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Old 1st February 2007, 00:34   #41  |  Link
LordIntruder
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Hi,


1) I would like to know what can be the drawbacks of settings Max i p b-frame Quantizer so low (4 or 5)? I can't find any info on that, I get thousands of messages by searching 'max i-frame'

I encoded a whole movie both with default XviD settings (1-31) and the same with 30% preset sett ings (3-5), Bitrate is 1400 aim at 2 CD.

I can't see any difference except on fast motion where I get a better result but I think it is due to the 'high bitrate scene degradation' setting that improve and give more bit.

Why force a so low i p b-frame quantizer then? Maybe the differences appear very clearly on low bitrate (1400 is already quite a good one)? I spend one hour to examine and compare both encodes and when I get a bad encoded sequence by using default settings (1-31 quantizer), the 30% preset encode looks same. I would like the opinion of those who made comparaisons, thanks.

Another thing: I use DRF Analyser, is that a good tool or is it something better to know how much frames use x quantizer?

2) By using DRF Analyser I get this:

Xvid Default Setting:
-------------------

DRF=1&2: 246 0.1%
DRF=3: 1570 0.9%
DRF=4: 19112 10.5%
DRF=5: 46989 25.7%
DRF=6: 15760 8.6%
DRF=7: 46021 25.2%
DRF=8: 38816 21.2%
DRF=9: 11393 6.2%
DRF>9: 2822 1.5%
KeyF/DeltaF: 0.66%
KeyDRF<4: 23
KeyDRF=4: 589
KeyDRF>4: 599

AverageKeyDRF: 4.78
MAXDRF: 22
AverageDRF: 6.44
Deviation: 1.61


30% preset settings:
-------------------

DRF=1&2: 0 0.0%
DRF=3: 2437 1.3%
DRF=4: 8570 4.7%
DRF=5: 60375 33.0%
DRF=6: 8713 4.8%
DRF=7: 31242 17.1%
DRF=8: 71392 39.1%
DRF=9: 0 0.0%
DRF>9: 0 0.0%
KeyF/DeltaF: 0.66%
KeyDRF<4: 18
KeyDRF=4: 894
KeyDRF>4: 299

AverageKeyDRF: 4.43
MAXDRF: 8
AverageDRF: 6.48
Deviation: 1.47


What I do not understand is that the 30% preset use Quantizer between 3 and 5 but my encode have quantizer 6, 7 and 8 used. Can someone explain me that?

3) I noticed ine MEGUI the 'I-frame boost' is set to '100' with those preset. Is it a bug or a correct setting? I think the correct value is '10' is it not?

Thanks you.
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Old 1st February 2007, 01:02   #42  |  Link
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Hi,

Those percentages and number won't give you the "whole" picture.

Without the correct info about i,p and b frames it'll probably mislead you.

For me still the best source for quant distribution and averages is the xvid status window.

Looking at the numbers I would say that you're getting i-frames 3-5 and b-frames 5 to 7 but that's only a guess.

Just my 5 cents.

All the best,

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Old 1st February 2007, 05:11   #43  |  Link
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Quote:
Originally Posted by LordIntruder View Post
1) I would like to know what can be the drawbacks of settings Max i p b-frame Quantizer so low (4 or 5)? I can't find any info on that, I get thousands of messages by searching 'max i-frame'
Hello
There are no drawbacks, apart from one, which I will name soon. Those values are set so tight (I personally loosen those settings usually, but not too much) to ensure you stick to the recommended profile (sounds crazy, I know, so let me explain):
While basing on the compressibility check, you could predict with more or less accuracy what preset to choose, nothing will ensure the final proper result/encode. It may happen, that you will get either undersized or oversized files:

1) Oversized encodes - it indicates you should either choose the preset one step lower or resize (downsize). It's always better imo to encode a smaller frame properly (lower resolution) than a bigger one with artifacts. It's always better to get a bit softer image by using a more compressable quantization matrice, than get artifacts with a stronger one, which coudl theoreticaly keep more details, but not within the filesize limits you've chosen.

2) Undersized encodes - it indicates you should try with a higher preset or higher resolution, if you want to. All the above applies here as well, but the other way round.

Without such narrow quantizers' settings you would usually get the proper filesize, which doesn't mean your encode would be ok. So, generally, thanks to those tight settings you can get sort of hints what to improve, if your final filesize doesn't meet the target one. Now you see the drawback: if comp. check was wrong, you should actually encode once again to improve quality (becasue it is possible), and the whole game starts again.

Another thing: more even, with less differences, quantizer distribution gives you imo a better overall impression, because the quality is equal throughout the film/clip. There are no jumps in visual quality, and I have seen many in my life (some scenes look really well, and then suddenly appear blocks by fast motion) - most probably because of not limiting the quantizers.

Ufff, everything I've written here so far had already been written earlier at least twice in the working thread. I know it's long, but it's worth reading, so that you can understand the idea better. And if you undestand the idea better, then you can start to experiment with presets on your own.

Hope that's clear (it's already 5 A.M. ).

Quote:
I can't see any difference except on fast motion where I get a better result...
As I said, presets are there to ensure you don't get any artifacts , especially on high motion.

Quote:
but I think it is due to the 'high bitrate scene degradation' setting that improve and give more bit.
Degradation means exactly what it means - "de-gra-da-tion" (comes from latin), making worse, taking some bits from high bitrate scenes. It's most probably because of better quantizer distribution or a softer matrice, so I assume.

Quote:
Why force a so low i p b-frame quantizer then? Maybe the differences appear very clearly on low bitrate (1400 is already quite a good one)?
The lower the quant the better. The rest as explained above.
1400 kbps for e.g. 1024x432 1:2.35 widescreen upsize is a poor bitrate. For an anomorphic encode it is a medicore one. For a downsized encode it should be a good one, unless your source is 4:3 29.970 fps NTSC, then it's nothing special (but I'm a quality freak ). And, as usual, everything depends on the source, how it compresses - hence the need for compresibility check.

I have no strength to try to answer the rest of your questions , but ...

Quote:
What I do not understand is that the 30% preset use Quantizer between 3 and 5 but my encode have quantizer 6, 7 and 8 used. Can someone explain me that?
Plz search ... It's because of b-frames, as Sharro wrote. The upper limit (5) is before multiplying by b-frame ratio and adding the offset afterwards. Gee, you don't have to read any guides to know this (I haven't) - there are tooltips when you move your mouse near each codec's setting, providing you have set sth manually at least once.

Quote:
3) I noticed ine MEGUI the 'I-frame boost' is set to '100' with those preset. Is it a bug or a correct setting? I think the correct value is '10' is it not?
10-20%, I-frames are already of much larger size than the rest of frames, so there's no need to boost their quality so much. I don't use megui, but I think tis might be a bug.


Quote:
Thanks you.
You're welcome, now I can go sleep finally (when I start sth I usually try to finish it, no matter what ) /good nite

@ Sharro
I'm gonna PM you on some matters, which I don't want to discuss in public

@ Tegedeeck
I'll post a few ideas about CC soon. Btw. are your presets closed & stiff (e.g. for using with megui) or is the discussion still open? 'cause I don't know if should post sth on the matter, since nobody seems to be interested in any further potential developement (x264, ehhh ). Cheers.
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Old 1st February 2007, 16:16   #44  |  Link
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Quote:
Originally Posted by HeadBangeR77 View Post

Hope that's clear (it's already 5 A.M. ).
Quite a good effort for that time of night.

Quote:
10-20%, I-frames are already of much larger size than the rest of frames, so there's no need to boost their quality so much. I don't use megui, but I think tis might be a bug.
Indeed, I'm gonna check.

Quote:
I'll post a few ideas about CC soon. Btw. are your presets closed & stiff (e.g. for using with megui) or is the discussion still open? 'cause I don't know if should post sth on the matter, since nobody seems to be interested in any further potential developement (x264, ehhh ). Cheers.
You're welcome to try and revive some discussion here - nothing's set in stone. What meets general approval should be adpted in the presets.
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Old 2nd February 2007, 02:18   #45  |  Link
LordIntruder
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Quote:
Originally Posted by HeadBangeR77 View Post

Ufff, everything I've written here so far had already been written earlier at least twice in the working thread. I know it's long, but it's worth reading, so that you can understand the idea better. And if you undestand the idea better, then you can start to experiment with presets on your own.

Hope that's clear (it's already 5 A.M. ).
In the working thread? You mean this one? Because I read it entirely but didn't find answers to my questions so I asked

However thanks to you now I better understand the whole thing behind the idea of reducing quantizer. It may be obvious some of you but in the past I never analyzed the quantizer distribution of my encoded stuff, I had no need for that, now I started to do it, it becames clear setting limits is an improvement on the final encode.


Quote:
Degradation means exactly what it means - "de-gra-da-tion" (comes from latin), making worse, taking some bits from high bitrate scenes. It's most probably because of better quantizer distribution or a softer matrice, so I assume.
You noticed it at 05h00 AM and not me at 00h30AM LOL

Don't know why, I had "degradation" in front of me eyes and was thinking about the opposite. Well, I will try to analyse this with my psy tomorrow . Now I see the whole idea, I agree with you, it must be a better quantizer distribution and that show how powerful the concept is, you take bits from high motion and at the end it is even better than with the default XviD settings encode that takes no bit.


Quote:
You're welcome, now I can go sleep finally (when I start sth I usually try to finish it, no matter what ) /good nite
hehe, again thanks you.

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Old 2nd February 2007, 02:45   #46  |  Link
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Quote:
Originally Posted by LordIntruder View Post
In the working thread? You mean this one? Because I read it entirely but didn't find answers to my questions so I asked
There's not much useful here, I must admit, apart from the actual presets. I meant the working thread here:
http://forum.doom9.org/showthread.php?t=107897

(I should have written: "use search!", "read the guides" )

Quote:
However thanks to you now I better understand the whole thing behind the idea of reducing quantizer. It may be obvious some of you but in the past I never analyzed the quantizer distribution of my encoded stuff, I had no need for that, now I started to do it, it becames clear setting limits is an improvement on the final encode.
I'm glad I could help and express myself rather clearly so late at night. The whole idea lies in even distribution, as already said, e.g. you get 2-3-4, 2-3-2-3, 2-3-4 in some parts and sometimes higher (means worse) values in others, but there are no jumps. After I have finally installed ffdshow I usually check qunatizers, while analyzing my encodes.

Quote:
You noticed it at 05h00 AM and not me at 00h30AM LOL
Maybe because of CBU* throttling at that time.

cheers.

@ Teegedeck - I hope I will post sth constructive within the next few days.

* stands for Central Brain Unit
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Old 2nd February 2007, 08:15   #47  |  Link
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Hi guys,

A few years ago, when Xvid hasn't reached the 1.0 version I've learned from the developpers that I should let "Xvid do it's magic" .

Meaning? Not capping the upper limit of quantizers, why ?

Because some scenes will look good with a higher quant and some won't look good with a 4 or even 3, if Xvid is capping the higher quants there might just not be space left for the lower quants and xvid is very smart at assigning bitrate where needed.

Let me put it this way, in a capped quant situation of lets say max 4 (I-frames), you won't get anything above 4 but also you will get much more q3 than q2 if you didn't cap (numbers...numbers) where you would probably get q5 and q6 but much more q2, visually on the scenes where you get q5 and q6 you would hardly notice any difference to q4, but with the lower quants the situation would probably be different.

Just my beggining of the day 5 cents.

All the best,

Sharro
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Old 2nd February 2007, 11:08   #48  |  Link
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Sharro, I know. I used to give that advice myself. The 'magic' you mention is curve-compression.

