RtpOpusReader.java
/*
* Copyright 2022 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.exoplayer.rtsp.reader;
import static androidx.media3.common.util.Assertions.checkArgument;
import static androidx.media3.common.util.Assertions.checkStateNotNull;
import static androidx.media3.exoplayer.rtsp.reader.RtpReaderUtils.toSampleTimeUs;
import androidx.media3.common.C;
import androidx.media3.common.Format;
import androidx.media3.common.util.Log;
import androidx.media3.common.util.ParsableByteArray;
import androidx.media3.common.util.Util;
import androidx.media3.exoplayer.rtsp.RtpPacket;
import androidx.media3.exoplayer.rtsp.RtpPayloadFormat;
import androidx.media3.extractor.ExtractorOutput;
import androidx.media3.extractor.OpusUtil;
import androidx.media3.extractor.TrackOutput;
import java.util.List;
import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
/**
* Parses an OPUS byte stream carried on RTP packets and extracts individual samples. Refer to
* RFC7845 for more details.
*/
/* package */ final class RtpOpusReader implements RtpPayloadReader {
private static final String TAG = "RtpOpusReader";
/* Opus uses a fixed 48KHz media clock RFC7845 Section 4. */
private static final int MEDIA_CLOCK_FREQUENCY = 48_000;
private final RtpPayloadFormat payloadFormat;
private @MonotonicNonNull TrackOutput trackOutput;
/**
* First received RTP timestamp. All RTP timestamps are dimension-less, the time base is defined
* by {@link #MEDIA_CLOCK_FREQUENCY}.
*/
private long firstReceivedTimestamp;
private long startTimeOffsetUs;
private int previousSequenceNumber;
private boolean foundOpusIDHeader;
private boolean foundOpusCommentHeader;
/** Creates an instance. */
public RtpOpusReader(RtpPayloadFormat payloadFormat) {
this.payloadFormat = payloadFormat;
this.firstReceivedTimestamp = C.INDEX_UNSET;
this.previousSequenceNumber = C.INDEX_UNSET;
}
// RtpPayloadReader implementation.
@Override
public void createTracks(ExtractorOutput extractorOutput, int trackId) {
trackOutput = extractorOutput.track(trackId, C.TRACK_TYPE_AUDIO);
trackOutput.format(payloadFormat.format);
}
@Override
public void onReceivingFirstPacket(long timestamp, int sequenceNumber) {
this.firstReceivedTimestamp = timestamp;
}
@Override
public void consume(
ParsableByteArray data, long timestamp, int sequenceNumber, boolean rtpMarker) {
checkStateNotNull(trackOutput);
/* RFC7845 Section 3.
* +---------+ +----------------+ +--------------------+ +-----
* |ID Header| | Comment Header | |Audio Data Packet 1 | | ...
* +---------+ +----------------+ +--------------------+ +-----
*/
if (!foundOpusIDHeader) {
validateOpusIdHeader(data);
List<byte[]> initializationData = OpusUtil.buildInitializationData(data.getData());
Format.Builder formatBuilder = payloadFormat.format.buildUpon();
formatBuilder.setInitializationData(initializationData);
trackOutput.format(formatBuilder.build());
foundOpusIDHeader = true;
} else if (!foundOpusCommentHeader) {
// Comment Header RFC7845 Section 5.2.
int sampleSize = data.limit();
checkArgument(sampleSize >= 8, "Comment Header has insufficient data");
String header = data.readString(8);
checkArgument(header.equals("OpusTags"), "Comment Header should follow ID Header");
foundOpusCommentHeader = true;
} else {
// Check that this packet is in the sequence of the previous packet.
int expectedSequenceNumber = RtpPacket.getNextSequenceNumber(previousSequenceNumber);
if (sequenceNumber != expectedSequenceNumber) {
Log.w(
TAG,
Util.formatInvariant(
"Received RTP packet with unexpected sequence number. Expected: %d; received: %d.",
expectedSequenceNumber, sequenceNumber));
}
// sending opus data.
int size = data.bytesLeft();
trackOutput.sampleData(data, size);
long timeUs =
toSampleTimeUs(
startTimeOffsetUs, timestamp, firstReceivedTimestamp, MEDIA_CLOCK_FREQUENCY);
trackOutput.sampleMetadata(
timeUs, C.BUFFER_FLAG_KEY_FRAME, size, /* offset*/ 0, /* cryptoData*/ null);
}
previousSequenceNumber = sequenceNumber;
}
@Override
public void seek(long nextRtpTimestamp, long timeUs) {
firstReceivedTimestamp = nextRtpTimestamp;
startTimeOffsetUs = timeUs;
}
// Internal methods.
/**
* Validates the OPUS ID Header at {@code data}'s current position, throws {@link
* IllegalArgumentException} if the header is invalid.
*
* <p>{@code data}'s position does not change after returning.
*/
private static void validateOpusIdHeader(ParsableByteArray data) {
int currPosition = data.getPosition();
int sampleSize = data.limit();
checkArgument(sampleSize > 18, "ID Header has insufficient data");
String header = data.readString(8);
// Identification header RFC7845 Section 5.1.
checkArgument(header.equals("OpusHead"), "ID Header missing");
checkArgument(data.readUnsignedByte() == 1, "version number must always be 1");
data.setPosition(currPosition);
}
}