webrtc视频采集

webrtc\src\webrtc\test 目录中的vcm_capturer.h 和 vcm_capturer.cc

如果仅仅是采集视频，可以参考或直接用这个例子；

也可以参考：webrtc58\src\webrtc\modules\video_capture\test\video_capture_unittest.cc；

一般仅仅是视频数据采集，Windows上直接用directshow就可以了；

移动端用相关平台sdk接口就可以了；

webrtc只是实现了上层接口的统一封装而已；

应用实例：

因为vcm_capturer.h 和 vcm_capturer.cc不是webrtc 库中的文件，所以要自己直接将文件添加到自己工程中；

class  CWebRtcVideoDivece : public rtc::VideoSinkInterface<webrtc::VideoFrame>
{
public:
CWebRtcVideoDivece( int iVideoDevice, size_t width, size_t height, size_t target_fps)
{
m_pVideoDivece = webrtc::test::VcmCapturer::Create(width, height, target_fps);


m_pVideoDivece->AddOrUpdateSink(this, rtc::VideoSinkWants());


m_pVideoDivece->Start();
}


~CWebRtcVideoDivece()
{
m_pVideoDivece->RemoveSink(this);


m_pVideoDivece->Stop();


delete m_pVideoDivece;
m_pVideoDivece = NULL;
}


private:
webrtc::test::VcmCapturer  * m_pVideoDivece;


private:


  void draw_imageBuf_to_wnd(unsigned char * pbuf, int widht, int height, HWND m_hWnd)
{




HDC hdc = ::GetDC(m_hWnd);




static BITMAPINFO bmi;




memset(&bmi, 0, sizeof(bmi));
bmi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
bmi.bmiHeader.biWidth = widht;
bmi.bmiHeader.biHeight = -height;
bmi.bmiHeader.biPlanes = 1;
bmi.bmiHeader.biBitCount = 24;
bmi.bmiHeader.biCompression = BI_RGB;

SetStretchBltMode(hdc, COLORONCOLOR);

::StretchDIBits(
hdc,
0, 0, 200, 200,
0, 0, widht, height,
pbuf, &bmi, DIB_RGB_COLORS, SRCCOPY);


::ReleaseDC(m_hWnd, hdc);
}


public:
void OnFrame(const webrtc::VideoFrame& frame) override
{
//frame: YUV; 
 
uint8_t * pY = (uint8_t *)(frame.video_frame_buffer()->DataY()); //only show Y;


int nSize = frame.width() * frame.height() * 3;
static uint8_t * pRGB = new uint8_t[nSize];


uint8_t * prgbTemp = pRGB;
for ( int i = 0; i<nSize/3; i++)
{
for (int n = 0; n<3; n++)
{
prgbTemp[n] = pY[i];
}

prgbTemp = prgbTemp + 3;

}


draw_imageBuf_to_wnd(pRGB, frame.width(), frame.height(), AfxGetApp()->m_pMainWnd->m_hWnd); 
 
}


};

可以看一下类关系：

class VcmCapturer
    : public VideoCapturer,
      public rtc::VideoSinkInterface<VideoFrame> 

class VideoCapturer : public rtc::VideoSourceInterface<VideoFrame> 

也就是说： VcmCapturer实现了 VideoSourceInterface；

void VideoSendStream::SetSource(
    rtc::VideoSourceInterface<webrtc::VideoFrame>* source,
    const DegradationPreference& degradation_preference) 

可以看出，第一个参数需要视频源，可以直接用这个了；

在webrtc内部，视频是通过各个平台实现的，当然，在Windows端，是通过directshow实现的视频采集；

void VideoBroadcaster::OnFrame(const webrtc::VideoFrame& frame) {
  rtc::CritScope cs(&sinks_and_wants_lock_);
  for (auto& sink_pair : sink_pairs()) {
    if (sink_pair.wants.rotation_applied &&
        frame.rotation() != webrtc::kVideoRotation_0) {
      // Calls to OnFrame are not synchronized with changes to the sink wants.
      // When rotation_applied is set to true, one or a few frames may get here
      // with rotation still pending. Protect sinks that don't expect any
      // pending rotation.
      LOG(LS_VERBOSE) << "Discarding frame with unexpected rotation.";
      continue;
    }
    if (sink_pair.wants.black_frames) {
      sink_pair.sink->OnFrame(webrtc::VideoFrame(
          GetBlackFrameBuffer(frame.width(), frame.height()), frame.rotation(),
          frame.timestamp_us()));
    } else {
      sink_pair.sink->OnFrame(frame);
    }
  }
}

通过循环，将注册的observe发送视频数据；