Advanced hints from "senior" G-Knot users?

[yosemite]

hi,

this question is for all of u who had work lot of time with Gordian Knot and have made there own "little tricks" in G-Knot, to get a better quality in the end!

so, please post ur personal "tricks"! Is there any setting u use that others cannot find in a guide, but gives u a better quality?

Tell us your experience! ;)

[Captain_Nipple]

My trick is to read the GKnot guides again & again.
Then, to print them off and sleep with them.
Finally, name your first born NanDub for a boy, GKnot for a girl.
Then maybe, if you are lucky, you will know the "Tricks"! needed to produce the best looking conversions.:)

Hope this helps.

Captain.

[cofferscuffs]

LOL :D. No seriously read Koepi's Nandub Options Explained (http://members.tripod.de/de_koepi/) and understand what you're actually doing, then you can 'perfect' your backups by using a combination of Gknot automation and manual Nandub.

[Captain_Nipple]

But remember, NanDub for boy, GKnot for girl. I made the mistake of using DivX4.12 for my second born and he didn't turn out right at all.

Captain.:)

[diji1]

hehehe :) :), good to read some ( genuinely - no snidey-ness ) humerous posts for a change! There'd have to be something wrong with the kid called Flask tho right ??

Dunno if id catagorise myself as a advanced user yet, but here's a small thing. When i follow the method as described in the "old guide" for gknot ( doom9, course ) i always manually set the min/max distances between keyframes in gknot's stats file editor. ( on stats file editor with your first pass stats file open, go to keyframes, push "clear", enter your min/max distance in frames then push "auto").

This modifies the stats file to strictly use these distances between kf's, i *usually* use min 50, max 250.

imo doing this has led to slightly higher quality in my movies with an extra 10 seconds of effort overall, plus it fixed a problem i was having with really excessive use of kf's by nandub on a certain rip.

Thanks poopity-poop for this handy tip. :)

[Captain_Nipple]

hey.
I sometimes find when I use the ecf file that scene changes are not marked as key frames. This results in really messed up films (4 so far) I have to manually edit the stat file and then run with the conversion. Any insight into this would be good. Maybe it's my stupidity, i don't know.
Must go now, my dog VirtualDub does not look so good.

Captain.

[cofferscuffs]

I get that a lot in some of my anime movies too... it's very time consuming to edit the stats file :(.

[manono]

Yeah, I also change the default keyframe settings. I set minimum at 2, and then do the Clear-Auto trick. That way, when you have them changing rapidly (music videos are notorious for this-or the opening songs in anime series), they'll be set correctly. Also, those grey ones that GKnot didn't pick up will become keyframes. The only place where you won't get them that way is with fade-ins. Then you can set them manually if you like (I don't). You may get too many that way, though. If the screen is flashing (like from gunfire or something), keyframes will be set, but I ignore that.

[Captain_Nipple]

That's right. I did the Foo Fighters video from Me,Myself & Irene dvd and it had ALOT of that. Was not to bad as it is 3 or so minutes long. But try checking the keyframes on Scarface and that's a different story. I must check your settings and see what it does my end. Thanks for feedback.

Captain.

[philippas]

I don't understand why there is a myth of the overuse of keyframes.
When there is a scene change a keyframe has to be inserted.
If it's not inserted the quality will be worse.

[TheWEF]

Originally posted by philippas
When there is a scene change a keyframe has to be inserted.
If it's not inserted the quality will be worse.

i do not agree.

wef.

[cofferscuffs]

No, the quality gets worse every frame (towards the next key frame) if there is a long duration without a key frame right? Too may keyframes take up too much space, and too little have an impact on quality - I think that anyway.

[Ripe73]

Hey!!
When i use Antishit it insert alot of keyframes is it better for me to use max dist:250 instead 300?
And a 2h.30min movie need more keyframes than a 1h.30min movie?

[diji1]

Lo again,

No, the quality gets worse every frame (towards the next key frame) if there is a long duration without a key frame right? Too may keyframes take up too much space, and too little have an impact on quality - I think that anyway.

Exactly what i noticed/think !

And a 2h.30min movie need more keyframes than a 1h.30min movie?

I don't think the length would have any bearing on optimum distances between keyframes (that's what u meant, right ?? )

[Ripe73]

Originally posted by diji1
Lo again,



I don't think the length would have any bearing on optimum distances between keyframes (that's what u meant, right ?? )
Yepp!!
A 90min movie with 300 keyframes and a 150min with 300 keyframes will there be no difference in quality?

[diji1]

oh, ok :)

There'd definitely be a quality difference ( i'm sorry, i misunderstood you ).

[philippas]

Consider the following example:
KDDDDDDDDDDK, where k = keyframes and D = delta frames

If you don't allow a keyframe at the beginning of the frame sequence the frame sequence will become: DDDDDDDDDDDD where the delta frames will be much larger than the delta frames from the initial sequence, because the delta frames within the second sequence will be almost as big as keyframes. On the other hand the delta frames within the initial sequence will have common parts with the keyframe at the beginning, so they will be much smaller than the delta frames from the second series.

So in my opinion not allowing a keyframe where there is scene change is degrading the quality.

[TheWEF]

ok, i just did a small test.

i took a short sequence from phantom menace, pal, 3800 frames, 640x272, did a dix3 first pass.

for the second pass i created two ecf-files.

the first one does allow only one keyframe at the beginning.
the second one sets a keyframe at every scene-change (i manually checked that).

for the second pass i did choose a bitrate of 942 kbit (0.22 bpp, 70%).

file one, no kf: 17950 kb
file two, with kfs: 18002 kb

so the two sequences came out at pretty much the same size. should be ok to compare.

watching both a few times i did not see a difference.

average quantizer in both files is (almost) the same:
nandub divx quality no kf: 69.053
nandub divx quality with kf: 70.239

then i loaded both in vdub and saved a bitmap-sequence to compare every single frame with acdsee.

it is impossible to see the difference between a frame that comes right after a keyframe in the one avi and the same frame in the second avi that is 3000 frames away from the last keyframe.
[yes, of course there is a little difference, but nobody would be able to say: this is from clipA, this from clipB. they are the same quality]

so, up to this point, i got what i expected and i thought i was right.
but i was surprised when i compared the keyframes (scene changes):

some of the delta frames have very small codec errors in them, mostly only one one macroblock in a slightly wrong color. they are gone in the next frame, so it's almost impossible to notice them when watching the movie.

i'll try to upload some samples so you can compare the frames yourself if you want.

so my conclusion is:
you are right, it is the best to have a keyframe on every scene change.
but you will definitely not notice a difference if you miss a few of them. i think you can trust gknot and/or nandub and should not worry too much about keyframes.

the worst thing is to have keyframes in the middle of a scene. it's noticeable when watching (very annoying) and a waste of bits. that's why gknot sets a max keyframe interval of 300 frames (12 sec in pal) - most scenes are shorter.

wef.

[TheWEF]

hmmm. i uploaded a zip-file. i see it, it's there, but i can not validate it.

doom9?

[Ripe73]

the worst thing is to have keyframes in the middle of a scene. it's noticeable when watching (very annoying) and a waste of bits. that's why gknot sets a max keyframe interval of 300 frames (12 sec in pal) - most scenes are shorter.



Hey
I have a lot of keyframes in middle of scenes from the Antishit and idont know what to do about it because i need it.Will a lower value of Antishit work and give less keyframes?
I use :16 :0 :50%
Anybody have a idea to this?

[TheWEF]

2820.

[TheWEF]

2821.

...why don't these attachments show up? and why does the first one?

:rolleyes:

wef.

[Captain_Nipple]

I have uploaded a couple of avi files which show what I was getting when the scene changes are not marked as keyframes. I later had to manually edit the stat file, which is a real pain because I had to scan the whole movie and then apply the changes. You will see that because of the failed keyframe insertion, the following delta frames are ruined until the next keyframe. (Excuse the crap quality, as this was just for testing & bitrate is fairly low too.)

