Pulse generator not in sync with external click

  • I built a Tap-Tempo-Function with the Tap Tempo-actor an the Pulse generator. In general it works but it does not seem to be precise. To test that I played a click from a clicktrack-audio-file and set the actor to the same BPM (e.g. 85mpb). Starting both at the same time after about 10 seconds they start to differ. Any Idea what goes wrong or is there a technical limit?

  • Izzy Guru


    It's true that the pulse generator will not stay precise after a short time, it follows the general service task you can set in Isadora's preference settings.

    ------------------------------ From the Isadora manual ------------------------------

    ...General Service Task (v1.3 an up) Refers to the frequency with which Isadora will try to service all actors except Movie related actors in all currently active scenes. Generally this setting relates to actors that have to do with time like the envelope generator, wave generator, pulse generator etc. The General Service Task is specified as a multiple of the Target Frame Rate; the actual period between service tasks is shown to the right of the popup menu....

    ...Cycles reports how many times per second Isadora can process all of the actors in the currently active Scene(s). The higher this number, the better Isadora’s performance. This maximum value of this number is directly related to the General Service Task setting in the General tab of the Preferences – higher Service Task rates will yield a higher number of cycles per second....

    Conclusion: As soon as Isadora can't keep up the general service task the clock will run out of sync. You can see the cycle on the right bottom dropping when you for example move your mouse very fast. So please file a feature request that time related actors do not follow the general service task but have their own clock that does not get out of sync over time.

    Best Michel

  • Question, What is the down side of changing this setting to it's fastest rate?

  • Tech Staff

    More processing... each cycle requires CPU.

    Being able to adjust it allows you to strike the best balance for your specific project. For instance if you are using audio frequencies to control parameters, you may want the service tasks to run more often so that the audio is sampled more regularly.

  • is it possible to get an external midi clock to send a pulse into isadora? Also it should recieve my taped tempo from isadora? I tried this: http://midiclock.com/ , but i dont get any signal into isadora.

    I also tried the midi clock from my akai mpd 266, but alos here i dont get any signal into the real time watcher. The monitor doesnt show any click.