Subject: Re: [linux-audio-dev] gain curves, interpolation, etc.
From: Roger Larsson (roger.larsson_AT_norran.net)
Date: Wed Nov 29 2000 - 01:28:44 EET
On Tuesday 28 November 2000 23:34, Paul Barton-Davis wrote:
> i'm looking for ideas on efficient ways of representing a gain curve
> so that it can be applied to audio data and modified.
>
> originally, i thought i could use a break-point style structure, but
> i'm not convinced this makes a lot of sense or is even computationally
> feasible.
>
> basically, i want to attach the gain curve object to a data structure
> that represents a contiguous section of audio data, and apply the
> curve to the data as it is is read (i.e. multiply them). extreme
> efficiency is called for here. interpolating each and every frame's
> gain value will not work.
>
> another approach i considered was to store the actual gain values
> one-or-one in a data buffer parallel to the one that holds the audio
> data. but this doubles the data storage requirements for any sections
> of audio with non-unity gain, and my sense that this is too great a
> burden to pay.
>
> any ideas ?
How about -
Approximate by a polynomial of grade N at load time.
Evaluate polynomial at run time.
Operations = 2 * N muls + N adds
/RogerL
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