为了使用 live555 接收 SDP 文件描述的 RTP 流，您需要：
- 从 SDP 创建一个
MediaSession（这将创建关联的 MediaSubsession）
- 启动
MediaSubsession 以打开将接收 RTP/RTCP 的 UDP 端口
- 创建一个重载的
MediaSink 来接收 RTP 帧
- 启动此接收器
受 testRTSPClient.cpp 启发的简单实现可能类似于：
#include "liveMedia.hh"
#include "BasicUsageEnvironment.hh"
UsageEnvironment& operator<<(UsageEnvironment& env, const MediaSubsession& subsession)
{
return env << subsession.mediumName() << "/" << subsession.codecName();
}
#define DUMMY_SINK_RECEIVE_BUFFER_SIZE 100000
class DummySink: public MediaSink
{
public:
static DummySink* createNew(UsageEnvironment& env,
MediaSubsession& subsession, // identifies the kind of data that's being received
char const* streamId = NULL) // identifies the stream itself (optional)
{
return new DummySink(env, subsession, streamId);
}
private:
DummySink(UsageEnvironment& env, MediaSubsession& subsession, char const* streamId)
: MediaSink(env), fSubsession(subsession)
{
fStreamId = strDup(streamId);
fReceiveBuffer = new u_int8_t[DUMMY_SINK_RECEIVE_BUFFER_SIZE];
}
virtual ~DummySink()
{
delete[] fReceiveBuffer;
delete[] fStreamId;
}
static void afterGettingFrame(void* clientData, unsigned frameSize,
unsigned numTruncatedBytes,
struct timeval presentationTime,
unsigned durationInMicroseconds)
{
DummySink* sink = (DummySink*)clientData;
sink->afterGettingFrame(frameSize, numTruncatedBytes, presentationTime, durationInMicroseconds);
}
void afterGettingFrame(unsigned frameSize, unsigned numTruncatedBytes,
struct timeval presentationTime, unsigned durationInMicroseconds)
{
if (fStreamId != NULL) envir() << "Stream \"" << fStreamId << "\"; ";
envir() << fSubsession.mediumName() << "/" << fSubsession.codecName() << ":\tReceived " << frameSize << " bytes";
if (numTruncatedBytes > 0) envir() << " (with " << numTruncatedBytes << " bytes truncated)";
char uSecsStr[6+1]; // used to output the 'microseconds' part of the presentation time
sprintf(uSecsStr, "%06u", (unsigned)presentationTime.tv_usec);
envir() << ".\tPresentation time: " << (int)presentationTime.tv_sec << "." << uSecsStr;
if (fSubsession.rtpSource() != NULL && !fSubsession.rtpSource()->hasBeenSynchronizedUsingRTCP())
{
envir() << "!"; // mark the debugging output to indicate that this presentation time is not RTCP-synchronized
}
envir() << "\tNPT: " << fSubsession.getNormalPlayTime(presentationTime);
envir() << "\n";
// Then continue, to request the next frame of data:
continuePlaying();
}
private:
virtual Boolean continuePlaying()
{
if (fSource == NULL) return False; // sanity check (should not happen)
fSource->getNextFrame(fReceiveBuffer, DUMMY_SINK_RECEIVE_BUFFER_SIZE, afterGettingFrame, this, onSourceClosure, this);
return True;
}
private:
u_int8_t* fReceiveBuffer;
MediaSubsession& fSubsession;
char* fStreamId;
};
int main(int argc, char** argv)
{
TaskScheduler* scheduler = BasicTaskScheduler::createNew();
UsageEnvironment* env = BasicUsageEnvironment::createNew(*scheduler);
if (argc < 2)
{
*env << "Usage: " << argv[0] << " file.sdp\n";
return 1;
}
const char* filename = argv[1];
FILE* file = fopen(filename,"r");
if (file == NULL)
{
*env << "Cannot open SDP file:" << filename << "\n";
return 1;
}
fseek(file, 0, SEEK_END);
long size = ftell(file);
fseek(file, 0, SEEK_SET);
char sdp[size];
fread(sdp,size,1,file);
fclose(file);
MediaSession* session = MediaSession::createNew(*env, sdp);
if (session == NULL)
{
*env << "Failed to create a MediaSession object from the SDP description: " << env->getResultMsg() << "\n";
return 1;
}
MediaSubsessionIterator iter(*session);
MediaSubsession* subsession = NULL;
while ((subsession = iter.next()) != NULL)
{
if (!subsession->initiate (0))
{
*env << "Failed to initiate the \"" << *subsession << "\" subsession: " << env->getResultMsg() << "\n";
}
else
{
subsession->sink = DummySink::createNew(*env, *subsession, filename);
if (subsession->sink == NULL)
{
*env << "Failed to create a data sink for the \"" << *subsession << "\" subsession: " << env->getResultMsg() << "\n";
}
else
{
subsession->sink->startPlaying(*subsession->rtpSource(), NULL, NULL);
}
}
}
char eventLoopWatchVariable = 0;
env->taskScheduler().doEventLoop(&eventLoopWatchVariable);
return 0;
}
运行程序，将包含 SDP 的文件的路径作为参数，将读取 RTP 流打印帧大小和每个帧的时间戳。
类似的东西：
Stream "ffmpeg.sdp"; video/H265: Received 5131 bytes. Presentation time: 1442350569.228804! NPT: 0.000000
Stream "ffmpeg.sdp"; video/H265: Received 7917 bytes. Presentation time: 1442350569.268804! NPT: 0.000000
Stream "ffmpeg.sdp"; video/H265: Received 2383 bytes. Presentation time: 1442350569.308804! NPT: 0.000000
Stream "ffmpeg.sdp"; video/H265: Received 7780 bytes. Presentation time: 1442350569.348804! NPT: 0.000000
Stream "ffmpeg.sdp"; video/H265: Received 1773 bytes. Presentation time: 1442350569.388804! NPT: 0.000000
Stream "ffmpeg.sdp"; video/H265: Received 9580 bytes. Presentation time: 1442350569.428804! NPT: 0.000000
Stream "ffmpeg.sdp"; video/H265: Received 7934 bytes. Presentation time: 1442350569.468804! NPT: 0.000000
Stream "ffmpeg.sdp"; video/H265: Received 2180 bytes. Presentation time: 1442350569.508804! NPT: 0.000000
Stream "ffmpeg.sdp"; video/H265: Received 10804 bytes. Presentation time: 1442350569.548804! NPT: 0.000000
Stream "ffmpeg.sdp"; video/H265: Received 7801 bytes. Presentation time: 1442350569.588804! NPT: 0.000000
Stream "ffmpeg.sdp"; video/H265: Received 7816 bytes. Presentation time: 1442350569.628804! NPT: 0.000000
Stream "ffmpeg.sdp"; video/H265: Received 4028 bytes. Presentation time: 1442350569.668804! NPT: 0.000000
Stream "ffmpeg.sdp"; video/H265: Received 7959 bytes. Presentation time: 1442350569.708804! NPT: 0.000000
Stream "ffmpeg.sdp"; video/H265: Received 8062 bytes. Presentation time: 1442350569.794000 NPT: 0.000000
Stream "ffmpeg.sdp"; video/H265: Received 8014 bytes. Presentation time: 1442350569.834000 NPT: 0.000000