Snapcast client for ESP32

Synchronous Multiroom audio streaming client for Snapcast ported to ESP32

Feature list

• FLAC, OPUS and PCM decoding currently supported
• Wifi setup from menuconfig or through espressif Android App "SoftAP Prov"
• Auto connect to snapcast server on network
• Buffers up to 758ms on Wroom modules (tested with 44100:16:2)
• Buffers more then enough on Wrover modules
• Multiroom sync delay controlled from Snapcast server (user has to ensure not to set this too high on the server)
• DSP / EQ functionality configurable through menuconfig and partly controllable through HTTP server running on ESP client (work in progress)

Description

I have continued the work from @badaix, @bridadan and @jorgenkraghjakobsen towards a ESP32 Snapcast client. Currently it support basic features like multiroom sync, network controlled volume and mute. For now it supports FLAC, OPUS, PCM 16bit audio streams with sample rates up to 48Khz maybe more, I didn't test.

Please check out the task list and feel free to fill in.

I dropped the usage of ADF completely but copied stripped down, needed components to this project (using ESP-ADF v2.6). This was necessary because ADF was using flac in closed source precompiled library which made it impossible to get good results for multiroom syncing.

Codebase

The codebase is split into components and build on ESP-IDF v5.1.1. I still have some refactoring on the todo list as the concept has started to settle and allow for new features can be added in a structured manner. In the code you will find parts that are only partly related features and still not on the task list. Also there is a lot of code clean up needed.

Components

• audio-board : taken from ADF, stripped down to strictly necessary parts for playback
• audio-hal : taken from ADF, stripped down to strictly necessary parts for playback
• audio-sal : taken from ADF, stripped down to strictly necessary parts for playback
• custom_board : generic board component to support easy integration of DACs
• dsp_processor : Audio Processor, low pass filters, effects, etc.
• esp-dsp : Submodule to the ESP-ADF done by David Douard
• esp-peripherals : taken from ADF, stripped down to strictly necessary parts for usage with Lyrat v4.3
• flac : flac audio encoder/decoder full submodule
• libmedian: Median Filter implementation. Many thanks to @accabog https://github.com/accabog/MedianFilter
• libbuffer : Generic buffer abstraction
• lightsnapcast :
  • snapcast module, port of @bridadan scapcast packages decode library
  • player module, which is responsible for sync and low level I2S control
• net_functions :
• opus : Opus audio coder/decoder full submodule
• ota_server :
• protocol :
• rtprx : Alternative RTP audio client UDP low latency also opus based
• websocket :
• websocket_if :
• wifi_interface : wifi provisoning and init code for wifi module and AP connection

The snapclient functionanlity are implemented in a task included in main - but should be refactored to a component at some point.

I did my own syncing implementation which is different than @jorgenkraghjakobsen's approach in the original repository, at least regarding syncing itself. I tried to replicate the behaivior of how badaix did it for his original snapclients.

The snapclient frontend handles communication with the server and after successfull hello hand shake it dispatches packages from the server. Normally these packages contain messages in the following order:

• SERVER_SETTING : volume, mute state, playback delay etc
• CODEC_HEADER : Setup client audio codec (FLAC, OPUS, OGG or PCM) bitrate, n channels and bits per sample
• WIRE_CHUNK : Coded audio data, also I calculate chunk duration here after decoding is done using received CODEC_HEADER parameters
• TIME : Ping pong time keeping packages to keep track of time diff from server to client

Each WIRE_CHUNK of audio data comes with a timestamp in server time and clients can use information from TIME and SERVER_SETTING messages to determine when playback has to be started. We handle this using a buffer with a length that compensate for for playback-delay, network jitter and DAC to speaker (determined through SERVER_SETTING).

In this implementation I have separated the sync task to a backend on the other end of a freeRTOS queue. Now the front end just needs to pass on the decoded audio data to the queue with the server timestamp and chunk size. The backend reads timestamps and waits until the audio chunk has the correct playback-delay to be written to the DAC amplifer speaker through i2s DMA. When the backend pipeline is in sync, any offset get rolled in by micro tuning the APLL on the ESP. No sample manipulation needed.

Hardware

You will need an ESP32 or ESP32-S2 and an I2S DAC. We recommend using a Lyrat board. For pinout see the config options.

-   ESP pinout                         MA12070P
------------------------------------------------------
                          ->            I2S_BCK        Audio Clock 3.072 MHz
                          ->            I2S_WS         Frame Word Select or L/R
                          ->            GND            Ground
                          ->            I2S_DI         Audio data 24bits LSB first
                          ->            MCLK           Master clk connect to I2S_BCK
                          ->            I2C_SCL        I2C clock
                          ->            I2C_SDA        I2C Data
                          ->            GND            Ground
                          ->            NENABLE        Amplifier Enable active low
                          ->            NMUTE          Amplifier Mute active low

