XviD Are these the best settings for my spec + VHQ question

[Skywalkerjen]

I have my own specification for using XviD and I would appreciate any comments. This was posted on hydrogenaudio.org and I wasn't convinced of a better setup. Please correct me so I get better!

My specification:
The XviD should be significantly smaller than the MPEG-2 (otherwise I would keep the MPEG-2).
I have 480GB of hard disc space and a DVD writer so files 3/4 the size of the VOB file are fine.

When the codec is not limited by a target filesize every frame is encoded at Quantizer = 2. The best quality encode must therefore be 1-pass Quantizer = 2. However as this produces a file too big for my specification, the next obvious setting would be 1-pass Quantizer = 3. I think the following 2-pass encode is even better than 1-pass quant 3 - am I right?

Keyframes (I-frames) are encoded with a fixed quantizer of 2 (max = 2, min = 2).
Deltaframes (P-frames) are encoded with a fixed quantizer 3 (max 3, min = 3).

This is a like a "refined" 1-pass encode where the keyframes and deltaframes are fixed, but scaled at different levels - not possible in a 1-pass (I've checked!). This will still allow the maximum Quant = 2 for the important keyframes within my filesize spec.

VHQ = 1: This improves quality? Would it improve the quality in MY case? VHQ 2,3 or 4 just reduce the bitrate and also reduce the quality slighty?

Finally (!) I keep reading that for XviD 1.0 the avisynth file should be set up in Gordian Knot, but the actual encode should be done directly in VirtyalDubMod. I can't find the reason for this, but isn't Godian Knot 0.28.7 good enough to do the whole show?

Thanks for reading.

Skywalkerjen

[zx50]

I think you are so confused here, where you say that you are not constraining/forcing the codec but just meeting you desired filesize, actually you are constraining the codec. Really you have to give the codec all the freedom it needs to encode your video for you, otherwise you will end up with one file that could look twice as better if done properly. If you limit the quantizers to 2 0r 3 and don't allow them to go higher then really all your doing is forcing the codec to use more bitrate to keep up with the quantizer. And as for keyframes, sorry but are you insane one every <b>25 FRAMES</b>, i have mine at 250 frames (come from the u.k). Have you read any XviD guides if not then you should. I'm not saying go strictly by what they say, just half of maybe what they say.

From numerous tests the codec is trying to encode everything at Q2. To let it do its job would be to not limit the desired filesize. When you do this it encodes everything at Q2. Forcing the quants to 5 and 6 for example would definitely be a bad idea, but forcing them to their maximum is not holding back the codec - only preventing me reaching a desired filesize - which I'm not. And setting them to quant 3 is the only way to meet my "smaller" filesize spec.

This you seriously have got mixed up, you say that you are not holding back the codec but you so are. Not holding back the codec means exactly that, you are not stopping it from doing anything, but in this case you are stopping it from using higher quantizers when it needs to.

P.S if you want to reach you desired filesize then where it say target bitrate, click it and it will change to target filesize and type in what you want (video only) and there you go, when you encode your video you will have the desired filesize, so no need for limiting quantizers after all.

[Skywalkerjen]

Many thanks for replying perfectionist - much appreciated

forcing the codec to use more bitrate to keep up with the quantizer

I've never looked at it like that before!

Not holding back the codec means exactly that, you are not stopping it from doing anything,

I am not sure about this though. If you do tests the codec will do as I have stated. Holding back the codec is to give it a limited target size so it has to use higher quants. If allowed it will compress everything as little as possible i.e. quant 2. However, looking at it differently - yes I am not using it as it was designed (good picture at low bitrates). It is certainly not restricting it though - giving it a massive target file size will only do exactly the same thing as limit the quantizers. Setting the quant to 2 just means (simplistically) that each frame will have the least compression. Certainly not an efficient way of doing it, but I am not too fussed about that.

P.S if you want to reach you desired filesize then where it say target bitrate, click it and it will change to target filesize and type in what you want (video only) and there you go, when you encode your video you will have the desired filesize, so no need for limiting quantizers after all.

You know - that is all I was after - EXACTLY - that is exactly what I shall do! I will do some tests but will likely go for something ludicrous like 2500 to 3000Kb (still half the size of the MPEG 2).

The thread going on at Hydrogenaudio.org didn't get anywhere near that quick (but had some very useful other stuff!)

Thanks very much for that!

Skywalkerjen

P.S. Anyone know the deal with VHQ?
I know the new VHQ set to 1 increases quality no matter what.
What about the other settings? I heard VHQ 2-4 just decreases filesize and reduces quality slightly.

Skywalkerjen

[zx50]

One other thing, when i said that you were actually restricting the codec when you have it fixed at 2 or whatever. What i meant was, when the codec comes across dark scenes it uses a higher quantizer in the dark areas and very light areas like sky or white where you can't see anything and uses lower quantizers in the light areas (i.e faces and thing's you can see) and uses the bitrate that would normally have been in the dark areas had you been using cbr or in your case a fixed quantizer, so therefore the faces and thing's you can see become more detailed. But in your case everything will get the same so you will basically end up with a file that's huge that really need'nt have been.

P.S but people like to encode in different ways so.....

[Fook Yu]

Hi Sky,

i read your thread at the other forum, but i was lost after 2-4 postings. Never new that codecs could raise tempers like that. However, i really wonder if going in such detail as you have choosen actually gives you any improvement in quality. I mean that you can see on tv/monitor. I did a test comparing divx/xvid but on a very simple level, compared to what you are doing. And i tell you that although differences were there i aso must say that i went on the border of kbps. I would normally never do this. First then i could notice differences that would justify detailed tweaking. If you say that it DOES matter i will dive into the frame settings aswell (rather not though). Just hardly can imagine a noticable difference, especially when these codecs are being developed smarter and smarter.
PS how do you run test?? Would you share your philosophy behind it?


By the way i do disagree with people that say there are no best basic settings. There always is every movie is made up of slow moving and fast moving scenes with the slow moving part lastin 80-90% of the time.....period, but then again i like to make things black and white. Home made movies are of course different but seldom last more then two hours.

[Soulhunter]

Re: XviD Are these the best settings for my spec + VHQ question

Originally posted by Skywalkerjen
When the codec is not limited by a target filesize every frame is encoded at Quantizer = 2. The best quality encode must therefore be 1-pass Quantizer = 2. However as this produces a file too big for my specification, the next obvious setting would be 1-pass Quantizer = 3. I think the following 2-pass encode is even better than 1-pass quant 3 - am I right?

Keyframes (I-frames) are encoded with a fixed quantizer of 2 (max = 2, min = 2).
Deltaframes (P-frames) are encoded with a fixed quantizer 3 (max 3, min = 3).

Try to use BVOP's !!!
Try 1/1/0 or 1/1/1 settings...


Bye