A question about zone?

[DanielSun]

How to encode "credits" using zones?

Do i need to make zone for credits in both passes?
Or just the second pass need a zone?

Sounds so stupid,but i use GKnot before,And now i am using VDMod manually.:(

[Teegedeck]

If you use the 'weight' option, you only have to set it in the 2nd pass. It's recommendable though to use a fixed quantizer for the credits in both passes.

[DanielSun]

Originally posted by Teegedeck
If you use the 'weight' option, you only have to set it in the 2nd pass. It's recommendable though to use a fixed quantizer for the credits in both passes.

Thank you for your kind reply!:)

And would you please explain your point a little more?

What will happen if i set credit zone in both passes using "weight"?
(I've already set a zone using "weight" in my 1st pass:( (RC4))

Why "weight" need only one pass,and "quantizer"need both?

Regards.
Danielsun.

[Teegedeck]

If you set a zone to be encoded at constant quantizer, that zone will be excluded from the whole bitrate calculation for 2nd pass - because it has got exactly the same size in both passes. This is more predictable than changing the 'weight' factor which will trigger XviD to attain an according fraction (for example 0.8 = 80% of what the zone would have gotten with weight 1.0) of the 'normal' 2nd pass bitrate to that zone. Credits at quant=20 will always be small while looking good enough, but credits with weight 0.1 may come out too big if you do a 3-CD encode but too ugly if you make a 1-CD encode, if you know what I mean.

[Nibor]

It doesn't hurt if you also set the weight in the first pass, don't worry...

[DanielSun]

Originally posted by Teegedeck
If you set a zone to be encoded at constant quantizer, that zone will be excluded from the whole bitrate calculation for 2nd pass - because it has got exactly the same size in both passes. This is more predictable than changing the 'weight' factor which will trigger XviD to attain an according fraction (for example 0.8 = 80% of what the zone would have gotten with weight 1.0) of the 'normal' 2nd pass bitrate to that zone. Credits at quant=20 will always be small, but credits with weight 0.1 may come out too big if you do a 3-CD encode but too ugly if you make a 1-CD encode, if you know what I mean.

Thank you for your great explanation !
I can understand your point very well.

And many thanks to Nibor too!

Here I've found another problem .It is about the bitrate calculator.
I didn't do the search bacause all the need is just a clarify.

when i press the ok button of the calculator window,I found the result (size and avg bitrate)in the xvid main config window are different from calculator window .(Do I made myself clear? ^_^!)

Is that normal?

PS:what quantizer do you usually use for credit? 20? that big?

[mikeX]

Regarding your Credits question, you can even go to q=31 most of the times

[atreya2011]

You can use Quant 31 with increased B frame sensitivity (maybe 5). That should reduce some ugly smearing.(You cant prevent it though)

[lordadmira]

I've gotten good credits results on 2-pass encoding by just setting that zone to 50% and grayscale. The letter edges are a little choppy but still fine. Also good for intro's and outtro's. The problem with setting a fixed quantizer is that if u pick the wrong one, u gotta start over the whole encode. Setting a percentage lets the codec decide how much quality to give it based on the whole video overall. The alternative is to encode the credits independantly and then join that to the main movie file later. That way u can experiment to get the smallest size and decent quality.

Another caveat about zones: if ur doing inverse telecining (IVT) or any other kind of framerate alteration, the zone has to have the post IVT frame number, not the original number displayed in ur app. So if they start at 20,000 in the original file they will now start at 20,000 x 80% = 16,000 in the frame sequence that Xvid gets from the app. (NTSC -> film)

LA

[DanielSun]

Originally posted by lordadmira

Another caveat about zones: if ur doing inverse telecining (IVT) or any other kind of framerate alteration, the zone has to have the post IVT frame number, not the original number displayed in ur app. So if they start at 20,000 in the original file they will now start at 20,000 x 80% = 16,000 in the frame sequence that Xvid gets from the app. (NTSC -> film)

LA

That's not gonna happen when i use a forced film d2v file in my avs,right?

I do not know the way you do your encode,but i think if you use .avs file and do IVTC or DEINTERLACE with avs script ,then open .avs in a player to find where credit begins,the frame number you get will be accurate.

PS: What about my bitrate calculator problem?Please?

Regards.
Danielsun.

