[Bf-committers] Help needed! Animation problems for 3D Audio GSoC

[Hart's Antler]

Maybe this is an option; having the audio playback as the main time keeper, and then dropping frames in the view-port if they fail to render within time (within frame accuracy).

But one problem is for a heavy scene this could mean that no frames are ever rendered in time and all are dropped, a work around could be: measure the average delay it takes to render a frame and skip ahead to rendering the next frame by that delay.

-brett
 

--- On Sun, 7/17/11, Martin Poirier <theeth at yahoo.com> wrote:

> From: Martin Poirier <theeth at yahoo.com>
> Subject: Re: [Bf-committers] Help needed! Animation problems for 3D Audio GSoC
> To: "bf-blender developers" <bf-committers at blender.org>
> Date: Sunday, 17 July, 2011, 2:37 PM
> Hi,
> 
> I'd like to ask people with good knowledge of Blender's
> animation and animation related structures to please
> consider this problem, this is rather important for neXyon's
> GSOC project.
> 
> Thanks,
> Martin
> 
> --- On Sun, 7/17/11, neXyon <nexyon at gmail.com>
> wrote:
> 
> > From: neXyon <nexyon at gmail.com>
> > Subject: [Bf-committers] Help needed! Animation
> problems for 3D Audio GSoC
> > To: bf-committers at blender.org
> > Received: Sunday, July 17, 2011, 2:31 AM
> > Hi guys!
> > 
> > There's a serious problem with the way how animation
> works
> > in regard to 
> > audio. The main problem is, that the animation system
> > pushes the output, 
> > so it sets the data, renders a frame, advances to
> next
> > frame (setting 
> > the data there) and renders again and so on, this
> works
> > pretty good for 
> > video. But it doesn't work with audio, especially as
> audio
> > has a very 
> > high temporal resolution (48000 eg. samples per
> second)
> > compared to 
> > video (eg 25 frames per second) and moreover for audio
> the
> > output device 
> > pulls the data, instead of the animation system
> pushing it,
> > so the other 
> > way round.
> > 
> > I talked to Martin (Poirier) and Joshua (Leung) and
> even we
> > three 
> > together cannot think up a nice solution for the
> problem,
> > maybe some 
> > genious mind here on the list who is more into the
> > animation code than I 
> > am has a really nice idea.
> > 
> > Here are specific problems in detail:
> > 
> > * Subsample Accuracy: To avoid stair steps as we
> currently
> > have in 
> > volume animation.
> > * Multi Threading: Audio runs in a separate thread.
> > * Speed: The access mechanism has to be realtime
> capable!
> > * Asynchronous access: Audio playback is ahead of
> video
> > playback 
> > normally (buffering the samples, feeding them to the
> output
> > device).
> > 
> > The first point can be solved easily with a proper
> > interpolation if you 
> > have two nearby samples, one in the past, one in the
> > future, so this 
> > basically requires the animation data to be
> cached/buffered
> > somehow or 
> > at least asynchronous accessible. As the cached data
> also
> > solves points 
> > 3 and 4 it's pretty obvious that we need the data
> cached,
> > we had that 
> > conclusion already.
> > 
> > Questionable is now how to get the cache? One obvious
> > solution is to 
> > require the user to "bake" it, but this heavily
> impacts how
> > easy the 
> > system can be used and as we also already concluded
> this is
> > a really 
> > ugly solution. Better is the automatic caching which
> leads
> > us to the 
> > problem point 2 multi threading. I don't know if it's
> > possible to cache 
> > in the main thread? I bet not. And as long as
> blenders
> > (animation) data 
> > isn't accessible multithreaded we still have no
> solution
> > for the problem.
> > 
> > So now your help is needed. Any ideas? If not I'll
> have to
> > do the baking 
> > solution to finish the project.
> > 
> > Regards
> > 
> > _______________________________________________
> > Bf-committers mailing list
> > Bf-committers at blender.org
> > http://lists.blender.org/mailman/listinfo/bf-committers
> > 
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