[Openh323-user] Re: [OpenH323]About Implementaion of VideoInputDevice for WinCE

[Derek S. <de...@in...>]

Hi,

The PVideoInputDevice copys data from the camera into a destination 
buffer.

The number of bytes copied is given in the argument:  bytesReturned
The pointer to the desination buffer is the argument: buffer

That you always get a green screen:
 You can try using a different video input 
  --videoinput X on ohphone.

Examine the fake video input devices.

These provide a clue as to how the PVideoInputDevice must work.
I suggest this class because you do not have the added complexity of 
making the hardware work.


Derek.

On Sun, 15 Jun 2003, Nina wrote:

> Hi all,
> 
> I'm implementing video communications between WinCE devices.
> My platform is Windows CE.NET 4.1 & x86 family processor.
> 
> As you know, there is no common APIs for capturing from camera
> device(like VFW stuff) in WinCE so, I made new class from PVideoDevice.
> 
> My camera sdk has only 4-5 for capturing, very simple. Capturing from
> camera looks ok, but if this data is processed and sent then this is
> displayed to "green still image". I have no idea, what I did wrong.
> Receiving & Displaying funtions are no problem with openphone in PC.
> 
> -----------------------------------------------------------------------------------------------
> My questions are these :
> 1. void VideoFrame::SetSize(int, int)
> -> this functions sets "frameptr" dynamically, but I don't understand why this buffer size should be "(width * height * 3) >>1"
> 
> 2. My grabber gets raw data from camera with YUV422 format. Is this no problem?
> 
> 3. Sender : Grabbing(YUV422) -> Encoding(H.261 QCIF) -> Transmitting
>    Receiver : Receiving -> Decoding -> Displaying (RGB24, converting from YUV422)
>    -------------------------
>    it displays just green still image, do you have any idea what i did wrong?
>    Receiver part is no problem with PC.
> 
> 4. I don't use thread(PThread) to run "PVideoInputDeviceInCE", is this no problem?
>     I know that "PVideoInputDevice" is run from PThread.
> -----------------------------------------------------------------------------------------------
> 
> 
> Below codes describe "GetFrameData"
> -----------------------------------------------------------------------------------------------
> // PVideoInputDevice class for WinCE
> class PVideoInputDeviceInCE : public PVideoDevice
> 
> // GetFrameData is called from PVideoChannel::Read Function directly
> bool PVideoInputDeviceInCE::GetFrameData (BYTE* buffer, PINDEX* bytesReturned)
> {
>     LPBYTE pOriginalBuffer = buffer;
>     
> < if it is first call, initialise camera device & start it.>
> 
>    // Get raw data from camera, YUV422 format
>     bool bResult = Capture_Frame_from_Camera (pCaptureBuff);
> 
>     // if "buffer" pointer has changed from other, don't write captured data in "buffer"
>     // it will cause problems.
>     if(pOriginalBuffer != buffer)        return TRUE;
>     buffer = pCaptureBuff;
> 
>     return bResult;
> }
> -----------------------------------------------------------------------------------------------
> 
> 
> 
> 
> 
> 
> 

-- 
Derek Smithies Ph.D.
IndraNet Technologies Ltd.
Email: de...@in...
ph +64 3 365 6485
Web: http://www.indranet-technologies.com/