Salih CALISKAN wrote: > > Hello, > > First off all, I am sory for my bad english. > > I am new at Fix point arithmetic and I want to use r4fft ( FFT > function from dsp62x.lib) on image that I stored in extarnel RAM. My > problem is, in documentation, it says all the inputs must be Q15 > format. For the fft coefficients, there is no problem because they are > in range of -1,1 however the pixel values are out of range (>1). How > can I use input values >1 for this function. Should I convert them Q15 > format (How??) > > Any commnet, docmentation or sample code will be appreciated > > Thank you in advance, > > Salih > > ---------------------------------- > > Note: If you do a simple "reply" with your email client, only the > author of this message will receive your answer. You need to do a > "reply all" if you want your answer to be distributed to the entire > group. > > _____________________________________ > About this discussion group: > > To Join: Send an email to > > To Post: Send an email to > > To Leave: Send an email to > > Archives: http://www.yahoogroups.com/group/c6x > > Other Groups: http://www.dsprelated.com > > --------------------------- > Yahoo! Groups Links > > * To Only twiddle factors should be in Q15. Inputs can be in 8Q8 {255} for a 256 point FFT, without overflow in a radix4 FFT as a 256 point FFT will be perfomed in 4 stages, and since each stage is 2 bits of growth, 8 bits input + 8 bits growth will just fit in 16 bits. Regds JS |