Sound level, Sound Frequency Analysis, latency, Scene jump glitch

  • Hi All,

    I having been playing around with using Isadora for a VJ-type purpose (images reacting to sound in realtime) and have come across a couple of stumbling blocks.
    1\. There seems to be a fair amount of latency with Izzy's sound level actor (i.e. the delay between the audio received and the variable being sent out of the actor) Has anyone else experienced this? I am comparing it to Modul8 running on the same machine, which is much more responsive.
    2\. A more serious problem for me is jumping from one scene to another - the dreaded glitch (which has largely disappeared when playing movies) seems to be back when dealing with two scenes containing sound level/analysis actors.
    I tried to get around this by using a single scene with all my sub-patches contained in macros. This solves the glitch but frame rates drop to unacceptable levels. I also tried placing a single Sound Level actor in an active scene and broadcasting to the other scenes but that didn't seem to help.
    Any insight would be much appreciated, thanks!
  • Izzy Guru

    Please post if you are using a Mac or PC, what OS and Izzy version you are using.


  • Dear Rawshark,

    Well, the latency should be very low depending on the sound input card you are using. There will always be some -- because there are at least 512 samples of delay as the data comes into the system. But, basically, I'm grabbing that information directly from the Core Audio sub-system as it reports it.
    Now, if your frame rate is low, then you'll see more lag. Again, all of the sound actors are "polled" at the rate specified by the "General Service Task" rate set in the preferences. If you're running at 30fps, and this is set to 8x, theoretically it should happen 240 times per second. However, the real value can be seen in the Status window, which reports the actual number of cycles per second at which your scene is executing.
    What does the Status Window say for you?
    I'm surprised however to hear of any kind of glitch which going from scene to scene. How are you experiencing this glitch? Knowing the underlying programming, this seems very unlikely to me. (I am trying to think about how one might measure this delay.
    Take a look at the attached clip. I used the Sound Level Watcher to trigger an Envelope Generator that turns the video input white and then fades it out. This is from the internal microphone on my computer. It seems pretty fast to me.
    On the other hand, if you want a continuous stream of numbers from a Sound Level Watcher, you might want to simply put a Sound Level Watcher -> Broadcaster actor in a Secondary Scene. (See the video tutorial "Activating Multiple Scenes" in the help menu) This should be extremely lightweight.
    Best Wishes,

  • Hi Mark & Michel, thanks for the responses! I'm a little under the gun right now preparing for an event so I will return to this later next week and let you know exactly what I am experiencing with details of the patch and symptoms.

    I was using 1.3.0f32 on a 2012 Mac Mini, 10.8.3