在android上通过udp:/显示mpegts流中的h264视频。
我已经试了几天了，想让这件事成功。我所拥有的是一个设备，它产生一个h264视频流，并通过原始udp（而不是rtp）在mpegts容器中进行多播。我正试图让这个在android上的自定义应用程序中显示。
我听说android内置的mediaplayer同时支持h264（avc）和mpegts，但是它不处理udp://streams，所以我不能使用它（这是目前为止最简单的）。相反，我尝试手动将mpegts流解析为一个基本流，并将其传递给一个通过surfaceview表面的mediacodec。无论我尝试什么，总会发生两件事（一旦我修复异常等）：
表面视图总是黑色的。
mediacodec总是接受大约6-9个缓冲区，然后dequeueInputBuffer就立即开始失败（返回-1），我不能对其他任何东西进行排队。
我可以将mpeg流分成ts包，然后将它们的有效负载加入到pes包中。我试过将完整的pes包（减去pes头）传递到mediacodec。
我也尝试过将pes数据包拆分为单独的nal单元，方法是在\x00\x00\x01上进行拆分并将它们分别传递到mediacodec中。
我也试过推迟传入nal unit，直到收到sps nal unit并先用BUFFER_FLAG_CODEC_CONFIG传递它。
所有这些都导致了上面提到的同样的事情。我不知道该尝试什么，所以任何帮助都将不胜感激。
我仍然不确定的是：
几乎所有我看到的例子都是从mediaextractor获得mediaformat的，我不能在流上使用它。少数几个没有使用mediaextractor显式设置csd-0和csd-1的bytestrings没有解释。我读到sps包可以放在缓冲区中，所以这就是我所尝试的。
我不知道该把什么变成表象。t s包有一个pcr，pes包有一个pts，但是我不知道api所期望的是什么以及它们之间的关系。
我不确定数据需要如何传递到mediacodec（这就是为什么它停止给我缓冲区的原因吗？）。我从这篇文章中得到了通过单个nal单元的想法：
Decoding Raw H264 stream in android?
我用来做这个例子的其他参考资料：
MPEG-TS Format
PES Format
PES Format
代码（抱歉太长）：
我刚刚从androidstudio的基本模板中创建了一个测试应用程序，其中大部分都是样板文件，所以我将只粘贴与视频相关的内容。
surfaceview是在xml中定义的，因此在创建/更改surfaceview时获取它并获取它
public class VideoPlayer extends Activity implements SurfaceHolder.Callback {
private static final String TAG = VideoPlayer.class.getName();
PlayerThread playerThread;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_video_player);
SurfaceView view = (SurfaceView) findViewById(R.id.surface);
view.getHolder().addCallback(this);
}
...
@Override
public void surfaceCreated(SurfaceHolder surfaceHolder) {
Log.d(TAG,"surfaceCreated");
}
@Override
public void surfaceChanged(SurfaceHolder surfaceHolder, int i, int i2, int i3) {
Log.d("main","surfaceChanged");
if( playerThread == null ) {
playerThread = new PlayerThread(surfaceHolder.getSurface());
playerThread.start();
}
}
...
playerThread是一个内部类，它从多播端口读取数据并将其传递给后台线程上的解析函数：
class PlayerThread extends Thread {
private final String TAG = PlayerThread.class.getName();
MediaExtractor extractor;
MediaCodec decoder;
Surface surface;
boolean running;
ByteBuffer[] inputBuffers;
public PlayerThread(Surface surface)
{
this.surface = surface;
MediaFormat format = MediaFormat.createVideoFormat("video/avc",720,480);
decoder = MediaCodec.createDecoderByType("video/avc");
decoder.configure(format, surface, null, 0);
decoder.start();
inputBuffers = decoder.getInputBuffers();
}
...
