Slow Freehand Drawing On Video Frame

Question

I am attempting to make an application, which allows user to do

freehand drawing on paused video surface.Or using mouse cursor to

simulate pen or brush movement on video frames. Currently my approcah is

to grab the paused frame as a bitmap and draw on this bitmap, then paste

it back to the video window.This method works fine for my Desktop PC, which

is AMD Athlon 64*2 Dual Core 4200+, 2,20GHz. However, when I tried using 

a release build on a TabletPC with Centrino Duo 1.83Hz, the drawing speed

suffers quite a bit.

I want to find out if there is any better approach to do this type of drawing

on video surface. Or is there a way to create a transparent video overlay on top of the 

paused frame and draw on this layer? 

Thanks.

Environment:

Windows XP. windows SDK 6.0, Visual Studio 2008, C++, MFC, GDI+ for graphics

I also used double buffering for GDI+

Answer 1

Intercept a click on the window, do SetCapture and draw directly on the window DC until user releases the button. Then duplicate the drawing on the paused frame and paste it back to the graph. Just do not paste video frame on every cough user makes, and you should be okay with the performance.

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http://alax.info/blog/tag/directshow

Answer 2

Thanks very much for your reply. But I am just wondering how to paste the drawing back to the graph? I am currently using VMR7 in windowless mode. I use GetCurrentImage() to grab the bitmap frame. The reason why I draw the video frame for every cough user makes is because I need to allow user to be able to select the drawings using mouse cursor and move it across the screen. Hence I need to refresh the video display area in order to erase the previous drawings. 

Answer 3

If you are using IVMRMixerBitmap Interface, video is updated with next main video stream frame, not with your alpha overlay update. To "paste" image back to graph you typically need your own filter in the chain to send a new frame to VMR.

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http://alax.info/blog/tag/directshow