Re: [OT] Don't draw every 10th sample(!) (Was Re: Best drawing technology for audio waveforms, envelopes, etc.?)
Re: [OT] Don't draw every 10th sample(!) (Was Re: Best drawing technology for audio waveforms, envelopes, etc.?)
- Subject: Re: [OT] Don't draw every 10th sample(!) (Was Re: Best drawing technology for audio waveforms, envelopes, etc.?)
- From: "I. Savant" <email@hidden>
- Date: Mon, 25 Jun 2007 14:30:36 -0400
On 6/25/07, Alastair Houghton <email@hidden> wrote:
No, no, no! :-) You *can't* do that, as I already pointed out.
You'll display totally the wrong thing if you pick every Nth sample.
I've lost count of the number of freeware/shareware audio apps
(across various systems) that do that.
Well, nobody ever claimed all my ideas are bright ones ... It does
save my ego just a *bit* of bruising to know my mistake isn't all that
uncommon, though. :-D I admit I skimmed much of this thread. Bad list
member, BAD!
and that line of samples might move up and down depending on where I
scroll to (it does in some programs I've seen). You can get many
other similarly unpleasant effects this way (I chose an extreme
example deliberately).
I admit I'm having trouble visualizing what you're describing, but I
do have a vague notion of the problem it presents now that you mention
it. This is getting off-topic for Cocoa, but if you feel like it, I'd
*very much welcome* a more detailed / alternate explanation off-list
(including Hans since it may or may not benefit him as well). I have
an in-house application that manipulates voice recordings which
sometimes have lengthy silences and it's been suggested before that I
add a waveform view, though the actual utility of such a thing in my
case is questionable ... :-/
> Also, for efficiency, only plot the samples that are visible
> on-screen (and the one before and the one after to allow lines to the
> previous-and-next clipped points).
Yes, that's certainly a good idea. It'd be crazy to plot the entire
waveform each time, though if you're buffering it to a bitmap then
you might take that approach.
As mentioned previously, it's best just to start with simple drawing
code then get trickier if performance calls for it.
--
I.S.
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| References: | |
| | >Best drawing technology for audio waveforms, envelopes, etc.? (From: "Hans Kuder" <email@hidden>) |
| | >Re: Best drawing technology for audio waveforms, envelopes, etc.? (From: Alastair Houghton <email@hidden>) |
| | >Re: Best drawing technology for audio waveforms, envelopes, etc.? (From: "Hans Kuder" <email@hidden>) |
| | >Re: Best drawing technology for audio waveforms, envelopes, etc.? (From: "I. Savant" <email@hidden>) |
| | >[OT] Don't draw every 10th sample(!) (Was Re: Best drawing technology for audio waveforms, envelopes, etc.?) (From: Alastair Houghton <email@hidden>) |