[lordadmira]

Yeah because ur looking at the post-IVTC frame number. I use Virtual Dub and that shows pre-IVTC frame numbers.

As for the birtrate calculator I think that's OK since it takes overhead into account in a funny way.

[Lord_KiRon]

Guys , just two probably extreamly stupid and newbee :scared: questions (but they bug me a long time):

- If I set the zone for a main movie to be 1.0 and credits zone let's say 0.2 will it do anything ? Or I have to set something like 0.8 for movie and 0.2 for credits ?


- If I encode in VDub few files as a batch using (different of cause) zones for each file/job . So is the zones really saved for each job like other codec settings (as I hope) or the codec use the last one for all files ?

[Pen-Pen]

Originally posted by lordadmira
Setting a percentage lets the codec decide how much quality to give it based on the whole video overall.


that's precisely the kind of things I try to avoid... Instead of allowing more bits to both the movie AND the credits, because the movie's overall compressibility's better, I'd rather put them all into the movie itself ;)

[Andrey]

>>Instead of allowing more bits to both the movie AND the credits, because the movie's overall compressibility's better, I'd rather put them all into the movie itself
There are very many solutons to this credits question, I see :)
For example, I always encode them to 6MB for one CD and to 15MB for 2CD.
This prevents me from playing with zone and quantizer setting. Just not to forget to add credits to main movie...

[Nibor]

Originally posted by Lord_KiRon
Guys , just two probably extreamly stupid and newbee :scared: questions (but they bug me a long time):

- If I set the zone for a main movie to be 1.0 and credits zone let's say 0.2 will it do anything ? Or I have to set something like 0.8 for movie and 0.2 for credits ?

Yes, it will encode the credits with '20% the quality' of the main movie.

And if you set 0.8 and for the credits 0.2, hmm, don't know what happens!..
Maybe it will encode the credits just as if you had entered 0.25 for them and 1.0 for the main movie because 0.2 / 0.8 * 1 = 0.25 ;)

- If I encode in VDub few files as a batch using (different of cause) zones for each file/job . So is the zones really saved for each job like other codec settings (as I hope) or the codec use the last one for all files ?
Well, it _should_ save them for each file :D It should... You have to test it, I'm not sure.

Have fun!
nibor

[lordadmira]

Originally posted by Pen-Pen
that's precisely the kind of things I try to avoid... Instead of allowing more bits to both the movie AND the credits, because the movie's overall compressibility's better, I'd rather put them all into the movie itself ;)

Yeah but there is the minimum allowable quality for the credits. If they're crushed too much u can't read em and if u can't read em then what's the point of having em there in the first place?

[Pen-Pen]

Originally posted by lordadmira
Yeah but there is the minimum allowable quality for the credits. If they're crushed too much u can't read em and if u can't read em then what's the point of having em there in the first place?

you do realise you contradict yourself, don't you ? using fixed quantizer is precisely meant to avoid to go under this "minimum allowable quality" without knowing about the credits' compressibility. On the contrary, weight settings for credits are completely unpredictable since you don't know the ratio (movie compressibility)/(credits compressibility)

lots of people don't seem to get what a quantizer really is, though there are LOADS of threads that explain it...

compressing at Q20 means :

* get rid of details with "level 20" (according to compressibility, since "more compressibility" roughly means "less details")

Quantizer-based encoding always takes the compressibility into account, otherwise, that would mean that 2 different "QX" movies (X being a constant) might show completely differents qualities... which is not the case

[lordadmira]

Yes, yes, I know all that. U misunderstand. I'm talking about picking the wrong quantizer. U describe a scenario where u *know* what quantizer to pick. What I'm saying is that people aren't usually going to know right off the bat what quantizer to pick, meaning they'll probably screw up their first attempt and then have to do the *whole* thing over again. This is the situation where picking a reletive quality is more time effective.

There is no fixed relationship between quantizer and output quality. One source can be unwatchable at quant 10, another source can be very good at quant 10.

LA

[Teegedeck]

Just speaking from experience, that doesn't happen. After all, it's usually only text. (We can't help people who want to encode credits with extra-footage from the movie appearing next to the text at quant=20 where it'd better be weight=1, of course...) Fixed quantizer=16-20 will always be OK.

[lordadmira]

Eeee, u have "experience" so that doesn't count. :D