On Wed, 2009-12-09 at 00:40 +0100, Derek Holzer wrote:
I'm trying to put together a simple oscilloscope abstraction that imitates the "trigger" function of a real one, so that the waveform can be seen from its starting point. In other words, a [tabwrite~] would graph on the upward swing of a zero crossing. To do this, I'd like to know if there is an audio object which gives a bang at a zero crossing, or perhaps even only at a crossing from the negative to the positive domain of the signal. I've thought of something with [expr~ $v1 < 0], but what comes out is still in the audio domain and isn't the bang which [tabwrite~] needs.
Other suggestions welcome.
It would be nice to be able to do something like that. Two problems need to be overcome first:
- I don't know of any object class, that creates timed[1] messages from
an audio signal. All object classes I can think of convert signal->message either triggered by a message like [vsnapshot~] or triggered by an internal [metro] (like [env~]/[avg~]). We would definitely need an object class, that generates timed messages according to the signal input without requiring any message. I haven't seen such a thing yet.
- [tabwrite~] only starts writing on block boundaries. The desired
behaviour in this case _could_ actually be emulated by delaying the signal in a manner, so that the zero-crossing is shifted exactly on block boundaries. However, it would be more straight-forward, if there'd be something like a [vtabwrite~].
Probably I am just uncreative and there actually _is_ a way. If so, I definitely want to learn it!
Roman
[1] by 'timed' I am referring to the mechanism used by [vline~] and co to get accurate timing.