ffdshow post-processing problem

[_migz_]

i've tried searching in google about this issue i'm having with ffdshow but i couldn't seem to find anyone with a similar problem.
first of all in ffdshow, when i enable post-processing there are times when you would see occasional blurs in the picture when playing an mpeg2 file (DVD). this would occur at times but there are also times when the same videos play perfectly without the blurs. i was thinking that my nvidia card was down throttling but i don't wanna do anything harsh to disable this feature. sometimes, even most of the picture is blurred. here's an example but i caught it only with a few blurs on the picture.


there are even times that most of the picture is blurred. here are the post-processing settings:


it looks like dirt and its annoying soo any leads would greatly be appreciated.

[jagabo]

It looks like the deblocking feature is making mistakes. This is easy enough to test -- turn off the deblocking and see if you still have the problem.

[_migz_]

oh thanks jagabo that solves the problem but do I really have to do this to solve this "glitch" of some sort? or is there another fix like to change some settings or something?

[Baldrick]

have you tried different versions of ffdshow?

[_migz_]

I tried the latest one from free-codecs.com (K-lite Mega Codec Pack) but it still makes the same mistakes as jagabo said. sometimes it plays perfectly though. i'm starting to think that my nvidia card is the problem? not sure though.

[jagabo]

I'm pretty sure all the erroneous post processing was done by ffdshow. Instead of using ffdshow you can try using a different MPEG 2 decoder that has its own deblocking functions. It may work better or worse. Or try using an Avisynth script with a deblocking filter.

Can you supply a short sample of that video in its original form?

Don't ever touch anything from K-lite. Their codec pack has been the source of many problems for many people.

[_migz_]

i really would be using avisynth if it wasn't so complicated. i've tried but i couldn't seem to get a right script that works nice. i'll post a link to rapidshare once the clip from the video uploads. i used mpeg2cut2. that's alright isn't it?

[jagabo]

Yes, a file from mpeg2cut will be perfect. Thanks.

A simple AviSynth script would look something like:

DirectShowSource("filename.ext")
Deblock()

Then just open that script in a media player.

[_migz_]

thanks for the explanation i'll try to find more avisynth how to's here in the site.
here's the video:
"http://rapidshare.com/files/224660440/Taken_clip.mpg"

its the part where most of the errors are evident.

[jagabo]

Thanks for the file. I won't have time to look at it until tomorrow but I'll let you know what I find.

[_migz_]

okay thanks for the help guys. it would really be nice if ffdshow would have a fix for this though.

[jagabo]

Forgot to reply to this yesterday...

Thanks for the clip.

I got the test clip and verified that ffdshow's deblocking algorithms make serious mistakes like you are seeing. The deblocking also removes lots of small details. I used an AviSynth script that let me compare deblocked and unfiltered frames interleaved together so it was easy to see the differences:

v1=DirectShowSource("Taken_clip.mpg").Subtitle("de blocked")
v2=MPEG2Source("Taken_clip.d2v").Subtitle("not").T rim(2,0)
Interleave(v1,v2)

I verified that ffdshow was being used by DirectShowSource() and not by MPEG2Source(), and that the two methods looked the same when ffdshow's deblocking was disabled.

You can play around with the deblocking settings to see if you can find a compromise (I found that Fast SSP Deblocking gave fewer errors than the others). That particular video was not blocky to start with so it's hard to tell where the happy medium might be.

AviSynth's Deblock() filter worked a lot better but since the video wasn't blocky it was hard to say whether it simply wasn't deblocking much or if it was doing a better job. I'm going to make some very blocky files and experiment with them later...

Some quick tests reveal that "Fast SPP Deblocking" deblocks blocky video well without screwing up video that isn't blocky. Enabling Nic's threshold's helps a lot with the mplayer algorithm.

[_migz_]

Thank you so much for the insights. i tried looking carefully and found that indeed, fast SSP was somehow a good way to go. i find it really weird that ffdshow's performance isn't consistent.
one question though, in ffdshow's configuration screen, you will see that there's an Avisynth checkbox right? can i like just type the script there to use Deblock() and then move it to the top? will that be a good replacement for the Post-processing feature of ffdshow?

[jagabo]

one question though, in ffdshow's configuration screen, you will see that there's an Avisynth checkbox right? can i like just type the script there to use Deblock() and then move it to the top? will that be a good replacement for the Post-processing feature of ffdshow?

I didn't know you could use AviSynth filters in ffdshow like that. I checked it out and the Deblock() filter worked very well there. My very blocky test file was nicely deblocked. Thanks for the tip!

[_migz_]

ohh sure no problem glad i was able to help. .. soooo i just use the Deblock() filter there and that would be better than using ffdshow's post-processing? did i get that right?

[jagabo]

Yes.

[_migz_]

oh okay thanks for the help man.