Table of Contents
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Audio
See also:
- dBu and dbm, dbV, dbv
- Gain structure: input and output levels
Filelocations
/usr/share/sounds/freedesktop/stereo/*.oga (play with sox's play)
Playback
Sox
To playback a mp3 file with sox's play program libsox-fmt-mp3 must be installed
Record
arecord filename.wav
From a stream
- Open Start > Multimedia > Sound Recorder (maybe install it first: gnome-sound-recorder)
- Start Volume Control: Open Start > Multimedia > Volume Control (pavucontrol)
- In the tab “Input Devices” make “Monitor of Build-in Audio Analog Stereo” active (unmute)
- Start recording
- Start the audio stream
- When the audio stream is finished stop recording
- The recording, a FLAC file, can be found in $HOME/Recordings
S/PDIF
S/PDIF is IEC 60958 type II (IEC 958 before 1998)
Some more programs
- audiolink
- The, for the command line, audiotools package
- multimedia-audio-utilities package
aumix
aumix -v q -b q -c q -i q -l q -m q -o q -p q -r q -s q -t q -w q -W q -x q -1 q -2 q -3 q show the status of all devices aumix can handle:
| Option | Output | Remark |
|---|---|---|
| -v | vol 50, 50 | |
| -b | bass 0, 0 | |
| -c | cd 0, 0 | |
| -i | igain 100, 100 | |
| -l | line 0, 0 | |
| -m | mic 0, 0 | |
| -o | ogain 0, 0 | |
| -p | speaker 0, 0 | |
| -r | rec 0, 0 | |
| -s | synth 0, 0 | |
| -t | treble 0, 0 | |
| -w | pcm 0, 0 | |
| -W | pcm2 0, 0 | |
| -x | mix 0, 0 | |
| -1 | line1 0, 0 | |
| -2 | line2 0, 0 | |
| -3 | line3 0, 0 | |
| aumix -q | dig1 100, 100 | As mentioned in the man page does not work (for us). We expeceted the levels for all items |
Mute
Mute the sound for three minutes:
amixer set Master mute 1> /dev/null; sleep 3m; amixer set Master unmute 1> /dev/null; xmessage -buttons OK -default OK -timeout 20 "Sound is back again!"
ALSA
If you want to work in a terminal you can use alsamixer for volume settings. It has some other, different, settings
ALSA commands
- alsaplayer - plays various sound files
- alsamixer
- alsactl - advanced controls for ALSA soundcard driver. root or sudo needed
- alsabat - command-line sound tester for ALSA sound card driver
- alsaloop - allows to create a PCM loopback between a PCM capture device and a PCM playback device
- alsatplg - ALSA Topology Compiler
- alsaucm - (ALSA Use Case Manager) is a program to use the ALSA Use Case Interface from the command line.
ALSA related packages
- alsa-utils
- alsa-ucm-conf
- alsa-topology-conf
- alsa-oss
- alsa-tools
- alsa-tools-gui
- alsamixergui
- alsaplayer-alsa
- alsaplayer-common
- alsaplayer-gtk
- alsaplayer-daemon
- alsaplayer-jack
- alsaplayer-nas
- alsaplayer-oss
- alsaplayer-text
- alsaplayer-xosd
- alsa-firmware-loaders
Root or sudo needed: alsabat-test, alsa-info
PulseAudio
PulseAudio is a network-capable sound server program
Debian on PulseAudio
Controls
CLI tools and man pages
| default.pa | PulseAudio Sound Server Startup Script |
| pacmd | Reconfigure a PulseAudio sound server during runtime |
| pactl | Control a running PulseAudio sound server |
| pulse-cli-syntax | PulseAudio Command Line Interface Syntax |
| pulseaudio | The PulseAudio Sound System |
| pulseaudio-ctl |
VU meter
The “PulseAudio Volume Meter” is a GUI vu meter program. In the terminal it is called pavumeter. If you do not need it your can uninstall it. Do aptitude uninstall pavumeter
Volume Control
This is part of PulseAudio
In this context pavucontrol = Volume Control = “Audio Mixer…“
This is the pavucontrol program which is part of the PulseAudio sound server system
The pavucontrol program has this 
icon. You can find it in or add it to the system tray. Left clicking brings you to some settings. You can also open Volume Control, here called “Audio Mixer…”, by right clicking on icon. “Audio Mixer…” is on the bottom line
The slider in the Playback tab can only have the same or a lower position then the slider in the Output Devices tab. If you slide the slider in the Playback tab above the value of the slider in the Output Devices tab the slider in the Output Devices tab will follow the slider in the Playback tab. They then have the same level set
We do not advice to use this icon. It can be confusing when you control the volume with it. We advice to use the Volume Control program in its own window
