feat: Add AAC transmuxer (shaka-project#5240)

This transmuxer is used in Firefox due the lack of support for
`audio/aac`

build/types/transmuxer

@@ -1,5 +1,7 @@
 # Optional plugins related to transmuxer.
 
++../../lib/transmuxer/aac_transmuxer.js
++../../lib/transmuxer/adts.js
 +../../lib/transmuxer/mp3_transmuxer.js
 +../../lib/transmuxer/mpeg_audio.js
 +../../lib/transmuxer/muxjs_transmuxer.js

lib/transmuxer/aac_transmuxer.js

@@ -0,0 +1,220 @@
+/*! @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() {
+    // Nothing
+  }
+
+
+  /**
+   * 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
+   */
+  getOrginalMimeType() {
+    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;
+    stream.codecs = info.codec;
+    stream.type = 'audio';
+
+    /** @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 = {
+      timescale: sampleRate,
+      duration: duration,
+      videoNalus: [],
+      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);