Hi!

I have problems to implement fast live-view from attached camera using Allegro 5. The camera streams uncompress color or grayscale images and I need to draw them inside my Allegro created fullscreen interface.

The problem is how to get frame data into bitmaps. When I use locking and filling the buffer with raw data, it is extremely slow and on a subpar graphics card (Intel 3150) I can get only about 15 FPS for 1024x768 images.

Surprisingly, when I wrote GDI application which uses SetDIBitsToDevice(), I could easily achieve 60 FPS at the same hardware. Why?

I would like to try to create offscreen bitmap, get a GDI drawing context for it and use the SetDIBitsToDevice(), but I do not know how. I found some examples for it, but these were for Allegro 4.

Thanks for help!

Try using a video bitmap that is the same size as your stream buffer, and lock it in WRITE_ONLY mode. That may speed things up some for you.

That's exactly what I am doing. It is slow.

Is there a way how to get HDC from ALLEGRO_BITMAP? There was such a method in Allegro 4.

Okay then, what if you use a memory bitmap buffer and then draw it to the backbuffer? Is that any faster? Are you also locking the bitmap in the same format as the bitmap?

Looks like the best you can get for now is al_get_d3d_video_texture. Allegro 4 only let you blit to and from an HDC, not create a new one.

Actually, I solved this by creating my own Direct3D texture with D3DUSAGE_DYNAMIC in D3DPOOL_DEFAULT. Locking such a texture is about 10x faster than locking the ALLEGRO_BITMAP whichever way it was created.

Of course, I had to supply my own Direct3D drawing from that texture using DrawPrimitiveUP() call, but it was worth it. Now I just hope that my D3D drawing works seamlessly with the rest of Allegro5.

I would suggest Allegro5 should add new bitmap flag indicating that the bitmap being created is dynamic or suitable for streaming. I guess SDL 1.3.x have such flag already.