/*
* 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.checkNotNull;
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.MimeTypes;
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.TrackOutput;
import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
/**
* Parses an AMR byte stream carried on RTP packets and extracts individual samples. Interleaving
* mode is not supported. Refer to RFC4867 for more details.
*/
/* package */ final class RtpAmrReader implements RtpPayloadReader {
private static final String TAG = "RtpAmrReader";
/**
* The frame size in bytes, including header (1 byte), for each of the 16 frame types for AMR-NB
* (narrow band). AMR-NB supports eight narrow band speech encoding modes with bit rates between
* 4.75 and 12.2 kbps defined in RFC4867 Section 3.1. Refer to table 1a in 3GPP TS 26.101 for the
* mapping definition.
*/
private static final int[] AMR_NB_FRAME_TYPE_INDEX_TO_FRAME_SIZE = {
13, // 4.75kbps
14, // 5.15kbps
16, // 5.90kbps
18, // 6.70kbps PDC-EFR
20, // 7.40kbps TDMA-EFR
21, // 7.95kbps
27, // 10.2kbps
32, // 12.2kbps GSM-EFR
6, // AMR SID
7, // GSM-EFR SID
6, // TDMA-EFR SID
6, // PDC-EFR SID
1, // Future use
1, // Future use
1, // Future use
1 // No data
};
/**
* The frame size in bytes, including header (1 byte), for each of the 16 frame types for AMR-WB
* (wide band). AMR-WB supports nine wide band speech encoding modes with bit rates between 6.6 to
* 23.85 kbps defined in RFC4867 Section 3.2. Refer to table 1a in 3GPP TS 26.201. for the mapping
* definition.
*/
private static final int[] AMR_WB_FRAME_TYPE_INDEX_TO_FRAME_SIZE = {
18, // 6.60kbps
24, // 8.85kbps
33, // 12.65kbps
37, // 14.25kbps
41, // 15.85kbps
47, // 18.25kbps
51, // 19.85kbps
59, // 23.05kbps
61, // 23.85kbps
6, // AMR-WB SID
1, // Future use
1, // Future use
1, // Future use
1, // Future use
1, // speech lost
1 // No data
};
private final RtpPayloadFormat payloadFormat;
private final boolean isWideBand;
private final int sampleRate;
private @MonotonicNonNull TrackOutput trackOutput;
private long firstReceivedTimestamp;
private long startTimeOffsetUs;
private int previousSequenceNumber;
public RtpAmrReader(RtpPayloadFormat payloadFormat) {
this.payloadFormat = payloadFormat;
this.isWideBand =
MimeTypes.AUDIO_AMR_WB.equals(checkNotNull(payloadFormat.format.sampleMimeType));
this.sampleRate = payloadFormat.clockRate;
this.firstReceivedTimestamp = C.TIME_UNSET;
this.previousSequenceNumber = C.INDEX_UNSET;
// Start time offset must be 0 before the first seek.
this.startTimeOffsetUs = 0;
}
// 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);
// Check that this packet is in the sequence of the previous packet.
if (previousSequenceNumber != C.INDEX_UNSET) {
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));
}
}
//
// AMR as RTP payload (RFC4867 Section 4.2).
//
// +----------------+-------------------+----------------
// | payload header | table of contents | speech data ...
// +----------------+-------------------+----------------
//
// Payload header (RFC4867 Section 4.4.1).
//
// The header won't contain ILL and ILP, as interleaving is not currently supported.
// +-+-+-+-+-+-+-+- - - - - - - -
// | CMR |R|R|R|R| ILL | ILP |
// +-+-+-+-+-+-+-+- - - - - - - -
//
// Skip CMR and reserved bits.
data.skipBytes(1);
// Loop over sampleSize to send multiple frames along with appropriate timestamp when compound
// payload support is added.
int frameType = (data.peekUnsignedByte() >> 3) & 0x0f;
int frameSize = getFrameSize(frameType, isWideBand);
int sampleSize = data.bytesLeft();
checkArgument(sampleSize == frameSize, "compound payload not supported currently");
trackOutput.sampleData(data, sampleSize);
long sampleTimeUs =
toSampleTimeUs(startTimeOffsetUs, timestamp, firstReceivedTimestamp, sampleRate);
trackOutput.sampleMetadata(
sampleTimeUs, C.BUFFER_FLAG_KEY_FRAME, sampleSize, /* offset= */ 0, /* cryptoData= */ null);
previousSequenceNumber = sequenceNumber;
}
@Override
public void seek(long nextRtpTimestamp, long timeUs) {
firstReceivedTimestamp = nextRtpTimestamp;
startTimeOffsetUs = timeUs;
}
// Internal methods.
public static int getFrameSize(int frameType, boolean isWideBand) {
checkArgument(
// Valid frame types are defined in RFC4867 Section 4.3.1.
(frameType >= 0 && frameType <= 8) || frameType == 15,
"Illegal AMR " + (isWideBand ? "WB" : "NB") + " frame type " + frameType);
return isWideBand
? AMR_WB_FRAME_TYPE_INDEX_TO_FRAME_SIZE[frameType]
: AMR_NB_FRAME_TYPE_INDEX_TO_FRAME_SIZE[frameType];
}
}