Add support for RTSP Opus

Added Opus RTP packet reader and added support for Opus
playback through RTSP

Change-Id: Ib6702bd8aafd0bd782e89127ab907061ff06ccb3

libraries/exoplayer_rtsp/src/main/java/androidx/media3/exoplayer/rtsp/RtpPayloadFormat.java

@@ -37,6 +37,7 @@ import java.util.Map;
 public final class RtpPayloadFormat {
 
   private static final String RTP_MEDIA_AC3 = "AC3";
+  private static final String RTP_MEDIA_OPUS = "OPUS";
   private static final String RTP_MEDIA_MPEG4_GENERIC = "MPEG4-GENERIC";
   private static final String RTP_MEDIA_H264 = "H264";
   private static final String RTP_MEDIA_H265 = "H265";
@@ -45,6 +46,7 @@ public final class RtpPayloadFormat {
   public static boolean isFormatSupported(MediaDescription mediaDescription) {
     switch (Ascii.toUpperCase(mediaDescription.rtpMapAttribute.mediaEncoding)) {
       case RTP_MEDIA_AC3:
+      case RTP_MEDIA_OPUS:
       case RTP_MEDIA_H264:
       case RTP_MEDIA_H265:
       case RTP_MEDIA_MPEG4_GENERIC:
@@ -71,6 +73,8 @@ public final class RtpPayloadFormat {
         return MimeTypes.VIDEO_H265;
       case RTP_MEDIA_MPEG4_GENERIC:
         return MimeTypes.AUDIO_AAC;
+      case RTP_MEDIA_OPUS:
+        return MimeTypes.AUDIO_OPUS;
       default:
         throw new IllegalArgumentException(mediaType);
     }

libraries/exoplayer_rtsp/src/main/java/androidx/media3/exoplayer/rtsp/RtspMediaTrack.java

@@ -121,6 +121,14 @@ import com.google.common.collect.ImmutableMap;
         checkArgument(!fmtpParameters.isEmpty());
         processAacFmtpAttribute(formatBuilder, fmtpParameters, channelCount, clockRate);
         break;
+      case MimeTypes.AUDIO_OPUS:
+        // RFC7587 Section 7
+        checkArgument(channelCount == 2, "Invalid channel count");
+        // RFC7587 Section 6.1
+        // the RTP timestamp is incremented with a 48000 Hz clock rate
+        // for all modes of Opus and all sampling rates.
+        checkArgument(clockRate == 48000, "Invalid sampling rate");
+        break;
       case MimeTypes.VIDEO_H264:
         checkArgument(!fmtpParameters.isEmpty());
         processH264FmtpAttribute(formatBuilder, fmtpParameters);

libraries/exoplayer_rtsp/src/main/java/androidx/media3/exoplayer/rtsp/reader/DefaultRtpPayloadReaderFactory.java

@@ -36,6 +36,8 @@ import androidx.media3.exoplayer.rtsp.RtpPayloadFormat;
         return new RtpAc3Reader(payloadFormat);
       case MimeTypes.AUDIO_AAC:
         return new RtpAacReader(payloadFormat);
+      case MimeTypes.AUDIO_OPUS:
+        return new RtpOpusReader(payloadFormat);
       case MimeTypes.VIDEO_H264:
         return new RtpH264Reader(payloadFormat);
       case MimeTypes.VIDEO_H265:

libraries/exoplayer_rtsp/src/main/java/androidx/media3/exoplayer/rtsp/reader/RtpOpusReader.java

@@ -0,0 +1,152 @@
+/*
+ * 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 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";
+
+  private final RtpPayloadFormat payloadFormat;
+  private @MonotonicNonNull TrackOutput trackOutput;
+  private long firstReceivedTimestamp;
+  private long startTimeOffsetUs;
+
+  private final int sampleRate;
+  private int previousSequenceNumber;
+  private boolean foundOpusIDHeader;
+  private boolean foundOpusCommentHeader;
+
+  public RtpOpusReader(RtpPayloadFormat payloadFormat) {
+    this.payloadFormat = payloadFormat;
+    this.firstReceivedTimestamp = C.INDEX_UNSET;
+    this.sampleRate = this.payloadFormat.clockRate;
+    this.previousSequenceNumber = C.INDEX_UNSET;
+    this.foundOpusIDHeader = false;
+    this.foundOpusCommentHeader = false;
+  }
+
+  // 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) {
+      int currPosition = data.getPosition();
+      checkArgument(isOpusIDHeader(data), "ID Header missing");
+
+      data.setPosition(currPosition);
+      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
+      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, sampleRate);
+      trackOutput.sampleMetadata(timeUs, C.BUFFER_FLAG_KEY_FRAME, size, 0, null);
+    }
+    previousSequenceNumber = sequenceNumber;
+  }
+
+  @Override
+  public void seek(long nextRtpTimestamp, long timeUs) {
+    firstReceivedTimestamp = nextRtpTimestamp;
+    startTimeOffsetUs = timeUs;
+  }
+
+  // Internal methods.
+
+  private static boolean isOpusIDHeader(ParsableByteArray data) {
+    int sampleSize = data.limit();
+    String header = data.readString(8);
+    // Identification header RFC7845 Section 5.1
+    if (sampleSize < 19 || !header.equals("OpusHead")) {
+      Log.e(
+          TAG,
+          Util.formatInvariant(
+              "first data octet of the RTP packet is not the beginning of a OpusHeader "
+                  + "Dropping current packet"));
+      return false;
+    }
+    checkArgument(data.readUnsignedByte() == 1, "version number must always be 1");
+    return true;
+  }
+
+  /** Returns the correct sample time from RTP timestamp, accounting for the OPUS sampling rate. */
+  private static long toSampleTimeUs(
+      long startTimeOffsetUs, long rtpTimestamp, long firstReceivedRtpTimestamp, int sampleRate) {
+    return startTimeOffsetUs
+        + Util.scaleLargeTimestamp(
+            rtpTimestamp - firstReceivedRtpTimestamp,
+            /* multiplier= */ C.MICROS_PER_SECOND,
+            /* divisor= */ sampleRate);
+  }
+}