9 May
2005
9 May
'05
9:29 p.m.
On Monday 09 May 2005 19:02, Paul Davis wrote:
if you allow arbitrary zoom scales, then the mapping
between pixel
position on screen (or some notional "unit" position as offered by
canvas widgets) and a sample is non-integral, which implies
rounding. that in turn implies errors of several different kinds.
moreover, if you are displaying large audio files, reading the audio
data itself is excrutiatingly slow. hence, peakfiles.
And here's another one in Qt, from Rivendell's Marker Editor:
http://www.salemradiolabs.com/rivendell/
Unpack the tarball and look in rdlibrary/edit_audio.cpp.
Paul is quite right about all the round-off and peak-file issues. Rivendell
handles that by assuming that the smallest atom of audio is always 1152
samples long -- which just happens to be the standard MPEG sample block size.
This gives acceptable precision for the marker editor, but would probably not
be adequate in a general purpose editor. Even the 'simplified' version is
quite headache-inducing enough, however... :)
Cheers!
|-------------------------------------------------------------------------|
| Frederick F. Gleason, Jr. | Director of Broadcast Software Development |
| | Salem Radio Labs |
|-------------------------------------------------------------------------|
| Never worry about theory as long as the machinery does what it's |
| supposed to do. |
| -- Robert A. Heinlein |
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