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分离mp4、flv，生成视频H264/mpeg和音频mp3或aac（无adts头）
下面是应用层mediaExtractor使用，分离一mp4文件，生成h264和aac，并添加adts头文件。
import android.media.MediaExtractor;
import android.media.MediaFormat;
import android.util.Log;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
/**
* mp4extractor 分离器
* 分离mp4 成h264 和 aac
* 分别生成h264和aac文件(无adts头)
* <p>
* android的无法分离高profile的h264文件，这里分离的是Baseline（profile）
* <p>
* 合成的时候，MP4,flv,rtmp都不需要adts头
* 合成的时候：hls,rtp,ts需要adts头
* 所以这里分离出来的aac是没有adts头的，mediainfo读取到的音频信息是从moov中box中读取的
*/
public class MP4VideoExtractor {
private static final String TAG = "MP4VideoExtractor";
//test3.mp4 h264,aac
public static void exactorMedia(String sdcard_path) {
FileOutputStream videoOutputStream = null;
FileOutputStream audioOutputStream = null;
MediaExtractor mediaExtractor = new MediaExtractor();
try {
//分离的视频文件
File videoFile = new File(sdcard_path, "output_video.h264");
//分离的音频文件
File audioFile = new File(sdcard_path, "output_audio.aac");
videoOutputStream = new FileOutputStream(videoFile);
audioOutputStream = new FileOutputStream(audioFile);
//输入文件,也可以是网络文件
//oxford.mp4 视频 h264/baseline 音频 aac/lc 44.1k 2 channel 128kb/s
mediaExtractor.setDataSource(sdcard_path + "/oxford.mp4");
//test3.mp4 视频h264 high 音频aac
// mediaExtractor.setDataSource(sdcard_path + "/test3.mp4");
//test2.mp4 视频mpeg4 音频MP3
// mediaExtractor.setDataSource(sdcard_path + "/test2.mp4");
//信道总数
int trackCount = mediaExtractor.getTrackCount();
Log.d(TAG, "trackCount:" + trackCount);
int audioTrackIndex = -1;
int videoTrackIndex = -1;
for (int i = 0; i < trackCount; i++) {
MediaFormat trackFormat = mediaExtractor.getTrackFormat(i);
String mineType = trackFormat.getString(MediaFormat.KEY_MIME);
//视频信道
if (mineType.startsWith("video/")) {
videoTrackIndex = i;
}
//音频信道
if (mineType.startsWith("audio/")) {
audioTrackIndex = i;
}
}
ByteBuffer byteBuffer = ByteBuffer.allocate(500 * 1024);
//切换到视频信道
mediaExtractor.selectTrack(videoTrackIndex);
while (true) {
int readSampleCount = mediaExtractor.readSampleData(byteBuffer, 0);
Log.d(TAG, "video:readSampleCount:" + readSampleCount);
if (readSampleCount < 0) {
break;
}
//保存视频信道信息
byte[] buffer = new byte[readSampleCount];
byteBuffer.get(buffer);
videoOutputStream.write(buffer);//buffer 写入到 videooutputstream中
byteBuffer.clear();
mediaExtractor.advance();
}
//切换到音频信道
mediaExtractor.selectTrack(audioTrackIndex);
while (true) {
int readSampleCount = mediaExtractor.readSampleData(byteBuffer, 0);
Log.d(TAG, "audio:readSampleCount:" + readSampleCount);
if (readSampleCount < 0) {
break;
}
//保存音频信息
byte[] buffer = new byte[readSampleCount];
byteBuffer.get(buffer);
/************************* 用来为aac添加adts头**************************/
byte[] aacaudiobuffer = new byte[readSampleCount + 7];
addADTStoPacket(aacaudiobuffer, readSampleCount + 7);
System.arraycopy(buffer, 0, aacaudiobuffer, 7, readSampleCount);
audioOutputStream.write(aacaudiobuffer);
/***************************************close**************************/
// audioOutputStream.write(buffer);
byteBuffer.clear();
mediaExtractor.advance();
}
} catch (IOException e) {
e.printStackTrace();
} finally {
Log.d(TAG, "mediaExtractor.release!\n");
mediaExtractor.release();
mediaExtractor = null;
try {
videoOutputStream.close();
audioOutputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
/** 这里之前遇到一个坑，以为这个packetLen是adts头的长度，也就是7，仔细看了下代码，发现这个不是adts头的长度，而是一帧音频的长度
* @param packet 一帧数据（包含adts头长度）
* @param packetLen 一帧数据（包含adts头）的长度
*/
private static void addADTStoPacket(byte[] packet, int packetLen) {
int profile = 2; // AAC LC
int freqIdx = getFreqIdx(44100);
int chanCfg = 2; // CPE
// fill in ADTS data
packet[0] = (byte) 0xFF;
packet[1] = (byte) 0xF9;
packet[2] = (byte) (((profile - 1) << 6) + (freqIdx << 2) + (chanCfg >> 2));
packet[3] = (byte) (((chanCfg & 3) << 6) + (packetLen >> 11));
packet[4] = (byte) ((packetLen & 0x7FF) >> 3);
packet[5] = (byte) (((packetLen & 7) << 5) + 0x1F);
packet[6] = (byte) 0xFC;
}
private static int getFreqIdx(int sampleRate) {
int freqIdx;
switch (sampleRate) {
case 96000:
freqIdx = 0;
break;
case 88200:
freqIdx = 1;
break;
case 64000:
freqIdx = 2;
break;
case 48000:
freqIdx = 3;
break;
case 44100:
freqIdx = 4;
break;
case 32000:
freqIdx = 5;
break;
case 24000:
freqIdx = 6;
break;
case 22050:
freqIdx = 7;
break;
case 16000:
freqIdx = 8;
break;
case 12000:
freqIdx = 9;
break;
case 11025:
freqIdx = 10;
break;
case 8000:
freqIdx = 11;
break;
case 7350:
freqIdx = 12;
break;
default:
freqIdx = 8;
break;
}
return freqIdx;
}
}