java.lang.Object
↳androidx.media3.extractor.Ac3Util
Gradle dependencies
compile group: 'androidx.media3', name: 'media3-extractor', version: '1.0.0-alpha03'
- groupId: androidx.media3
- artifactId: media3-extractor
- version: 1.0.0-alpha03
Artifact androidx.media3:media3-extractor:1.0.0-alpha03 it located at Google repository (https://maven.google.com/)
Overview
Utility methods for parsing Dolby TrueHD and (E-)AC-3 syncframes. (E-)AC-3 parsing follows the
definition in ETSI TS 102 366 V1.4.1.
Summary
Methods |
---|
public static int | findTrueHdSyncframeOffset(java.nio.ByteBuffer buffer)
Returns the offset relative to the buffer's position of the start of a TrueHD syncframe, or
C.INDEX_UNSET if no syncframe was found. |
public static Format | parseAc3AnnexFFormat(ParsableByteArray data, java.lang.String trackId, java.lang.String language, DrmInitData drmInitData)
Returns the AC-3 format given data containing the AC3SpecificBox according to Annex F. |
public static int | parseAc3SyncframeAudioSampleCount(java.nio.ByteBuffer buffer)
Reads the number of audio samples represented by the given (E-)AC-3 syncframe. |
public static Ac3Util.SyncFrameInfo | parseAc3SyncframeInfo(ParsableBitArray data)
Returns (E-)AC-3 format information given data containing a syncframe. |
public static int | parseAc3SyncframeSize(byte[] data[])
Returns the size in bytes of the given (E-)AC-3 syncframe. |
public static Format | parseEAc3AnnexFFormat(ParsableByteArray data, java.lang.String trackId, java.lang.String language, DrmInitData drmInitData)
Returns the E-AC-3 format given data containing the EC3SpecificBox according to Annex
F. |
public static int | parseTrueHdSyncframeAudioSampleCount(byte[] syncframe[])
Returns the number of audio samples represented by the given TrueHD syncframe, or 0 if the
buffer is not the start of a syncframe. |
public static int | parseTrueHdSyncframeAudioSampleCount(java.nio.ByteBuffer buffer, int offset)
Reads the number of audio samples represented by a TrueHD syncframe. |
from java.lang.Object | clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Fields
public static final int
AC3_MAX_RATE_BYTES_PER_SECONDMaximum rate for an AC-3 audio stream, in bytes per second.
public static final int
E_AC3_MAX_RATE_BYTES_PER_SECONDMaximum rate for an E-AC-3 audio stream, in bytes per second.
public static final int
TRUEHD_MAX_RATE_BYTES_PER_SECONDMaximum rate for a TrueHD audio stream, in bytes per second.
public static final int
TRUEHD_RECHUNK_SAMPLE_COUNTThe number of samples to store in each output chunk when rechunking TrueHD streams. The number
of samples extracted from the container corresponding to one syncframe must be an integer
multiple of this value.
public static final int
TRUEHD_SYNCFRAME_PREFIX_LENGTHThe number of bytes that must be parsed from a TrueHD syncframe to calculate the sample count.
Methods
Returns the AC-3 format given data containing the AC3SpecificBox according to Annex F.
The reading position of data will be modified.
Parameters:
data: The AC3SpecificBox to parse.
trackId: The track identifier to set on the format.
language: The language to set on the format.
drmInitData: DrmInitData to be included in the format.
Returns:
The AC-3 format parsed from data in the header.
Returns the E-AC-3 format given data containing the EC3SpecificBox according to Annex
F. The reading position of data will be modified.
Parameters:
data: The EC3SpecificBox to parse.
trackId: The track identifier to set on the format.
language: The language to set on the format.
drmInitData: DrmInitData to be included in the format.
Returns:
The E-AC-3 format parsed from data in the header.
Returns (E-)AC-3 format information given data containing a syncframe. The reading
position of data will be modified.
Parameters:
data: The data to parse, positioned at the start of the syncframe.
Returns:
The (E-)AC-3 format data parsed from the header.
public static int
parseAc3SyncframeSize(byte[] data[])
Returns the size in bytes of the given (E-)AC-3 syncframe.
