audio2pipe

audio2pipe is a set of utilities to pipe sound towards other software

audio2pipe is a set of scripts and services to better handle pipe creation for audio streamers leveraging cpiped under the hood. Recommended in conjunction with OwnTone

Contents

• Contents
• Features
• Getting Started
  • Prerequisites
  • Installation
• Usage
  • scripts/A2PSourceProcess.sh
  • scripts/A2POutputselector.py
  • scripts/A2PToggle.sh
  • service/cpiped_Template.service
  • Configuration
• ToDo(s)
• Acknowledgments
  • Top contributors:

Features

• systemd service to manage cpiped instances supporting different sample rates
• Multiple input device supported with dedicated configuration
• Interlock to avoid out of sequence triggering of per device script
• Automatic OwnTone output selection on sound detection

Getting Started

Prerequisites

audio2pipe requires

• bash
• cpiped
• python >= v3.11.2
  • requests 2.28.1

Installation

1. Clone the repository

   git clone https://github.com/ale275/audio2pipe.git

2. Install scripts in audio2pipe base dir defined by A2P_HOME env variable and setup needed symlink

   cd audio2pipe
   export A2P_HOME=/home/user
   install  -m 755 -D scripts/* -t "${A2P_HOME}/bin"
   ln -s "${A2P_HOME}/bin/A2PSourceProcess.sh" "${A2P_HOME}/bin/A2PSourceProcessPre"
   ln -s "${A2P_HOME}/bin/A2PSourceProcess.sh" "${A2P_HOME}/bin/A2PSourceProcessDetect"
   ln -s "${A2P_HOME}/bin/A2PSourceProcess.sh" "${A2P_HOME}/bin/A2PSourceProcessSilence"
   ln -s "${A2P_HOME}/bin/A2PSourceProcess.sh" "${A2P_HOME}/bin/A2PSourceProcessStop"
   ln -s "${A2P_HOME}/bin/A2PToggle.sh" "${A2P_HOME}/bin/A2PToggle"

   To configure autmatic output selection on sound detect please refer to scripts/A2POutputselector.py section.

3. Create per device systemd service file starting from template. More details in configuration section

   export A2P_HOME=/home/user
   export A2P_DEVNAME=Test_Device
   cp "service/cpiped_Template.service" "service/cpiped_${A2P_DEVNAME}.service"
   nano "service/cpiped_${A2P_DEVNAME}.service"

4. Install and activate the service

   export A2P_HOME=/home/user
   export A2P_DEVNAME=Test_Device
   sudo cp "service/cpiped_${A2P_DEVNAME}.service" "/lib/systemd/system/"
   sudo systemctl daemon-reload
   sudo systemctl enable cpiped_${A2P_DEVNAME}.service
   sudo systemctl start cpiped_${A2P_DEVNAME}

Usage

audio2pipe scripts functionality description

scripts/A2PSourceProcess.sh

Main bash script taking various ENV variable as configuration to make, monitor and clean-up audio pipes, pid monitoring and output selection via callback function.

Script has three execution phases from now on <A2P_ExecPhase>

• Pre: running all the preparatory check before cpiped is started. Executed only once at service start
• Detect: Section run at sound detect. It runs python output selector callback script. Script can be replaced at user discretion by replacing the symlinked script
• Silence: Performs all the files clean-up when audio source is stopped

Lockfile and pipe filling PID checks prevent parallel command execution and multiple pipe fillings resulting in unpleasant white noise blasting from speakers. These features are especially useful when audio is sourced from record players.

On sound detect a python callback script is used, in the repository an OwnTone output selection script is provided.

scripts/A2POutputselector.py

Python script using OwnTone http API(s) to select the output(s) defined in ENV variable at sound detect phase. It's usage is not mandatory

To be invoked script must be located in <A2P_HOME>/bin and named A2P_OT_OUT_SEL_<A2P_DEVNAME>

export A2P_HOME=/home/user
export A2P_DEVNAME=Test_Device
ln -s "${A2P_HOME}/bin/A2POutputSelector.py" "${A2P_HOME}/bin/A2P_OT_OUT_SEL_${A2P_DEVNAME}"

scripts/A2PToggle.sh

Script to toggle the various cpiped services. Must be run as sudo

service/cpiped_Template.service

Systemd service

Configuration

Script configuration are mainly managed though ENV variables

Variable name	Description	Type	Default	Range/Format	Required?
A2P_HOME	audio2pipe basedir Folder structure: bin: contains all the scripts var/pipes: contains all the detect pipes needed by cpiped var/run: contains pid files and lockfiles for audio2pipe and cpiped	string	$HOME		No
A2P_DEVNAME	Device input name Mnemonic that will define all the specialized file name Audio pipe: <A2P_OT_LIB>/<A2P_DEVNAME> Audio pipe filling PID file: var/run/A2P_<A2P_DEVNAME>.pid cpiped PID file: var/run/A2P_<A2P_DEVNAME>.pid Detect pipe: var/pipes/A2P_<A2P_DEVNAME>.detectpipe Lockfile file: var/run/A2P_<A2P_DEVNAME>.lock.<A2P_ExecPhase> systemd service file: cpiped_<A2P_DEVNAME>.service	string			Yes
A2P_CP_SF	Audio device sample rate to be passed to cpiped in hz cpiped will then set env variables CPIPED_SR, CPIPED_SS, CPIPED_CC, respectively for sample rate, sample size and capture channel directly	integer	44100	16000 - 192000	No
A2P_CP_SOUNDCARD	Audio capture soundcard to be passed to cpiped in ALSA format	string	'default'	hw:<card>,<device>	No
A2P_CP_SL	cpiped silence level	integer	100	1 - 32767	No
A2P_OT_LIB	OwnTone library folder. Where the audio pipe will be created and filled on sound detection	string			No
A2P_OT_HOST	OwnTone server hostname	string	localhost		No
A2P_OT_OUT_LIST	OwnTone output(s) label to be selected at sound detect	string comma separated list			No
A2P_DEBUG	Make log more verbose. Accepts True or False values	string	False	True - False	No

Usage of following variable is not recommended

Variable name	Description	Type	Default	Range/Format	Required?
A2P_DEVFORMAT	Concatenation of sample format and sample frequency separated by two underscores Example: sample format 16bit Little Endian and sample frequency 48kHz will be S16_LE__48000 Default sample rate 41000Hz Default sample size 16bit Default capture channel 2 **Preferred** approach is to read cpiped env variables CPIPED_SR, CPIPED_SS, CPIPED_CC, respectively for sample rate, sample size and capture channel directly	string		<Sample format>__<Sample rate>	Not recomended

ToDo(s)

• Sysvinit scripts
• Move ENV variable setup from Service file to EnvironFile to define monitoring pipe in pre stage. Under evaluation
• Rework detect pipe section that is prone to config error
• Create install script
• Add command line parameters to scripts/A2POutputselector.py
• Add command line parameters to scripts/A2PToggle.sh
• Change detect pipe extension from .pipe to .detectpipe
• Add cpiped existence check in <A2P_ExecPhase>==Pre
• Improve systemd service ExecStop section of script to stop the device specific instance of cpiped and not all of them
• Fix systemd service KillMode warning

See the open issues for a full list of proposed features (and known issues).

Acknowledgments

Based on Making an Analog In to Airplay RPi-Transmitter from ownTone wiki

Created to be used with OwnTone

Top contributors: