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fix: allow the playback on platforms when low latency APIs are not supported #4485

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merged 4 commits into from
Sep 22, 2022
Merged

fix: allow the playback on platforms when low latency APIs are not supported #4485

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fix: allow the playback on platforms when low latency APIs are not su…
avelad Sep 14, 2022
ad61740
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avelad Sep 19, 2022
30bddad
Add clarification
avelad Sep 22, 2022
288b9fb
fix typo
avelad Sep 22, 2022
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37 changes: 36 additions & 1 deletion lib/media/streaming_engine.js
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Original file line number Diff line number Diff line change
Expand Up @@ -1240,7 +1240,16 @@ shaka.media.StreamingEngine = class {
if (this.config_.lowLatencyMode && isReadableStreamSupported && isMP4 &&
!reference.hlsAes128Key) {
let remaining = new Uint8Array(0);
let processingResult = false;
let callbackCalled = false;
const streamDataCallback = async (data) => {
if (processingResult) {
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// If the fallback result processing was triggered, don't also
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Am I correct in my understanding, that this shouldn't happen? In theory, if the fallback has executed, the streamDataCallback shouldn't fire after that, correct?

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The theory tells me that it should never happen, but... I have found a case in an old TV :(

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Oh, yikes. Well, maybe add some mention of that in the comments. Otherwise, some well-meaning person might "optimize" this check away later.

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Added!

// append the buffer here. In theory this should never happen,
// but it does on some older TVs.
return;
}
callbackCalled = true;
this.destroyer_.ensureNotDestroyed();
if (this.fatalError_) {
return;
Expand Down Expand Up @@ -1271,7 +1280,33 @@ shaka.media.StreamingEngine = class {
}
};

await this.fetch_(mediaState, reference, streamDataCallback);
const result =
await this.fetch_(mediaState, reference, streamDataCallback);
if (!callbackCalled) {
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// In some environments, we might be forced to use network plugins
// that don't support streamDataCallback. In those cases, as a
// fallback, append the buffer here.
processingResult = true;
this.destroyer_.ensureNotDestroyed();
if (this.fatalError_) {
return;
}

// If the text stream gets switched between fetch_() and append_(),
// the new text parser is initialized, but the new init segment is
// not fetched yet. That would cause an error in
// TextParser.parseMedia().
// See http://b/168253400
if (mediaState.waitingToClearBuffer) {
shaka.log.info(logPrefix, 'waitingToClearBuffer, skip append');
mediaState.performingUpdate = false;
this.scheduleUpdate_(mediaState, 0);
return;
}

await this.append_(
mediaState, presentationTime, stream, reference, result);
}
} else {
if (this.config_.lowLatencyMode && !isReadableStreamSupported) {
shaka.log.warning('Low latency streaming mode is enabled, but ' +
Expand Down