Parameters:
data: The syncframe to parse.
Returns:
The syncframe size in bytes. C.LENGTH_UNSET if the input is invalid.
public static int
parseAc3SyncframeAudioSampleCount(java.nio.ByteBuffer buffer)
Reads the number of audio samples represented by the given (E-)AC-3 syncframe. The buffer's
position is not modified.
Parameters:
buffer: The java.nio.ByteBuffer
from which to read the syncframe.
Returns:
The number of audio samples represented by the syncframe.
public static int
findTrueHdSyncframeOffset(java.nio.ByteBuffer buffer)
Returns the offset relative to the buffer's position of the start of a TrueHD syncframe, or
C.INDEX_UNSET if no syncframe was found. The buffer's position is not modified.
Parameters:
buffer: The java.nio.ByteBuffer
within which to find a syncframe.
Returns:
The offset relative to the buffer's position of the start of a TrueHD syncframe, or
C.INDEX_UNSET if no syncframe was found.
public static int
parseTrueHdSyncframeAudioSampleCount(byte[] syncframe[])
Returns the number of audio samples represented by the given TrueHD syncframe, or 0 if the
buffer is not the start of a syncframe.
Parameters:
syncframe: The bytes from which to read the syncframe. Must be at least Ac3Util.TRUEHD_SYNCFRAME_PREFIX_LENGTH bytes long.
Returns:
The number of audio samples represented by the syncframe, or 0 if the buffer doesn't
contain the start of a syncframe.
public static int
parseTrueHdSyncframeAudioSampleCount(java.nio.ByteBuffer buffer, int offset)
Reads the number of audio samples represented by a TrueHD syncframe. The buffer's position is
not modified.
Parameters:
buffer: The java.nio.ByteBuffer
from which to read the syncframe.
offset: The offset of the start of the syncframe relative to the buffer's position.
Returns:
The number of audio samples represented by the syncframe.
Source
/*
* Copyright (C) 2016 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 androidx.media3.extractor;
import static java.lang.annotation.ElementType.TYPE_USE;
import androidx.annotation.IntDef;
import androidx.annotation.Nullable;
import androidx.media3.common.C;
import androidx.media3.common.DrmInitData;
import androidx.media3.common.Format;
import androidx.media3.common.MimeTypes;
import androidx.media3.common.util.ParsableBitArray;
import androidx.media3.common.util.ParsableByteArray;
import androidx.media3.common.util.UnstableApi;
import androidx.media3.common.util.Util;
import androidx.media3.extractor.Ac3Util.SyncFrameInfo.StreamType;
import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.nio.ByteBuffer;
/**
* Utility methods for parsing Dolby TrueHD and (E-)AC-3 syncframes. (E-)AC-3 parsing follows the
* definition in ETSI TS 102 366 V1.4.1.
*/
@UnstableApi
public final class Ac3Util {
/** Holds sample format information as presented by a syncframe header. */
public static final class SyncFrameInfo {
/**
* AC3 stream types. See also E.1.3.1.1. One of {@link #STREAM_TYPE_UNDEFINED}, {@link
* #STREAM_TYPE_TYPE0}, {@link #STREAM_TYPE_TYPE1} or {@link #STREAM_TYPE_TYPE2}.
*/
@Documented
@Retention(RetentionPolicy.SOURCE)
@Target(TYPE_USE)
@IntDef({STREAM_TYPE_UNDEFINED, STREAM_TYPE_TYPE0, STREAM_TYPE_TYPE1, STREAM_TYPE_TYPE2})
public @interface StreamType {}
/** Undefined AC3 stream type. */
public static final int STREAM_TYPE_UNDEFINED = -1;
/** Type 0 AC3 stream type. */
public static final int STREAM_TYPE_TYPE0 = 0;
/** Type 1 AC3 stream type. */
public static final int STREAM_TYPE_TYPE1 = 1;
/** Type 2 AC3 stream type. */
public static final int STREAM_TYPE_TYPE2 = 2;
/**
* The sample mime type of the bitstream. One of {@link MimeTypes#AUDIO_AC3} and {@link
* MimeTypes#AUDIO_E_AC3}.
