OpenCV edit captured ip camera - c++

Question

Can I use OpenCV to edit video captured from Ip camera with Dahua SDK?
Here are the portion of Dahua sample code:
// initialized play list
BOOL bOpenRet = PLAY_OpenStream(g_lRealPort, 0, 0, 1024 * 500);
if (bOpenRet)
{
// start play
BOOL bPlayRet = PLAY_Play(g_lRealPort, hMainWnd);
if (bPlayRet)
{
// monitor preview
long lRealHandle = CLIENT_RealPlayEx(lLoginHandle, nChannelID, 0);
if (0 != lRealHandle)
{
// set recall function handling data
CLIENT_SetRealDataCallBackEx(lRealHandle, RealDataCallBackEx, (DWORD)0, 0x1f);
}
else
{
//printf("Fail to play!\n");
PLAY_Stop(g_lRealPort);
PLAY_CloseStream(g_lRealPort);
}
}
else
{
PLAY_CloseStream(g_lRealPort);
}
}
The code above is connecting to cam using TCP and the streaming the video, the call back function RealDataCallBackEx is called for streaming, I can display the video on a Window, but how can I let OpenCV library to deal with it?
Here are the code of the RealDataCallBackEx function:
void __stdcall RealDataCallBackEx(LONG lRealHandle, DWORD dwDataType, BYTE *pBuffer, DWORD dwBufSize, LONG lParam, DWORD dwUser)
{
BOOL bInput = FALSE;
bInput = PLAY_InputData(g_lRealPort, pBuffer, dwBufSize);
}

Answer 1

If the IP camera uses certain standards you should be able to grab an image using the following OpenCV code (adapt where needed, i copied it from one of my own programs). I think you can also test this by pasting the url in your browser with the correct ip, port and login. I left the port at 88 because that is normally where you can send these commands to for an ip camera.
Mat returnFrame;
string url = "http://";
url.append("192.168.1.108");
url.append(":88/cgi-bin/CGIProxy.fcgi?cmd=snapPicture2&usr=");
url.append("admin");
url.append("&pwd=");
url.append("admin");
VideoCapture cap(url);
if (cap.isOpened()) {
Mat frame;
if (cap.read(frame) == false) {
cout << "Unable to grab frame" << endl;
} else returnFrame = frame.clone();
cap.release();
} else cout << "Can't open URL" << endl;
if (returnFrame.empty()) cout << "No frame to grab for cam!" << endl;
else cout << "Cam Grabbed frame succesfully" << endl;
If you want to turn a byte buffer into a OpenCV Mat you can use the following code:
byte buf[] = new byte[100];
//fill buffer here
Mat m = new Mat(1, 100, CvType.CV_8UC1);
m.put(0, 0, buf);
Be sure to define the size and type correctly. In this example it is a 1 channel Mat of 1 x 100 pixels.

Answer 2

I only succeeded with the function CLIENT_SnapPictureEx
CLIENT_SetSnapRevCallBack(OnSnapRevMessage, dwUser);
NET_SNAP_PARAMS _netSnapParam;
_netSnapParam.Channel = (uint)ChannelNum;
_netSnapParam.mode = 1;
CLIENT_SnapPictureEx(lLoginID, _netSnapParam, reserved);
private void SnapRevCallBack(IntPtr lLoginID, IntPtr pBuf, uint RevLen, uint EncodeType, uint CmdSerial, IntPtr dwUser)
{
byte[] data = new byte[RevLen];
Marshal.Copy(pBuf, data, 0, (int)RevLen);
img = Cv2.ImDecode(data, ImreadModes.Color);
}