Current version

v1.10.4 (stable)

Navigation

Main page
Archived news
Downloads
Documentation
   Capture
   Compiling
   Processing
   Crashes
Features
Filters
Plugin SDK
Knowledge base
Donate
Contact info
Forum
 
Other projects
   Altirra

Search

Archives

01 Dec - 31 Dec 2013
01 Oct - 31 Oct 2013
01 Aug - 31 Aug 2013
01 May - 31 May 2013
01 Mar - 31 Mar 2013
01 Feb - 29 Feb 2013
01 Dec - 31 Dec 2012
01 Nov - 30 Nov 2012
01 Oct - 31 Oct 2012
01 Sep - 30 Sep 2012
01 Aug - 31 Aug 2012
01 June - 30 June 2012
01 May - 31 May 2012
01 Apr - 30 Apr 2012
01 Dec - 31 Dec 2011
01 Nov - 30 Nov 2011
01 Oct - 31 Oct 2011
01 Sep - 30 Sep 2011
01 Aug - 31 Aug 2011
01 Jul - 31 Jul 2011
01 June - 30 June 2011
01 May - 31 May 2011
01 Apr - 30 Apr 2011
01 Mar - 31 Mar 2011
01 Feb - 29 Feb 2011
01 Jan - 31 Jan 2011
01 Dec - 31 Dec 2010
01 Nov - 30 Nov 2010
01 Oct - 31 Oct 2010
01 Sep - 30 Sep 2010
01 Aug - 31 Aug 2010
01 Jul - 31 Jul 2010
01 June - 30 June 2010
01 May - 31 May 2010
01 Apr - 30 Apr 2010
01 Mar - 31 Mar 2010
01 Feb - 29 Feb 2010
01 Jan - 31 Jan 2010
01 Dec - 31 Dec 2009
01 Nov - 30 Nov 2009
01 Oct - 31 Oct 2009
01 Sep - 30 Sep 2009
01 Aug - 31 Aug 2009
01 Jul - 31 Jul 2009
01 June - 30 June 2009
01 May - 31 May 2009
01 Apr - 30 Apr 2009
01 Mar - 31 Mar 2009
01 Feb - 29 Feb 2009
01 Jan - 31 Jan 2009
01 Dec - 31 Dec 2008
01 Nov - 30 Nov 2008
01 Oct - 31 Oct 2008
01 Sep - 30 Sep 2008
01 Aug - 31 Aug 2008
01 Jul - 31 Jul 2008
01 June - 30 June 2008
01 May - 31 May 2008
01 Apr - 30 Apr 2008
01 Mar - 31 Mar 2008
01 Feb - 29 Feb 2008
01 Jan - 31 Jan 2008
01 Dec - 31 Dec 2007
01 Nov - 30 Nov 2007
01 Oct - 31 Oct 2007
01 Sep - 30 Sep 2007
01 Aug - 31 Aug 2007
01 Jul - 31 Jul 2007
01 June - 30 June 2007
01 May - 31 May 2007
01 Apr - 30 Apr 2007
01 Mar - 31 Mar 2007
01 Feb - 29 Feb 2007
01 Jan - 31 Jan 2007
01 Dec - 31 Dec 2006
01 Nov - 30 Nov 2006
01 Oct - 31 Oct 2006
01 Sep - 30 Sep 2006
01 Aug - 31 Aug 2006
01 Jul - 31 Jul 2006
01 June - 30 June 2006
01 May - 31 May 2006
01 Apr - 30 Apr 2006
01 Mar - 31 Mar 2006
01 Feb - 29 Feb 2006
01 Jan - 31 Jan 2006
01 Dec - 31 Dec 2005
01 Nov - 30 Nov 2005
01 Oct - 31 Oct 2005
01 Sep - 30 Sep 2005
01 Aug - 31 Aug 2005
01 Jul - 31 Jul 2005
01 June - 30 June 2005
01 May - 31 May 2005
01 Apr - 30 Apr 2005
01 Mar - 31 Mar 2005
01 Feb - 29 Feb 2005
01 Jan - 31 Jan 2005
01 Dec - 31 Dec 2004
01 Nov - 30 Nov 2004
01 Oct - 31 Oct 2004
01 Sep - 30 Sep 2004
01 Aug - 31 Aug 2004

Stuff

Powered by Pivot  
XML: RSS feed 
XML: Atom feed 

§ Scheduling bottlenecks in 3D filter acceleration

As I noted last time, there are reasons why VirtualDub's 3D filter acceleration has problems if a display mode switch is triggered. There are, however, also some performance bottlenecks in the implementation in 1.9.5 that I'm working on resolving. Here's an example:

This is a screenshot from VirtualDub's real-time profiler, showing CPU usage during a video analysis pass using a mix of CPU and GPU filters (warp sharp on GPU + rotate2 on CPU). The main things to notice are the long V-Filter section on the Processor and the idle times on the Filter 3D Accel thread. This is the time during which the video filter system runs. The basic problem here is that the video filter system is single-threaded and all calls into the accelerator are done as blocking calls, synchronizing the threads. The result is that the processing thread is blocked while the readback is occurring (the long operation with Poll and Readback blocks) and then the acceleration thread goes idle while the processing thread is busy doing other tasks. This limits concurrency between the CPU and the GPU.

In my current dev branch, the situation has changed a bit.

The first thing to notice... is the lack of color. That's because I'm currently redoing the profiling architecture to be lighter weight and to capture a performance log instead of just per-second snapshots. I didn't think it would make a lot of difference, but now it definitely seems harder to read without the color coding.

That aside, you can see the the accelerator thread (top thread) is much more busy in this version. There are two reasons for this. The first is that in this build the filter system has the ability to "hand off" a particular invocation of a filter instance. For various reasons the filter system cannot currently be run multithreaded, but the filter instances can -- so what the filter system does is set up a frame, hand it off for asynchronous execution, and then later closes the frame and collects the output once the filter is done. The second reason for the improvement is that the render pipeline can now queue more than one frame request in the filter system. It still isn't possible to allow a single filter instance to process multiple frames in parallel, since the filters have mutable state which generally prohibits this, but this does permit different filters to queue up behind each other, so that the accelerator can work on the warpsharp instance for one frame and then download another frame without intervention from the main processing thread. The result is a modest increase in frame rate for this chain, going from about 17 fps to 20 fps for about a 20% improvement.

Comments

Comments posted:


good luck in solving
this option helps much to accelerate fps

Hunter - 24 08 09 - 18:53


20 % improvement by simple virtue of better resourcing ? I wouldn't call that modest. It's quite significant. I wouldn't know how much you can still push this, but that's already a big improvement.

ParkerLewis - 26 08 09 - 08:32

Comment form


Please keep comments on-topic for this entry. If you have unrelated comments about VirtualDub, the forum is a better place to post them.
Name:  
Remember personal info?

Email (Optional):
Your email address is only revealed to the blog owner and is not shown to the public.
URL (Optional):
Comment: /

An authentication dialog may appear when you click Post Comment. Simply type in "post" as the user and "now" as the password. I have had to do this to stop automated comment spam.



Small print: All html tags except <b> and <i> will be removed from your comment. You can make links by just typing the url or mail-address.