1 /*
2  * Copyright (C) 2016 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 package com.google.android.exoplayer2.extractor.flv;
17 
18 import android.util.Pair;
19 import com.google.android.exoplayer2.C;
20 import com.google.android.exoplayer2.Format;
21 import com.google.android.exoplayer2.extractor.TrackOutput;
22 import com.google.android.exoplayer2.util.CodecSpecificDataUtil;
23 import com.google.android.exoplayer2.util.MimeTypes;
24 import com.google.android.exoplayer2.util.ParsableByteArray;
25 import java.util.Collections;
26 
27 /**
28  * Parses audio tags from an FLV stream and extracts AAC frames.
29  */
30 /* package */ final class AudioTagPayloadReader extends TagPayloadReader {
31 
32   private static final int AUDIO_FORMAT_MP3 = 2;
33   private static final int AUDIO_FORMAT_ALAW = 7;
34   private static final int AUDIO_FORMAT_ULAW = 8;
35   private static final int AUDIO_FORMAT_AAC = 10;
36 
37   private static final int AAC_PACKET_TYPE_SEQUENCE_HEADER = 0;
38   private static final int AAC_PACKET_TYPE_AAC_RAW = 1;
39 
40   private static final int[] AUDIO_SAMPLING_RATE_TABLE = new int[] {5512, 11025, 22050, 44100};
41 
42   // State variables
43   private boolean hasParsedAudioDataHeader;
44   private boolean hasOutputFormat;
45   private int audioFormat;
46 
AudioTagPayloadReader(TrackOutput output)47   public AudioTagPayloadReader(TrackOutput output) {
48     super(output);
49   }
50 
51   @Override
seek()52   public void seek() {
53     // Do nothing.
54   }
55 
56   @Override
parseHeader(ParsableByteArray data)57   protected boolean parseHeader(ParsableByteArray data) throws UnsupportedFormatException {
58     if (!hasParsedAudioDataHeader) {
59       int header = data.readUnsignedByte();
60       audioFormat = (header >> 4) & 0x0F;
61       if (audioFormat == AUDIO_FORMAT_MP3) {
62         int sampleRateIndex = (header >> 2) & 0x03;
63         int sampleRate = AUDIO_SAMPLING_RATE_TABLE[sampleRateIndex];
64         Format format = Format.createAudioSampleFormat(null, MimeTypes.AUDIO_MPEG, null,
65             Format.NO_VALUE, Format.NO_VALUE, 1, sampleRate, null, null, 0, null);
66         output.format(format);
67         hasOutputFormat = true;
68       } else if (audioFormat == AUDIO_FORMAT_ALAW || audioFormat == AUDIO_FORMAT_ULAW) {
69         String type = audioFormat == AUDIO_FORMAT_ALAW ? MimeTypes.AUDIO_ALAW
70             : MimeTypes.AUDIO_ULAW;
71         int pcmEncoding = (header & 0x01) == 1 ? C.ENCODING_PCM_16BIT : C.ENCODING_PCM_8BIT;
72         Format format = Format.createAudioSampleFormat(null, type, null, Format.NO_VALUE,
73             Format.NO_VALUE, 1, 8000, pcmEncoding, null, null, 0, null);
74         output.format(format);
75         hasOutputFormat = true;
76       } else if (audioFormat != AUDIO_FORMAT_AAC) {
77         throw new UnsupportedFormatException("Audio format not supported: " + audioFormat);
78       }
79       hasParsedAudioDataHeader = true;
80     } else {
81       // Skip header if it was parsed previously.
82       data.skipBytes(1);
83     }
84     return true;
85   }
86 
87   @Override
parsePayload(ParsableByteArray data, long timeUs)88   protected void parsePayload(ParsableByteArray data, long timeUs) {
89     if (audioFormat == AUDIO_FORMAT_MP3) {
90       int sampleSize = data.bytesLeft();
91       output.sampleData(data, sampleSize);
92       output.sampleMetadata(timeUs, C.BUFFER_FLAG_KEY_FRAME, sampleSize, 0, null);
93     } else {
94       int packetType = data.readUnsignedByte();
95       if (packetType == AAC_PACKET_TYPE_SEQUENCE_HEADER && !hasOutputFormat) {
96         // Parse the sequence header.
97         byte[] audioSpecificConfig = new byte[data.bytesLeft()];
98         data.readBytes(audioSpecificConfig, 0, audioSpecificConfig.length);
99         Pair<Integer, Integer> audioParams = CodecSpecificDataUtil.parseAacAudioSpecificConfig(
100             audioSpecificConfig);
101         Format format = Format.createAudioSampleFormat(null, MimeTypes.AUDIO_AAC, null,
102             Format.NO_VALUE, Format.NO_VALUE, audioParams.second, audioParams.first,
103             Collections.singletonList(audioSpecificConfig), null, 0, null);
104         output.format(format);
105         hasOutputFormat = true;
106       } else if (audioFormat != AUDIO_FORMAT_AAC || packetType == AAC_PACKET_TYPE_AAC_RAW) {
107         int sampleSize = data.bytesLeft();
108         output.sampleData(data, sampleSize);
109         output.sampleMetadata(timeUs, C.BUFFER_FLAG_KEY_FRAME, sampleSize, 0, null);
110       }
111     }
112   }
113 
114 }
115