*/
@Nullable public final String mimeType;
/**
* The type of the stream if {@link #mimeType} is {@link MimeTypes#AUDIO_E_AC3}, or {@link
* #STREAM_TYPE_UNDEFINED} otherwise.
*/
public final @StreamType int streamType;
/** 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(
@Nullable String mimeType,
@StreamType int streamType,
int channelCount,
int sampleRate,
int frameSize,
int sampleCount) {
this.mimeType = mimeType;
this.streamType = streamType;
this.channelCount = channelCount;
this.sampleRate = sampleRate;
this.frameSize = frameSize;
this.sampleCount = sampleCount;
}
}
/** Maximum rate for an AC-3 audio stream, in bytes per second. */
public static final int AC3_MAX_RATE_BYTES_PER_SECOND = 640 * 1000 / 8;
/** Maximum rate for an E-AC-3 audio stream, in bytes per second. */
public static final int E_AC3_MAX_RATE_BYTES_PER_SECOND = 6144 * 1000 / 8;
/** Maximum rate for a TrueHD audio stream, in bytes per second. */
public static final int TRUEHD_MAX_RATE_BYTES_PER_SECOND = 24500 * 1000 / 8;
/**
* The number of samples to store in each output chunk when rechunking TrueHD streams. The number
* of samples extracted from the container corresponding to one syncframe must be an integer
* multiple of this value.
*/
public static final int TRUEHD_RECHUNK_SAMPLE_COUNT = 16;
/**
* The number of bytes that must be parsed from a TrueHD syncframe to calculate the sample count.
*/
public static final int TRUEHD_SYNCFRAME_PREFIX_LENGTH = 10;
/** The number of new samples per (E-)AC-3 audio block. */
private static final int AUDIO_SAMPLES_PER_AUDIO_BLOCK = 256;
/** Each syncframe has 6 blocks that provide 256 new audio samples. See subsection 4.1. */
private static final int AC3_SYNCFRAME_AUDIO_SAMPLE_COUNT = 6 * AUDIO_SAMPLES_PER_AUDIO_BLOCK;
/** Number of audio blocks per E-AC-3 syncframe, indexed by numblkscod. */
private static final int[] BLOCKS_PER_SYNCFRAME_BY_NUMBLKSCOD = new int[] {1, 2, 3, 6};
/** Sample rates, indexed by fscod. */
private static final int[] SAMPLE_RATE_BY_FSCOD = new int[] {48000, 44100, 32000};
/** Sample rates, indexed by fscod2 (E-AC-3). */
private static final int[] SAMPLE_RATE_BY_FSCOD2 = new int[] {24000, 22050, 16000};
/** Channel counts, indexed by acmod. */
private static final int[] CHANNEL_COUNT_BY_ACMOD = new int[] {2, 1, 2, 3, 3, 4, 4, 5};
/** Nominal bitrates in kbps, indexed by frmsizecod / 2. (See table 4.13.) */
private static final int[] BITRATE_BY_HALF_FRMSIZECOD =
new int[] {
32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 384, 448, 512, 576, 640
};
/** 16-bit words per syncframe, indexed by frmsizecod / 2. (See table 4.13.) */
private static final int[] SYNCFRAME_SIZE_WORDS_BY_HALF_FRMSIZECOD_44_1 =
new int[] {
69, 87, 104, 121, 139, 174, 208, 243, 278, 348, 417, 487, 557, 696, 835, 975, 1114, 1253,
1393
};
/**
* Returns the AC-3 format given {@code data} containing the AC3SpecificBox according to Annex F.
* The reading position of {@code data} will be modified.
*
* @param data The AC3SpecificBox 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-3 format parsed from data in the header.
*/
public static Format parseAc3AnnexFFormat(
ParsableByteArray data, String trackId, String language, @Nullable DrmInitData drmInitData) {
int fscod = (data.readUnsignedByte() & 0xC0) >> 6;
int sampleRate = SAMPLE_RATE_BY_FSCOD[fscod];
int nextByte = data.readUnsignedByte();
int channelCount = CHANNEL_COUNT_BY_ACMOD[(nextByte & 0x38) >> 3];
if ((nextByte & 0x04) != 0) { // lfeon
channelCount++;
}
return new Format.Builder()
.setId(trackId)
.setSampleMimeType(MimeTypes.AUDIO_AC3)
.setChannelCount(channelCount)
.setSampleRate(sampleRate)
.setDrmInitData(drmInitData)
.setLanguage(language)
.build();
}
/**
* Returns the E-AC-3 format given {@code data} containing the EC3SpecificBox according to Annex
* F. The reading position of {@code data} will be modified.
