[PD] problem with switch~ and downsampling in 0.38-0test7
Matthias Blau
blau_m at web.de
Mon Feb 21 21:51:30 CET 2005
In my opinion, the whole thing looks like switch~ sometimes does the
switching in the upsampled (parent patch) domain although it sits in the
subpatch, thereby generating high-frequency components at the interface
between parent (upsampled) patch and subpatch.
In any case, if switch~ is used without downsampling, and the
downsampling is then done in yet another subpatch using block~, then all
problems disappear.
Thus, it appears that one should not use switch~ together with downsampling.
--Matthias
IOhannes m zmoelnig schrieb:
> Matthias Blau wrote:
>
>> Hi all,
>
>
>> Therefore I made a subpatch with [switch~ 64 1 0.5] which works most of
>
> ...
>
>>
>> Sometimes however, I get strong high frequency disturbances. I suspect
>> a bug in switch, but maybe I am missing something?
>>
>
> you might have problems with aliasing.
> the up/downsampling does very little (to no) pre-filtering.
> upsampling: depending on the argument the iolet~s will do linear
> interpolation between 2 original samples at the best(!!!); this is not
> very good; the default is zero-padding which is really awful (but is
> there by intent, as you will very soon notice, that "something" is going
> on)
> downsampling: if i remember correctly, it just takes every nth sample
> (even if you specify "linear" there is no smoothing or whatever)
>
> so make sure that you filter your signal before/after down/upsampling.
>
> mfg.asd.r
> IOhannes
>
> _______________________________________________
> PD-list at iem.at mailing list
> UNSUBSCRIBE and account-management ->
> http://iem.at/cgi-bin/mailman/listinfo/pd-list
More information about the Pd-list
mailing list