[linux-audio-dev] Traps in floating point code

[Steve Harris]

On Mon, Jun 28, 2004 at 12:23:37 +0200, Maarten de Boer wrote:
> Hi Erik,
> 
> Depending on the ranges of your increment, and the accuracy you
> want to obtain, you might consider doing this with integers only.

Yes, for this kind of accumulator thing I often use a hacked up
fixedpoint representation:

typedef union {
        int32_t all;
        struct {
                uint16_t fr;
                int16_t in;
        } part;
} fixp16;

as you're only ever adding to them, you dont gain much by using floats,
getting the interger part out is really cheap and easy (foo.part.in) and
the fractional part is foo.part.fr / 2^16. Accumulation is done with
accum.all += delta.all. The 32.32 form should be obvious.

I think the struct components need to be the other way round for bigendian
machines though. I really must do something about making that work...

- Steve