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Fix float operations to make a little more sense.

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This commit is contained in:
Travis Ralston 2021-03-29 21:25:06 -06:00
parent a848febd3d
commit e523ce6036
3 changed files with 18 additions and 24 deletions
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24
src/voice/VoiceRecorder.ts
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@ -19,6 +19,7 @@ import encoderPath from 'opus-recorder/dist/encoderWorker.min.js';
import {MatrixClient} from "matrix-js-sdk/src/client";
import CallMediaHandler from "../CallMediaHandler";
import {SimpleObservable} from "matrix-widget-api";
import {percentageOf} from "../utils/numbers";
const CHANNELS = 1; // stereo isn't important
const SAMPLE_RATE = 48000; // 48khz is what WebRTC uses. 12khz is where we lose quality.
@ -133,23 +134,18 @@ export class VoiceRecorder {
// The time domain is the input to the FFT, which means we use an array of the same
// size. The time domain is also known as the audio waveform. We're ignoring the
// output of the FFT here (frequency data) because we're not interested in it.
//
// We use bytes out of the analyser because floats have weird precision problems
// and are slightly more difficult to work with. The bytes are easy to work with,
// which is why we pick them (they're also more precise, but we care less about that).
const data = new Uint8Array(this.recorderFFT.fftSize);
this.recorderFFT.getByteTimeDomainData(data);
const data = new Float32Array(this.recorderFFT.fftSize);
this.recorderFFT.getFloatTimeDomainData(data);
// Because we're dealing with a uint array we need to do math a bit differently.
// If we just `Array.from()` the uint array, we end up with 1s and 0s, which aren't
// what we're after. Instead, we have to use a bit of manual looping to correctly end
// up with the right values
// We can't just `Array.from()` the array because we're dealing with 32bit floats
// and the built-in function won't consider that when converting between numbers.
// However, the runtime will convert the float32 to a float64 during the math operations
// which is why the loop works below. Note that a `.map()` call also doesn't work
// and will instead return a Float32Array still.
const translatedData: number[] = [];
for (let i = 0; i < data.length; i++) {
// All we're doing here is inverting the amplitude and putting the metric somewhere
// between zero and one. Without the inversion, lower values are "louder", which is
// not super helpful.
translatedData.push(1 - (data[i] / 128.0));
// We're clamping the values so we can do that math operation mentioned above.
translatedData.push(percentageOf(data[i], 0, 1));
}
this.observable.update({