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/*
* Copyright (C) 2018 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.extractor.ts;
import org.mozilla.thirdparty.com.google.android.exoplayer2.C;
import org.mozilla.thirdparty.com.google.android.exoplayer2.util.ParsableByteArray;
/** Utilities method for extracting MPEG-TS streams. */
public final class TsUtil {
/**
* Returns the position of the first TS_SYNC_BYTE within the range [startPosition, limitPosition)
* from the provided data array, or returns limitPosition if sync byte could not be found.
*/
public static int findSyncBytePosition(byte[] data, int startPosition, int limitPosition) {
int position = startPosition;
while (position < limitPosition && data[position] != TsExtractor.TS_SYNC_BYTE) {
position++;
}
return position;
}
/**
* Returns the PCR value read from a given TS packet.
*
* @param packetBuffer The buffer that holds the packet.
* @param startOfPacket The starting position of the packet in the buffer.
* @param pcrPid The PID for valid packets that contain PCR values.
* @return The PCR value read from the packet, if its PID is equal to {@code pcrPid} and it
* contains a valid PCR value. Returns {@link C#TIME_UNSET} otherwise.
*/
public static long readPcrFromPacket(
ParsableByteArray packetBuffer, int startOfPacket, int pcrPid) {
packetBuffer.setPosition(startOfPacket);
if (packetBuffer.bytesLeft() < 5) {
// Header = 4 bytes, adaptationFieldLength = 1 byte.
return C.TIME_UNSET;
}
// Note: See ISO/IEC 13818-1, section 2.4.3.2 for details of the header format.
int tsPacketHeader = packetBuffer.readInt();
if ((tsPacketHeader & 0x800000) != 0) {
// transport_error_indicator != 0 means there are uncorrectable errors in this packet.
return C.TIME_UNSET;
}
int pid = (tsPacketHeader & 0x1FFF00) >> 8;
if (pid != pcrPid) {
return C.TIME_UNSET;
}
boolean adaptationFieldExists = (tsPacketHeader & 0x20) != 0;
if (!adaptationFieldExists) {
return C.TIME_UNSET;
}
int adaptationFieldLength = packetBuffer.readUnsignedByte();
if (adaptationFieldLength >= 7 && packetBuffer.bytesLeft() >= 7) {
int flags = packetBuffer.readUnsignedByte();
boolean pcrFlagSet = (flags & 0x10) == 0x10;
if (pcrFlagSet) {
byte[] pcrBytes = new byte[6];
packetBuffer.readBytes(pcrBytes, /* offset= */ 0, pcrBytes.length);
return readPcrValueFromPcrBytes(pcrBytes);
}
}
return C.TIME_UNSET;
}
/**
* Returns the value of PCR base - first 33 bits in big endian order from the PCR bytes.
*
* <p>We ignore PCR Ext, because it's too small to have any significance.
*/
private static long readPcrValueFromPcrBytes(byte[] pcrBytes) {
return (pcrBytes[0] & 0xFFL) << 25
| (pcrBytes[1] & 0xFFL) << 17
| (pcrBytes[2] & 0xFFL) << 9
| (pcrBytes[3] & 0xFFL) << 1
| (pcrBytes[4] & 0xFFL) >> 7;
}
private TsUtil() {
// Prevent instantiation.
}
}
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