Audio Unit for video sync signal - help needed
Audio Unit for video sync signal - help needed
- Subject: Audio Unit for video sync signal - help needed
- From: Voluptuous Media <email@hidden>
- Date: Thu, 21 Sep 2006 02:20:09 +0930
Hello, I looked through the archive but couldn't find anything on
this topic there.
I'd like to make an AU which is a modification to the SimplePlayThru
xcode example. A collaborator and I want to add a video sync signal
to an audio stream.
At the moment, we take a video signal, process it with audio tools
and then put the output to both a projector and an audio mixing desk.
This is unlistenable and headache-inducing by most people's
standards, I know, but we've been enjoying the experiment so far.
Problem:
At the moment, time-based effects and signal generators tend to smear
the video frame across the sync signal, disturbing the viewing device
(tv, projector, etc)
I can record a video signal that goes into an audio input, and I can
see the 'sync' signal between video frames: here in Australia, it's
50hz. Each frame of video lasts .017 sec with a .003 second sync
signal (this is the 'black bar' you could see when adjusting the
vertical hold on a tv/vcr. Incidentally, it also hold the teletext
stream). In the US it would be 60hz.
I'd like to modify the SimplePlayThru example so that it would
replace the audio stream with the .003 second sync signal (about 140
samples @ 44.1 khz) every .020 seconds (the audio stream would go
through for .017sec, or ~745 samples).
Does anyone know how to do this? I know a little programming, but I'm
mainly familiar with video related areas for Quartz Composer
experiments.
Attached is a 4kb .wav of the 140 samples, for those of you who'd
like to add the PAL video sync to your iTunes library!
Luke
PS My friend and I are the supporting act for "The Same Girl" (http://
www.soundimplant.com/same_girl/) playing in Adelaide, South Australia
at DeLaCatessen tonight at 8pm, if there's anybody on the list who'd
like to come along and see the current setup :)
Attachment:
video-sync.wav
Description: Wave audio
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