@Override
public void run() {
running = true;
try {
String mcg = "239.255.0.1";
MulticastSocket ms;
ms = new MulticastSocket(1841);
ms.joinGroup(new InetSocketAddress(mcg, 1841), NetworkInterface.getByName("eth0"));
ms.setSoTimeout(4000);
ms.setReuseAddress(true);
byte[] buffer = new byte[65535];
DatagramPacket dp = new DatagramPacket(buffer, buffer.length);
while (running) {
try {
ms.receive(dp);
parse(dp.getData());
} catch (SocketTimeoutException e) {
Log.d("thread", "timeout");
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
接收工作正常，每个数据包包含两个ts包。它们被传递给parse函数：
boolean first = true;
ByteArrayOutputStream current = new ByteArrayOutputStream();
void parse(byte[] data) {
ByteBuffer stream = ByteBuffer.wrap(data);
// mpeg-ts stream header is 4 bytes starting with the sync byte
if( stream.get(0) != 0x47 ) {
Log.w(TAG, "got packet w/out mpegts header!");
return;
}
ByteBuffer raw = stream.duplicate();
// ts packets are 188 bytes
raw.limit(188);
TSPacket ts = new TSPacket(raw);
if( ts.pid == 0x10 ) {
processTS(ts);
}
// move to second packet
stream.position(188);
stream.limit(188*2);
if( stream.get(stream.position()) != 0x47 ) {
Log.w(TAG, "missing mpegts header!");
return;
}
raw = stream.duplicate();
raw.limit(188*2);
ts = new TSPacket(raw);
if( ts.pid == 0x10 ) {
processTS(ts);
}
}
TS数据包由TSPacket类解析：
public class TSPacket {
private final static String TAG = TSPacket.class.getName();
class AdaptationField {
boolean di;
boolean rai;
boolean espi;
boolean hasPcr;
boolean hasOpcr;
boolean spf;
boolean tpdf;
boolean hasExtension;
byte[] data;
public AdaptationField(ByteBuffer raw) {
// first byte is size of field minus size byte
int count = raw.get() & 0xff;
// second byte is flags
BitSet flags = BitSet.valueOf(new byte[]{ raw.get()});
di = flags.get(7);
rai = flags.get(6);
espi = flags.get(5);
hasPcr = flags.get(4);
hasOpcr = flags.get(3);
spf = flags.get(2);
tpdf = flags.get(1);
hasExtension = flags.get(0);
// the rest is 'data'
if( count > 1 ) {
data = new byte[count-1];
raw.get(data);
}
}
}
boolean tei;
boolean pus;
boolean tp;
int pid;
boolean hasAdapt;
boolean hasPayload;
int counter;
AdaptationField adaptationField;
byte[] payload;
public TSPacket(ByteBuffer raw) {
// check for sync byte
if( raw.get() != 0x47 ) {
Log.e(TAG, "missing sync byte");
throw new InvalidParameterException("missing sync byte");
}
// next 3 bits are flags
byte b = raw.get();
BitSet flags = BitSet.valueOf(new byte[] {b});
tei = flags.get(7);
pus = flags.get(6);
tp = flags.get(5);
// then 13 bits for pid
pid = ((b << 8) | (raw.get() & 0xff) ) & 0x1fff;
b = raw.get();
flags = BitSet.valueOf(new byte[]{b});
// then 4 more flags
if( flags.get(7) || flags.get(6) ) {
Log.e(TAG, "scrambled?!?!");
// todo: bail on this packet?
}
hasAdapt = flags.get(5);
hasPayload = flags.get(4);
// counter
counter = b & 0x0f;
// optional adaptation field
if( hasAdapt ) {
adaptationField = new AdaptationField(raw);
}
// optional payload field
if( hasPayload ) {
payload = new byte[raw.remaining()];
raw.get(payload);
}
}
}
然后传递给processts函数：
// a PES packet can span multiple TS packets, so we keep track of the 'current' one
PESPacket currentPES;
void processTS(TSPacket ts) {
// payload unit start?
if( ts.pus ) {
if( currentPES != null ) {
Log.d(TAG,String.format("replacing pes: len=%d,size=%d", currentPES.length, currentPES.data.size()));
}
// start of new PES packet
currentPES = new PESPacket(ts);
} else if (currentPES != null ) {
// continued PES
currentPES.Add(ts);
} else {
// haven't got a start pes yet
return;
}
if( currentPES.isFull() ) {
long pts = currentPES.getPts();
byte[] data = currentPES.data.toByteArray();
int idx = 0;
do {
int sidx = idx;
// find next NAL prefix
idx = Utility.indexOf(data, sidx+4, data.length-(sidx+4), new byte[]{0,0,1});
byte[] NAL;
if( idx >= 0 ) {
NAL = Arrays.copyOfRange(data, sidx, idx);
} else {
NAL = Arrays.copyOfRange(data, sidx, data.length);
}
// send SPS NAL before anything else
if( first ) {
byte type = NAL[3] == 0 ? NAL[4] : NAL[3];
if( (type & 0x1f) == 7 ) {
Log.d(TAG, "found sps!");
int ibs = decoder.dequeueInputBuffer(1000);
if (ibs >= 0) {
ByteBuffer sinput = inputBuffers[ibs];
sinput.clear();
sinput.put(NAL);
decoder.queueInputBuffer(ibs, 0, NAL.length, 0, MediaCodec.BUFFER_FLAG_CODEC_CONFIG);
Log.d(TAG, "sent sps");
first = false;
} else
Log.d(TAG, String.format("could not send sps! %d", ibs));
}
} else {
// put in decoder?
