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Groups > comp.arch.embedded > #26618

Re: Sync to Android frame rate

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> I'm looking for a way to synchronize some code activity to the Android
> display frame rate. It's a short bit of code that will simply set the
> color of a small display region, nothing more. Is there some sort of
> method or hook that I can exploit for this purpose?

I'll answer my own question, partially that is.  It appears one solution 
is to use the Choreographer class which provides a way to hook a 
callback function into the frame rate.  Below is the code.  It executes 
but the timing is sloppy.

I can time the calls to doFrame() using System.nanoTime().  A little 
testing shows me the timing of calls to doFrame() is not uniform 
(ranging from 12 msec to 20 msec, expecting about 16 msec).  The 
callback argument is rock steady (about 16 msec) which makes me think 
it's a value that is computed at initialization time.

It's a solution but it's not doing what I wanted because the callback is 
not timing precisely enough.  Still seeking advice, thank you.

JJS

///////////////////////////////////////////////////////////////

private FrameCallback frameCallback = null;
private boolean frameCallbackPending = false;

public void armVSyncHandler() {
     if(!frameCallbackPending) {
         frameCallbackPending = true;
         if(frameCallback == null)
         {
             frameCallback = new FrameCallback() {
                 @Override
                 public void doFrame(long frameTimeNanos) {
                     frameCallbackPending = false;

                     // Do some work here

                     armVSyncHandler();
                 }
             };
         }
         Choreographer.getInstance().postFrameCallback(frameCallback);
     }
}

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Sync to Android frame rate John Speth <johnspeth@yahoo.com> - 2017-05-17 17:23 -0700
  Re: Sync to Android frame rate John Speth <johnspeth@yahoo.com> - 2017-05-18 11:59 -0700
    Re: Sync to Android frame rate rickman <gnuarm@gmail.com> - 2017-05-18 21:53 -0400
      Re: Sync to Android frame rate Theo Markettos <theom+news@chiark.greenend.org.uk> - 2017-05-19 18:28 +0100
        Re: Sync to Android frame rate rickman <gnuarm@gmail.com> - 2017-05-19 13:47 -0400
        Re: Sync to Android frame rate John Speth <johnspeth@yahoo.com> - 2017-05-19 12:47 -0700
    Re: Sync to Android frame rate John Speth <johnspeth@yahoo.com> - 2017-05-19 12:51 -0700
      Re: Sync to Android frame rate Theo Markettos <theom+news@chiark.greenend.org.uk> - 2017-05-22 11:00 +0100
        Re: Sync to Android frame rate John Speth <johnspeth@yahoo.com> - 2017-05-22 09:24 -0700
          Re: Sync to Android frame rate Theo Markettos <theom+news@chiark.greenend.org.uk> - 2017-05-22 22:30 +0100

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