如何使用 Gstreamermm 传递帧

Question

我需要将一些 H.264 帧解码为原始格式 (YUV420)。我通过某些自定义协议收到包含帧的数据包。

如何将接收到的 H.264 帧传递给 GStreamermm API 进行解码？

目前我阅读了它们 tutorials（不幸的是这是 GST - API 的 C 版本），但找不到实际的 GStreamermm API 文档。请在任何文档或示例中指出我如何做。

Answer 1

我能够通过管道实现传输数据并使用 C++ 版本检索解码原始视频帧。这是原始示例：

struct WebPipeline {
    Glib::RefPtr<Gst::AppSrc>   appsrc;
    Glib::RefPtr<Gst::AppSink>  appdst;
    Glib::RefPtr<Gst::Element>  h264parser;
    Glib::RefPtr<Gst::Element>  avdec_h264;
    Glib::RefPtr<Gst::Element>  jpegenc;
    Glib::RefPtr<Gst::Pipeline> pipe;
    bool accepts_data {false}; 
};

WebPipePtr ExampleClass::CreatePipeline() {
    auto web_pipe = std::make_shared<WebPipeline>();

    web_pipe->appsrc = Gst::AppSrc::create("web_appsrc");
    if (!web_pipe->appsrc) {
        throw std::runtime_error("Can't create AppSrc");
    }

    web_pipe->appdst = Gst::AppSink::create("web_appdst");
    if (!web_pipe->appdst) {
        throw std::runtime_error("Can't create AppSink");
    }

    web_pipe->h264parser = Gst::ElementFactory::create_element("h264parse", "h264_parser");
    if (!web_pipe->h264parser) {
        throw std::runtime_error("Can't create h264parse");
    }

    web_pipe->avdec_h264 = Gst::ElementFactory::create_element("avdec_h264", "avdec264");
    if (!web_pipe->avdec_h264) {
        throw std::runtime_error("Can't create avdec_h264");
    }

    web_pipe->jpegenc = Gst::ElementFactory::create_element("jpegenc");
    if (!web_pipe->jpegenc) {
        throw std::runtime_error("Can't create jpegenc");
    }

    web_pipe->pipe = Gst::Pipeline::create("websocket_pipe");
    if (!web_pipe->pipe) {
        throw std::runtime_error("Can't create pipeline");
    }

    web_pipe->appdst->property_emit_signals() = true;
    web_pipe->appdst->set_sync(false);
    web_pipe->appdst->signal_new_sample().connect(sigc::bind(sigc::mem_fun(this, &ExampleClass::PullFromPipe), web_pipe->appdst));

    web_pipe->appsrc->property_emit_signals() = true;
    web_pipe->appsrc->signal_need_data().connect(sigc::bind(sigc::mem_fun(this, &ExampleClass::EnableAcceptance), web_pipe));
    web_pipe->appsrc->signal_enough_data().connect(sigc::bind(sigc::mem_fun(this, &ExampleClass::DisableAcceptance), web_pipe));

    web_pipe->pipe->add(web_pipe->appsrc)->add(web_pipe->h264parser)->add(web_pipe->avdec_h264)->add(web_pipe->jpegenc)->add(web_pipe->appdst);
    web_pipe->appsrc->link(web_pipe->h264parser)->link(web_pipe->avdec_h264)->link(web_pipe->jpegenc)->link(web_pipe->appdst);

    web_pipe->pipe->set_state(Gst::STATE_PLAYING);

    return web_pipe;
}

void ExampleClass::EnableAcceptance(guint, WebPipePtr pipe) {
    if (!pipe->accepts_data) {
        BOOST_LOG_SEV(GetLogger(), log::info) << "Begin push frames";
        pipe->accepts_data = true;
    }
}


void ExampleClass::DisableAcceptance(WebPipePtr pipe) {
    if (pipe->accepts_data) {
        BOOST_LOG_SEV(GetLogger(), log::info) << "Begin drop frames";
        pipe->accepts_data = false;
    }
}


void ExampleClass::PushToPipe(WebPipePtr pipe, std::vector<uint8_t>&& frames) {
    if (!pipe->accepts_data) {
        return Gst::FLOW_CUSTOM_ERROR;
    }
    GstBuffer* buffer = gst_buffer_new_wrapped_full(static_cast<GstMemoryFlags>(GST_MEMORY_FLAG_READONLY | GST_MEMORY_FLAG_PHYSICALLY_CONTIGUOUS),
                                                    const_cast<uint8_t*>(frame.data()),
                                                    frame.size(),
                                                    0,
                                                    frame.size(),
                                                    reinterpret_cast<gpointer>(frame_ref), // inner implementation of some sort of wrapper
                                                    destroy); // lamda-destructor 

    buffer->set_pts(time);
    return pipe->appsrc->push_buffer(buffer);
}


Gst::FlowReturn ExampleClass::PullFromPipe(const Glib::RefPtr<Gst::AppSink>& appsink) {
    auto sample = appsink->pull_sample();
    if (!sample) {
        return Gst::FLOW_ERROR;
    }

    if (appsink->property_eos()) {
        return Gst::FLOW_EOS;
    }

    Gst::ClockTime timestamp = 0;
    {
        auto buffer = sample->get_buffer();
        if (!buffer) {
            throw std::runtime_error("Can't get buffer from sample");
        }
        timestamp = buffer->get_pts();
    }

    // process sample...

    return Gst::FLOW_OK;
}

如何使用 Gstreamermm 传递帧

How to pass frames with Gstreamermm

c++

gstreamer

h.264