feat: Add AC3 transmuxer (shaka-project#5297)

build/types/transmuxer

@@ -1,6 +1,8 @@
 # Optional plugins related to transmuxer.
 
 +../../lib/transmuxer/aac_transmuxer.js
++../../lib/transmuxer/ac3.js
++../../lib/transmuxer/ac3_transmuxer.js
 +../../lib/transmuxer/adts.js
 +../../lib/transmuxer/mp3_transmuxer.js
 +../../lib/transmuxer/mpeg_audio.js

lib/transmuxer/ac3.js

@@ -0,0 +1,151 @@
+/*! @license
+ * Shaka Player
+ * Copyright 2016 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+goog.provide('shaka.transmuxer.Ac3');
+
+
+/**
+ * AC3 utils
+ */
+shaka.transmuxer.Ac3 = class {
+  /**
+   * @param {!Uint8Array} data
+   * @param {!number} offset
+   * @return {?{sampleRate: number, channelCount: number,
+   *          audioConfig: !Uint8Array, frameLength: number}}
+   */
+  static parseFrame(data, offset) {
+    if (offset + 8 > data.length) {
+      // not enough bytes left
+      return null;
+    }
+
+    if (data[offset] !== 0x0b || data[offset + 1] !== 0x77) {
+      // invalid magic
+      return null;
+    }
+
+    // get sample rate
+    const samplingRateCode = data[offset + 4] >> 6;
+    if (samplingRateCode >= 3) {
+      // invalid sampling rate
+      return null;
+    }
+
+    const samplingRateMap = [48000, 44100, 32000];
+
+    // get frame size
+    const frameSizeCode = data[offset + 4] & 0x3f;
+    const frameSizeMap = [
+      64, 69, 96, 64, 70, 96, 80, 87, 120, 80, 88, 120, 96, 104, 144, 96, 105,
+      144, 112, 121, 168, 112, 122, 168, 128, 139, 192, 128, 140, 192, 160,
+      174, 240, 160, 175, 240, 192, 208, 288, 192, 209, 288, 224, 243, 336,
+      224, 244, 336, 256, 278, 384, 256, 279, 384, 320, 348, 480, 320, 349,
+      480, 384, 417, 576, 384, 418, 576, 448, 487, 672, 448, 488, 672, 512,
+      557, 768, 512, 558, 768, 640, 696, 960, 640, 697, 960, 768, 835, 1152,
+      768, 836, 1152, 896, 975, 1344, 896, 976, 1344, 1024, 1114, 1536, 1024,
+      1115, 1536, 1152, 1253, 1728, 1152, 1254, 1728, 1280, 1393, 1920, 1280,
+      1394, 1920,
+    ];
+
+    const frameLength = frameSizeMap[frameSizeCode * 3 + samplingRateCode] * 2;
+    if (offset + frameLength > data.length) {
+      return null;
+    }
+
+    // get channel count
+    const channelMode = data[offset + 6] >> 5;
+    let skipCount = 0;
+    if (channelMode === 2) {
+      skipCount += 2;
+    } else {
+      if ((channelMode & 1) && channelMode !== 1) {
+        skipCount += 2;
+      }
+      if (channelMode & 4) {
+        skipCount += 2;
+      }
+    }
+
+    const lowFrequencyEffectsChannelOn =
+      (((data[offset + 6] << 8) | data[offset + 7]) >> (12 - skipCount)) & 1;
+
+    const channelsMap = [2, 1, 2, 3, 3, 4, 4, 5];
+
+    // Audio config for DAC3 box
+    const bitStreamIdentification = data[offset + 5] >> 3;
+    const bitStreamMode = data[offset + 5] & 7;
+
+    const config = new Uint8Array([
+      (samplingRateCode << 6) |
+          (bitStreamIdentification << 1) |
+          (bitStreamMode >> 2),
+      ((bitStreamMode & 3) << 6) |
+          (channelMode << 3) |
+          (lowFrequencyEffectsChannelOn << 2) |
+          (frameSizeCode >> 4),
+      (frameSizeCode << 4) & 0xe0,
+    ]);
+
+    return {
+      sampleRate: samplingRateMap[samplingRateCode],
+      channelCount: channelsMap[channelMode] + lowFrequencyEffectsChannelOn,
+      audioConfig: config,
+      frameLength: frameLength,
+    };
+  }
+
+  /**
+   * @param {!Uint8Array} data
+   * @param {!number} offset
+   * @return {boolean}
+   */
+  static canParse(data, offset) {
+    return offset + 64 < data.length;
+  }
+
+  /**
+   * @param {!Uint8Array} data
+   * @param {!number} offset
+   * @return {boolean}
+   */
+  static probe(data, offset) {
+    // look for the ac-3 sync bytes
+    if (data[offset] === 0x0b &&
+      data[offset + 1] === 0x77) {
+      // check the bsid (bitStreamIdentification) to confirm ac-3
+      let bsid = 0;
+      let numBits = 5;
+      offset += numBits;
+      /** @type {?number} */
+      let temp = null;
+      /** @type {?number} */
+      let mask = null;
+      /** @type {?number} */
+      let byte = null;
+      while (numBits > 0) {
+        byte = data[offset];
+        // read remaining bits, upto 8 bits at a time
+        const bits = Math.min(numBits, 8);
+        const shift = 8 - bits;
+        mask = (0xff000000 >>> (24 + shift)) << shift;
+        temp = (byte & mask) >> shift;
+        bsid = !bsid ? temp : (bsid << bits) | temp;
+        offset += 1;
+        numBits -= bits;
+      }
+      if (bsid < 16) {
+        return true;
+      }
+    }
+    return false;
+  }
+};
+
+/**
+ * @const {number}
+ */
+shaka.transmuxer.Ac3.AC3_SAMPLES_PER_FRAME = 1536;

