/* * 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 org.mozilla.thirdparty.com.google.android.exoplayer2.audio; import androidx.annotation.Nullable; import org.mozilla.thirdparty.com.google.android.exoplayer2.C; import org.mozilla.thirdparty.com.google.android.exoplayer2.Format; import org.mozilla.thirdparty.com.google.android.exoplayer2.drm.DrmInitData; import org.mozilla.thirdparty.com.google.android.exoplayer2.util.MimeTypes; import org.mozilla.thirdparty.com.google.android.exoplayer2.util.ParsableBitArray; import org.mozilla.thirdparty.com.google.android.exoplayer2.util.ParsableByteArray; import java.nio.ByteBuffer; /** Utility methods for parsing AC-4 frames, which are access units in AC-4 bitstreams. */ public final class Ac4Util { /** Holds sample format information as presented by a syncframe header. */ public static final class SyncFrameInfo { /** 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; 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; } } public static final int AC40_SYNCWORD = 0xAC40; public static final int AC41_SYNCWORD = 0xAC41; /** The channel count of AC-4 stream. */ // TODO: Parse AC-4 stream channel count. private static final int CHANNEL_COUNT_2 = 2; /** * The AC-4 sync frame header size for extractor. The seven bytes are 0xAC, 0x40, 0xFF, 0xFF, * sizeByte1, sizeByte2, sizeByte3. See ETSI TS 103 190-1 V1.3.1, Annex G */ public static final int SAMPLE_HEADER_SIZE = 7; /** * 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, @Nullable 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; } /** 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(SAMPLE_HEADER_SIZE); 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); } 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() {} }