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videoLayers.ts
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videoLayers.ts
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export type OptimalVideoLayer = RTCRtpEncodingParameters & {
width: number;
height: number;
};
export const findOptimalVideoLayers = async (mediaStream: MediaStream) => {
const steps: [number, number, number][] = [
// [4096, 2160], // 4K
// [1920, 1080, 3_072_000], // Full-HD
[1280, 720, 1280_000], // HD
[640, 480, 768000], // VGA
[320, 240, 384000], // QVGA
[160, 120, 128000],
];
const optimalVideoLayers: OptimalVideoLayer[] = [];
for (let step = 0; step < steps.length; step++) {
const [w, h] = steps[step];
const [videoTrack] = mediaStream.getVideoTracks();
const settings = videoTrack.getSettings();
// found ideal layer
if (w === settings.width && h === settings.height) {
let scaleFactor: number = 1;
['f', 'h', 'q'].forEach((rid, i) => {
const [width, height, bitrate] = steps[step + i];
optimalVideoLayers.push({
rid,
width,
height,
maxBitrate: bitrate,
scaleResolutionDownBy: scaleFactor,
});
scaleFactor *= 2;
});
break;
}
}
return optimalVideoLayers;
};
export const defaultVideoLayers: OptimalVideoLayer[] = [
{
rid: 'f',
maxBitrate: 1280000,
width: 1280,
height: 720,
},
{
rid: 'h',
maxBitrate: 768000,
width: 640,
height: 480,
scaleResolutionDownBy: 2.0,
},
{
rid: 'q',
maxBitrate: 384000,
width: 480,
height: 360,
scaleResolutionDownBy: 4.0,
},
];