*
* @param data The EC3SpecificBox 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 E-AC-3 format parsed from data in the header.
*/
public static Format parseEAc3AnnexFFormat(
ParsableByteArray data, String trackId, String language, @Nullable DrmInitData drmInitData) {
data.skipBytes(2); // data_rate, num_ind_sub
// Read the first independent substream.
int fscod = (data.readUnsignedByte() & 0xC0) >> 6;
int sampleRate = SAMPLE_RATE_BY_FSCOD[fscod];
int nextByte = data.readUnsignedByte();
int channelCount = CHANNEL_COUNT_BY_ACMOD[(nextByte & 0x0E) >> 1];
if ((nextByte & 0x01) != 0) { // lfeon
channelCount++;
}
// Read the first dependent substream.
nextByte = data.readUnsignedByte();
int numDepSub = ((nextByte & 0x1E) >> 1);
if (numDepSub > 0) {
int lowByteChanLoc = data.readUnsignedByte();
// Read Lrs/Rrs pair
// TODO: Read other channel configuration
if ((lowByteChanLoc & 0x02) != 0) {
channelCount += 2;
}
}
String mimeType = MimeTypes.AUDIO_E_AC3;
if (data.bytesLeft() > 0) {
nextByte = data.readUnsignedByte();
if ((nextByte & 0x01) != 0) { // flag_ec3_extension_type_a
mimeType = MimeTypes.AUDIO_E_AC3_JOC;
}
}
return new Format.Builder()
.setId(trackId)
.setSampleMimeType(mimeType)
.setChannelCount(channelCount)
.setSampleRate(sampleRate)
.setDrmInitData(drmInitData)
.setLanguage(language)
.build();
}
/**
* Returns (E-)AC-3 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 (E-)AC-3 format data parsed from the header.
*/
public static SyncFrameInfo parseAc3SyncframeInfo(ParsableBitArray data) {
int initialPosition = data.getPosition();
data.skipBits(40);
// Parse the bitstream ID for AC-3 and E-AC-3 (see subsections 4.3, E.1.2 and E.1.3.1.6).
boolean isEac3 = data.readBits(5) > 10;
data.setPosition(initialPosition);
@Nullable String mimeType;
@StreamType int streamType = SyncFrameInfo.STREAM_TYPE_UNDEFINED;
int sampleRate;
int acmod;
int frameSize;
int sampleCount;
boolean lfeon;
int channelCount;
if (isEac3) {
// Subsection E.1.2.
data.skipBits(16); // syncword
switch (data.readBits(2)) { // strmtyp
case 0:
streamType = SyncFrameInfo.STREAM_TYPE_TYPE0;
break;
case 1:
streamType = SyncFrameInfo.STREAM_TYPE_TYPE1;
break;
case 2:
streamType = SyncFrameInfo.STREAM_TYPE_TYPE2;
break;
default:
streamType = SyncFrameInfo.STREAM_TYPE_UNDEFINED;
break;
}
data.skipBits(3); // substreamid
frameSize = (data.readBits(11) + 1) * 2; // See frmsiz in subsection E.1.3.1.3.
