9 Nov
2008
9 Nov
'08
9:59 a.m.
OrazioPirataDelloSpazio (Lorenzo) wrote:
Hi all,
I need to use a microphone input as a trigger. In other words my idea is
to connect a switch to the microphone input. In this way, when the
switch is turned on it generates a spike in the captured track.
I would like to create a program that trigger an event every spike it
receives.
one option is to rip some code from a ladspa gate plugin and use that to
create a software event.
or you could use a midi trigger and receive a midi event.
I succeed in capturing the mic input through a simple
program that uses
alsa driver, but I don't know how to "parse" the raw data to search for
the spikes. Any hints?
the easiest approach is to rms the data to get loudness information, and
then generate an event if a certain threshold is reached. further
refinements could be variable attack and hold times and a bandpass to
filter out unwanted noise.
take a look at any noise gate implementation.
Second question: on a "full duplex" sound
card, can I capture at 8 bit,
mono, 22.050 bit/s , and on the same time playback at 16 bit, stereo,
44.100 ?
generally, no. but you can capture at 16bit/44k1. afterwards it is a
trivial operation to resample and decimate if necessary.
--
jörn nettingsmeier
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phone://+49/201/491621
Kurt is up in Heaven now.