int ibs = decoder.dequeueInputBuffer(1000);
if (ibs >= 0) {
ByteBuffer sinput = inputBuffers[ibs];
sinput.clear();
sinput.put(NAL);
decoder.queueInputBuffer(ibs, 0, NAL.length, 0, 0);
Log.d(TAG, "buffa");
}
}
} while( idx >= 0 );
// finished with this pes
currentPES = null;
}
}
PES数据包由PESPacket类解析：
public class PESPacket {
private final static String TAG = PESPacket.class.getName();
int id;
int length;
boolean priority;
boolean dai;
boolean copyright;
boolean origOrCopy;
boolean hasPts;
boolean hasDts;
boolean hasEscr;
boolean hasEsRate;
boolean dsmtmf;
boolean acif;
boolean hasCrc;
boolean pesef;
int headerDataLength;
byte[] headerData;
ByteArrayOutputStream data = new ByteArrayOutputStream();
public PESPacket(TSPacket ts) {
if( ts == null || !ts.pus) {
Log.e(TAG, "invalid ts passed in");
throw new InvalidParameterException("invalid ts passed in");
}
ByteBuffer pes = ByteBuffer.wrap(ts.payload);
// start code
if( pes.get() != 0 || pes.get() != 0 || pes.get() != 1 ) {
Log.e(TAG, "invalid start code");
throw new InvalidParameterException("invalid start code");
}
// stream id
id = pes.get() & 0xff;
// packet length
length = pes.getShort() & 0xffff;
// this is supposedly allowed for video
if( length == 0 ) {
Log.w(TAG, "got zero-length PES?");
}
if( id != 0xe0 ) {
Log.e(TAG, String.format("unexpected stream id: 0x%x", id));
// todo: ?
}
// for 0xe0 there is an extension header starting with 2 bits '10'
byte b = pes.get();
if( (b & 0x30) != 0 ) {
Log.w(TAG, "scrambled ?!?!");
// todo: ?
}
BitSet flags = BitSet.valueOf(new byte[]{b});
priority = flags.get(3);
dai = flags.get(2);
copyright = flags.get(1);
origOrCopy = flags.get(0);
flags = BitSet.valueOf(new byte[]{pes.get()});
hasPts = flags.get(7);
hasDts = flags.get(6);
hasEscr = flags.get(5);
hasEsRate = flags.get(4);
dsmtmf = flags.get(3);
acif = flags.get(2);
hasCrc = flags.get(1);
pesef = flags.get(0);
headerDataLength = pes.get() & 0xff;
if( headerDataLength > 0 ) {
headerData = new byte[headerDataLength];
pes.get(headerData);
}
WritableByteChannel channel = Channels.newChannel(data);
try {
channel.write(pes);
} catch (IOException e) {
e.printStackTrace();
}
// length includes optional pes header,
length = length - (3 + headerDataLength);
}
public void Add(TSPacket ts) {
if( ts.pus ) {
Log.e(TAG, "don't add start of PES packet to another packet");
throw new InvalidParameterException("ts packet marked as new pes");
}
int size = data.size();
int len = length - size;
len = ts.payload.length > len ? len : ts.payload.length;
data.write(ts.payload, 0, len);
}
public boolean isFull() {
return (data.size() >= length );
}
public long getPts() {
if( !hasPts || headerDataLength < 5 )
return 0;
ByteBuffer hd = ByteBuffer.wrap(headerData);
long pts = ( ((hd.get() & 0x0e) << 29)
| ((hd.get() & 0xff) << 22)
| ((hd.get() & 0xfe) << 14)
| ((hd.get() & 0xff) << 7)
| ((hd.get() & 0xfe) >>> 1));
return pts;
}
}
最佳答案
所以我最终发现，即使我使用的是一个输出曲面，我也必须手动排出输出缓冲区。通过调用decoder.dequeueOutputBuffer然后decoder.releaseOutputBuffer，输入缓冲区按预期工作。
我也可以通过传入单独的nal单元和完全访问单元（每个pes包一个）来获得输出，但是通过传入完全访问单元，我获得了最清晰的视频。