int fscod = data.readBits(2);
int audioBlocks;
int numblkscod;
if (fscod == 3) {
numblkscod = 3;
sampleRate = SAMPLE_RATE_BY_FSCOD2[data.readBits(2)];
audioBlocks = 6;
} else {
numblkscod = data.readBits(2);
audioBlocks = BLOCKS_PER_SYNCFRAME_BY_NUMBLKSCOD[numblkscod];
sampleRate = SAMPLE_RATE_BY_FSCOD[fscod];
}
sampleCount = AUDIO_SAMPLES_PER_AUDIO_BLOCK * audioBlocks;
acmod = data.readBits(3);
lfeon = data.readBit();
channelCount = CHANNEL_COUNT_BY_ACMOD[acmod] + (lfeon ? 1 : 0);
data.skipBits(5 + 5); // bsid, dialnorm
if (data.readBit()) { // compre
data.skipBits(8); // compr
}
if (acmod == 0) {
data.skipBits(5); // dialnorm2
if (data.readBit()) { // compr2e
data.skipBits(8); // compr2
}
}
if (streamType == SyncFrameInfo.STREAM_TYPE_TYPE1 && data.readBit()) { // chanmape
data.skipBits(16); // chanmap
}
if (data.readBit()) { // mixmdate
if (acmod > 2) {
data.skipBits(2); // dmixmod
}
if ((acmod & 0x01) != 0 && acmod > 2) {
data.skipBits(3 + 3); // ltrtcmixlev, lorocmixlev
}
if ((acmod & 0x04) != 0) {
data.skipBits(6); // ltrtsurmixlev, lorosurmixlev
}
if (lfeon && data.readBit()) { // lfemixlevcode
data.skipBits(5); // lfemixlevcod
}
if (streamType == SyncFrameInfo.STREAM_TYPE_TYPE0) {
if (data.readBit()) { // pgmscle
data.skipBits(6); // pgmscl
}
if (acmod == 0 && data.readBit()) { // pgmscl2e
data.skipBits(6); // pgmscl2
}
if (data.readBit()) { // extpgmscle
data.skipBits(6); // extpgmscl
}
int mixdef = data.readBits(2);
if (mixdef == 1) {
data.skipBits(1 + 1 + 3); // premixcmpsel, drcsrc, premixcmpscl
} else if (mixdef == 2) {
data.skipBits(12); // mixdata
} else if (mixdef == 3) {
int mixdeflen = data.readBits(5);
if (data.readBit()) { // mixdata2e
data.skipBits(1 + 1 + 3); // premixcmpsel, drcsrc, premixcmpscl
if (data.readBit()) { // extpgmlscle
data.skipBits(4); // extpgmlscl
}
if (data.readBit()) { // extpgmcscle
data.skipBits(4); // extpgmcscl
}
if (data.readBit()) { // extpgmrscle
data.skipBits(4); // extpgmrscl
}
if (data.readBit()) { // extpgmlsscle
data.skipBits(4); // extpgmlsscl
}
if (data.readBit()) { // extpgmrsscle
data.skipBits(4); // extpgmrsscl
}
if (data.readBit()) { // extpgmlfescle
data.skipBits(4); // extpgmlfescl
}
if (data.readBit()) { // dmixscle
data.skipBits(4); // dmixscl
}
if (data.readBit()) { // addche
if (data.readBit()) { // extpgmaux1scle
data.skipBits(4); // extpgmaux1scl
}
if (data.readBit()) { // extpgmaux2scle
data.skipBits(4); // extpgmaux2scl
}
}
}
if (data.readBit()) { // mixdata3e
data.skipBits(5); // spchdat
if (data.readBit()) { // addspchdate
data.skipBits(5 + 2); // spchdat1, spchan1att
if (data.readBit()) { // addspdat1e
data.skipBits(5 + 3); // spchdat2, spchan2att
}
}
}
data.skipBits(8 * (mixdeflen + 2)); // mixdata
data.byteAlign(); // mixdatafill
}
if (acmod < 2) {
if (data.readBit()) { // paninfoe
data.skipBits(8 + 6); // panmean, paninfo
}
if (acmod == 0) {
if (data.readBit()) { // paninfo2e
data.skipBits(8 + 6); // panmean2, paninfo2
}
}
}
if (data.readBit()) { // frmmixcfginfoe
if (numblkscod == 0) {
data.skipBits(5); // blkmixcfginfo[0]
} else {
for (int blk = 0; blk < audioBlocks; blk++) {
if (data.readBit()) { // blkmixcfginfoe
data.skipBits(5); // blkmixcfginfo[blk]
}
}
}
}
}
}
if (data.readBit()) { // infomdate
data.skipBits(3 + 1 + 1); // bsmod, copyrightb, origbs
if (acmod == 2) {
data.skipBits(2 + 2); // dsurmod, dheadphonmod
