shaka-player
Version:
DASH/EME video player library
474 lines (415 loc) • 15 kB
JavaScript
/*! @license
* Shaka Player
* Copyright 2016 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
goog.provide('shaka.text.TextEngine');
goog.require('goog.asserts');
goog.require('shaka.Deprecate');
goog.require('shaka.media.ClosedCaptionParser');
goog.require('shaka.text.Cue');
goog.require('shaka.util.BufferUtils');
goog.require('shaka.util.IDestroyable');
goog.require('shaka.util.MimeUtils');
// TODO: revisit this when Closure Compiler supports partially-exported classes.
/**
* @summary Manages text parsers and cues.
* @implements {shaka.util.IDestroyable}
* @export
*/
shaka.text.TextEngine = class {
/** @param {shaka.extern.TextDisplayer} displayer */
constructor(displayer) {
/** @private {?shaka.extern.TextParser} */
this.parser_ = null;
/** @private {shaka.extern.TextDisplayer} */
this.displayer_ = displayer;
/** @private {boolean} */
this.segmentRelativeVttTiming_ = false;
/** @private {number} */
this.timestampOffset_ = 0;
/** @private {number} */
this.appendWindowStart_ = 0;
/** @private {number} */
this.appendWindowEnd_ = Infinity;
/** @private {?number} */
this.bufferStart_ = null;
/** @private {?number} */
this.bufferEnd_ = null;
/** @private {string} */
this.selectedClosedCaptionId_ = '';
/** @private {shaka.extern.TextParser.ModifyCueCallback} */
this.modifyCueCallback_ = (cue, uri) => {};
/**
* The closed captions map stores the CEA closed captions by closed captions
* id and start and end time.
* It's used as the buffer of closed caption text streams, to show captions
* when we start displaying captions or switch caption tracks, we need to be
* able to get the cues for the other language and display them without
* re-fetching the video segments they were embedded in.
* Structure of closed caption map:
* closed caption id -> {start and end time -> cues}
* @private {!Map<string, !Map<string, !Array<shaka.text.Cue>>>}
*/
this.closedCaptionsMap_ = new Map();
}
/**
* @param {string} mimeType
* @param {!shaka.extern.TextParserPlugin} plugin
* @export
*/
static registerParser(mimeType, plugin) {
shaka.text.TextEngine.parserMap_.set(mimeType, plugin);
}
/**
* @param {string} mimeType
* @export
*/
static unregisterParser(mimeType) {
shaka.text.TextEngine.parserMap_.delete(mimeType);
}
/**
* @return {?shaka.extern.TextParserPlugin}
* @export
*/
static findParser(mimeType) {
return shaka.text.TextEngine.parserMap_.get(mimeType);
}
/**
* @param {string} mimeType
* @return {boolean}
*/
static isTypeSupported(mimeType) {
if (shaka.text.TextEngine.parserMap_.has(mimeType)) {
// An actual parser is available.
return true;
}
if (mimeType == shaka.util.MimeUtils.CEA608_CLOSED_CAPTION_MIMETYPE ||
mimeType == shaka.util.MimeUtils.CEA708_CLOSED_CAPTION_MIMETYPE ) {
return !!shaka.media.ClosedCaptionParser.findDecoder();
}
return false;
}
// TODO: revisit this when the compiler supports partially-exported classes.
/**
* @override
* @export
*/
destroy() {
this.parser_ = null;
this.displayer_ = null;
this.closedCaptionsMap_.clear();
return Promise.resolve();
}
/**
* @param {!shaka.extern.TextDisplayer} displayer
*/
setDisplayer(displayer) {
this.displayer_ = displayer;
}
/**
* Initialize the parser. This can be called multiple times, but must be
* called at least once before appendBuffer.
*
* @param {string} mimeType
* @param {boolean} sequenceMode
* @param {boolean} segmentRelativeVttTiming
* @param {string} manifestType
*/
initParser(mimeType, sequenceMode, segmentRelativeVttTiming, manifestType) {
// No parser for CEA, which is extracted from video and side-loaded
// into TextEngine and TextDisplayer.
if (mimeType == shaka.util.MimeUtils.CEA608_CLOSED_CAPTION_MIMETYPE ||
mimeType == shaka.util.MimeUtils.CEA708_CLOSED_CAPTION_MIMETYPE) {
this.parser_ = null;
return;
}
const factory = shaka.text.TextEngine.parserMap_.get(mimeType);
goog.asserts.assert(
factory, 'Text type negotiation should have happened already');
this.parser_ = factory();
if (this.parser_.setSequenceMode) {
this.parser_.setSequenceMode(sequenceMode);
} else {
shaka.Deprecate.deprecateFeature(5,
'Text parsers w/ setSequenceMode',
'Text parsers should have a "setSequenceMode" method!');
}
if (this.parser_.setManifestType) {
this.parser_.setManifestType(manifestType);
} else {
shaka.Deprecate.deprecateFeature(5,
'Text parsers w/ setManifestType',
'Text parsers should have a "setManifestType" method!');
}
this.segmentRelativeVttTiming_ = segmentRelativeVttTiming;
}
/** @param {shaka.extern.TextParser.ModifyCueCallback} modifyCueCallback */
setModifyCueCallback(modifyCueCallback) {
this.modifyCueCallback_ = modifyCueCallback;
}
/**
* @param {BufferSource} buffer
* @param {?number} startTime relative to the start of the presentation
* @param {?number} endTime relative to the start of the presentation
* @param {?string=} uri
* @return {!Promise}
*/
async appendBuffer(buffer, startTime, endTime, uri) {
goog.asserts.assert(
this.parser_, 'The parser should already be initialized');
// Start the operation asynchronously to avoid blocking the caller.
