ffdshow avisynth Buffer back/ahead

mark0077 · 6th April 2013, 12:08

Hi,

Does anyone know in what circumstances the buffer back / ahead is needed in ffdshow. I'm asking as I'm using mpc-hc with LAV filters, with ffdshow solely to use SVP frame interpolation via avisynth scripts.

The SVP guys say the buffer ahead is crucial to SVP working correctly but I'm finding that even with it completely disabled in ffdshow, I'm getting absolutely perfect frame interpolation. This ffdshow page here seems to indicate the buffer ahead / back is only a workaround in ffdshow for filters that don't support being asked for a particular frame.

http://ffdshow-tryout.sourceforge.net/wiki/video:avisynth#buffer_back_ahead

Has anyone any experience with that, and maybe LAV Filers supports this? I'm getting some audio sync differences between the buffer being enabled / disabled, or enabled with different values so I want to basically nail down if the buffers are needed at all in your guys experience with different filters and maybe I can go from there on the audio sync problems its causing.

vood007 · 6th April 2013, 12:39

When you turn off Buffers a copy of the current frame is served if the requested frame is not available. Filters dont break this way but they also do NOT work for anything temporal. Use FFDShow OSD and select "Avisynth Info" to show requested and served frames. Audio desync may come from heavy multithreaded scripts that eat too much CPUs...

mark0077 · 6th April 2013, 12:59

hmm, with SVP enabled, ffdshow osd is saying that none are requested at all :S Audio desync in my case I think is being caused by incorrect timestamps I think rather than cpu / gpu as those are very low atm. I'll bring this back to the SVP guys.

6th April 2013, 12:08	#1 \| Link
mark0077 Registered User Join Date: Apr 2008 Posts: 1,106	ffdshow avisynth Buffer back/ahead Hi, Does anyone know in what circumstances the buffer back / ahead is needed in ffdshow. I'm asking as I'm using mpc-hc with LAV filters, with ffdshow solely to use SVP frame interpolation via avisynth scripts. The SVP guys say the buffer ahead is crucial to SVP working correctly but I'm finding that even with it completely disabled in ffdshow, I'm getting absolutely perfect frame interpolation. This ffdshow page here seems to indicate the buffer ahead / back is only a workaround in ffdshow for filters that don't support being asked for a particular frame. http://ffdshow-tryout.sourceforge.net/wiki/video:avisynth#buffer_back_ahead Has anyone any experience with that, and maybe LAV Filers supports this? I'm getting some audio sync differences between the buffer being enabled / disabled, or enabled with different values so I want to basically nail down if the buffers are needed at all in your guys experience with different filters and maybe I can go from there on the audio sync problems its causing. Last edited by mark0077; 6th April 2013 at 12:19.

6th April 2013, 12:39	#2 \| Link
vood007 Registered User Join Date: Jan 2011 Posts: 84	When you turn off Buffers a copy of the current frame is served if the requested frame is not available. Filters dont break this way but they also do NOT work for anything temporal. Use FFDShow OSD and select "Avisynth Info" to show requested and served frames. Audio desync may come from heavy multithreaded scripts that eat too much CPUs... Last edited by vood007; 6th April 2013 at 12:44.

6th April 2013, 12:59	#3 \| Link
mark0077 Registered User Join Date: Apr 2008 Posts: 1,106	hmm, with SVP enabled, ffdshow osd is saying that none are requested at all :S Audio desync in my case I think is being caused by incorrect timestamps I think rather than cpu / gpu as those are very low atm. I'll bring this back to the SVP guys.