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Merge pull request #47 from ittiam-systems:rtp-vp8
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206
...ary/rtsp/src/main/java/com/google/android/exoplayer2/source/rtsp/reader/RtpVp8Reader.java
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| /* | ||
| * 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 com.google.android.exoplayer2.source.rtsp.reader; | ||
|
|
||
| import static com.google.android.exoplayer2.util.Assertions.checkStateNotNull; | ||
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| import com.google.android.exoplayer2.C; | ||
| import com.google.android.exoplayer2.extractor.ExtractorOutput; | ||
| import com.google.android.exoplayer2.extractor.TrackOutput; | ||
| import com.google.android.exoplayer2.source.rtsp.RtpPacket; | ||
| import com.google.android.exoplayer2.source.rtsp.RtpPayloadFormat; | ||
| import com.google.android.exoplayer2.util.Log; | ||
| import com.google.android.exoplayer2.util.ParsableByteArray; | ||
| import com.google.android.exoplayer2.util.Util; | ||
| import org.checkerframework.checker.nullness.qual.MonotonicNonNull; | ||
|
|
||
| /** | ||
| * Parses a VP8 byte stream carried on RTP packets, and extracts VP8 individual video frames as | ||
| * defined in RFC7741. | ||
| */ | ||
| /* package */ final class RtpVp8Reader implements RtpPayloadReader { | ||
| private static final String TAG = "RtpVP8Reader"; | ||
|
|
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| /** VP9 uses a 90 KHz media clock (RFC7741 Section 4.1). */ | ||
| private static final long MEDIA_CLOCK_FREQUENCY = 90_000; | ||
|
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| private final RtpPayloadFormat payloadFormat; | ||
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| private @MonotonicNonNull TrackOutput trackOutput; | ||
|
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| /** | ||
| * First received RTP timestamp. All RTP timestamps are dimension-less, the time base is defined | ||
| * by {@link #MEDIA_CLOCK_FREQUENCY}. | ||
| */ | ||
| private long firstReceivedTimestamp; | ||
|
|
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| private int previousSequenceNumber; | ||
| /** The combined size of a sample that is fragmented into multiple RTP packets. */ | ||
| private int fragmentedSampleSizeBytes; | ||
|
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| private long startTimeOffsetUs; | ||
| /** | ||
| * Whether the first packet of one VP8 frame is received. A VP8 frame can be split into two RTP | ||
| * packets. | ||
| */ | ||
| private boolean gotFirstPacketOfVp8Frame; | ||
|
|
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| private boolean isKeyFrame; | ||
| private boolean isOutputFormatSet; | ||
|
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| /** Creates an instance. */ | ||
| public RtpVp8Reader(RtpPayloadFormat payloadFormat) { | ||
| this.payloadFormat = payloadFormat; | ||
| firstReceivedTimestamp = C.TIME_UNSET; | ||
| previousSequenceNumber = C.INDEX_UNSET; | ||
| fragmentedSampleSizeBytes = C.LENGTH_UNSET; | ||
| // The start time offset must be 0 until the first seek. | ||
| startTimeOffsetUs = 0; | ||
| gotFirstPacketOfVp8Frame = false; | ||
| isKeyFrame = false; | ||
| isOutputFormatSet = false; | ||
| } | ||
|
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| @Override | ||
| public void createTracks(ExtractorOutput extractorOutput, int trackId) { | ||
| trackOutput = extractorOutput.track(trackId, C.TRACK_TYPE_VIDEO); | ||
| trackOutput.format(payloadFormat.format); | ||
| } | ||
|
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| @Override | ||
| public void onReceivingFirstPacket(long timestamp, int sequenceNumber) {} | ||
|
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| @Override | ||
| public void consume( | ||
| ParsableByteArray data, long timestamp, int sequenceNumber, boolean rtpMarker) { | ||
| checkStateNotNull(trackOutput); | ||
|
|
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| boolean isValidVP8Descriptor = validateVp8Descriptor(data, sequenceNumber); | ||
| if (isValidVP8Descriptor) { | ||
| // VP8 Payload Header is defined in RFC7741 Section 4.3. | ||
| if (fragmentedSampleSizeBytes == C.LENGTH_UNSET && gotFirstPacketOfVp8Frame) { | ||
