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Re: MusicPlayer with OpenGL interfere with UIGestureRecognizer
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Re: MusicPlayer with OpenGL interfere with UIGestureRecognizer

  • Subject: Re: MusicPlayer with OpenGL interfere with UIGestureRecognizer
  • From: Gregory Wieber <email@hidden>
  • Date: Thu, 19 Feb 2015 14:54:29 -0800
On which thread are you allocating your graph?

Sent from my iPhone

On Feb 19, 2015, at 1:26 PM, Dave O'Neill <email@hidden> wrote:

The actual refresh rate is unaffected at a verified 60FPS with a CADisplayLink.  The little demo I made is drawing just two triangles with 10-15% CPU. It is only the touch that is not being updated, when I animate programmatically there is no lag at all even with unrelated touch tracking happening simultaneously.  I think that somehow the MusicPlayer framework causes the thread that tracks touch (which I had assumed was the main thread) to wait on the audio render cycle.  What's interesting is that the main thread doesn't get blocked, only the updating of touch events.  I know that AUGraph (which is utilized by a MusicSequence by default) can block, but I don't know if that's what's happening.  

Dave

On Thu, Feb 19, 2015 at 1:04 PM, Steven Clark <email@hidden> wrote:

If you have limitless CPU cycles then it would be a weird interaction.  It sounds very very much like the sort of behavior you get if there aren’t enough CPU cycles for everything, and the system is optimized for something other than what you’re trying to do.

 

I had serious trouble with an iOS app that needed to track finger movement and display video at the same time.  It appears that iOS prioritizes tracking movement over anything else (at least, anything else that the app was doing).  The video got really choppy etc. whenever you’d move your finger, and clear up immediately when you move your finger away.  I found that the tracking loop was running as fast as it could, at the expense of all other computation.  (The system is optimized for visual user interaction responsiveness.)  I solved the problem by having my tracking routine do nothing and return immediately something like 4 times out of 5.  Response to finger movement was slightly affected negatively, but video was substantially improved.  I might have solved it by increasing the priority of the video processing thread, but that would have involved screwing around with Mach thread prioritization and hoping the app would still be approved by Apple for iTunes.

 

Steven J. Clark

VGo Communications

 

From: coreaudio-api-bounces+steven.clark=email@hidden [mailto:coreaudio-api-bounces+steven.clark=email@hidden] On Behalf Of Dave O'Neill
Sent: Thursday, February 19, 2015 3:21 PM
To: Ian Kemmish
Cc: email@hidden
Subject: Re: MusicPlayer with OpenGL interfere with UIGestureRecognizer

 

Really what I'm trying get to the bottom of, bug or no bug,  is how can these three seemingly unrelated api conflict? 

On Thursday, February 19, 2015, Ian Kemmish <email@hidden> wrote:


On 18 Feb 2015, at 17:00, "Dave O'Neill" <email@hidden> wrote:

> Once you see it being choppy press the play/stop button and see how
> the choppiness stops.  Weirdest bug ever.

Unless the gesture recognition software you're using is documented as making guarantees about latency, then it's not a bug.  It's life.


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  • Follow-Ups:
    • Re: MusicPlayer with OpenGL interfere with UIGestureRecognizer
      • From: "Dave O'Neill" <email@hidden>
References: 
 >Re: MusicPlayer with OpenGL interfere with UIGestureRecognizer (From: Ian Kemmish <email@hidden>)
 >Re: MusicPlayer with OpenGL interfere with UIGestureRecognizer (From: "Dave O'Neill" <email@hidden>)
 >RE: MusicPlayer with OpenGL interfere with UIGestureRecognizer (From: Steven Clark <email@hidden>)
 >Re: MusicPlayer with OpenGL interfere with UIGestureRecognizer (From: "Dave O'Neill" <email@hidden>)

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