ALSA without PulseAudio and PipeWire

igorzwx · 2024-05-30 03:06:21

It is not difficult to remove PulseAudio and PipeWire.
The problem is how to configure a software mixer for ALSA.

Such mixer might be needed, if one wants to use ALSA just like MacOS users are using the sound system on MacBooks: for video conferencing with Discord or similar app, or playing HiRes audio files without distortions produced by crappy resamplers. This implies that the desired software mixer should have a high quality real-time codec (resampler and format converter).

These problems can be solved through the help of the fftrate plugin
https://github.com/PetrovSE/fftrate

Debian packages:

libasound2-plugin-fftrate_1.6.3_amd64.deb
alsa-config-utils_1.6.3_amd64.deb
pcm-utils_1.6.3_amd64.deb

They provide:

libasound_module_rate_fftrate.so — ALSA plugin (FFT resampler/converter)
arateconf  —  utility to generate ~/.asoundrc  
pcm_conv  —  standalone FFT resampler/converter

How to compile fftrate plugin

Install "build-essential", etc.

sudo apt update
sudo apt-get install build-essential git debhelper
sudo apt install libasound2-dev libasound2-plugins swh-plugins

Install gcc-10 and g++-10 from Devuan's oldstable repositories.

$ cat /etc/apt/sources.list | grep oldstable
# oldstable repositories
deb http://deb.devuan.org/merged oldstable main contrib non-free
deb-src http://deb.devuan.org/merged oldstable main contrib non-free

Enable the oldstable repositories and update

sudo apt update

$ apt search g* | grep "gcc-10/\|g++-10/"
g++-10/oldstable,now 10.2.1-6 amd64 
gcc-10/oldstable,now 10.2.1-6 amd64

sudo apt install gcc-10 g++-10

$ whereis gcc-10 g++-10
gcc-10: /usr/bin/gcc-10 
g++-10: /usr/bin/g++-10

To compile the code you should configure "make" to use gcc-10 and g++-10, instead of the default gcc-12 and g++-12.
To build the deb packages, you have to specify "compatibility level 13" in debian/compat

$ man debhelper-compat-upgrade-checklist | grep "recommended mode"
          v13 This is the recommended mode of operation.

Compilation

mkdir petrov-fftrate
cd petrov-fftrate
git clone https://github.com/PetrovSE/fftrate.git

Now you have to edit two files inside the package "fftrate":

./fftrate/src/lib/makedef.mk
./fftrate/packets/debian/compat

Enable gcc-10 and g++-10:

$ cat ./fftrate/src/lib/makedef.mk | grep gcc -A1
CC      = gcc-10
CPP     = g++-10

Change compat to "13":

$ cat ./fftrate/packets/debian/compat
13

Now you can compile:

cd  ./fftrate/packets

$ ls -1
Makefile
debian
etc
mk_dpkg

Compilte the code:

make

Make debian packages:

./mk_dpkg

$ ls ../ | grep .deb
alsa-config-utils_1.6.3_amd64.deb
libasound2-plugin-fftrate_1.6.3_amd64.deb
pcm-utils_1.6.3_amd64.deb

How to install fftrate

Install dependencies (if they are not already installed):

sudo apt install libasound2 libasound2-plugins swh-plugins

Install fftrate:

sudo dpkg -i libasound2-plugin-fftrate_1.6.3_amd64.deb alsa-config-utils_1.6.3_amd64.deb pcm-utils_1.6.3_amd64.deb

Open /etc/fftrate.conf with a text editor:

sudo nano /etc/fftrate.conf

Enable fft resampler:

$ cat /etc/fftrate.conf | grep "Transform type" -A3
# Transform type
# Available: dct, fft (default: dct)
#transform = dct
transform = fft

Run arateconf (interactive mode) to generate ~/.asoundrc

arateconf

Press 0 to select the first sound card.
Press 1 to select the second sound card.
Press F to change format

For Intel HDA codec on motherboard, try 32bit 192000Hz
For USB headsets, try 16bit 48Hz

Run TEST (press T).
If all tests have been passed successfully, save the setting (press S) and exit (ESC).

EXAMPLE: Intel HDA

===============
|  Main menu  |
---------------

    Curr. | Used | Play (def) | Rec (def) | Available cards
----------|------|------------|-----------|-----------------------------------
0 - >>>>> |  *   |  *     *   |  *    *   | HDA-Intel - HDA Intel PCH
1 -       |  *   |  *         |  *        | USB-Audio - iMic USB audio system

U - Toggle used flag
P - Set this device as default player
R - Set this device as default recorder

O - Output device: PCH,0
I - Input device : PCH,0

F - Format: 192000 Hz, 2 ch, 'S32_LE'
C - Converter: fftrate

A - Show all plugins [ ]
M - Plug-ins:
 [X] Convert,  [ ] Expand, [X] Asym
 [ ] Play Vol, [X] Dmix
 [ ] Rec. Vol, [X] Dsnoop
 [ ] Phonon,   [ ] Normalizator

T - Test
S - Save to '/home/devuan/.asoundrc'
X - Delete '/home/devuan/.asoundrc'

ESC - Exit

EXAMPLE: iMic USB

===============
|  Main menu  |
---------------

    Curr. | Used | Play (def) | Rec (def) | Available cards
----------|------|------------|-----------|-----------------------------------
0 -       |  *   |  *     *   |  *    *   | HDA-Intel - HDA Intel PCH
1 - >>>>> |  *   |  *         |  *        | USB-Audio - iMic USB audio system

U - Toggle used flag
P - Set this device as default player
R - Set this device as default recorder

O - Output device: system,0
I - Input device : system,0

F - Format: 48000 Hz, 2 ch, 'S16_LE'
C - Converter: fftrate

A - Show all plugins [ ]
M - Plug-ins:
 [X] Convert,  [ ] Expand, [X] Asym
 [ ] Play Vol, [X] Dmix
 [ ] Rec. Vol, [X] Dsnoop
 [ ] Phonon,   [ ] Normalizator

T - Test
S - Save to '/home/devuan/.asoundrc'
X - Delete '/home/devuan/.asoundrc'

ESC - Exit

TEST

> t
Testing H/W compatibility ...

Device: PCH
Output:
 Open device "hw:PCH,0" ... Ok.
 Set rate 192000 Hz ... Ok.
 Set channels 2 ... Ok.
 Set format 'S32_LE' ... Ok.
 Set buffer size 30720 -> 30720
 Set period size 7680 -> 7680
Input:
 Open device "hw:PCH,0" ... Ok.
 Set rate 192000 Hz ... Ok.
 Set format 'S32_LE' ... Ok.
 Set buffer size 30720 -> 30720
 Set period size 7680 -> 7680

Device: system
Output:
 Open device "hw:system,0" ... Ok.
 Set rate 48000 Hz ... Ok.
 Set channels 2 ... Ok.
 Set format 'S16_LE' ... Ok.
 Set buffer size 7680 -> 7680
 Set period size 1920 -> 1920
Input:
 Open device "hw:system,0" ... Ok.
 Set rate 48000 Hz ... Ok.
 Set format 'S16_LE' ... Ok.
 Set buffer size 7680 -> 7680
 Set period size 1920 -> 1920

Press any key ...

S - Save to '/home/devuan/.asoundrc'

> s
Saving config file...
Test: 'default' ... Ok.
Test: 'default' ... Ok.
Ok.

Testing playback/recording

$ aplay *.wav
Playing WAVE 'audio_test_48kHz_16bit.wav' : Signed 16 bit Little Endian, Rate 48000 Hz, Stereo
Input:  48000 Hz, 2 ch, 's16_le' (0x2): dummy = 0, period = 1920
Output: 192000 Hz, 2 ch, 's32_le' (0xa): dummy = 0, period = 7680
Rates:  48000 --> 192000 (J: 0.00%, T: FFT, W: Vorbis)
Ok.

$ arecord -V stereo -f S16_LE -r 48000 -c 2 1-fft-exp_rec_alsa.wav
Recording WAVE '1-fft-exp_rec_alsa.wav' : Signed 16 bit Little Endian, Rate 48000 Hz, Stereo
Input:  192000 Hz, 2 ch, 's32_le' (0xa): dummy = 0, period = 7680
Output: 48000 Hz, 2 ch, 's16_le' (0x2): dummy = 0, period = 1920
Rates:  192000 --> 48000 (J: 0.00%, T: FFT, W: Vorbis)
Ok.

$ aplay 1-fft-exp_rec_alsa.wav
Playing WAVE '1-fft-exp_rec_alsa.wav' : Signed 16 bit Little Endian, Rate 48000 Hz, Stereo
Input:  48000 Hz, 2 ch, 's16_le' (0x2): dummy = 0, period = 1920
Output: 192000 Hz, 2 ch, 's32_le' (0xa): dummy = 0, period = 7680
Rates:  48000 --> 192000 (J: 0.00%, T: FFT, W: Vorbis)
Ok.

Now you can install apulse and run discord

apulse discord

You may also need ALSA mixer

alsamixer

man alsamixer

Last edited by igorzwx (2024-05-31 00:40:14)

swanson · 2024-05-30 08:58:22

Thank you! Looks very interesting.

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#1 2024-05-30 03:06:21

ALSA without PulseAudio and PipeWire

#2 2024-05-30 08:58:22

Re: ALSA without PulseAudio and PipeWire

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