how do you know the perfect size.?

[assa69]

hello


I capture from the VCR using dazzle 2 then try encod teh clips to xvid using virdubmod
sttings are all of using 2 pass and h263 and vhq in wide search and ultra high for msp i didnt test mpeg my question is :-

1:- when i capture from dazzle i use 10 mb/s biterate would it be better if i used mpeg instead of h263 when i encode to xvid

2.when i set the second pass it asks me for the desired file size what size is good with that will produce good quality i know it differ according to the time of the clip and how much is its resolution but isnt there way to calculate this .?

thanks

[kadajawi]

1. Depends on your source and what you like. afaik h263 softens, mpeg sharpens. I would simply try what looks better on the source.

2. the 2 pass mode is for the case that you want to put the file on one CD for example. You can't really calculate what size you have to set for good quality... (well, maybe 5 GB for a 10 minute clip... ;) ). It really depends on the source, how much detail, how much movement, etc. If size doesn't matter, just set a fixed quantizer. Just try out a few values, the smaller the number the better the quality and the bigger the file. For music videos I usually select values around 3.5.

[assa69]

thanks for the answer i am new to all this

so what you say is there is no diffrent between 2 pass encoding and single pass but the first is to caluclate the size only i see now because i tried the same biterate of single pass and 2 pass and i got the asame quality and i was ondering why was the diffrnce between them then but i wonder about a thing i get little blocks on teh picture not very much though but the exist in some areas where i do see the movies i download from the net are very good why is that

also i am using koopi bulid for beta 2 5/12 and there is no fixed quantizer and of course size matter so what bit rate you i should use and do i use qpel or chroma etc i know you will say it depend on the source but can anyoen give soem hints

thanks

[kadajawi]

Well, I'm working with QPEL, GMC, hvs good matrix, Adaptive quants, b frames at default, motion search precision 6, vhq 4, chroma motion. Some filtering, depending on the noise (analog TV source). Results in 3 fps.
Blocks, probably too high quant I'd say. With 2 the picture quality is near perfect for me, but then it takes too much space. You can select the quant in the main configuration window of XviD, select the 0 in the table with Frame, Weight (Q) etc. thing. Press edit, there you can find the quantiser.

[assa69]

i have tried some tests

but i like to ask what is diffrence between quantization tab and bit rate i mean when i press edit as you said and go to quant. and increase it i get good quality for the same bit rate but then what is the diffrence between this and increseing the bite rate i mean i can increase teh bit rate to get good quality too so what is the diffrnce between those 2 please.....?

thanks

[Tommy Carrot]

Basicly (and simplified), the codec with single pass bitrate mode is dinamically changes the quantizers to reach a specific bitrate. The quality is not constant, for the harder scenes (which would require more bitrate than the rest) the quality is degrading.

Quantizer mode always delivers constant quality, but the resulting bitrate is unpredictable, because everything depends on how difficult is the source material.

2-pass mode unify the benefits of both mode. The quality is more or less constant (of course is adjustable to favouring high or low motion), and you can set the exact bitrate.

[assa69]

thanks Tommy Carrot for the ansewr

but i think there is some misunderstanding bewtween us what i think (and may be I am wrong) is that you think you can contorl thr bitrate or the quantaztion when u r encoding and not both of them in the same time i used to see this in old bulids of xvid but now in build 5 12 can change both i mean i do change the bitrate and can press edit and change the quant too i assumed that cuz u said :-

(Quantizer mode always delivers constant quality, but the resulting bitrate is unpredictable, because everything depends on how difficult is the source material.)

there is no quant mod in build 5 12 u can contorl both at same time and do both

am i wrong..?

so if u can play with the 2 factors at same time and that takes back to my7 first question why not just simply increse the bit rate insteaed of the qunat

I mean for a bit rate when i get bad quailty i can increase the quant resultign in larger file size and get good quality but i also increse the bit rate too instead of the quant ang get good quality so what is the diffrnce then ALSO i can increse both of them at same time

and there is another thing about what you said

2-pass mode unify the benefits of both mode. The quality is more or less constant (of course is adjustable to favouring high or low motion), and you can set the exact bitrate.

did you ment exact bit rate or exact size...?

so when i use 2 pass i dont set a bit rate ( i can though ) but i use target size i mean what use is then for 2 pass if size wasnt important for you dont they use 2 pass to determine the size ..?


thanks

[kadajawi]

Its quite hard to understand what you were asking.
What build are you talking about? Better use XviD 1.0 Beta 3. You can limit the bitrate when using quants to avoid giving extreme high bitrates to a complex scene. Different scenes require different bitrates, but with constant bitrate all scenes get the same bitrate. Lets say a movie starts with a totally black picture. Of course this doesn't require a lot of space. But when there are a lot of details, a lot of data needs to be saved to preserve the detail. Now lets say you have set a fixed bitrate. Scene one uses the same bitrate as scene two, so either you waste a lot of space on scene one or you don't waste that much space on scene one, but loose a lot detail (get blocks) on scene two.

The 2 pass question: Hmm... 2 pass has the advantage that it keeps a rather constant quality while giving the ability to control the file size. You can set either the average bitrate you're aiming at or the filesize you're aiming at (only video, not including sound).

[Assault]

@ assa69

As you realized you can set a specific quantizer for your movie in the zones tab. When you do that in single pass mode the chosen bitrate has no influence anymore. The whole movie will be encoded with a constant quantizer no matter how high or low the chosen bitrate is. When you want to encode with a specific bitrate then you have to create one zone with a weight of 1. I hope that helps.

Assault

[assa69]

thanks that did clear the matter

if anyoen have any more explinations please do post

[assa69]

kadajawi i have read your post now i didnt notcied before sorry

i downloaded the bulid you talked about but about what you say in arranging the matter so the high detail scenes get high bit rate and low detail secens get little how can i do that..?

[kadajawi]

use quants :)

[assa69]

thanks

but what value you think is i use 3.5 andit gives me good results

[kadajawi]

hehe, try out. 2 gives near perfect, 31 is the lowest value. You can try out... thats what I do. Usually 2.5 (with some heavy filtering and low motion no problem), to 4. Gives around 30 to 80 MB in musicvideos.

[assa69]

well.. I didnt try what you said yet but can you tell me little about the filters you use

i use resize filter after cropping also field bob if the source had interlace artifacts

and by the way do you know anything about the last build ofthe xvid beta 3 it causes problems with me like some of the clips i encoded using beta 2 apears up side down but what is worst virtualdub or mod both of them dont encode anymore i mean as soom i choose xivd and hit start buttom to start encode the program crashs i unintsalled beta 3 and reintsatlled beta 2 and everything is fine now why is that...?

[kadajawi]

I had that it does nothing bug with Beta 2 IIRC, the latest VDubMod version solved it somehow. Against the upsidedown thing there is some switch, look for it in the Beta 3 and 2 thread... somewhere there it should be explained.

I'm only filtering against noise using VagueDenoiser and Convolution3D, but I haven't done real testing there... I just know it works :)

[assa69]

i dont understand what you mean

do you mean that there is bug in virtual dub

i am using version 1.5.10

and by the way

i also noticed (but thats not now but some time a goand has nothing to do with my probelm) that the clips you encode using xvid compression still can be played after you uninstall xvid from you computer but the player see the clips as divx file is this normal or what.?

thanks

[kadajawi]

I don't know if it was a VDub bug or whatever, I just know that 1.5.10.1 solved the problem. :confused: