Add support for RTSP Mp4a-Latm

Added Mp4a-latm RTP Packet reader and added support for Mp4a-latm
playback through RTSP.

Change-Id: Ia590393f53ca880af926907843f6bea9ff0f4b35

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

@@ -55,6 +55,7 @@ public final class RtpPayloadFormat {
   private static final String RTP_MEDIA_PCMU = "PCMU";
   private static final String RTP_MEDIA_VP8 = "VP8";
   private static final String RTP_MEDIA_VP9 = "VP9";
+  public static final String RTP_MEDIA_MPEG4_AUDIO = "MP4A-LATM";
 
   /** Returns whether the format of a {@link MediaDescription} is supported. */
   public static boolean isFormatSupported(MediaDescription mediaDescription) {
@@ -66,6 +67,7 @@ public final class RtpPayloadFormat {
       case RTP_MEDIA_H263_2000:
       case RTP_MEDIA_H264:
       case RTP_MEDIA_H265:
+      case RTP_MEDIA_MPEG4_AUDIO:
       case RTP_MEDIA_MPEG4_VIDEO:
       case RTP_MEDIA_MPEG4_GENERIC:
       case RTP_MEDIA_OPUS:
@@ -97,6 +99,7 @@ public final class RtpPayloadFormat {
       case RTP_MEDIA_AMR_WB:
         return MimeTypes.AUDIO_AMR_WB;
       case RTP_MEDIA_MPEG4_GENERIC:
+      case RTP_MEDIA_MPEG4_AUDIO:
         return MimeTypes.AUDIO_AAC;
       case RTP_MEDIA_OPUS:
         return MimeTypes.AUDIO_OPUS;
@@ -142,6 +145,7 @@ public final class RtpPayloadFormat {
   public final Format format;
   /** The format parameters, mapped from the SDP FMTP attribute (RFC2327 Page 22). */
   public final ImmutableMap<String, String> fmtpParameters;
+  public final String mediaEncoding;
 
   /**
    * Creates a new instance.
@@ -154,12 +158,13 @@ public final class RtpPayloadFormat {
    *     empty if unset. The keys and values are specified in the RFCs for specific formats. For
    *     instance, RFC3640 Section 4.1 defines keys like profile-level-id and config.
    */
-  public RtpPayloadFormat(
+  public RtpPayloadFormat(Format format, int rtpPayloadType, int clockRate, Map<String,
-      Format format, int rtpPayloadType, int clockRate, Map<String, String> fmtpParameters) {
+      String> fmtpParameters, String mediaEncoding) {
     this.rtpPayloadType = rtpPayloadType;
     this.clockRate = clockRate;
     this.format = format;
     this.fmtpParameters = ImmutableMap.copyOf(fmtpParameters);
+    this.mediaEncoding = mediaEncoding;
   }
 
   @Override

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

@@ -267,7 +267,8 @@ import com.google.common.collect.ImmutableMap;
     }
 
     checkArgument(clockRate > 0);
-    return new RtpPayloadFormat(formatBuilder.build(), rtpPayloadType, clockRate, fmtpParameters);
+    return new RtpPayloadFormat(
+        formatBuilder.build(), rtpPayloadType, clockRate, fmtpParameters, mediaEncoding);
   }
 
   private static int inferChannelCount(int encodingParameter, String mimeType) {

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

@@ -35,7 +35,11 @@ import androidx.media3.exoplayer.rtsp.RtpPayloadFormat;
       case MimeTypes.AUDIO_AC3:
         return new RtpAc3Reader(payloadFormat);
       case MimeTypes.AUDIO_AAC:
+        if(payloadFormat.mediaEncoding.equals(RtpPayloadFormat.RTP_MEDIA_MPEG4_AUDIO)){
+          return new RtpMp4aPayloadReader(payloadFormat);
+        } else {
           return new RtpAacReader(payloadFormat);
+        }
       case MimeTypes.AUDIO_AMR_NB:
       case MimeTypes.AUDIO_AMR_WB:
         return new RtpAmrReader(payloadFormat);

libraries/exoplayer_rtsp/src/main/java/androidx/media3/exoplayer/rtsp/reader/RtpMp4aPayloadReader.java

