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Handle stalls when seeking into buffer gaps
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Rob Walch committed Dec 3, 2019
1 parent a4732c3 commit 3f94299
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Showing 3 changed files with 72 additions and 44 deletions.
46 changes: 24 additions & 22 deletions src/controller/gap-controller.ts
View file
Expand Up @@ -38,9 +38,9 @@ export default class GapController {
*/
public poll (lastCurrentTime: number) {
const { config, media, stalled } = this;
const tnow = self.performance.now();
const { currentTime, seeking } = media;
const seeked = this.seeking && !seeking;
const beginSeek = !this.seeking && seeking;

this.seeking = seeking;

Expand All @@ -50,7 +50,8 @@ export default class GapController {
if (stalled !== null) {
// The playhead is now moving, but was previously stalled
if (this.stallReported) {
logger.warn(`playback not stuck anymore @${currentTime}, after ${Math.round(tnow - stalled)}ms`);
const stalledDuration = self.performance.now() - stalled;
logger.warn(`playback not stuck anymore @${currentTime}, after ${Math.round(stalledDuration)}ms`);
this.stallReported = false;
}
this.stalled = null;
Expand All @@ -59,8 +60,8 @@ export default class GapController {
return;
}

// Clear stalled state after seeked so that we don't report stalls coming out of a seek
if (seeked) {
// Clear stalled state when beginning or finishing seeking so that we don't report stalls coming out of a seek
if (beginSeek || seeked) {
this.stalled = null;
}

Expand All @@ -79,27 +80,30 @@ export default class GapController {
}

if (seeking) {
if (isBuffered) {
// Waiting for seeking in a buffered range to complete
// Waiting for seeking in a buffered range to complete
const hasEnoughBuffer = bufferInfo.len > MAX_START_GAP_JUMP;
// Next buffered range is too far ahead to jump to while still seeking
const noBufferGap = !nextStart || nextStart - currentTime > MAX_START_GAP_JUMP;
if (hasEnoughBuffer || noBufferGap) {
return;
} else if (nextStart < MAX_START_GAP_JUMP) {
// Reset moved state when seeking back to a point before a start gap
this.moved = false;
}
// Reset moved state when seeking to a point in or before a gap
this.moved = false;
}

// Skip start gaps if we haven't played, but the last poll detected the start of a stall
// The addition poll gives the browser a chance to jump the gap for us
if (!this.moved && this.stalled) {
// Jump start gaps within jump threshold
const startJump = Math.max(nextStart, ((bufferInfo.start || 0) - currentTime));
const startJump = Math.max(nextStart, bufferInfo.start || 0) - currentTime;
if (!seeking && startJump > 0 && startJump <= MAX_START_GAP_JUMP) {
this._trySkipBufferHole(null);
return;
}
}

// Start tracking stall time
const tnow = self.performance.now();
if (stalled === null) {
this.stalled = tnow;
return;
Expand All @@ -112,7 +116,7 @@ export default class GapController {
}

const bufferedWithHoles = BufferHelper.bufferInfo(media, currentTime, config.maxBufferHole);
this._tryFixBufferStall(bufferInfo, bufferedWithHoles, stalledDuration);
this._tryFixBufferStall(bufferedWithHoles, stalledDuration);
}

/**
Expand All @@ -121,7 +125,7 @@ export default class GapController {
* @param stalledDurationMs - The amount of time Hls.js has been stalling for.
* @private
*/
private _tryFixBufferStall (bufferInfo: BufferInfo, bufferedWithHoles: BufferInfo, stalledDurationMs: number) {
private _tryFixBufferStall (bufferInfo: BufferInfo, stalledDurationMs: number) {
const { config, fragmentTracker, media } = this;
const currentTime = media.currentTime;

Expand All @@ -141,16 +145,14 @@ export default class GapController {
// we may just have to "nudge" the playlist as the browser decoding/rendering engine
// needs to cross some sort of threshold covering all source-buffers content
// to start playing properly.
if (stalledDurationMs > config.highBufferWatchdogPeriod * 1000) {
if (bufferedWithHoles.len > config.maxBufferHole ||
bufferInfo.len === 0 && bufferInfo.nextStart && bufferInfo.nextStart < config.maxBufferHole) {
logger.warn('Trying to nudge playhead over buffer-hole');
// Try to nudge currentTime over a buffer hole if we've been stalling for the configured amount of seconds
// We only try to jump the hole if it's under the configured size
// Reset stalled so to rearm watchdog timer
this.stalled = null;
this._tryNudgeBuffer();
}
if (bufferInfo.len > config.maxBufferHole &&
stalledDurationMs > config.highBufferWatchdogPeriod * 1000) {
logger.warn('Trying to nudge playhead over buffer-hole');
// Try to nudge currentTime over a buffer hole if we've been stalling for the configured amount of seconds
// We only try to jump the hole if it's under the configured size
// Reset stalled so to rearm watchdog timer
this.stalled = null;
this._tryNudgeBuffer();
}
}

