23-05-2017, 06:34 PM
(This post was last modified: 23-05-2017, 06:35 PM by ppppenguin.)

There are 2 palces where you need to think about number of bits. First is the coefficients. Here 8 bits are ample. The multipliers in the FPGAs are always wider than this so, unlike the days of discrete logic, you don't have to worry about it. If you want to be able to multiply by unity as against 255/256 then just add an extra bit. Or with 8 bits use 0-128. It's still enough.

The other question is how closely you define the position of each output line. AFAIK, 5 bit resolution here is ample. That's placing each line within 1/32 of a line width. I reckon you could halve that and get away with it. I see little point in going to any more bits, it just increases the size of the coefficient memories.

Since the results of different apertures etc are subjective it's very easy to fool yourself. Even with Test Card and direct A/B switch comparison.

The other question is how closely you define the position of each output line. AFAIK, 5 bit resolution here is ample. That's placing each line within 1/32 of a line width. I reckon you could halve that and get away with it. I see little point in going to any more bits, it just increases the size of the coefficient memories.

Since the results of different apertures etc are subjective it's very easy to fool yourself. Even with Test Card and direct A/B switch comparison.

Jeffrey Borinsky http://www.borinsky.co.uk