereo Microphone], device 0: USB Audio [USB Audio]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 2: PCH [HDA Intel PCH], device 0: CX8200 Analog [CX8200 Analog]

So we've got:

  • an external USB soundcard on card 0, device 0
  • a USB microphone on card 1, device 0
  • an embedded USB soundcard on card 2, device 0 (you can't guess it from output, but by unplugging everything and running again)

Check both soundcard work correctly

Some soundcard may not work from the start.

Here's an example. For the sake of completeness I include a test.

To play sound file, we'll use ALSA playback tool aplay

We'll tell aplay> to send the sound to each soundcards trough a <SOUNDCARD>,<DEVICE> pattern aplay -Dhw:<SOUNDCARD>,<DEVICE>, eg aplay -Dhw:0,0 for internal USB

To avoid such hassle, I used environment variable 

EXTERNAL_SOUNDCARD=0,0
INTERNAL_SOUNDCARD=2,0

Testing 44Khz standard sample rate 

curl https://www.kozco.com/tech/organfinale.wav > organ-13s-44khz.wav
aplay -Dhw:$INTERNAL_SOUNDCARD organ-13s-44khz.wav
aplay -Dhw:$EXTERNAL_SOUNDCARD organ-13s-44khz.wav

Testing 48kHz sample rate 

curl https://www.kozco.com/tech/organfinale.wav > organ-13s-44khz.waw
aplay -Dhw:$INTERNAL_SOUNDCARD Piano-7s-48khz.wav
aplay -Dhw:$EXTERNAL_SOUNDCARD Piano-7s-48khz.wav

Note: aplay --rate argument does NOT modify input sample rate. Rather, it overwrite detected sample rate. From manual 

For supported soundfile formats, the sampling rate, bit depth, and so forth can be automatically determined from the soundfile header.

The detected sample is displayed while playing, here 48Khz 

Playing WAVE 'Piano-7s-48khz.wav' : Signed 16 bit Little Endian, Rate 48000 Hz, Stereo

Check default soundcard in applications

Check with alsa player aplay organ-13s-44khz.wav

Check with external player 

sudo apt install sox    
play organ-13s-44khz.wav

Check on browser (Firefox / Chrome / Chromium behaviour vary)

You can alter output on browser (or nay application) if needed with Pulse Audio control, section "Playback" pavucontrol
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