It was mostly directed at the problem that people capped quants regardless of compressibility. The result of people capping quants back then were often under-/oversizing problems. And there's no reason to cap the minimum quant to 4 with a very compressible file; there is no reason to cap the maximum quant to 4 with a badly compressible file. It only throws curve-compression off-balance. That's what happened then.

Also 'back then' more positive impact was generally attributed to curve-compression than now. The use-case 'back then' was mostly 'fixed resolution, fixed filesize, fixed XviD settings' (H.263, VHQ=1, MSP=5 or something). In the presets we do things by changing the CQM, or by changing VHQ-levels instead of simply raising quantizers. And quantizer-restrictions have become a way to enforce the use of the correct preset instead of a 'magic-cure-for- reaching-good-quality even-if-one-doesn't-know-a-thing-about-XviD-settings-otherwise' . Curve-compression takes place like it should within the boundaries of the presets. But the quantizer, and with it curve compression, is no longer the most important factor of quality.

Now we know that curve-compression is mostly valuable when strong compression is asked for; but for highest quality we want as little quantizer fluctuation as possible. BUT: this is only attainable at very lenient compression. If you now wonder why the higher-quality presets don't have much narrower quant-restrictions than the 30%-presets, the answer is that the high-quality CQMs make for a more lenient curve compression all by themselves - the difference in size between the SixOfNine CQM at quant=3 and quant=4 is nowhere as big as the difference between the ULRv3 CQM at quant=3 and quant=4.
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Old 2nd February 2007, 16:53   #49  |  Link
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@ Sharro, I must agree with Teegedeck. I didn't particapte much in those days, but most of people seemed to encode either with H.263 or MPEG, that you've described as a quality solution in those early days (I mean the PM from you). HVS Best you've been using for so long is also just a bit less compressable than MPEG. So limiting quantizers so tightly, as it is done in the presets now, didn't make much sense back then. Now every preset has a carefully chosen CQM, so it does make sense imho.

@ Teegedeck: I wrote sth about pre-filtering with a denosing filter once... Now I'm into "grain-retention", if you would like to have a look.

http://forum.doom9.org/showthread.ph...775#post947775

cheers,
HDBR77

PS. I still have nothing against the default MPEG matrice - has its uses still, even for me (and I'm a quality freak ).
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Old 2nd February 2007, 22:03   #50  |  Link
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Interestingly enough, I haven't found a satisfying way to encode grainy TV-series at strong compression and acceptable speed with x.264; the result always was that I would either have had to encode at insanely low encoding speed in order to gain an advantage over XviD, or to resort to using strong deblocking in x.264. That way the outcome didn't look at all like the input but very unnaturally smooth, as you probably can imagine. So in spite of x.264 being the 'natural' choice for medium-quality, strongly compressing encoding, I ended up encoding '"24", season 2, with XviD and the '30% HQ'-preset. And it certainly looked surprisingly good without resizing at quantizer=4 and ~250 MBs per episode (video only). Not transparent but certainly closer to the original. (Note that I switched off AQ because at constant quantizer it really doesn't make any sense.)
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Old 5th February 2007, 00:46   #51  |  Link
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Quote:
(Note that I switched off AQ because at constant quantizer it really doesn't make any sense.)
Why doesn't it make sense?

It does make sense if you want base quant but also want some portions of the image which is more compressable 1 or 2 quant up from the base quant (much the same as with using b-frames which are 1 or 2 quants higher than the constant quant used).
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Old 5th February 2007, 18:34   #52  |  Link
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The question is: do you want to save 0,5% bitrate in exchange for the risk of blocking in dark areas of the picture (which I would call a degradation of quality)?

IMHO AQ only makes sense in two-pass where the 0,5% of bitrate are redistributed across the movie. And this only if we are very tight on available filespace. Also, I still have to figure out whether the risk of blocking is so big that I'll have to dump my beloved AQ for good, after I've put up such a long struggle...

