Telecide(post=4) versus vthresh parameter

[bilu]

Please read this, but answer in this thread, not the linked one:

http://forum.doom9.org/showthread.php?s=&postid=408369#post408369

I'd like to see opinions on this issue.
I may have found a solution or just misunderstood a problem :)

Also reported in http://neuron2.net/ipw-web/bulletin/bb/viewtopic.php?p=2724#2724

Best regards,
Bilu

[bilu]

As no one answered yet, I'll assume that my explanation wasn't enough detailed.

Neuron2 has posted this some months ago about the Star Trek TNG hybrid clip:

http://forum.doom9.org/showthread.php?s=&postid=337685#post337685
This works good for me for the challenge clip:

telecide(order=1,guide=1,post=4,vthresh=45,hints=true)
decimate(mode=3,threshold=0.6)

Two points: 1. You need to get the threshold right for mode=3. 2. It's important not to have too low a vthresh with post=4, because it will force backward matches that declare out-of-pattern and thus force video decimation.

I'm planning a new attack on hybrid clips. But first we have to nail this crashing problem with guide=1 for betas 11 and beyond.As you can see this was posted before beta 11 of Decomb 5.0, and may be fixed for some time already. Also I may have misunderstood what he's saying.

Why do I consider this a bug?

Vthresh: frames that exceed it will be considered combed and will be post-processed (deinterlaced).

As you know post-processing means modifying the original fields of the frame.

Post=4: try to do a field match with the FILM pattern. If it can't it will deinterlace (post-process) the current frame instead of trying to match with the best field available. This will be useful for Decimate hybrid modes: they will recognize this as VIDEO and treat accordingly.

If fields get matched AFTER post-processing, they may not match well, isn't it?

So what neuron2 seems to be saying is: if vthresh is low frames will be post-processed, and this may lead to bad matches in post=4 pattern detection, so there is a risk that FILM gets treated as VIDEO both in Telecide and Decimate.

I don't know if this problem is solved, and I think vthresh should somewhat be disabled during hybrid processing: after all, frames will be post-processed by post=4 whenever they don't fit the FILM pattern.

EDIT: The better situation would be vthresh usage AFTER field matching to check which frames remain combed and have to be deinterlaced. If it happened that way it would never get out of pattern as neuron2 posted.
But that's was a long time ago. And I would really like to know if this was addressed since Decomb 5.0 beta 10.

Best regards,
Bilu

[bilu]

From both Decomb's 5.0b10 and 5.1.0 reference manual:
By default, Telecide runs postprocessing on the recovered frames. This postprocessing checks each frame to see if it is combed (some combed frames may come through the field-matching process [see below]), and if a frame is combed, it is deinterlaced, otherwise it is not touched.It makes sense that post-processing occurs after the field matching.
But it makes little sense to me that effect described by neuron2 : It's important not to have too low a vthresh with post=4, because it will force backward matches that declare out-of-pattern and thus force video decimation.

IMHO, vthresh shouldn't affect field matching at all.

[bilu]

Good news: I wasn't able to recreate the problem.

Even with an insane vthresh=0 (mark all frames for post-processing) I wasn't able to make it go out-of-pattern - it never got jerky.

telecide(order=1,guide=1,post=4)
decimate(mode=3,threshold=0.6)

works just fine on this clip :)

THE END


Bilu

[zurv]

it works.. but still not that best fix in the world. Ie, it isn't jerky any more, but it does go slightly blurry on the parts that had been jerky. One doesn't notice it that much on live video, but anime... :)

still.. much better than jerky!!

[DoW]

Did you try simply removing guide=1? In LH, that tends to cause jerkyness for me and wrong matches.

[zurv]

that was the first thing to go :)

a good example of it being jerk is here:
http://www.the-easy-tiger.net/[KAA]_Last_Exile_1-4.DVD(widescreen).torrent (if the darn tracker ever works!)

progressive... with post=0,guide=0 and decimate(cycle=5,mode=2,quality=3)

with mode 3 and threshold, it took most of the "jerky" away, but was replaced with a hint of blurry (but i was looking for it..)..
i should have forced film on it... but.. most of the stuff i have is with mixed 23/29 fps anime and it echos the same effect.

[bilu]

Matroska VFR Proof of Concept
http://forum.doom9.org/showthread.php?s=&threadid=64314

Hybrid Matroska Example
http://forum.doom9.org/showthread.php?s=&postid=395247#post395247

YATTA
http://forum.doom9.org/showthread.php?s=&threadid=64440


The only way to avoid blending or interlaced is the variable framerate path. MKV only :)


Bilu