await Promise.resolve();
// Check that TextEngine hasn't been destroyed.
if (!this.parser_ || !this.displayer_) {
return;
}
if (startTime == null || endTime == null) {
this.parser_.parseInit(shaka.util.BufferUtils.toUint8(buffer));
return;
}
const vttOffset = this.segmentRelativeVttTiming_ ?
startTime : this.timestampOffset_;
/** @type {shaka.extern.TextParser.TimeContext} **/
const time = {
periodStart: this.timestampOffset_,
segmentStart: startTime,
segmentEnd: endTime,
vttOffset: vttOffset,
};
// Parse the buffer and add the new cues.
const allCues = this.parser_.parseMedia(
shaka.util.BufferUtils.toUint8(buffer), time, uri, /* images= */ []);
for (const cue of allCues) {
this.modifyCueCallback_(cue, uri || null, time);
}
const cuesToAppend = allCues.filter((cue) => {
return cue.startTime >= this.appendWindowStart_ &&
cue.startTime < this.appendWindowEnd_;
});
this.displayer_.append(cuesToAppend);
// NOTE: We update the buffered range from the start and end times
// passed down from the segment reference, not with the start and end
// times of the parsed cues. This is important because some segments
// may contain no cues, but we must still consider those ranges
// buffered.
if (this.bufferStart_ == null) {
this.bufferStart_ = Math.max(startTime, this.appendWindowStart_);
} else {
// We already had something in buffer, and we assume we are extending
// the range from the end.
goog.asserts.assert(
this.bufferEnd_ != null,
'There should already be a buffered range end.');
goog.asserts.assert(
(startTime - this.bufferEnd_) <= 1,
'There should not be a gap in text references >1s');
}
this.bufferEnd_ = Math.min(endTime, this.appendWindowEnd_);
}
/**
* @param {number} startTime relative to the start of the presentation
* @param {number} endTime relative to the start of the presentation
* @return {!Promise}
*/
async remove(startTime, endTime) {
// Start the operation asynchronously to avoid blocking the caller.
await Promise.resolve();
if (this.displayer_ && this.displayer_.remove(startTime, endTime)) {
if (this.bufferStart_ == null) {
goog.asserts.assert(
this.bufferEnd_ == null, 'end must be null if startTime is null');
} else {
goog.asserts.assert(
this.bufferEnd_ != null,
'end must be non-null if startTime is non-null');
// Update buffered range.
if (endTime <= this.bufferStart_ || startTime >= this.bufferEnd_) {
// No intersection. Nothing was removed.
} else if (startTime <= this.bufferStart_ &&
endTime >= this.bufferEnd_) {
// We wiped out everything.
this.bufferStart_ = this.bufferEnd_ = null;
} else if (startTime <= this.bufferStart_ &&
endTime < this.bufferEnd_) {
// We removed from the beginning of the range.
this.bufferStart_ = endTime;
} else if (startTime > this.bufferStart_ &&
endTime >= this.bufferEnd_) {
// We removed from the end of the range.
this.bufferEnd_ = startTime;
} else {
// We removed from the middle? StreamingEngine isn't supposed to.
goog.asserts.assert(
false, 'removal from the middle is not supported by TextEngine');
}
}
}
}
/** @param {number} timestampOffset */
setTimestampOffset(timestampOffset) {
this.timestampOffset_ = timestampOffset;
}
/**
* @param {number} appendWindowStart
* @param {number} appendWindowEnd
*/
setAppendWindow(appendWindowStart, appendWindowEnd) {
this.appendWindowStart_ = appendWindowStart;
this.appendWindowEnd_ = appendWindowEnd;
}
/**
* @return {?number} Time in seconds of the beginning of the buffered range,
* or null if nothing is buffered.
*/
bufferStart() {
return this.bufferStart_;
}
/**
* @return {?number} Time in seconds of the end of the buffered range,
* or null if nothing is buffered.