Installation

Clone this repo:

git clone https://github.com/CarlosDerSeher/snapclient
cd snapclient

Update third party code (opus, flac and esp-dsp):

git submodule update --init

ESP-IDF environnement configuration

• If you're on Windows : Install ESP-IDF v5.1.1 locally (More info).
• If you're on Linux (docker) : Use the image for ESP-IDF by following docker build doc
• If you're on Linux : follow official Espressif instructions For debian based systems you'll need to do the following:

  sudo apt-get install git wget flex bison gperf python3 python3-pip python3-venv cmake ninja-build ccache libffi-dev libssl-dev dfu-util libusb-1.0-0
  mkdir -p ~/esp
  cd ~/esp
  git clone -b v5.1.1 --recursive https://github.com/espressif/esp-idf.git
  cd ~/esp/esp-idf
  ./install.sh esp32
  . ./export.sh
  

Snapcast ESP Configuration

Frist copy one of the template sdkconfig files and rename it to sdkconfig

cp sdkconfig_lyrat_v4.3 sdkconfig

then configure your platform:

idf.py menuconfig

Configure to match your setup

• Audio HAL : Choose your audio board
  • Lyrat (4.3, 4.2)
  • Lyrat TD (2.2, 2.1) --> not supported yet
  • Lyrat Mini (1.1)
  • KORVO DU1906 --> not supported yet
  • ESP32-S2 Kaluga (1.2) --> not supported yet
  • Or a custom board
• Custom Audio Board : Configure your DAC and GPIO
  • DAC Chip :
    • TI PCM51XX/TAS57XX DAC (PCM51XX are stereo DAC in TSSOP package and TAS57XX are class-D amp in HTSSOP package. Both have i2s input and i2c control)
    • TI PCM5102A DAC (Very basic stereo DAC WITHOUT i2c control)
    • Infineon MA120X0 (High power class-D amp in QFN package)
    • Analog Devices ADAU1961 (Stereo DAC with multiple analog inputs in LFCSP package)
    • Analog Devices MAX98357 (Very popular basic mono AMP without i2c control)
  • DAC I2C control interface : Choose GPIO pin of your I2C line and address of the DAC. If your DAC doesn't support I2C (PCM5102A or equivalent), put unused GPIO values.
  • I2C master interface : GPIO pin of your DAC I2S bus.
  • DAC interface configuration : Configure specific GPIO for your DAC functionnalities. Use ? to have more info.
• ESP32 DSP processor config :
  • DSP flow : Choose between Stereo, Bassboost, Bi-amp or Bass/Treble EQ. You can further configure it on the ESP web interface/
  • Use asm version of Biquad_f32 : Optimized version of the DSP algorithm only for ESP32. Don't work on ESP32-S2
  • Use software volume : Handle snapcast volume in the ESP. Activate this if your DAC do not provide a volume control (no I2C like PCM5102A or MAX98357)
• WiFi Configuration :
  • WiFi Provisioning : Use the Espressif "ESP SoftAP Prov" APP to configure your wifi network.
  • SSID : The SSID to connect to or the provisioning SSID.
  • Password : The password of your WiFi network or the provisioning netword.
  • Maximum retry: Use 0 for no limit.
• Snapclient configuration :
  • Use mDNS : The client will search on the network for the snapserver automatically. Your network must support mDNS.
  • Snapserver host : IP or URL of the server if mDNS is disabled or the mDNS resolution fail.
  • Snapserver port : Port of your snapserver, default is 1704.
  • Snapclient name : The name under wich your ESP will appear on the Snapserver.
  • HTTP Server Setting : The ESP create a basic webpage. You can configure the port to view this page and configure the DSP.

Compile and flash

idf.py build flash monitor

Merge bin to flash at 0x0 with web.esphome.io

esptool.py --chip esp32  merge_bin -o merged.bin --flash_size 4MB --flash_freq 80m 0x1000 build/bootloader/bootloader.bin 0x8000 build/partition_table/partition-table.bin 0xd000 build/ota_data_initial.bin 0x10000 build/snapclient.bin 0x370000 build/storage.bin

Test

Setup a snapcast server on your network

On a linux box:

Clone snapcast build and start the server

./snapserver

Pipe some audio to the snapcast server fifo

mplayer http://ice1.somafm.com/secretagent-128-aac -ao pcm:file=/tmp/snapfifo -af format=s16LE -srate 48000

Test the server config on other knowen platform

./snapclient  from the snapcast repo

Android : snapclient from the app play store

Contribute

You are very welcome to help and provide Pull Requests to the project.

We strongly suggest you activate pre-commit hooks in this git repository before starting to hack and make commits.

Assuming you have pre-commit installed on your machine (using pip install pre-commit or, on a debian-like system, sudo apt install pre-commit), type:

:~/snapclient$ pre-commit install
pre-commit installed at .git/hooks/pre-commit

Then on every git commit, a few sanity/formatting checks will be performed.

Task list

• put kconfig to better locations in tree
• add missing codec's (ogg)
• dsp_processor: add equalizer
• Control interface for equalizer (component: ui_http_server)
• clean and polish code (remove all unused variables etc.)
• Improve Documentation
• Throw out ADF copied components from project tree and use CmakeLists.txt to pull in necessary files from ADF

Minor task

• fill in missing component descriptions in Readme.md