Colin Shaw wrote: > > > What about YUV420 to RGB565 fast conversion routines? Any hints? > > > That depends what you mean by fast. My stuff is all C++ but uses > > precomputed lookup tables to achieve pretty good speed. I havn't > > benchmarked it against any of the MMX implementations - if you want one > > of those then any of the MPEG or DVD players is going to include > > optimized conversion code. > > It is clear that a table lookup from, say YUV420 to any of the RGB formats > would be pretty small, but what do you do about the size of a table for > converting from say RGB888 to YUV420 where the space spanned by the result > is significantly smaller than that of the original. It would appear that > this lookup table would require about 2^24 entries and would only map to > 64 possible YUV420 colors. Do you apply granularity to the RGB888 > pointers so that it doesn't hog so much memory? Are there any obvious > shortcuts that I am overlooking? :-) The secret is to break down the conversion such that you can express each of the r/g/b (or y/u/v) conversions as a sum of lookups into mutliple tables indexed by 8bit values. Thus the table sizes are very small with no loss of accuracy, and you've still replaced a bunch of nasty floating point equations with a few array accesses and integer additions. Check out rgb2yuv.h/cpp in my tarball at: http://planeta.terra.com.br/informatica/gleicon/video4linux/ Ben
