如何编写Live555 FramedSource以允许我实时播放H.264

Question

I've been trying to write a class that derives from FramedSource in Live555 that will allow me to stream live data from my D3D9 application to an MP4 or similar.

What I do each frame is grab the backbuffer into system memory as a texture, then convert it from RGB -> YUV420P, then encode it using x264, then ideally pass the NAL packets on to Live555. I made a class called H264FramedSource that derived from FramedSource basically by copying the DeviceSource file. Instead of the input being an input file, I've made it a NAL packet which I update each frame.

I'm quite new to codecs and streaming, so I could be doing everything completely wrong. In each doGetNextFrame() should I be grabbing the NAL packet and doing something like

memcpy(fTo, nal->p_payload, nal->i_payload)

I assume that the payload is my frame data in bytes? If anybody has an example of a class they derived from FramedSource that might at least be close to what I'm trying to do I would love to see it, this is all new to me and a little tricky to figure out what's happening. Live555's documentation is pretty much the code itself which doesn't exactly make it easy for me to figure out.

Answer 1

Ok, I finally got some time to spend on this and got it working! I'm sure there are others who will be begging to know how to do it so here it is.

You will need your own FramedSource to take each frame, encode, and prepare it for streaming, I will provide some of the source code for this soon.

Essentially throw your FramedSource into the H264VideoStreamDiscreteFramer, then throw this into the H264RTPSink. Something like this

scheduler = BasicTaskScheduler::createNew();
env = BasicUsageEnvironment::createNew(*scheduler);   

framedSource = H264FramedSource::createNew(*env, 0,0);

h264VideoStreamDiscreteFramer 
= H264VideoStreamDiscreteFramer::createNew(*env, framedSource);

// initialise the RTP Sink stuff here, look at 
// testH264VideoStreamer.cpp to find out how

videoSink->startPlaying(*h264VideoStreamDiscreteFramer, NULL, videoSink);

env->taskScheduler().doEventLoop();

Now in your main render loop, throw over your backbuffer which you've saved to system memory to your FramedSource so it can be encoded etc. For more info on how to setup the encoding stuff check out this answer How does one encode a series of images into H264 using the x264 C API?

My implementation is very much in a hacky state and is yet to be optimised at all, my d3d application runs at around 15fps due to the encoding, ouch, so I will have to look into this. But for all intents and purposes this StackOverflow question is answered because I was mostly after how to stream it. I hope this helps other people.

As for my FramedSource it looks a little something like this

concurrent_queue<x264_nal_t> m_queue;
SwsContext* convertCtx;
x264_param_t param;
x264_t* encoder;
x264_picture_t pic_in, pic_out;


EventTriggerId H264FramedSource::eventTriggerId = 0;
unsigned H264FramedSource::FrameSize = 0;
unsigned H264FramedSource::referenceCount = 0;

int W = 720;
int H = 960;

H264FramedSource* H264FramedSource::createNew(UsageEnvironment& env,
                                              unsigned preferredFrameSize, 
                                              unsigned playTimePerFrame) 
{
        return new H264FramedSource(env, preferredFrameSize, playTimePerFrame);
}

H264FramedSource::H264FramedSource(UsageEnvironment& env,
                                   unsigned preferredFrameSize, 
                                   unsigned playTimePerFrame)
    : FramedSource(env),
    fPreferredFrameSize(fMaxSize),
    fPlayTimePerFrame(playTimePerFrame),
    fLastPlayTime(0),
    fCurIndex(0)
{
        if (referenceCount == 0) 
        {

        }
        ++referenceCount;

        x264_param_default_preset(&param, "veryfast", "zerolatency");
        param.i_threads = 1;
        param.i_width = 720;
        param.i_height = 960;
        param.i_fps_num = 60;
        param.i_fps_den = 1;
        // Intra refres:
        param.i_keyint_max = 60;
        param.b_intra_refresh = 1;
        //Rate control:
        param.rc.i_rc_method = X264_RC_CRF;
        param.rc.f_rf_constant = 25;
        param.rc.f_rf_constant_max = 35;
        param.i_sps_id = 7;
        //For streaming:
        param.b_repeat_headers = 1;
        param.b_annexb = 1;
        x264_param_apply_profile(&param, "baseline");


        encoder = x264_encoder_open(&param);
        pic_in.i_type            = X264_TYPE_AUTO;   
        pic_in.i_qpplus1         = 0;
        pic_in.img.i_csp         = X264_CSP_I420;   
        pic_in.img.i_plane       = 3;


        x264_picture_alloc(&pic_in, X264_CSP_I420, 720, 920);

        convertCtx = sws_getContext(720, 960, PIX_FMT_RGB24, 720, 760, PIX_FMT_YUV420P, SWS_FAST_BILINEAR, NULL, NULL, NULL);


        if (eventTriggerId == 0) 
        {
            eventTriggerId = envir().taskScheduler().createEventTrigger(deliverFrame0);
        }
}