Expand Down
49 changes: 43 additions & 6 deletions tests/functional/auto/setup.js
View file
Expand Up @@ -89,7 +89,7 @@ async function testLoadedData (url, config) {
url,
config
);
expect(result.code).to.equal('loadeddata');
expect(result, JSON.stringify(result, null, 2)).to.have.property('code').which.equals('loadeddata');
}

async function testSmoothSwitch (url, config) {
Expand Down Expand Up @@ -121,7 +121,7 @@ async function testSmoothSwitch (url, config) {
url,
config
);
expect(result.code).to.be.true;
expect(result, JSON.stringify(result, null, 2)).to.have.property('code').which.equals(true);
}

async function testSeekOnLive (url, config) {
Expand All @@ -142,7 +142,7 @@ async function testSeekOnLive (url, config) {
url,
config
);
expect(result.code).to.equal('seeked');
expect(result, JSON.stringify(result, null, 2)).to.have.property('code').which.equals('seeked');
}

async function testSeekOnVOD (url, config) {
Expand All @@ -163,7 +163,7 @@ async function testSeekOnVOD (url, config) {
url,
config
);
expect(result.code).to.equal('ended');
expect(result, JSON.stringify(result, null, 2)).to.have.property('code').which.equals('ended');
}

async function testSeekEndVOD (url, config) {
Expand All @@ -184,7 +184,7 @@ async function testSeekEndVOD (url, config) {
url,
config
);
expect(result.code).to.equal('ended');
expect(result, JSON.stringify(result, null, 2)).to.have.property('code').which.equals('ended');
}

async function testIsPlayingVOD (url, config) {
Expand Down Expand Up @@ -218,7 +218,37 @@ async function testIsPlayingVOD (url, config) {
url,
config
);
expect(result.playing).to.be.true;
expect(result, JSON.stringify(result, null, 2)).to.have.property('playing').which.is.true;
}

async function testSeekBackToStart (url, config) {
const result = await browser.executeAsyncScript(
(url, config) => {
const callback = arguments[arguments.length - 1];
self.startStream(url, config, callback);
const video = self.video;
video.ontimeupdate = function () {
if (video.currentTime > 0 && !video.paused) {
self.setTimeout(function () {
video.onseeked = function () {
delete video.onseeked;
video.ontimeupdate = function () {
if (video.currentTime > 0 && !video.paused) {
delete video.ontimeupdate;
callback({ playing: true });
}
};
};
video.currentTime = 0;
delete video.ontime;
}, 500);
}
};
},
url,
config
);
expect(result, JSON.stringify(result, null, 2)).to.have.property('playing').which.is.true;
}

describe(`testing hls.js playback in the browser on "${browserDescription}"`, function () {
Expand Down Expand Up @@ -330,6 +360,13 @@ describe(`testing hls.js playback in the browser on "${browserDescription}"`, fu
testLoadedData.bind(null, url, config)
);

if (stream.startSeek) {
it(
`seek back to start and play for ${stream.description}`,
testSeekBackToStart.bind(null, url, config)
);
}

if (stream.abr) {
it(
`should "smooth switch" to highest level and still play(readyState === 4) after 12s for ${stream.description}`,
Expand Down
21 changes: 5 additions & 16 deletions tests/unit/controller/gap-controller.js
View file
Expand Up @@ -72,37 +72,26 @@ describe('checkBuffer', function () {

describe('_tryFixBufferStall', function () {
it('should nudge when stalling close to the buffer end', function () {
const mockBufferInfo = { len: 0.5, nextStart: 1 };
const mockBufferWithHoles = { len: 1 };
const mockStallDuration = (config.highBufferWatchdogPeriod + 1) * 1000;
const nudgeStub = sandbox.stub(gapController, '_tryNudgeBuffer');
gapController._tryFixBufferStall(mockBufferInfo, mockBufferWithHoles, mockStallDuration);
expect(nudgeStub).to.have.been.calledOnce;
});

it('should nudge when in between buffered ranges', function () {
media.currentTime = 4;
const mockBufferInfo = { len: 0, nextStart: 4.08 };
const mockBufferWithHoles = { len: 5 };
const mockBufferInfo = { len: 1 };
const mockStallDuration = (config.highBufferWatchdogPeriod + 1) * 1000;
const nudgeStub = sandbox.stub(gapController, '_tryNudgeBuffer');
gapController._tryFixBufferStall(mockBufferInfo, mockBufferWithHoles, mockStallDuration);
gapController._tryFixBufferStall(mockBufferInfo, mockStallDuration);
expect(nudgeStub).to.have.been.calledOnce;
});

it('should not nudge when briefly stalling close to the buffer end', function () {
const mockBufferInfo = { len: 1 };
const mockStallDuration = (config.highBufferWatchdogPeriod / 2) * 1000;
const nudgeStub = sandbox.stub(gapController, '_tryNudgeBuffer');
gapController._tryFixBufferStall(mockBufferInfo, mockBufferInfo, mockStallDuration);
gapController._tryFixBufferStall(mockBufferInfo, mockStallDuration);
expect(nudgeStub).to.have.not.been.called;
});

it('should not nudge when too close to the buffer end', function () {
it('should not nudge when too far from the buffer end', function () {
const mockBufferInfo = { len: 0.25 };
const mockStallDuration = (config.highBufferWatchdogPeriod + 1) * 1000;
const nudgeStub = sandbox.stub(gapController, '_tryNudgeBuffer');
gapController._tryFixBufferStall(mockBufferInfo, mockBufferInfo, mockStallDuration);
gapController._tryFixBufferStall(mockBufferInfo, mockStallDuration);
expect(nudgeStub).to.have.not.been.called;
});

Expand Down

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