[linux-audio-dev] things to port to the gp2x ..

[Steve Harris]

On Wed, Jan 11, 2006 at 03:01:28PM +0100, Alfons Adriaensen wrote:
> On Wed, Jan 11, 2006 at 01:53:25PM +0000, Steve Harris wrote:
> 
> > I agree about ARM assembly, I have written some (not DSP related) many
> > years ago and it was quite straightforward.
> 
> Another ex Acorn user ???

Damn, does it show ;)
 
> > Does this ARM chip have real fixedpoint hardware, or do you have to do bit
> > manipulations to get the numbers?
> 
> It doesn't have anything specific fixed point. It's all integer, and you,
> as the programmer, have to imagine a binary point somewhere in your data
> and keep track of it.

Yeah, some of my LADPSA code uses pseudo-fixedpoint to track things like
phases. I found it slightly simpler than floating point, and things like
modulos and finding what quadrant its in is really cheap.
 
> What helps enormously on the ARM is that all arithmetic instructions can
> include a (no overhead) shift on one of the operands. There are some
> other unique things, such as the 16 conditions on *all* instructions.

I see, that is helpful. I imagine that coding things like IIR filters is
still quite time consuming though. I would expect that you need to switch
between different point positions a lot.

- Steve