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async function measureDelayFromStats(t, receiver, cycles, targetDelay, tolerance) {
let oldInboundStats;
for (let i = 0; i < cycles; i++) {
const statsReport = await receiver.getStats();
const inboundStats = [...statsReport.values()].find(({type}) => type == "inbound-rtp");
if (inboundStats) {
if (oldInboundStats) {
const emittedCount = inboundStats.jitterBufferEmittedCount - oldInboundStats.jitterBufferEmittedCount;
if (emittedCount) {
const delay = 1000 * (inboundStats.jitterBufferDelay - oldInboundStats.jitterBufferDelay) / emittedCount;
if (Math.abs(delay - targetDelay) < tolerance) {
return true;
}
}
}
oldInboundStats = inboundStats;
}
await new Promise(r => t.step_timeout(r, 1000));
}
return false;
}
async function applyJitterBufferTarget(t, kind, target) {
const caller = new RTCPeerConnection();
t.add_cleanup(() => caller.close());
const callee = new RTCPeerConnection();
t.add_cleanup(() => callee.close());
const stream = await getNoiseStream({[kind]:true});
t.add_cleanup(() => stream.getTracks().forEach(track => track.stop()));
caller.addTransceiver(stream.getTracks()[0], {streams: [stream]});
exchangeIceCandidates(caller, callee);
await exchangeOffer(caller, callee);
await exchangeAnswer(caller, callee);
const receiver = callee.getReceivers()[0];
// Workaround for Chromium to pull audio from jitter buffer.
if (kind === "audio") {
const audio = document.createElement("audio");
audio.srcObject = new MediaStream([receiver.track]);
audio.play();
}
assert_equals(receiver.jitterBufferTarget, null,
`jitterBufferTarget supported for ${kind}`);
let result = await measureDelayFromStats(t, receiver, 5, 0, 100);
assert_true(result, 'jitter buffer is not stabilised');
receiver.jitterBufferTarget = target;
assert_equals(receiver.jitterBufferTarget, target,
`jitterBufferTarget increase target for ${kind}`);
result = await measureDelayFromStats(t, receiver, 10, target, 20);
assert_true(result, 'jitterBuffer does not reach target');
receiver.jitterBufferTarget = 0;
assert_equals(receiver.jitterBufferTarget, 0,
`jitterBufferTarget decrease target for ${kind}`);
result = await measureDelayFromStats(t, receiver, 10, 0, 100);
assert_true(result, 'jitter buffer delay is not back to normal');
}