Is this something I might be doing wrong. The examples are from Scarface, but I have seen the same issue with other movies. Pity I don't have a screenshot of GKnot stat editor.

Captain.

[Captain_Nipple]

http://rilanparty.com/vbb/attachment.php?s=&postid=63486

[philippas]

@ WEF
the worst thing is to have keyframes in the middle of a scene.

I agree with you.

[TheWEF]

Originally posted by Captain_Nipple
I have uploaded a couple of avi files which show what I was getting when the scene changes are not marked as keyframes. I later had to manually edit the stat file, which is a real pain because I had to scan the whole movie and then apply the changes. You will see that because of the failed keyframe insertion, the following delta frames are ruined until the next keyframe.

this is "shit", the divx3 codec error that everybody talks about.

you could try to prevent this with "anti-shit" or use divx4.

wef.

[Captain_Nipple]

As far as I recall, I was using Anti-shite. (setting 16db)
I played with a few of the settings to see if it was something I was doing but these bad looking scenes would not go away. I remember later looking at these in the stat editor and noticed some scene changes had both green boxes filled, which I presume is what should happen as these scenes looked ok. But it was different on the uploaded clips. The box for "Keyframe" was not green. This is where I later had to manually mark as keyframe and this cured the problem frames.

Am I wrong here or is this really where the "Anti-shit" does it's magic? Mind you, I hardly find myself using Anti-shite. I think Doom9 also advises not using it too.

P.S I could only upload to the test forum and then post the url to the files in this forum.

Captain. ;)

[TheWEF]

believe me, this is shit.

anti-shit does no magic...

actually it seems like it already inserted 2 extra keyframes (frame 4 and 5 in example 1) right before it finally happens: a dropped frame.

what did you set for minimum bitrate? (going below 270 here can cause a dropped frame).

if you have more problems like this the only real solution is to switch to divx4 (or buy a new computer :p )

wef.

[philippas]

@ WEF
I just checked your first 2 sample frames and i can't see any difference in them.
The only bad think that i can see is that two blocks are black (they shouldn't be black) which occurs in both frames.
I remember that there was a patch that fixed a bug in divx 3.11 which would cause not matching colours in a frame.
Maybe that patch would help to avoid similar problems and might be faster than using antishit in nandub.
I hadn't tested it then and i can't find it anymore in Doom9's page.

[philippas]

@Captain_Nipple
I checked the avi's also,i agree with the WEF. I think also that the atrifacts are caused by very low bitRate.
If you noticed before the dropped frame the DRF was 9 which is very high for a high motion scene.
Try and limit the DRF's more and use antishit.

[TheWEF]

Originally posted by philippas
The only bad think that i can see is that two blocks are black (they shouldn't be black) which occurs in both frames.

if you are talking about the one black pixel at the top left and the other one at the bottom right...

they are in the original dvd-frame. i'm sure that lucas adds this to make the computer-stuff look more like real grainy film :p

btw... this is not a block! a block has 16x16 pixels. then it has visible sub-divisions of 8x8 pixels. i don't know how the codec works exactly, but normally a codec error is at least a square of 8x8 pixels.

(well, you could see one of these in frame 2820 if i could get this damn attachment-thing to work...)

wef.

[philippas]

Yes i meant the two black pixels. I might do a test on my own tommorow if the attachments won't work.

[Captain_Nipple]

Don't worry Wef, I believe you. I did not notice that dropped keyframe in example1:eek: I think min bitrate was 270. This must be the reason. Not the system anyway(AMD1.4)
What would you advised for min. I think I heard 460 is a beter setting? Oh yeah, I hate DivX4:p

Thanks for fast reply (Do ya ever sleep?;) )

P.S that patch philippas refers too can be found here
http://divxbox.phear.com:81/divxpatch

Captain.

[Demone]

I'm one of those mad ppl that edit the stat file keyframes one by one:eek: and I find its really a pain in the @ss.
I push 'Clear', put 999 for max, 2 for min and push 'Auto', after I
look at the entire movie to correct some (there r everytime).

@Wef
I'm still waiting for some buttons to move from keyframe to keyframe in the stats....hoping :)