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|
Softmixer controller for 4A (AGL Advance Audio Architecture).
------------------------------------------------------------
* Object: Simulate a hardware mixer through and snd-aloop driver and a user space mixer
* Status: In Progress
* Author: Fulup Ar Foll fulup@iot.bzh
* Author: Thierry Bultel thierry.bultel@iot.bzh
* Date : July-2018
## Features
* Definition of multiple audio zones, and multiple audio cards
* Usage of streams to access audio zones
* Direct read from HW capture devices (eg radio chips & microphones)
## Compile
```
mkdir build
cd build
cmake ..
make
```
## Install Alsa Loopback Driver
```
sudo modprobe snd-aloop
```
## Assert LUA config file match your config
```
vim $PROJECT_ROOT/conf.d/project/lua.d/softmixer-01.lua
# make sure both your loopback and targeted sound card path are valid
```
## Run from shell
```
afb-daemon --name 4a-softmixer-afbd --port=1234 --workdir=/home/fulup/Workspace/Audio-4a/4a-softmixer/build \
--binding=package/lib/softmixer-binding.so --roothttp=package/htdocs --token= --tracereq=common --verbose
# lua test script should return a response looking like
response= {
[1] = { ["uid"] = navigation,["runid"] = 101,["alsa"] = hw:5,0,6,["volid"] = 103,}
, ["params"] = { ["channels"] = 2,["format"] = 2,["rate"] = 48000,["access"] = 3,}
,[2] = { ....
}
# runid: pause/resume alsa control you may change it with 'amixer -D hw:Loopback cset numid=101 on|off
# volid: volume alsa control you may change it from 'alsamixer -Dhw:Loppback' or with 'amixer -D hw:Loopback cset numid=103 NN (o-100%)
```
Retrieve audio-stream alsa endpoint from response to 'L2C:snd_streams' command. Depending on your config 'hw:XXX' will change.
Alsa snd-aloop impose '0' as playback device. Soft mixer will start from last subdevice and allocates one subdev for each audio-stream.
## Play some music
snd-aloop only supports these audio formats:
S16_LE
S16_BE
S32_LE
S32_BE
FLOAT_LE
FLOAT_BE
Using gstreamer is a simple way to perform the conversion, if your audio file is not of one of these.
```
gst-launch-1.0 filesrc location=insane.wav ! wavparse ! audioconvert ! audioresample ! alsasink device=hw:Loopback,0,2
```
## Warning
Alsa tries to automatically store current state into /var/lib/alsa/asound.state when developing/testing this may create impossible
situation. In order to clean up your Alsa snd-aloop config, a simple "rmmod" might not be enough in some case you may have to delete
/var/lib/alsa/asound.state before applying "modprobe".
In case of doubt check with folling command that you start from a clear green field
```
rmmod snd-aloop && modprobe --first-time snd-aloop && amixer -D hw:Loopback controls | grep vol
```
## Work in Progress
* Support capture from bluez
## Known issues
* From times to times, playing an audio file make the sound output with higher pitch
* The playback loop could be improved, using direct access to the ring buffer instead
of copies to stack (could save some CPU time)
|