Analog Stereo Duplex: Both Input and Output are active
The Volume Control window has 5 tabs:
| Tab | Function | Remark |
|---|---|---|
| Playback | A list of programs producing sound | Like mpv and Firefox. For every program which is playing sound or is paused or has, like Firefox can have, a tab open which plays, is paused and / or muted or has played sound you can find an entry here. Programs can disappear from the list when they are done playing the sound or are closed. Here you can also select on which Output Device (third tab, Output Devices) the sound should be played |
| Recording | Here you can see the programs which are running and can record audio | You can select the device of which the audio should be recorded from from the roll down menu on the right side |
| Output Devices | A list of the hardware devices in or on the computer | Like a soundcard on the motherboard, a soundcard in a PCI or PCIe slot on the motherboard or an USB soundcard. Here you can also select on which soundport the sound is offered like Speakers, Line Out (mostly a 3,5 mm jack connector) or Headphones (mostly a 3,5 mm jack connector). Advice: Set the volume here to 100% and adjust the volume in “Playback” to you needs |
| Input Devices | A list of the hardware devices which can record audio. It is possible that a device also has a Monitor function | Check if the device is unmuted if you want to use it |
| Configuration | A list of devices. Here you can select the output modus or switch the device off | Some options which can be found here: Off, Analog Stereo Duplex, Analog Stereo Input, Analog Stereo Output |
Setting the volume
This can be done in or on
- the amplifier
- the computer
- In the tab Playback with the slider of the device or stream which is playing
- When you set the volume with the tray
icon the volume of all the channels in this tab is set accordingly. So it is better not to use the tray icon for volume control if you have more then one device or stream playing or open
- In the tab Output devices with the slider of the device or stream which is playing
- This is also what you see and can adjust from the tray icon
Audio mixers and Interfaces
In general:
Audio mixers and Audio Interfaces with an USB connection do not deliver enough signal level
On a mixer much more signal level can be obtained via the analog, Main Out, connection
The advantage of an audio interface can be a higher sampling rate and a nicer box. A mixer has more options and a higher analog signal output
FX
The FX signal from the individual channels on a mixer is added up in the Fx send output of the mixer. From there it can be connected to an external effects unit which is most commonly a reverb unit. You can have a look at this video on Youtube to get an idea
Pad button
The PAD button will reduce the input gain on your channel by a fixed amount of usually 20-26dB. This prevents distortion by loud input signals because which can overload the pre-amplifier and thereby cause clipping of the signal
In schematic
Input > PAD circuit > Pre-amplifier > The other parts of the mixer
Stream
How to stream music over the network to multiple computers with PulseAudio:
- Install paprefs
- Start > Settings > PulsAudio preferences
- Tab Network access > Make discoverable PulseAudio network sound devices available locally > On
- Allow other machines on the LAN to discover local sound devices > On
- Don't require authentication > On
- Tab Network Server > Enable network access to local sound devices > On
- Tab Multicast/RTP > Multicast/RTP receiver > On
- In /etc/pulse/default.pa uncomment:
- load-module module-esound-protocol-tcp
- load-module module-native-protocol-tcp
- load-module module-zeroconf-publish
- For RTP sender uncomment:
- load-module module-null-sink sink_name=rtp format=s16be channels=2 rate=44100 description=“RTP Multicast Sink”
- load-module module-rtp-send source=rtp.monitor
- Optimizing sound qualitity in the /etc/pulse/daemon.conf
- On the client run mpg123 http://serverIP:serverPort
Try Pipewire
Useful links
Solving a headphone issue
Change default Pulseaudio profile to analog stereo duplex
aplay card and device selection with aplay -l and aplay -L
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