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Merge pull request #5303 from DolbyLaboratories:dev-v2-ac4
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library/core/src/main/java/com/google/android/exoplayer2/audio/Ac4Util.java
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| /* | ||
| * Copyright (C) 2019 The Android Open Source Project | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
| package com.google.android.exoplayer2.audio; | ||
|
|
||
| import com.google.android.exoplayer2.C; | ||
| import com.google.android.exoplayer2.Format; | ||
| import com.google.android.exoplayer2.drm.DrmInitData; | ||
| import com.google.android.exoplayer2.util.MimeTypes; | ||
| import com.google.android.exoplayer2.util.ParsableBitArray; | ||
| import com.google.android.exoplayer2.util.ParsableByteArray; | ||
| import java.nio.ByteBuffer; | ||
|
|
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| /** Utility methods for parsing AC-4 frames, which are access units in AC-4 bitstreams. */ | ||
| public final class Ac4Util { | ||
|
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| /** Holds sample format information as presented by a syncframe header. */ | ||
| public static final class SyncFrameInfo { | ||
|
|
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| /** The bitstream version. */ | ||
| public final int bitstreamVersion; | ||
| /** The audio sampling rate in Hz. */ | ||
| public final int sampleRate; | ||
| /** The number of audio channels */ | ||
| public final int channelCount; | ||
| /** The size of the frame. */ | ||
| public final int frameSize; | ||
| /** Number of audio samples in the frame. */ | ||
| public final int sampleCount; | ||
|
|
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| private SyncFrameInfo( | ||
| int bitstreamVersion, int channelCount, int sampleRate, int frameSize, int sampleCount) { | ||
| this.bitstreamVersion = bitstreamVersion; | ||
| this.channelCount = channelCount; | ||
| this.sampleRate = sampleRate; | ||
| this.frameSize = frameSize; | ||
| this.sampleCount = sampleCount; | ||
| } | ||
| } | ||
|
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| public static final int AC40_SYNCWORD = 0xAC40; | ||
| public static final int AC41_SYNCWORD = 0xAC41; | ||
|
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| /** The channel count of AC-4 stream. */ | ||
| // TODO: Parse AC-4 stream channel count. | ||
| private static final int CHANNEL_COUNT_2 = 2; | ||
| /** | ||
| * The header size for AC-4 parser. Only needs to be as big as we need to read, not the full | ||
| * header size. | ||
| */ | ||
| public static final int HEADER_SIZE_FOR_PARSER = 16; | ||
| /** | ||
| * Number of audio samples in the frame. Defined in IEC61937-14:2017 table 5 and 6. This table | ||
| * provides the number of samples per frame at the playback sampling frequency of 48 kHz. For 44.1 | ||
| * kHz, only frame_rate_index(13) is valid and corresponding sample count is 2048. | ||
| */ | ||
| private static final int[] SAMPLE_COUNT = | ||
| new int[] { | ||
| /* [ 0] 23.976 fps */ 2002, | ||
| /* [ 1] 24 fps */ 2000, | ||
| /* [ 2] 25 fps */ 1920, | ||
| /* [ 3] 29.97 fps */ 1601, // 1601 | 1602 | 1601 | 1602 | 1602 | ||
| /* [ 4] 30 fps */ 1600, | ||
| /* [ 5] 47.95 fps */ 1001, | ||
| /* [ 6] 48 fps */ 1000, | ||
| /* [ 7] 50 fps */ 960, | ||
| /* [ 8] 59.94 fps */ 800, // 800 | 801 | 801 | 801 | 801 | ||
| /* [ 9] 60 fps */ 800, | ||
| /* [10] 100 fps */ 480, | ||
| /* [11] 119.88 fps */ 400, // 400 | 400 | 401 | 400 | 401 | ||
| /* [12] 120 fps */ 400, | ||
| /* [13] 23.438 fps */ 2048 | ||
| }; | ||
|
|
||
| /** | ||
| * Returns the AC-4 format given {@code data} containing the AC4SpecificBox according to ETSI TS | ||
| * 103 190-1 Annex E. The reading position of {@code data} will be modified. | ||
| * | ||
| * @param data The AC4SpecificBox to parse. | ||
| * @param trackId The track identifier to set on the format. | ||
| * @param language The language to set on the format. | ||
| * @param drmInitData {@link DrmInitData} to be included in the format. | ||
| * @return The AC-4 format parsed from data in the header. | ||
| */ | ||
| public static Format parseAc4AnnexEFormat( | ||
| ParsableByteArray data, String trackId, String language, DrmInitData drmInitData) { | ||
| data.skipBytes(1); // ac4_dsi_version, bitstream_version[0:5] | ||
| int sampleRate = ((data.readUnsignedByte() & 0x20) >> 5 == 1) ? 48000 : 44100; | ||
| return Format.createAudioSampleFormat( | ||
| trackId, | ||
| MimeTypes.AUDIO_AC4, | ||
| /* codecs= */ null, | ||
| /* bitrate= */ Format.NO_VALUE, | ||
| /* maxInputSize= */ Format.NO_VALUE, | ||
| CHANNEL_COUNT_2, | ||
| sampleRate, | ||
| /* initializationData= */ null, | ||
| drmInitData, | ||
| /* selectionFlags= */ 0, | ||
| language); | ||
