support for VU meter values

[fmalcher]

This PR adds support for VU information.

---

Discussion points

1. Is there anything that should be renamed or restructured?
2. VU messages are sent in a 30-60 ms interval. Should we throttle them to keep the processing load lower?
3. Is anything missing in the documentation or in the API?

Docs (from the README)

Volume levels can be consumed through the VuProcessor class, fully separated from the MasterChannel class.
The VU information is published through streams, separated by channel.
Please be aware that only channels on the master bus are available.

conn.vuProcessor.input(1);
conn.vuProcessor.aux(2);

Call on VuProcessor	Description
master()	Master
input(2)	Input 2
line(1)	Line Input 1
player(1)	Player channel 1
aux(2)	AUX channel 2
fx(3)	FX channel 3
sub(3)	Sub group 3

Each of the method calls directly returns an Observable that can be subscribed to.
The streams emit objects with different VU values.
They are always published as linear values between 0 and 1.

// for input channels
{
  vuPre: 0.5; // input level before processing (EQ, Gate, Comp)
  vuPost: 0.5; // level after processing, represented by the blue bars in the Web UI
  vuPostFader: 0.5; // actual channel output level, represented by the colored bars in the Web UI
}

The vuPre field is only available on input channels (input, player and line).
Master, FX and Sub groups publish stereo information, so the object is structured as follows:

// for FX, sub group and master
{
  vuPostL: 0.3,
  vuPostR: 0.3,
  vuPostFaderL: 0.4,
  vuPostFaderR: 0.4,
}

Processing of the VU information happens lazily: VU messages from the mixer are ignored until the first VU stream is subscribed to. The messages are only processed if VU information is actually consumed.

All channels

The vuData$ field on VuProcessor publishes a raw object with all channel VU information available.
This can be used to process all information at once, e.g. for a VU meter dashboard across all channels.

conn.vuProcessor.vuData$;

VU values in dB

All VU values are linear values between 0 and 1. To express the level in dB you need to project the value to the dB range of the meter (-80..0 dB).
The exported utility function vuValueToDB() helps with that task and can be used as follows:

conn.vuProcessor
  .master()
  .pipe(map(data => vuValueToDB(data.vuPostFaderL)))
  .subscribe(/* ... */);

[nx-cloud]

☁️ Nx Cloud Report

CI is running/has finished running commands for commit c5c2235. As they complete they will appear below. Click to see the status, the terminal output, and the build insights.

📂 See all runs for this CI Pipeline Execution

---

✅ Successfully ran 2 targets

• nx affected -t lint test build
• nx-cloud record -- nx format:check

---

Sent with 💌 from NxCloud.

[fmalcher]

@yleguern64 Can you please review this, especially the API surface?
Can you also test this on a Ui12? If you don't want to install the project on your machine, I can deploy the testbed application publicly for testing.

[yleguern64]

I'm going to test that, and I'll reply soon for confirmation or add code for changes.

Thank you for this great feature !

[yleguern64]

For me, everything works perfectly !

Thank you.

    try {
       mixer = new SoundcraftUI(config.mixer.ip);
       await mixer.connect();
    } catch (e) {
        console.log(`Cannot connect to mixer : ${e}`);
        process.exit(-1);
    }

    const modulo = 50;
    let iModuloL = 0;
    let iModuloR = 0;
    mixer.vuProcessor.line(1).subscribe(value => {
        if (iModuloL % modulo === 0) {
            const v = Math.round(value.vuPost * 10000) / 100;
            if (v > 3 || v === 0) {
                console.log("L : " + v);
            }
        }
        iModuloL++;
    });
    mixer.vuProcessor.line(2).subscribe(value => {
        if (iModuloR % modulo === 0) {
            const v = Math.round(value.vuPost * 10000) / 100;
            if (v > 3 || v === 0) {
                console.log("R : " + v);
            }
        }
        iModuloR++;
    });

[yleguern64]

Great job !

Next step ;) Merge to main and tag 👍