Hey all I'm trying to make a webcam application. Originally I thought I should grab individual frames from the camera, compress them, and then send them. But doing that gives me vast images. A 160x120 JPEG compressed image is 5Kb, and that means about 2FPS if I'm sending over a typical internet connection. I thought I should probably be using MJPEG, since this is what its best at. However, how do I read the data it produces? I'd like to add a MJPEG compressor to my graph, and then somehow read the output, and send it through a socket, where it can be read at the other end. Is there a way to render to a memory buffer or something in DirectShow? I know I can render to a preview window, a file, or to a NullRenderer, but I can't find any documentation on rendering to a buffer. Is it possible? Cheers, Steve EDIT: This should maybe be in the DirectX forum. Mods feel free to move it. [Edited by - Evil Steve on September 13, 2004 1:01:47 PM]

I see. I assume I'll have to write these filters, they don't already exist in DirectShow? I can't find any reference to them in the docs anyway. I'm having a look around the MSDN for information about writing a custom filter at the moment.

Cheers,
Steve

Quote:Original post by Martin Foerster
Why don't you use the AVIFile-API?

It has got compression, can capture too, is low-level enough
to be very flexible, but high-level-enough to be implemented
in a few minutes.

Look at your MSDN-Lib.

I had a look at it before, but I couldn't find any functions to read from a capture device, only from a file.

Ok, thanks.

Does anyone have any links to tutorials for this stuff? The MSDN is confusing at best, and I'm not entirely sure about all the COM stuff. I understand that I need to register a class factory with COM, and that factory should create my filters - but I'm not sure how to register my stuff with COM, or if I need the 7 or 8 Co*() methods in my DLL...

I've managed to get something working with the help of the code from the base classes (but I'm writing my own classes, not using them).
I can't get COM to realise that my class factories are actually in the DLL. I've tried using CoRegisterClassObject(), but that doesn't seem to work. I don't really want to have to add my filters to the registry. Anyway, it seems to work by sidestepping COMs initialisation and just doing IBaseFilter* pFilter = new CSocketSink(). Which I'm sure is horrible, but its working for now.

The problem I'm having at the moment is that I don't know exactly what I should have for my media type. The camera gives a media type of MEDIATYPE_Video and MEDIASUBTYPE_RGB24, with the format set to video, and the VIDEOINFOHEADER set up accordingly.
Whenever I call RenderStream(), I get error code 0x80040217 (VFW_E_CANNOT_CONNECT). If I put breakpoints everywhere, I can see CEnumMediaTypes::Next() being called 11 times. I return only one media type, which is exactly the same as the one thats returned by the camera.

Anyone know whats wrong here?

Cheers,
Steve

*bump*
Has noone tried to write a custom DirectShow filter before?

I'm still totally stuck with this [sad]