[Bf-committers] Screen-cast issues

Nathan Letwory nathan at letworyinteractive.com
Tue Sep 28 10:58:28 CEST 2010

Hash: SHA1

On 28.9.2010 8:42, Andrew Green wrote:
> I have been playing with the blender screen-cast functionality. I have
> noticed the timing never seems right for me.
> Even when I modify the settings for screen-cast to represent what
> should be a real time recording.
> It is off by a lot. if i record for 30 seconds i will get 15 or 20
> seconds video from it.

That's because in user preferences FPS for screen casting is by default
on 10. If you screencast directly to a movie, make sure you have the
same FPS.


> I think it's due to a couple of things.
> After it has written one frame it will simply sleep for x ms and then
> write the next frame. I'm pretty sure when it sleeps it will
> overshoot. Also there is the extra time to actually save the frame.
> This makes it worse over time.
> There is also the possibility that an image has not been grabbed
> yet(which is done separately by the job manager) when the loop resumes
> which means it will go and sleep for an extra x ms.
> I really haven't given it much thought. Would it be the best idea to
> get the system time when recording is started. Then use this to
> determine when a frame should be written. This way a frame may be
> saved slightly off time. Though the results wouldn't accumulate and
> throw the results completely off.
> Heres what i was thinking in a tiny bit more detail. It's simple plus
> if there is a system pause for 1 second when many frames should have
> been written it will write those frames and make sure the time match
> of the video and the real world.
> diffTime=currentTime-startTime;
> if(diffTime>=framePause){
>      saveCurrentFrame();
>      startTime+=framePause;
> }
> Would you guys agree that this is the cause of the issue?
> Do you guys feel this is sensible solution for me to implement? Or do
> you think I am crazy?
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- -- 
Nathan Letwory
Letwory Interactive
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