IP Camera代码分析
IP Camera代码分析
2013-1-14
一、大概流程
1. new一个MediaRecorder并开始录制，2s后停掉？
2. 检测"/sdcard/ipcam/myvideo.mp4"中mdat的位置和SPS/PPS信息；
3. 建立camera和http的localsocket接口并传递至C++层；
4. 通知doCapture和doStreaming在localsocket准备收/发数据并处理（recv/send）；
5. new一个MediaRecorder，并把数据输出至先前建立的localsocket接口；
6. doCapture会直接从mdat数据开始位置接收NAL并自己打上时间戳，AMR未做处理。
二、代码跟踪
private void setup()
btnStart.setOnClickListener(startAction);
private OnClickListener startAction = newOnClickListener() {
@Override
public void onClick(View v) {
doAction();
}
};
private void doAction() {
if( inServer == false) {
myCamView.PrepareMedia(targetWid,targetHei);// myMediaRecorder = new MediaRecorder();
boolean ret =myCamView.StartRecording(checkingFile);..................................... .........................................1
myCamView.StopMedia();
if ( NativeAgent.NativeCheckMedia(targetWid, targetHei, checkingFile) ) ....................................................2
startServer();............................................................................................................................................3
}
}
1. 录制成本地文件"/sdcard/ipcam/myvideo.mp4"
public boolean StartRecording(StringtargetFile) {
myMediaRecorder.setOutputFile(targetFile);
returnrealyStart();
}
private boolean realyStart()
myMediaRecorder.prepare();
myMediaRecorder.start();
2. 从本地文件得知mdat的位置并搜索SPS/PPS
static public boolean NativeCheckMedia(int wid,int hei, String filename)
nativeCheckMedia(wid,hei, filename)
JNIEXPORT jint JNICALLJNIDEFINE(nativeCheckMedia)(JNIEnv* env, jclass clz, jint wid, jint hei,jstring file_path)
CheckMedia(wid,hei, mp4_file);
//找到mdat的位置；
//获取SPS/PPS
3. 启动camera loop和http loop
private void startServer()
strServer= new StreamingServer(8080, resourceDirectory);
strServer.setOnRequestListen(streamingRequest);
StreamingServer.OnRequestListenstreamingRequest = new StreamingServer.OnRequestListen()
startStreaming()
private boolean startStreaming()
cameraLoop.InitLoop();
httpLoop.InitLoop();
nativeAgt.NativeStartStreamingMedia(cameraLoop.getReceiverFileDescriptor(), httpLoop.getSenderFileDescriptor());...................................4
myCamView.PrepareMedia(targetWid, targetHei); // myMediaRecorder = newMediaRecorder();
boolean ret =myCamView.StartStreaming(cameraLoop.getSenderFileDescriptor());...........................................................................................5
4. 向C层传递cameracapture socket fd和httpd发送socket fd
static public voidNativeStartStreamingMedia(FileDescriptor in, FileDescriptor out)
nativeStartStreamingMedia(in, out);
JNIEXPORT jint JNICALL JNIDEFINE(nativeStartStreamingMedia)(JNIEnv*env, jclass clz, jobject infdesc, jobject outfdesc)
intinfd = getNativeFd(env, clz, infdesc);
int outfd = getNativeFd(env, clz, outfdesc);
StartStreamingMedia(infd, outfd);
int StartStreamingMedia(int infd, intoutfd)
mediaBuffer= new MediaBuffer(32, 120, MAX_VIDEO_PACKAGE, 1024);
mediaStreamer= new MediaStreamer(infd, outfd);
mediaStreamer->Start();
void MediaStreamer::Start()
captureThread->Post(this, MSG_BEGIN_CAPTURE_TASK);
streamingThread->Post(this,MSG_BEGIN_STREAMING_TASK);
开始捕捉camera过来的数据和向外发送打包过的只有视频的flv数据
voidMediaStreamer::OnMessage(talk_base::Message *msg) {
switch( msg->message_id) {
case MSG_BEGIN_CAPTURE_TASK:
doCapture();......................................................................................6
break;
case MSG_BEGIN_STREAMING_TASK:
doStreaming();..................................................................................7
break;
default:
break;
}
}
5. 又new一个MediaRecorder并设置为流式输出
public boolean StartStreaming(FileDescriptortargetFd)
myMediaRecorder.setOutputFile(targetFd);
myMediaRecorder.setMaxDuration(9600000); // Set max duration 4 hours
//myMediaRecorder.setMaxFileSize(1600000000);// Set max file size 16G
myMediaRecorder.setOnInfoListener(streamingEventHandler);
returnrealyStart();
private boolean realyStart()
myMediaRecorder.prepare();
myMediaRecorder.start();
6.
void MediaStreamer::doCapture()
if( buf[0] == 0x00 ) {
//recvH264 NAL单元；
//重新计算每个NAL单元的时间；
}else{//参见8.