| } | ||
|
|
||
| /** | ||
| * Returns AC-4 format information given {@code data} containing a syncframe. The reading position | ||
| * of {@code data} will be modified. | ||
| * | ||
| * @param data The data to parse, positioned at the start of the syncframe. | ||
| * @return The AC-4 format data parsed from the header. | ||
| */ | ||
| public static SyncFrameInfo parseAc4SyncframeInfo(ParsableBitArray data) { | ||
| int headerSize = 0; | ||
| int syncWord = data.readBits(16); | ||
| headerSize += 2; | ||
| int frameSize = data.readBits(16); | ||
| headerSize += 2; | ||
| if (frameSize == 0xFFFF) { | ||
| frameSize = data.readBits(24); | ||
| headerSize += 3; // Extended frame_size | ||
| } | ||
| frameSize += headerSize; | ||
| if (syncWord == AC41_SYNCWORD) { | ||
| frameSize += 2; // crc_word | ||
| } | ||
| int bitstreamVersion = data.readBits(2); | ||
| if (bitstreamVersion == 3) { | ||
| bitstreamVersion += readVariableBits(data, /* bitsPerRead= */ 2); | ||
| } | ||
| int sequenceCounter = data.readBits(10); | ||
| if (data.readBit()) { // b_wait_frames | ||
| if (data.readBits(3) > 0) { // wait_frames | ||
| data.skipBits(2); // reserved | ||
| } | ||
| } | ||
| int sampleRate = data.readBit() ? 48000 : 44100; | ||
| int frameRateIndex = data.readBits(4); | ||
| int sampleCount = 0; | ||
| if (sampleRate == 44100 && frameRateIndex == 13) { | ||
| sampleCount = SAMPLE_COUNT[frameRateIndex]; | ||
| } else if (sampleRate == 48000 && frameRateIndex < SAMPLE_COUNT.length) { | ||
| sampleCount = SAMPLE_COUNT[frameRateIndex]; | ||
| switch (sequenceCounter % 5) { | ||
| case 1: // fall through | ||
| case 3: | ||
| if (frameRateIndex == 3 || frameRateIndex == 8) { | ||
| sampleCount++; | ||
| } | ||
| break; | ||
| case 2: | ||
| if (frameRateIndex == 8 || frameRateIndex == 11) { | ||
| sampleCount++; | ||
| } | ||
| break; | ||
| case 4: | ||
| if (frameRateIndex == 3 || frameRateIndex == 8 || frameRateIndex == 11) { | ||
| sampleCount++; | ||
| } | ||
| break; | ||
| default: | ||
| break; | ||
| } | ||
| } | ||
| return new SyncFrameInfo(bitstreamVersion, CHANNEL_COUNT_2, sampleRate, frameSize, sampleCount); | ||
| } | ||
|
|
||
| /** | ||
| * Returns the size in bytes of the given AC-4 syncframe. | ||
| * | ||
| * @param data The syncframe to parse. | ||
| * @param syncword The syncword value for the syncframe. | ||
| * @return The syncframe size in bytes, or {@link C#LENGTH_UNSET} if the input is invalid. | ||
| */ | ||
| public static int parseAc4SyncframeSize(byte[] data, int syncword) { | ||
| if (data.length < 7) { | ||
| return C.LENGTH_UNSET; | ||
| } | ||
| int headerSize = 2; // syncword | ||
| int frameSize = ((data[2] & 0xFF) << 8) | (data[3] & 0xFF); | ||
| headerSize += 2; | ||
| if (frameSize == 0xFFFF) { | ||
| frameSize = ((data[4] & 0xFF) << 16) | ((data[5] & 0xFF) << 8) | (data[6] & 0xFF); | ||
| headerSize += 3; | ||
| } | ||
| if (syncword == AC41_SYNCWORD) { | ||
| headerSize += 2; | ||
| } | ||
| frameSize += headerSize; | ||
| return frameSize; | ||
| } | ||
|
|
||
| /** | ||
| * Reads the number of audio samples represented by the given AC-4 syncframe. The buffer's | ||
| * position is not modified. | ||
| * | ||
| * @param buffer The {@link ByteBuffer} from which to read the syncframe. | ||
| * @return The number of audio samples represented by the syncframe. | ||
| */ | ||
| public static int parseAc4SyncframeAudioSampleCount(ByteBuffer buffer) { | ||
| byte[] bufferBytes = new byte[HEADER_SIZE_FOR_PARSER]; | ||
| int position = buffer.position(); | ||
| buffer.get(bufferBytes); | ||
| buffer.position(position); | ||
| return parseAc4SyncframeInfo(new ParsableBitArray(bufferBytes)).sampleCount; | ||
| } | ||
|
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| /** Populates {@code buffer} with an AC-4 sample header for a sample of the specified size. */ | ||
| public static void getAc4SampleHeader(int size, ParsableByteArray buffer) { | ||
| // See ETSI TS 103 190-1 V1.3.1, Annex G. | ||
| buffer.reset(/* limit= */ 7); | ||
| buffer.data[0] = (byte) 0xAC; | ||
| buffer.data[1] = 0x40; | ||
| buffer.data[2] = (byte) 0xFF; | ||
| buffer.data[3] = (byte) 0xFF; | ||
| buffer.data[4] = (byte) ((size >> 16) & 0xFF); | ||
| buffer.data[5] = (byte) ((size >> 8) & 0xFF); | ||
| buffer.data[6] = (byte) (size & 0xFF); | ||
| } | ||
|
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| private static int readVariableBits(ParsableBitArray data, int bitsPerRead) { | ||
| int value = 0; | ||
| while (true) { | ||
| value += data.readBits(bitsPerRead); | ||
| if (!data.readBit()) { | ||
| break; | ||
| } | ||
| value++; | ||
| value <<= bitsPerRead; | ||
| } | ||
| return value; | ||
| } | ||
|
|
||
| private Ac4Util() {} | ||
| } |
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