#1243 tabread4~ doesn't correctly deliver first or last sample

[Anonymous]

Hi,
tabread4~ can not correctly deliver the first or last sample of a table. Instead it delivers the second, or one but last, respectively, instead.
tabread~ (without interpolation) does work correctly, so i suspect the interpolation algorithm to be faulty.

[Alexandre Porres]

from its help file

"incoming signal is index. Indices should range from 1 to (size-2) so that the 4-point interpolation is meaningful. You can shift-drag the number box to see the effect of interpolation."

so yeah, it's because of the lagrange interpolation and it is known and documented

[Thomas Grill]

Looking into the tabread4~ code, it becomes obvious that this behavior is on purpose.
Nevertheless, for many applications, like interpolating window functions or ramps, it is undesirable, and potentially dangerous.

For my UPP framework, i made workarounds, one tabread2~ implementation, and a 'fixed' tabread4~ replacement, which resorts to linear interpolation at the front and back of the table area.
https://github.com/grrrr/upp/blob/master/upp.tabread2~.pd
https://github.com/grrrr/upp/blob/master/upp.tabread4~.pd

best, Thomas

Am 10.05.2016 um 23:23 schrieb Ticket 1243 1243@bugs.pure-data.p.re.sf.net:

[bugs:#1243] tabread4~ doesn't correctly deliver first or last sample

Status: open
Group: v0.46
Labels: bug
Created: Tue May 10, 2016 09:23 PM UTC by Anonymous
Last Updated: Tue May 10, 2016 09:23 PM UTC
Owner: nobody

Hi,
tabread4~ can not correctly deliver the first or last sample of a table. Instead it delivers the second, or one but last, respectively, instead.
tabread~ (without interpolation) does work correctly, so i suspect the interpolation algorithm to be faulty.

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