So BACKVIDEO would be the quickest as it is writing to video memory and doing a pan or flip. Where as the BACKSYSTEM is implemented to do a copy from system memory (or video ram) to the visible frambuffer. Sinced the BACKSYSTEM is a memcpy is would be slower than the BACKVIDEO. (Unless the memcpy is implemented in away to use DMA or some other processor like a DSP that shares tha same memory).
The reason for the clairification is I am looking at implementing support for the IBitBlit from TI that is a plugin for the Codec Engine 2 from TI. If I can speed up the BACKSYSTEM using there IBitBlit I suspect my app will use less of the ARM and execute a bit faster as there will be no memcpy from the BACKSYSTEM buffer by the ARM. Thanks, Craig On Tuesday 29 September 2009 12:28:20 am Lionel Landwerlin wrote: > Le lundi 28 septembre 2009 à 20:13 -0600, Craig Matsuura a écrit : > > I want to get some clarification on the BACKSYSTEM, BACKVIDEO and > > FRONTONLY. > > > > > > > > Here is my understanding: > > > > > > > > BACKSYSTEM uses a virtual framebuffer of the screen (Some place in > > RAM) and DirectFB draws on this screen (surface), once a Flip is > > called the virtual framebuffer is copied to the Real/Visible > > framebuffer. > > Yes, in DirectFB, BACKSYSTEM describe a memory part that is not directly > displayable by the video device. > > But after all, it depends of hardware. For some system the video memory > is at a particular place in RAM, for some BACKSYSTEM is just like > BACKVIDEO. > > > BACKVIDEO use the off screen video memory and draws in the screen > > (surface) that is off screen. When a Flip is called the framebuffer > > starting position is changed to the off screen position to make the > > screen visible. The next frame is draw on the off screen and the > > process is repeated. > > Yes. > > > FRONTONLY, draw directly to the visible framebuffer. > > Yes. -- Craig Matsuura - Principal Engineer Control4 11734 South Election Road - Suite 200 Salt Lake City, UT 84020-6432 PH: 801-523-3161 FX: 801-523-3199
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