lib/transmuxer/ac3_transmuxer.js

@@ -0,0 +1,208 @@
+/*! @license
+ * Shaka Player
+ * Copyright 2016 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+goog.provide('shaka.transmuxer.Ac3Transmuxer');
+
+goog.require('shaka.media.Capabilities');
+goog.require('shaka.transmuxer.Ac3');
+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.Mp4Generator');
+goog.require('shaka.util.Uint8ArrayUtils');
+
+
+/**
+ * @implements {shaka.extern.Transmuxer}
+ * @export
+ */
+shaka.transmuxer.Ac3Transmuxer = 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.isAc3Container_(mimeType)) {
+      return false;
+    }
+    const ContentType = shaka.util.ManifestParserUtils.ContentType;
+    return Capabilities.isTypeSupported(
+        this.convertCodecs(ContentType.AUDIO, mimeType));
+  }
+
+
+  /**
+   * Check if the mimetype is 'audio/ac3'.
+   * @param {string} mimeType
+   * @return {boolean}
+   * @private
+   */
+  isAc3Container_(mimeType) {
+    return mimeType.toLowerCase().split(';')[0] == 'audio/ac3';
+  }
+
+
+  /**
+   * @override
+   * @export
+   */
+  convertCodecs(contentType, mimeType) {
+    if (this.isAc3Container_(mimeType)) {
+      return 'audio/mp4; codecs="ac-3"';
+    }
+    return mimeType;
+  }
+
+
+  /**
+   * @override
+   * @export
+   */
+  getOrginalMimeType() {
+    return this.originalMimeType_;
+  }
+
+
+  /**
+   * @override
+   * @export
+   */
+  transmux(data, stream, reference, duration) {
+    const Ac3 = shaka.transmuxer.Ac3;
+    const Uint8ArrayUtils = shaka.util.Uint8ArrayUtils;
+
+    const uint8ArrayData = shaka.util.BufferUtils.toUint8(data);
+
+    const id3Data = shaka.util.Id3Utils.getID3Data(uint8ArrayData);
+    let offset = id3Data.length;
+    for (; offset < uint8ArrayData.length; offset++) {
+      if (Ac3.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);
+      }
+    }
+
+    /** @type {number} */
+    let sampleRate = 0;
+
+    /** @type {!Uint8Array} */
+    let audioConfig = new Uint8Array([]);
+
+    /** @type {!Array.<shaka.util.Mp4Generator.Mp4Sample>} */
+    const samples = [];
+
+    while (offset < uint8ArrayData.length) {
+      const frame = Ac3.parseFrame(uint8ArrayData, offset);
+      if (!frame) {
+        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 = frame.sampleRate;
+      stream.channelsCount = frame.channelCount;
+      sampleRate = frame.sampleRate;
+      audioConfig = frame.audioConfig;
+
+      const frameData = uint8ArrayData.subarray(
+          offset, offset + frame.frameLength);
+
+      samples.push({
+        data: frameData,
+        size: frame.frameLength,
+        duration: Ac3.AC3_SAMPLES_PER_FRAME,
+        cts: 0,
+        flags: {
+          isLeading: 0,
+          isDependedOn: 0,
+          hasRedundancy: 0,
+          degradPrio: 0,
+          dependsOn: 2,
+          isNonSync: 0,
+        },
+      });
+      offset += frame.frameLength;
+    }
+    /** @type {number} */
+    const baseMediaDecodeTime = Math.floor(timestamp * sampleRate / 1000);
+
+    /** @type {shaka.util.Mp4Generator.StreamInfo} */
+    const streamInfo = {
+      timescale: sampleRate,
+      duration: duration,
+      videoNalus: [],
+      audioConfig: audioConfig,
+      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/ac3',
+    () => new shaka.transmuxer.Ac3Transmuxer('audio/ac3'),
+    shaka.transmuxer.TransmuxerEngine.PluginPriority.FALLBACK);

lib/util/mp4_generator.js

@@ -310,12 +310,14 @@ shaka.util.Mp4Generator = class {
         break;
       case ContentType.AUDIO:
         if (this.stream_.mimeType === 'audio/mpeg' ||
-        this.stream_.codecs.includes('mp3') ||
-        this.stream_.codecs.includes('mp4a.40.34')) {
+            this.stream_.codecs.includes('mp3') ||
+            this.stream_.codecs.includes('mp4a.40.34')) {
           bytes = this.mp3_();
-        } else if (this.stream_.codecs.includes('ac-3')) {
+        } else if (this.stream_.mimeType === 'audio/ac3' ||
+            this.stream_.codecs.includes('ac-3')) {
           bytes = this.ac3_();
-        } else if (this.stream_.codecs.includes('ec-3')) {
+        } else if (this.stream_.mimeType === 'audio/ec3' ||
+            this.stream_.codecs.includes('ec-3')) {
           bytes = this.ec3_();
         } else {
           bytes = this.mp4a_();