Re: Resampling
- From: robert bristow-johnson <rbj@xxxxxxxxxxxxxxxxxxxx>
- Date: Tue, 01 Nov 2005 17:13:43 -0500
in article 1130882481.528510.213690@xxxxxxxxxxxxxxxxxxxxxxxxxxxx,
rhnlogic@xxxxxxxxx at rhnlogic@xxxxxxxxx wrote on 11/01/2005 17:01:
> cs_post...@xxxxxxxxxxx wrote:
>> robert bristow-johnson wrote:
>>>> I want to resample a real signal from for instance 1024 -> 1027 samples.
>>>> I prefer not to do it in the temporal domain, in order to avoid large
>>>> upsampling and downsampling steps.
>>>
>>> where do these guys pick up these misconceptions? is there some textbook
>>> somewhere that is saying that you first upsample by an integer factor of
>>> 1027, then pick out 1 sample in every 1024 thus throwing away the other
>>> 1023? does it not occur to people that, if all you're gonna do with the
>>> other 1023 samples is throw them away, maybe you don't have to compute
>>> them in the first place?
>
> Agree.
>
>> You don't have to compute all of them in the first place, but you do
>> have to compute smoothed intermediate samples at a wide variety of
>> possible points in between the input ones. Do you have a way of
>> computing only those that are needed?
>
> Yes. It's all interpolation. Just interpolate the samples needed,
> doesn't matter where they are or what their spacing is.
well, i dunno about that. some sample locations or spacings require more
coefficient memory or sample computation than others.
> Using a simple windowed Sinc, you can recalculate your filter
> coefficients for each output sample anywhere, given sufficient
> compute power.
that's true. but it does make a difference on compute power what the SRC
ratio is.
--
r b-j rbj@xxxxxxxxxxxxxxxxxxxx
"Imagination is more important than knowledge."
.
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