Hi, I have two implementations of video capture and display using SDL, and I am trying to figure out the reason for differences in performance and appearance between them. Everything here is using the V4L2 driver for Videum boards. Implementation 1: Native DirectFB Primary Surface in video memory. Secondary surface in system memory. Control loop: - grab video frame, copy it into secondary surface. - image process the data in the secondary surface. - Stretched blit of secondary surface into primary surface. Code timing show that I am churning through 30fps, though I don't think that this is the rate at which frames are actually appearing on the screen (maybe frames are being clobbered between refreshes?) Implementation 2: Over SDL over DirectFB (modelled using the effectv code). Control loop - grab video frame, bring it into system memory. - stretch it by pixel doubling using the CPU. - copy data into primary SDL surface. Code timing show that I am churning through 21 fps, I think that this is the rate at which frames are actually appearing on the screen. (If I don't do the pixel doubling step, I get 30fps). Bottom line: implementation 2 looks much smoother on the screen than implementation 1, and I am trying to figure out why. I moved to DirectFB because I am using a Matrox G400 and I figured that on-board stretched blits would be much faster than CPU-based pixel doubling. Frame rates show that the DirectFB implementation chews through frames much faster, but qualitatively, the SDL over DirectFB implementation looks much smoother. I suspect it may be because I am blitting several frames to the Matrox card before it has a chance to actually show them to me on the screen--is this possible? Can someone offer some suggestions--obviously the folks who wrote the back end of SDL -> DirectFB know how to do it right. Thanks Bilal _________________________________________________________________ Chat with friends online, try MSN Messenger: http://messenger.msn.com
