Subject: Re: [linux-audio-dev] gain curves, interpolation, etc.
From: Paul Barton-Davis (pbd_AT_Op.Net)
Date: Wed Nov 29 2000 - 15:35:41 EET
>Paul: the thing you need to calculate the polynomial given some control
>points is the Lagrange function, see Numerical Recipies, Ch. 3
>http://www.ulib.org/webRoot/Books/Numerical_Recipes/bookcpdf.html
thanks for the pointer.
>Can't you just use a sparse array structure? It will be data intesive for
>exponential fades, but long, flat gain changes will be cheap. You could
>linearly interpolate long shallow stretches if you wanted to, as long as
>the 2nd derivative is continuous you usually OK.
yes, that was another obvious option. the question is really whether
common usage will see a non-unity gain for most of a session or
not. if we have lots of changes, i expect them to be exponential by
default, with the result that we effectively double the storage
requirements for most of the audio stream. OTOH, if such sections are
rare, then a sparse array will work very well.
as a related question, i am consider gain structures to "belong" to
specific audio data, so that if you delete a section of audio, you
also deleted its gain structure. i trust that this seems right to
others as well - i thought about it for a while, and it seemed fairly
clear to me that this was the right thing to do.
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