H264FramedSource::~H264FramedSource() 
{
    --referenceCount;
    if (referenceCount == 0) 
    {
        // Reclaim our 'event trigger'
        envir().taskScheduler().deleteEventTrigger(eventTriggerId);
        eventTriggerId = 0;
    }
}

void H264FramedSource::AddToBuffer(uint8_t* buf, int surfaceSizeInBytes)
{
    uint8_t* surfaceData = (new uint8_t[surfaceSizeInBytes]);

    memcpy(surfaceData, buf, surfaceSizeInBytes);

    int srcstride = W*3;
    sws_scale(convertCtx, &surfaceData, &srcstride,0, H, pic_in.img.plane, pic_in.img.i_stride);
    x264_nal_t* nals = NULL;
    int i_nals = 0;
    int frame_size = -1;


    frame_size = x264_encoder_encode(encoder, &nals, &i_nals, &pic_in, &pic_out);

    static bool finished = false;

    if (frame_size >= 0)
    {
        static bool alreadydone = false;
        if(!alreadydone)
        {

            x264_encoder_headers(encoder, &nals, &i_nals);
            alreadydone = true;
        }
        for(int i = 0; i < i_nals; ++i)
        {
            m_queue.push(nals[i]);
        }   
    }
    delete [] surfaceData;
    surfaceData = NULL;

    envir().taskScheduler().triggerEvent(eventTriggerId, this);
}

void H264FramedSource::doGetNextFrame() 
{
    deliverFrame();
}

void H264FramedSource::deliverFrame0(void* clientData) 
{
    ((H264FramedSource*)clientData)->deliverFrame();
}

void H264FramedSource::deliverFrame() 
{
    x264_nal_t nalToDeliver;

    if (fPlayTimePerFrame > 0 && fPreferredFrameSize > 0) {
        if (fPresentationTime.tv_sec == 0 && fPresentationTime.tv_usec == 0) {
            // This is the first frame, so use the current time:
            gettimeofday(&fPresentationTime, NULL);
        } else {
            // Increment by the play time of the previous data:
            unsigned uSeconds   = fPresentationTime.tv_usec + fLastPlayTime;
            fPresentationTime.tv_sec += uSeconds/1000000;
            fPresentationTime.tv_usec = uSeconds%1000000;
        }

        // Remember the play time of this data:
        fLastPlayTime = (fPlayTimePerFrame*fFrameSize)/fPreferredFrameSize;
        fDurationInMicroseconds = fLastPlayTime;
    } else {
        // We don't know a specific play time duration for this data,
        // so just record the current time as being the 'presentation time':
        gettimeofday(&fPresentationTime, NULL);
    }

    if(!m_queue.empty())
    {
        m_queue.wait_and_pop(nalToDeliver);

        uint8_t* newFrameDataStart = (uint8_t*)0xD15EA5E;

        newFrameDataStart = (uint8_t*)(nalToDeliver.p_payload);
        unsigned newFrameSize = nalToDeliver.i_payload;

        // Deliver the data here:
        if (newFrameSize > fMaxSize) {
            fFrameSize = fMaxSize;
            fNumTruncatedBytes = newFrameSize - fMaxSize;
        }
        else {
            fFrameSize = newFrameSize;
        }

        memcpy(fTo, nalToDeliver.p_payload, nalToDeliver.i_payload);

        FramedSource::afterGetting(this);
    }
}

Oh and for those who want to know what my concurrent queue is, here it is, and it works brilliantly http://www.justsoftwaresolutions.co.uk/threading/implementing-a-thread-safe-queue-using-condition-variables.html

Enjoy and good luck!

Answer 2

The deliverFrame method lacks the following check at its start:

if (!isCurrentlyAwaitingData()) return;    

see DeviceSource.cpp in LIVE