*/
bufferEnd() {
return this.bufferEnd_;
}
/**
* @param {number} t A timestamp
* @return {boolean}
*/
isBuffered(t) {
if (this.bufferStart_ == null || this.bufferEnd_ == null) {
return false;
}
return t >= this.bufferStart_ && t < this.bufferEnd_;
}
/**
* @param {number} t A timestamp
* @return {number} Number of seconds ahead of 't' we have buffered
*/
bufferedAheadOf(t) {
if (this.bufferEnd_ == null || this.bufferEnd_ < t) {
return 0;
}
goog.asserts.assert(
this.bufferStart_ != null,
'start should not be null if end is not null');
return this.bufferEnd_ - Math.max(t, this.bufferStart_);
}
/**
* Set the selected closed captions id.
* Append the cues stored in the closed captions map until buffer end time.
* This is to fill the gap between buffered and unbuffered captions, and to
* avoid duplicates that would be caused by any future video segments parsed
* for captions.
*
* @param {string} id
* @param {number} bufferEndTime Load any stored cues up to this time.
*/
setSelectedClosedCaptionId(id, bufferEndTime) {
this.selectedClosedCaptionId_ = id;
const captionsMap = this.closedCaptionsMap_.get(id);
if (captionsMap) {
for (const startAndEndTime of captionsMap.keys()) {
/** @type {Array<!shaka.text.Cue>} */
const cues = captionsMap.get(startAndEndTime)
.filter((c) => c.endTime <= bufferEndTime);
if (cues) {
this.displayer_.append(cues);
}
}
}
}
/**
* @param {!shaka.text.Cue} cue the cue to apply the timestamp to recursively
* @param {number} videoTimestampOffset the timestamp offset of the video
* @private
*/
applyVideoTimestampOffsetRecursive_(cue, videoTimestampOffset) {
cue.startTime += videoTimestampOffset;
cue.endTime += videoTimestampOffset;
for (const nested of cue.nestedCues) {
this.applyVideoTimestampOffsetRecursive_(nested, videoTimestampOffset);
}
}
/**
* Store the closed captions in the text engine, and append the cues to the
* text displayer. This is a side-channel used for embedded text only.
*
* @param {!Array<!shaka.extern.ICaptionDecoder.ClosedCaption>} closedCaptions
* @param {?number} startTime relative to the start of the presentation
* @param {?number} endTime relative to the start of the presentation
* @param {number} videoTimestampOffset the timestamp offset of the video
* stream in which these captions were embedded
*/
storeAndAppendClosedCaptions(
closedCaptions, startTime, endTime, videoTimestampOffset) {
const startAndEndTime = startTime + ' ' + endTime;
/** @type {!Map<string, !Map<string, !Array<!shaka.text.Cue>>>} */
const captionsMap = new Map();
for (const caption of closedCaptions) {
const id = caption.stream;
const cue = caption.cue;
if (!captionsMap.has(id)) {
captionsMap.set(id, new Map());
}
if (!captionsMap.get(id).has(startAndEndTime)) {
captionsMap.get(id).set(startAndEndTime, []);
}
// Adjust CEA captions with respect to the timestamp offset of the video
// stream in which they were embedded.
this.applyVideoTimestampOffsetRecursive_(cue, videoTimestampOffset);
const keepThisCue =
cue.startTime >= this.appendWindowStart_ &&
cue.startTime < this.appendWindowEnd_;
if (!keepThisCue) {
continue;
}
captionsMap.get(id).get(startAndEndTime).push(cue);
if (id == this.selectedClosedCaptionId_) {
this.displayer_.append([cue]);
}
}
for (const id of captionsMap.keys()) {
if (!this.closedCaptionsMap_.has(id)) {
this.closedCaptionsMap_.set(id, new Map());
}
for (const startAndEndTime of captionsMap.get(id).keys()) {
const cues = captionsMap.get(id).get(startAndEndTime);
this.closedCaptionsMap_.get(id).set(startAndEndTime, cues);
}
}
if (this.bufferStart_ == null) {
this.bufferStart_ = Math.max(startTime, this.appendWindowStart_);
} else {
this.bufferStart_ = Math.min(
this.bufferStart_, Math.max(startTime, this.appendWindowStart_));
}
this.bufferEnd_ = Math.max(
this.bufferEnd_, Math.min(endTime, this.appendWindowEnd_));
}
/**
* Get the number of closed caption channels.
*
* This function is for TESTING ONLY. DO NOT USE in the library.
*
* @return {number}
*/
getNumberOfClosedCaptionChannels() {
return this.closedCaptionsMap_.size;
}
/**
* Get the number of closed caption cues for a given channel. If there is
* no channel for the given channel id, this will return 0.
*
* This function is for TESTING ONLY. DO NOT USE in the library.
*
* @param {string} channelId
* @return {number}
*/
getNumberOfClosedCaptionsInChannel(channelId) {
const channel = this.closedCaptionsMap_.get(channelId);
return channel ? channel.size : 0;
}
};
/** @private {!Map<string, !shaka.extern.TextParserPlugin>} */
shaka.text.TextEngine.parserMap_ = new Map();