On Tue, 16 Dec 2003, Richard Ellis wrote: > > 6 or 8GB/s L2. The cache size is 256k/CPU, 64k L1. At 550MB/s, it > > SHOULD be able to push enough to keep the frames encoding at 100% > > CPU, in theory. > > Yes, but just one 720x480 DVD quality frame is larger than 256k in > size, so a 256k cache per CPU isn't helping too much overall > considering how many frames there are in a typical video to be
A 720x480 4:2:0 frame is about 512KB, at 550MB/sec there is enough memory bandwidth to encode at about 1000 frames/sec if all you had to do was read the data. Obviously the encoder runs somewhat slower than that, so each byte of data must be accessed multiple times. That's where the cache helps. > Of course, Andrew would be much better suited to discuss mpeg2enc's > memory access patterns during encoding, which depending on how it > does go about accessing memory can better make use of the 256k of > cache, or cause the 256k of cache to be constantly thrashed in and > out. I seem to recall that one of the biggest performance bottlenecks of mpeg2enc is they way it accesses memory. It runs each step of the encoding processes and en entire frame at a time. It's much more cache friendly run every stage of the encoding process on a single macroblock before moving on the to next macroblock. ------------------------------------------------------- This SF.net email is sponsored by: IBM Linux Tutorials. Become an expert in LINUX or just sharpen your skills. Sign up for IBM's Free Linux Tutorials. Learn everything from the bash shell to sys admin. Click now! http://ads.osdn.com/?ad_id=1278&alloc_id=3371&op=click _______________________________________________ Mjpeg-users mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/mjpeg-users