}
if (acmod >= 6) {
data.skipBits(2); // dsurexmod
}
if (data.readBit()) { // audioprodie
data.skipBits(5 + 2 + 1); // mixlevel, roomtyp, adconvtyp
}
if (acmod == 0 && data.readBit()) { // audioprodi2e
data.skipBits(5 + 2 + 1); // mixlevel2, roomtyp2, adconvtyp2
}
if (fscod < 3) {
data.skipBit(); // sourcefscod
}
}
if (streamType == SyncFrameInfo.STREAM_TYPE_TYPE0 && numblkscod != 3) {
data.skipBit(); // convsync
}
if (streamType == SyncFrameInfo.STREAM_TYPE_TYPE2
&& (numblkscod == 3 || data.readBit())) { // blkid
data.skipBits(6); // frmsizecod
}
mimeType = MimeTypes.AUDIO_E_AC3;
if (data.readBit()) { // addbsie
int addbsil = data.readBits(6);
if (addbsil == 1 && data.readBits(8) == 1) { // addbsi
mimeType = MimeTypes.AUDIO_E_AC3_JOC;
}
}
} else /* is AC-3 */ {
mimeType = MimeTypes.AUDIO_AC3;
data.skipBits(16 + 16); // syncword, crc1
int fscod = data.readBits(2);
if (fscod == 3) {
// fscod '11' indicates that the decoder should not attempt to decode audio. We invalidate
// the mime type to prevent association with a renderer.
mimeType = null;
}
int frmsizecod = data.readBits(6);
frameSize = getAc3SyncframeSize(fscod, frmsizecod);
data.skipBits(5 + 3); // bsid, bsmod
acmod = data.readBits(3);
if ((acmod & 0x01) != 0 && acmod != 1) {
data.skipBits(2); // cmixlev
}
if ((acmod & 0x04) != 0) {
data.skipBits(2); // surmixlev
}
if (acmod == 2) {
data.skipBits(2); // dsurmod
}
sampleRate =
fscod < SAMPLE_RATE_BY_FSCOD.length ? SAMPLE_RATE_BY_FSCOD[fscod] : Format.NO_VALUE;
sampleCount = AC3_SYNCFRAME_AUDIO_SAMPLE_COUNT;
lfeon = data.readBit();
channelCount = CHANNEL_COUNT_BY_ACMOD[acmod] + (lfeon ? 1 : 0);
}
return new SyncFrameInfo(
mimeType, streamType, channelCount, sampleRate, frameSize, sampleCount);
}
/**
* Returns the size in bytes of the given (E-)AC-3 syncframe.
*
* @param data The syncframe to parse.
* @return The syncframe size in bytes. {@link C#LENGTH_UNSET} if the input is invalid.
*/
public static int parseAc3SyncframeSize(byte[] data) {
if (data.length < 6) {
return C.LENGTH_UNSET;
}
// Parse the bitstream ID for AC-3 and E-AC-3 (see subsections 4.3, E.1.2 and E.1.3.1.6).
boolean isEac3 = ((data[5] & 0xF8) >> 3) > 10;
if (isEac3) {
int frmsiz = (data[2] & 0x07) << 8; // Most significant 3 bits.
frmsiz |= data[3] & 0xFF; // Least significant 8 bits.
return (frmsiz + 1) * 2; // See frmsiz in subsection E.1.3.1.3.
} else {
int fscod = (data[4] & 0xC0) >> 6;
int frmsizecod = data[4] & 0x3F;
return getAc3SyncframeSize(fscod, frmsizecod);
}
}
/**
* Reads the number of audio samples represented by the given (E-)AC-3 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 parseAc3SyncframeAudioSampleCount(ByteBuffer buffer) {
// Parse the bitstream ID for AC-3 and E-AC-3 (see subsections 4.3, E.1.2 and E.1.3.1.6).
boolean isEac3 = ((buffer.get(buffer.position() + 5) & 0xF8) >> 3) > 10;
if (isEac3) {
int fscod = (buffer.get(buffer.position() + 4) & 0xC0) >> 6;
int numblkscod = fscod == 0x03 ? 3 : (buffer.get(buffer.position() + 4) & 0x30) >> 4;
return BLOCKS_PER_SYNCFRAME_BY_NUMBLKSCOD[numblkscod] * AUDIO_SAMPLES_PER_AUDIO_BLOCK;
} else {
return AC3_SYNCFRAME_AUDIO_SAMPLE_COUNT;
}
}
/**
* Returns the offset relative to the buffer's position of the start of a TrueHD syncframe, or
* {@link C#INDEX_UNSET} if no syncframe was found. The buffer's position is not modified.
