Re: [linux-audio-dev] waveform overview

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Subject: Re: [linux-audio-dev] waveform overview
From: Stefan Kost (kost_AT_imn.htwk-leipzig.de)
Date: Mon Oct 14 2002 - 16:20:31 EEST

Hi Thomas,
> Hi all,
> can anyone give me pointers on how the overview cache for a zoomable
> waveform display is organized?
> One can see accurate and fast displays in a lot of applications but i guess
> the rendering of this is not straightforward.
>
> best greetings,
> Thomas

I am thinking about this at the moment as well. My idea is to :
1.) start with N frames (e.g. 65536), segment the whole sample into N blocks and
store min and max values for each frame. Just make sure that the initial frames
are still big enough, so that the cache gives the advantage of reading less data.
2.) repeat 1 several times and double the frame size each time (thus half the
number of frames), you can easily build min/max values here from former data.
3.) Depending on the width of the window and the displayed range, seek in the
cache to the right position.
4.) when scrolling/zooming, keep the file opened !

Stefan 

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