Seriously, if you encode at constant quantizer all that AQ gets you is some macroblocks with degraded quality and one or two MBs saved that you don't really have use for because constant-quantizer encodings have quite an unpredictable filesize anyway.
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Old 5th February 2007, 20:29   #53  |  Link
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I've recently been using this matrix, and it gives fine sharp results on my stand-alone (Denon DVD-1920):



What's your opinion about this one ?

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Old 5th February 2007, 20:40   #54  |  Link
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I guess this is not a CQM discussion thread and doing it here would make presets enter on a loop.

Just my 5 cents.

All the best,

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Old 5th February 2007, 20:43   #55  |  Link
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Isn't it Soulhunter's V3?
If so, then it's one of my favourites, but for certain uses, for instance it keeps filmgrain very well.

Could be a good alternative for the following presets: XviD>45% HQ or XviD>58% fast.

PS. But basically I must agree with Sharro - if you proposed the one for presets, with some more descirption etc. that would be fine.
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Old 5th February 2007, 20:47   #56  |  Link
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Teegedeck:
Actually I regularly save 10 to 20% bitrate with AQ turned on. I'm not doing any reencoding of mpeg-2 files like most here though, but mostly 80s VHS caps in xvid's interlaced mode.

I appreciate those 10-20% saved bits much although they of course come at the expense of some quality degradation. But with 1-pass encodings the only other way to save the same amount of bits is to use higher base quant/different matrix (or even higher b-frame quants but that would be just silly), and compared to those alternatives I'd much rather use AQ, as the quality degradation is supposedly happening in areas where quality matters less. At least I don't tend to experience blocking in dark areas and I concluded from my testing that AQ is doing a good job. Certainly, sometimes there's a little difference you can spot but it's far less than the difference would be if you had used one higher quant to begin with on all i/p-frames.

From limited experience I would also assume problems with blocking in dark areas would be much more common when transcoding from a lossy format, rather than encoding a lossless capture of an analog stream.
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Old 5th February 2007, 22:41   #57  |  Link
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Isn't it Soulhunter's V3?
...
Nope, Intra-Matrix is different. Should compress slightly better.

All the best,

Sharro

@HeadBangeR77, see my PM

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Old 6th February 2007, 11:51   #58  |  Link
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Quote:
Originally Posted by HeadBangeR77 View Post
Isn't it Soulhunter's V3?
If so, then it's one of my favourites, but for certain uses, for instance it keeps filmgrain very well.

Could be a good alternative for the following presets: XviD>45% HQ or XviD>58% fast.

PS. But basically I must agree with Sharro - if you proposed the one for presets, with some more descirption etc. that would be fine.
Actually ... i've taken this one from DVD-RB's Matrix editor addon. When you install the addd-on with DVD-RB, you can choose this one for use with CCE. It's the "High-Low" matrix (the "3rd best").

There are 2 matrices that are supposed to be "better" ("High-Medium" and "High-High"). One of them is equal to the one I posted, but has flat 8's in the inter-matrix (in stead of 16's).

I'm going to try that one in the next few days, but i predict that it won't work with my stand allone because of the 8's in the inter-matrix ... but you never know :P

I wouldn't even have guessed that the MPEG2 matrices would be acceptible with XviD

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Old 7th February 2007, 01:59   #59  |  Link
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Originally Posted by G_M_C View Post
I wouldn't even have guessed that the MPEG2 matrices would be acceptible with XviD
Now you know, and I know where you've taken the matrice from.
I'm using Fox Home Entertainment occasionally, but it's really high bitrate for XviD encodes.
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Old 7th February 2007, 13:25   #60  |  Link
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Hi all,

My SP does not like b-frames for encodes with high bitrates (>1500) and couple of audio tracks.

Will "XVID Presets" still have sense with disabled b-frames? (I do not mean "special purpose" presets.)

Thanks.
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