18 Oct
2006
18 Oct
'06
8:12 a.m.
--- Steve Harris <S.W.Harris(a)ecs.soton.ac.uk> wrote:
But all that can still be done at 44.1/48, it is only
the final sample multiplication that needs its inputs
band limited and thus potentially needs the upsampler.
The usual half band impulse convolution based
approach.
> But that puts potentially expensive gain
> calculations into the fast sr code, also I was
rather planning
on using the
impulse used for the upsampler to
provide the band limiting for free.
the gain calculations are relativly cheap, its
converting those gain
levels back into a gain coefficient on the output
that's expensive (from
what I remember). BEAST was the
project that had the SSE 2* up/down
sampler code that seems to be reasonably quick.
But what interpolation function? If you something
obvious and cheap you
may as well not bother, as you wont get accurate
peak interpolation. I dont think a streaming resampler is more
challenging than a correct one
that runs on buffers. You just have to preserve
state with every call,
rather than at the buffer boundaries.
But that breaks the ability to use the vectorisation
capability of modern compilers and besides the call
and return overhead will end up costing as much as the
convolution!
We seem to be discussing two separate problems here,
aliasing in the gain cell and real 'audio' peak
discovery, they are peripherally related byt are not
the same thing.
Regards Dan (Who really now has to go and do some work).
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