@@ -0,0 +1,157 @@
+/*
+ * 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.checkState;
+import static androidx.media3.common.util.Assertions.checkStateNotNull;
+import static androidx.media3.common.util.Assertions.checkArgument;
+import static androidx.media3.common.util.Util.castNonNull;
+
+import androidx.annotation.Nullable;
+import androidx.media3.common.C;
+import androidx.media3.common.ParserException;
+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.exoplayer.rtsp.RtpPayloadFormat;
+import androidx.media3.extractor.ExtractorOutput;
+import androidx.media3.extractor.TrackOutput;
+
+import com.google.common.collect.ImmutableMap;
+import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
+
+/**
+ * Parses an MP4A-LATM byte stream carried on RTP packets, and extracts MP4A-LATM Access Units.
+ * Refer to RFC3016 for more details.
+ */
+@UnstableApi
+/* package */ final class RtpMp4aPayloadReader  implements RtpPayloadReader {
+  private static final String TAG = "RtpMp4aLatmReader";
+
+  private static final String PARAMETER_MP4A_CONFIG = "config";
+
+  private final RtpPayloadFormat payloadFormat;
+  private @MonotonicNonNull TrackOutput trackOutput;
+  private long firstReceivedTimestamp;
+  /** The combined size of a sample that is fragmented into multiple subFrames. */
+  private int fragmentedSampleSizeBytes;
+  private long startTimeOffsetUs;
+
+  /** Creates an instance. */
+  public RtpMp4aPayloadReader(RtpPayloadFormat payloadFormat) {
+    this.payloadFormat = payloadFormat;
+    firstReceivedTimestamp = C.TIME_UNSET;
+    fragmentedSampleSizeBytes = 0;
+    // The start time offset must be 0 until the first seek.
+    startTimeOffsetUs = 0;
+  }
+
+  @Override
+  public void createTracks(ExtractorOutput extractorOutput, int trackId) {
+    trackOutput = extractorOutput.track(trackId, C.TRACK_TYPE_VIDEO);
+    castNonNull(trackOutput).format(payloadFormat.format);
+  }
+
+  @Override
+  public void onReceivingFirstPacket(long timestamp, int sequenceNumber) {
+    checkState(firstReceivedTimestamp == C.TIME_UNSET);
+    firstReceivedTimestamp = timestamp;
+  }
+
+  @Override
+  public void consume(
+      ParsableByteArray data, long timestamp, int sequenceNumber, boolean rtpMarker)
+      throws ParserException {
+    checkStateNotNull(trackOutput);
+
+    int sampleOffset = 0;
+    int numSubFrames = getNumOfSubframesFromMpeg4AudioConfig(payloadFormat.fmtpParameters);
+    for (int subFrame = 0; subFrame <= numSubFrames; subFrame++) {
+      int sampleLength = 0;
+
+      /* Each subframe starts with a variable length encoding */
+      for (; sampleOffset < data.bytesLeft(); sampleOffset++) {
+        sampleLength += data.getData()[sampleOffset] & 0xff;
+        if ((data.getData()[sampleOffset] & 0xff) != 0xff) {
+          break;
+        }
+      }
+      sampleOffset++;
+      data.setPosition(sampleOffset);
+
+      // Write the audio sample
+      trackOutput.sampleData(data, sampleLength);
+      sampleOffset += sampleLength;
+      fragmentedSampleSizeBytes += sampleLength;
+    }
+    if (rtpMarker) {
+      long timeUs =
+          toSampleUs(startTimeOffsetUs, timestamp, firstReceivedTimestamp, payloadFormat.clockRate);
+      trackOutput.sampleMetadata(
+          timeUs, C.BUFFER_FLAG_KEY_FRAME, fragmentedSampleSizeBytes, 0, null);
+      fragmentedSampleSizeBytes = 0;
+    }
+  }
+
+  @Override
+  public void seek(long nextRtpTimestamp, long timeUs) {
+    firstReceivedTimestamp = nextRtpTimestamp;
+    fragmentedSampleSizeBytes = 0;
+    startTimeOffsetUs = timeUs;
+  }
+
+  // Internal methods.
+  private static long toSampleUs(
+      long startTimeOffsetUs, long rtpTimestamp, long firstReceivedRtpTimestamp, int sampleRate) {
+    return startTimeOffsetUs
+        + Util.scaleLargeTimestamp(
+        rtpTimestamp - firstReceivedRtpTimestamp,
+        /* multiplier= */ C.MICROS_PER_SECOND,
+        /* divisor= */ sampleRate);
+  }
+
+  /**
+   * Parses an MPEG-4 Audio Stream Mux configuration, as defined in ISO/IEC14496-3. FMTP attribute
+   * contains config which is a byte array containing the MPEG-4 Audio Stream Mux configuration to
+   * parse.
+   *
+   * @param fmtpAttributes The format parameters, mapped from the SDP FMTP attribute.
+   * @return The number of subframes.
+   * @throws ParserException If the MPEG-4 Audio Stream Mux configuration cannot be parsed due to
+   *     unsupported audioMuxVersion.
+   */
+  public static Integer getNumOfSubframesFromMpeg4AudioConfig(
+      ImmutableMap<String, String> fmtpAttributes) throws ParserException {
+    @Nullable String configInput = fmtpAttributes.get(PARAMETER_MP4A_CONFIG);
+    int numSubFrames = 0;
+    if (configInput != null && configInput.length() % 2 == 0) {
+      byte[] configBuffer = Util.getBytesFromHexString(configInput);
+      ParsableBitArray scratchBits = new ParsableBitArray(configBuffer);
+      int audioMuxVersion = scratchBits.readBits(1);
+      if (audioMuxVersion == 0) {
+        checkArgument(scratchBits.readBits(1) == 1, "Invalid allStreamsSameTimeFraming.");
+        numSubFrames = scratchBits.readBits(6);
+        checkArgument(scratchBits.readBits(4) == 0, "Invalid numProgram.");
+        checkArgument(scratchBits.readBits(3) == 0, "Invalid numLayer.");
+      } else {
+        throw ParserException.createForMalformedDataOfUnknownType(
+            "unsupported audio mux version: " + audioMuxVersion, null);
+      }
+    }
+    return numSubFrames;
+  }
+}