[ecasound] Metronome (was RE: huge todo-list)

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Subject: [ecasound] Metronome (was RE: huge todo-list)
From: Rob Coker (rcs@birch.net)
Date: Sun Oct 29 2000 - 04:42:29 EET

>Kai Vehmanen
> Hmm, is the pulse envelope implemented as a native effect or LADSPA
> plugin? Anyway, if you want, you can send me the current source and I'll
> take a look at it. Possible solutions: using a preset to combine the
> needed operators into a single operator (of course, now we need a preset
> parameter: tempo), or write it as a native effect.

The pulse envelope is native. I created an envelope modulation file. I
intend to add tremolo to it before long. The preset idea sounds great.

The format for the pulse modulation is -eemp:freqInHz,DutyCycleIn%

This isn't the way you want a metronome though (Hz as opposed to beats/sec)
so if you implemented a preset (or want to use it as is) it would need to:

1. divide beats/sec input to generate Hz eemp input
2. multiply the Hz input by 5 to generate a 50msec pulse duration

The syntax I use right now to get a metronome (at 120 beats/sec) is:

ecasound -i:null -o:/dev/dsp el:sine_fcac,880,1 -eemp:2,10 -ef3:1000,1,1

Without the lowpass filter on the end you get a pretty obnoxious clicking
sound as predicted by Fourier. I tried some different ways to get rid of it
in the pulse modulation itself and didn't have much luck. So I went with
adding the lowpass filter.

The attached audiofx_... are new code. The eca-static... is a modified
version of 1.7.9r13. The only thing I did was add a line to the map for the
envelope modulation. Makefile obviously enough has to be changed.

Thanks for the great work on this project. The code was very easy to work
with/in. Thanks also for integrating this stuff.

Is cvs accessible anonomously? or does one need to get special write
priveleges? As I already mentioned I want to add tremolo in.

Rob Coker

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