A loudness-measuring web-app for monitoring multiple streams at once.
It takes audio inputs from JACK, measures their loudness according to EBU R 128, and then streams that data to a simple web UI.
Only tested on linux, but JACK is apparently supported on other platforms.
Compile the binary using cargo build --release, and the resulting executable will be in target/release/loudness-server. The binary dynamically links against JACK, so pipewire is supported via pipewire-jack.
Create a config file like the example, and name it config.json:
{
"web": {
// host and port for the web server to listen on
"host": "::1",
"port": 8080
},
"inputs": {
// Internal ID, used to name JACK input ports
"live_high": {
// Display name, used in the web UI
"name": "Online (live-high)",
// optional, number of channels this input has
"channels": 2
},
"fm_send": {
"name": "FM (send)"
},
"dab_send": {
"name": "DAB (send)"
}
},
"jack": {
// Optional, defaults to "loudness_meter"
"client_name": "loudness"
}
}Run the executable, and open the web UI using the port you configured.
You'll need to link things to the input ports in JACK to feed audio into the server. This can be done with jack_connect. Input ports are named as {id}_{i} where {i} is the index of the channel, starting from zero.
For example, with the configuration above, to link a stereo input (say from a liquidsoap script) to the input named live_high, you could use the following:
jack_connect live_high:out_0 loudness:live_high_0
jack_connect live_high:out_1 loudness:live_high_1The path to the config file can be changed with the environment variable CONFIG_PATH.