14 Oct
2002
14 Oct
'02
6:47 a.m.
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
14 Oct
14 Oct
7:11 a.m.
You just store the peak amplitudes (+ve and -ve sepratly) for every N
samples.
I think typically you have two seperate peak files, eg. one for every 2^8
samples and one for every 2^16.
The eqivalent in large images uses one "peakfile" for every power of two,
but audio people seem to be more conservative - for one thing scaling
audio is much cheaper.
You could look at sweep, snd, ardour, audacity etc. to see how it is done.
- Steve
On Mon, Oct 14, 2002 at 10:45:20AM +0200, Thomas Grill wrote:
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
11:25 a.m.
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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15 Oct
15 Oct
5:48 a.m.
always a perennial favorite.
here is the way i did it way back when.
http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/eponymous/gtkwv/
and the requisite screenshot http://www.arcsin.org/editor.jpg
have fun,
rob
On Mon, Oct 14, 2002 at 10:45:20AM +0200, Thomas Grill wrote:
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
----
Robert Melby
Georgia Institute of Technology, Atlanta Georgia, 30332
uucp: ...!{decvax,hplabs,ncar,purdue,rutgers}!gatech!prism!gt4255a
Internet: async(a)cc.gatech.edu
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participants (4)
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Stefan Kost -
Steve Harris -
Thomas Grill