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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,78 @@ | ||
| // Original implementation: https://github.com/wobbals/opentok-mos-estimator | ||
| // I just adjusted the code to our needs. | ||
| // This implementation reflects the score for the last second rather than for the entire session. | ||
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| type VideoParams = { | ||
| width: number, | ||
| height: number, | ||
| bitrate: number, | ||
| } | ||
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| const targetBitrateForPixelCount = function(pixelCount: number) { | ||
| // power function maps resolution to target bitrate, based on rumor config | ||
| // values, with r^2 = 0.98. We're ignoring frame rate, assume 30. | ||
| const y = 2.069924867 * Math.pow(Math.log10(pixelCount), 0.6250223771); | ||
| return Math.pow(10, y); | ||
| }; | ||
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| const MIN_VIDEO_BITRATE = 30000; | ||
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| export const calculateOpenTokVideoScore = ({ width, height, bitrate }: VideoParams) => { | ||
| const targetBitrate = targetBitrateForPixelCount(width * height); | ||
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| if (bitrate < MIN_VIDEO_BITRATE) { | ||
| return 0; | ||
| } | ||
| const newBitrate = Math.min(bitrate, targetBitrate); | ||
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| return (Math.log(newBitrate / MIN_VIDEO_BITRATE) / | ||
| Math.log(targetBitrate / MIN_VIDEO_BITRATE)) * 4 + 1; | ||
| }; | ||
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| type AudioParams = { | ||
| packetLoss: number, | ||
| roundTripTime: number, | ||
| } | ||
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| export const calculateOpenTokAudioScore = ({ packetLoss, roundTripTime }: AudioParams) => { | ||
| const audioScore = function(rtt: number, plr: number) { | ||
| const LOCAL_DELAY = 20; //20 msecs: typical frame duration | ||
| function H(x) { | ||
| return (x < 0 ? 0 : 1); | ||
| } | ||
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| const a = 0; // ILBC: a=10 | ||
| const b = 19.8; | ||
| const c = 29.7; | ||
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| //R = 94.2 − Id − Ie | ||
| const R = function(rtt: number, packetLoss: number) { | ||
| const d = rtt + LOCAL_DELAY; | ||
| const Id = 0.024 * d + 0.11 * (d - 177.3) * H(d - 177.3); | ||
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| const P = packetLoss; | ||
| const Ie = a + b * Math.log(1 + c * P); | ||
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| const R = 94.2 - Id - Ie; | ||
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| return R; | ||
| }; | ||
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| //For R < 0: MOS = 1 | ||
| //For 0 R 100: MOS = 1 + 0.035 R + 7.10E-6 R(R-60)(100-R) | ||
| //For R > 100: MOS = 4.5 | ||
| const MOS = function(R) { | ||
| if (R < 0) { | ||
| return 1; | ||
| } | ||
| if (R > 100) { | ||
| return 4.5; | ||
| } | ||
| return 1 + 0.035 * R + 7.10 / 1000000 * R * (R - 60) * (100 - R); | ||
| }; | ||
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| return MOS(R(rtt, plr)); | ||
| }; | ||
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| return audioScore(roundTripTime, packetLoss); | ||
| }; |