| isKeyFrame = (data.peekUnsignedByte() & 0x01) == 0; | ||
| } | ||
| if (!isOutputFormatSet) { | ||
| // Parsing frame data to get width and height, RFC6386 Section 19.1. | ||
| int currPosition = data.getPosition(); | ||
| // Skips the frame_tag and start_code. | ||
| data.setPosition(currPosition + 6); | ||
| // RFC6386 Section 19.1 specifically uses little endian. | ||
| int width = data.readLittleEndianUnsignedShort() & 0x3fff; | ||
| int height = data.readLittleEndianUnsignedShort() & 0x3fff; | ||
| data.setPosition(currPosition); | ||
|
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||
| if (width != payloadFormat.format.width || height != payloadFormat.format.height) { | ||
| trackOutput.format( | ||
| payloadFormat.format.buildUpon().setWidth(width).setHeight(height).build()); | ||
| } | ||
| isOutputFormatSet = true; | ||
| } | ||
|
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| int fragmentSize = data.bytesLeft(); | ||
| trackOutput.sampleData(data, fragmentSize); | ||
| fragmentedSampleSizeBytes += fragmentSize; | ||
|
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| if (rtpMarker) { | ||
| if (firstReceivedTimestamp == C.TIME_UNSET) { | ||
| firstReceivedTimestamp = timestamp; | ||
| } | ||
| long timeUs = toSampleUs(startTimeOffsetUs, timestamp, firstReceivedTimestamp); | ||
| trackOutput.sampleMetadata( | ||
| timeUs, | ||
| isKeyFrame ? C.BUFFER_FLAG_KEY_FRAME : 0, | ||
| fragmentedSampleSizeBytes, | ||
| /* offset= */ 0, | ||
| /* cryptoData= */ null); | ||
| fragmentedSampleSizeBytes = C.LENGTH_UNSET; | ||
| gotFirstPacketOfVp8Frame = false; | ||
| } | ||
| previousSequenceNumber = sequenceNumber; | ||
| } | ||
| } | ||
|
|
||
| @Override | ||
| public void seek(long nextRtpTimestamp, long timeUs) { | ||
| firstReceivedTimestamp = nextRtpTimestamp; | ||
| fragmentedSampleSizeBytes = C.LENGTH_UNSET; | ||
| startTimeOffsetUs = timeUs; | ||
| } | ||
|
|
||
| /** | ||
| * Returns {@code true} and sets the {@link ParsableByteArray#getPosition() payload.position} to | ||
| * the end of the descriptor, if a valid VP8 descriptor is present. | ||
| */ | ||
| private boolean validateVp8Descriptor(ParsableByteArray payload, int packetSequenceNumber) { | ||
| // VP8 Payload Descriptor is defined in RFC7741 Section 4.2. | ||
| int header = payload.readUnsignedByte(); | ||
| if (!gotFirstPacketOfVp8Frame) { | ||
| // TODO(b/198620566) Consider using ParsableBitArray. | ||
| // For start of VP8 partition S=1 and PID=0 as per RFC7741 Section 4.2. | ||
| if ((header & 0x10) != 0x1 || (header & 0x07) != 0) { | ||
| Log.w(TAG, "RTP packet is not the start of a new VP8 partition, skipping."); | ||
| return false; | ||
| } | ||
| gotFirstPacketOfVp8Frame = true; | ||
| } else { | ||
| // Check that this packet is in the sequence of the previous packet. | ||
| int expectedSequenceNumber = RtpPacket.getNextSequenceNumber(previousSequenceNumber); | ||
| if (packetSequenceNumber != expectedSequenceNumber) { | ||
| Log.w( | ||
| TAG, | ||
| Util.formatInvariant( | ||
| "Received RTP packet with unexpected sequence number. Expected: %d; received: %d." | ||
| + " Dropping packet.", | ||
| expectedSequenceNumber, packetSequenceNumber)); | ||
| return false; | ||
| } | ||
| } | ||
|
|
||
| // Check if optional X header is present. | ||
| if ((header & 0x80) != 0) { | ||
| int xHeader = payload.readUnsignedByte(); | ||
|
|
||
| // Check if optional I header is present. | ||
| if ((xHeader & 0x80) != 0) { | ||
| int iHeader = payload.readUnsignedByte(); | ||
| // Check if I header's M bit is present. | ||
| if ((iHeader & 0x80) != 0) { | ||
| payload.skipBytes(1); | ||
| } | ||
| } | ||
|
|
||
| // Check if optional L header is present. | ||
| if ((xHeader & 0x40) != 0) { | ||
| payload.skipBytes(1); | ||
| } | ||
|
|
||
| // Check if optional T or K header(s) is present. | ||
| if ((xHeader & 0x20) != 0 || (xHeader & 0x10) != 0) { | ||
| payload.skipBytes(1); | ||
| } | ||
| } | ||
| return true; | ||
| } | ||
|
|
||
| private static long toSampleUs( | ||
| long startTimeOffsetUs, long rtpTimestamp, long firstReceivedRtpTimestamp) { | ||
| return startTimeOffsetUs | ||
| + Util.scaleLargeTimestamp( | ||
| (rtpTimestamp - firstReceivedRtpTimestamp), | ||
| /* multiplier= */ C.MICROS_PER_SECOND, | ||
| /* divisor= */ MEDIA_CLOCK_FREQUENCY); | ||
| } | ||
| } |