*
* @param buffer The {@link ByteBuffer} within which to find a syncframe.
* @return The offset relative to the buffer's position of the start of a TrueHD syncframe, or
* {@link C#INDEX_UNSET} if no syncframe was found.
*/
public static int findTrueHdSyncframeOffset(ByteBuffer buffer) {
int startIndex = buffer.position();
int endIndex = buffer.limit() - TRUEHD_SYNCFRAME_PREFIX_LENGTH;
for (int i = startIndex; i <= endIndex; i++) {
// The syncword ends 0xBA for TrueHD or 0xBB for MLP.
if ((Util.getBigEndianInt(buffer, i + 4) & 0xFFFFFFFE) == 0xF8726FBA) {
return i - startIndex;
}
}
return C.INDEX_UNSET;
}
/**
* Returns the number of audio samples represented by the given TrueHD syncframe, or 0 if the
* buffer is not the start of a syncframe.
*
* @param syncframe The bytes from which to read the syncframe. Must be at least {@link
* #TRUEHD_SYNCFRAME_PREFIX_LENGTH} bytes long.
* @return The number of audio samples represented by the syncframe, or 0 if the buffer doesn't
* contain the start of a syncframe.
*/
public static int parseTrueHdSyncframeAudioSampleCount(byte[] syncframe) {
// See "Dolby TrueHD (MLP) high-level bitstream description" on the Dolby developer site,
// subsections 2.2 and 4.2.1. The syncword ends 0xBA for TrueHD or 0xBB for MLP.
if (syncframe[4] != (byte) 0xF8
|| syncframe[5] != (byte) 0x72
|| syncframe[6] != (byte) 0x6F
|| (syncframe[7] & 0xFE) != 0xBA) {
return 0;
}
boolean isMlp = (syncframe[7] & 0xFF) == 0xBB;
return 40 << ((syncframe[isMlp ? 9 : 8] >> 4) & 0x07);
}
/**
* Reads the number of audio samples represented by a TrueHD syncframe. The buffer's position is
* not modified.
*
* @param buffer The {@link ByteBuffer} from which to read the syncframe.
* @param offset The offset of the start of the syncframe relative to the buffer's position.
* @return The number of audio samples represented by the syncframe.
*/
public static int parseTrueHdSyncframeAudioSampleCount(ByteBuffer buffer, int offset) {
// TODO: Link to specification if available.
boolean isMlp = (buffer.get(buffer.position() + offset + 7) & 0xFF) == 0xBB;
return 40 << ((buffer.get(buffer.position() + offset + (isMlp ? 9 : 8)) >> 4) & 0x07);
}
private static int getAc3SyncframeSize(int fscod, int frmsizecod) {
int halfFrmsizecod = frmsizecod / 2;
if (fscod < 0
|| fscod >= SAMPLE_RATE_BY_FSCOD.length
|| frmsizecod < 0
|| halfFrmsizecod >= SYNCFRAME_SIZE_WORDS_BY_HALF_FRMSIZECOD_44_1.length) {
// Invalid values provided.
return C.LENGTH_UNSET;
}
int sampleRate = SAMPLE_RATE_BY_FSCOD[fscod];
if (sampleRate == 44100) {
return 2 * (SYNCFRAME_SIZE_WORDS_BY_HALF_FRMSIZECOD_44_1[halfFrmsizecod] + (frmsizecod % 2));
}
int bitrate = BITRATE_BY_HALF_FRMSIZECOD[halfFrmsizecod];
if (sampleRate == 32000) {
return 6 * bitrate;
} else { // sampleRate == 48000
return 4 * bitrate;
}
}
private Ac3Util() {}
}