//recvAMR数据，但并没有PushBuffer，也就是没有把AMR数据送给httpd；
}
详细代码：
// this method only support H.264 + AMR_NB
void MediaStreamer::doCapture() {
unsigned char *buf;
buf = new unsigned char[MAX_VIDEO_PACKAGE];
unsigned int aseq = 0;
unsigned int vseq = 0;
const unsigned int STACK_SIZE = 128;
std::list<int64_t> timestack;
unsigned long last_ts = 0;
// skip none useable heaer bytes
fillBuffer( buf, mediaInfo.begin_skip);
// fectching real time video data from camera
while(1) {
if ( fillBuffer(buf, 4) < 0)
break;
checking_buffer:
if ( buf[0] == 0x00 ) {
unsigned int vpkg_len = (buf[1] << 16) + (buf[2] << 8) +buf[3];
if ( fillBuffer(&buf[4], vpkg_len ) < 0)
break;
vpkg_len += 4;
if ( vpkg_len > (unsigned int)MAX_VIDEO_PACKAGE ) {
LOGD("ERROR: Drop big videoframe....");
vseq++;
fillBuffer(vpkg_len);
continue;
}
int slice_type = 0;
if ( (buf[5] & 0xF8 ) == 0xB8) {
slice_type = 1;
} else if ( ((buf[5] & 0xFF) == 0x88)
&& ((buf[5] &0x80) == 0x80) ) {
slice_type = 1;
} else if ( (buf[5] & 0xE0) == 0xE0) {
slice_type = 0;
} else if ( (buf[5] & 0xFE) == 0x9A) {
slice_type = 0;
}
buf[0] = 0x00;
buf[1] = 0x00;
buf[2] = 0x00;
buf[3] = 0x01;
#if 1
// computing the current package's timestamp
int64_t cts = getCurrentTime() / 1000;
if( timestack.size() >= STACK_SIZE) {
timestack.pop_back();
timestack.push_front(cts);
} else {
timestack.push_front(cts);
}
if ( timestack.size() <STACK_SIZE) {
cts = (timestack.size() - 1) *100; // default = 10 fps
last_ts = (unsigned long)cts;
} else {
unsigned long total_ms;
total_ms = timestack.front() -timestack.back();
cts = last_ts + total_ms /(STACK_SIZE - 1);
last_ts = cts;
}
mediaBuffer->PushBuffer( buf, vpkg_len, last_ts, slice_type ?MEDIA_TYPE_VIDEO_KEYFRAME : MEDIA_TYPE_VIDEO);
#else
vseq ++;
mediaBuffer->PushBuffer( buf, vpkg_len, vseq * 1000 /mediaInfo.video_frame_rate, slice_type ? MEDIA_TYPE_VIDEO_KEYFRAME :MEDIA_TYPE_VIDEO);
#endif
} else {
// fetching AMR_NB audio package
static const unsigned char packed_size[16] = {12, 13, 15, 17, 19, 20,26, 31, 5, 0, 0, 0, 0, 0, 0, 0};
unsigned int mode = (buf[0]>>3) & 0x0F;
unsigned int size = packed_size[mode] + 1;
if ( size > 4) {
if ( fillBuffer(&buf[4], size -4) < 0)
break;
aseq ++;
//SignalNewPackage(buf, 32,ats, MEDIA_TYPE_AUDIO);
} else {
fillBuffer(&buf[4], size );
for(int i = 0; i < 4; i++)
buf[i] = buf[size+i];
//SignalNewPackage(buf, 32,ats, MEDIA_TYPE_AUDIO);
goto checking_buffer;
}
}
}
delete buf;
}
7. doStreaming主要是打包成flv向外发数据，不做细究。
8. 此表说明AMR的头字节不可能为0x00
| 规格 |
帧大小 |
帧头（1字节） |
| AMR 4.75 |
13 |
04 (0000 0100) |
| AMR 5.15 |
14 |
0C (0000 1100) |
| AMR 5.9 |
16 |
14 (0001 0100) |
| AMR 6.7 |
18 |
1C (0001 1100) |
| AMR 7.4 |
20 |
24 (0010 0100) |
| AMR 7.95 |
21 |
2C (0010 1100) |
| AMR 10.12 |
27 |
34 (0011 0100) |
| AMR 12.2 |
32 |
3C (0011 1100) |
三、实验数据