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aac_transmuxer.js
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aac_transmuxer.js
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/*! @license
* Shaka Player
* Copyright 2016 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
goog.provide('shaka.transmuxer.AacTransmuxer');
goog.require('shaka.media.Capabilities');
goog.require('shaka.transmuxer.ADTS');
goog.require('shaka.transmuxer.TransmuxerEngine');
goog.require('shaka.util.BufferUtils');
goog.require('shaka.util.Error');
goog.require('shaka.util.Id3Utils');
goog.require('shaka.util.ManifestParserUtils');
goog.require('shaka.util.MimeUtils');
goog.require('shaka.util.Mp4Generator');
goog.require('shaka.util.Uint8ArrayUtils');
/**
* @implements {shaka.extern.Transmuxer}
* @export
*/
shaka.transmuxer.AacTransmuxer = class {
/**
* @param {string} mimeType
*/
constructor(mimeType) {
/** @private {string} */
this.originalMimeType_ = mimeType;
/** @private {number} */
this.frameIndex_ = 0;
/** @private {!Map.<number, !Uint8Array>} */
this.initSegments = new Map();
}
/**
* @override
* @export
*/
destroy() {
this.initSegments.clear();
}
/**
* Check if the mime type and the content type is supported.
* @param {string} mimeType
* @param {string=} contentType
* @return {boolean}
* @override
* @export
*/
isSupported(mimeType, contentType) {
const Capabilities = shaka.media.Capabilities;
if (!this.isAacContainer_(mimeType)) {
return false;
}
const ContentType = shaka.util.ManifestParserUtils.ContentType;
return Capabilities.isTypeSupported(
this.convertCodecs(ContentType.AUDIO, mimeType));
}
/**
* Check if the mimetype is 'audio/aac'.
* @param {string} mimeType
* @return {boolean}
* @private
*/
isAacContainer_(mimeType) {
return mimeType.toLowerCase().split(';')[0] == 'audio/aac';
}
/**
* @override
* @export
*/
convertCodecs(contentType, mimeType) {
if (this.isAacContainer_(mimeType)) {
const codecs = shaka.util.MimeUtils.getCodecs(mimeType);
return `audio/mp4; codecs="${codecs || 'mp4a.40.2'}"`;
}
return mimeType;
}
/**
* @override
* @export
*/
getOriginalMimeType() {
return this.originalMimeType_;
}
/**
* @override
* @export
*/
transmux(data, stream, reference, duration) {
const ADTS = shaka.transmuxer.ADTS;
const Uint8ArrayUtils = shaka.util.Uint8ArrayUtils;
const uint8ArrayData = shaka.util.BufferUtils.toUint8(data);
// Check for the ADTS sync word
// Look for ADTS header | 1111 1111 | 1111 X00X | where X can be
// either 0 or 1
// Layer bits (position 14 and 15) in header should be always 0 for ADTS
// More info https://wiki.multimedia.cx/index.php?title=ADTS
const id3Data = shaka.util.Id3Utils.getID3Data(uint8ArrayData);
let offset = id3Data.length;
for (; offset < uint8ArrayData.length; offset++) {
if (ADTS.probe(uint8ArrayData, offset)) {
break;
}
}
let timestamp = reference.endTime * 1000;
const frames = shaka.util.Id3Utils.getID3Frames(id3Data);
if (frames.length && reference) {
const metadataTimestamp = frames.find((frame) => {
return frame.description ===
'com.apple.streaming.transportStreamTimestamp';
});
if (metadataTimestamp) {
timestamp = /** @type {!number} */(metadataTimestamp.data);
}
}
const info = ADTS.parseInfo(uint8ArrayData, offset);
if (!info) {
return Promise.reject(new shaka.util.Error(
shaka.util.Error.Severity.CRITICAL,
shaka.util.Error.Category.MEDIA,
shaka.util.Error.Code.TRANSMUXING_FAILED));
}
stream.audioSamplingRate = info.sampleRate;
stream.channelsCount = info.channelCount;
/** @type {!Array.<shaka.util.Mp4Generator.Mp4Sample>} */
const samples = [];
while (offset < uint8ArrayData.length) {
const header = ADTS.parseHeader(uint8ArrayData, offset);
if (!header) {
return Promise.reject(new shaka.util.Error(
shaka.util.Error.Severity.CRITICAL,
shaka.util.Error.Category.MEDIA,
shaka.util.Error.Code.TRANSMUXING_FAILED));
}
const length = header.headerLength + header.frameLength;
if (offset + length <= uint8ArrayData.length) {
const data = uint8ArrayData.subarray(
offset + header.headerLength, offset + length);
samples.push({
data: data,
size: header.frameLength,
duration: ADTS.AAC_SAMPLES_PER_FRAME,
cts: 0,
flags: {
isLeading: 0,
isDependedOn: 0,
hasRedundancy: 0,
degradPrio: 0,
dependsOn: 2,
isNonSync: 0,
},
});
}
offset += length;
}
/** @type {number} */
const sampleRate = info.sampleRate;
/** @type {number} */
const baseMediaDecodeTime = Math.floor(timestamp * sampleRate / 1000);
/** @type {shaka.util.Mp4Generator.StreamInfo} */
const streamInfo = {
id: stream.id,
type: shaka.util.ManifestParserUtils.ContentType.AUDIO,
codecs: info.codec,
encrypted: stream.encrypted && stream.drmInfos.length > 0,
timescale: sampleRate,
duration: duration,
videoNalus: [],
audioConfig: new Uint8Array([]),
videoConfig: new Uint8Array([]),
hSpacing: 0,
vSpacing: 0,
data: {
sequenceNumber: this.frameIndex_,
baseMediaDecodeTime: baseMediaDecodeTime,
samples: samples,
},
stream: stream,
};
const mp4Generator = new shaka.util.Mp4Generator([streamInfo]);
let initSegment;
if (!this.initSegments.has(stream.id)) {
initSegment = mp4Generator.initSegment();
this.initSegments.set(stream.id, initSegment);
} else {
initSegment = this.initSegments.get(stream.id);
}
const segmentData = mp4Generator.segmentData();
this.frameIndex_++;
const transmuxData = Uint8ArrayUtils.concat(initSegment, segmentData);
return Promise.resolve(transmuxData);
}
};
shaka.transmuxer.TransmuxerEngine.registerTransmuxer(
'audio/aac',
() => new shaka.transmuxer.AacTransmuxer('audio/aac'),
shaka.transmuxer.TransmuxerEngine.PluginPriority.FALLBACK);