Gnot calculate 1.6GB, DivX5 Pro makes 1.1GB

[yosemite]

hi,

it's strange! Gknot tells me that my video (without audio) will 1,6GB but in the end after encoding with VD it is just 1,1 GB.

Failure?

[ffroms]

That's nothing strange in that . There is something called compressibility of movie . Of course if you used B frame option thats extra reduction in file size. Try to set higher bitrate.

FFS

[yosemite]

sure, but how can I know which bitrate I should take?

in worst case, my movie is in the end much bigger than wished...

or is there something I can say:

100 kbps (video-bitrate) more or 100MB more, too?

[sierrafoxtrot]

i've found that setting a higher bitrate will make the codec less predictable. try increasing the resolution instead, if you're off by about 500Mb, increase resolution until the total pixels per frame goes up by 20-30%. give it a shot, it might work ;)

[theReal]

I think if you can't reach the desired size with a bitrate x, even increasing x to 10000 wouldn't help to make the final file bigger. Maximum quality was reached, so all you can do is increase the resolution, avoid any filters and use sharp bicubic resizing.

[rui]

What we need is some kind of comp check using divx5. Jonny has made a thread about this, and i too made some tests using his directions.
You can read it here : http://forum.doom9.org/showthread.php?s=&threadid=19927

[dragoman]

Hi,

If you want a totally predictable encode using DivX 5 Pro, turn off b-frames. Most of the time this is what was causing your problems.

In the smaller number of cases where the max quality is reached, you are out of luck. Use ac3 audio, extra audio tracks, etc... to fill in extra space.

dragoman

[tripnotik]

Originally posted by dragoman

If you want a totally predictable encode using DivX 5 Pro, turn off b-frames. Most of the time this is what was causing your problems.


I hope you realize that by doing what you said, he would have an encode that is bigger, and with less quality. Come on! The objective isn't to fill the CD, it's to have great quality! If the file is 1.1 GB with quantizers 2, it must have a great quality so there is no quality to be gained by disabling b-frames and filling the 1.6 GB with an encode with average quantizer maybe more than 2.

[ffroms]

As I understand, B-frame is compressed more then P frame (delta frame) , so B frame is for use if you want smaller file size with same bitrate . Video quality is equal in both cases (or maybe better without B-frame). Yosemite didn't say what he was using but I guess it was 2pass not 1pass-qulity .
I must agree with dragoman . Turn off B-frame ,and if that don't help try using Divx4Log prog. to edit log from 1st pass and change quantizer .

FFS

P.S. I'm not sure is B-frame simply better compressed or it's used higher quantizer ?!
Sorry , I wrote this P.S. before I saw dragoman’s post and –h’s replay about same thing.
(Sorry for my bad english , but I'm geting better :))

[yosemite]

yop, I used 2pass encoding?

or is 1pass quality encoding better than that?

[ffroms]

1pass quality is better 'couse it don't use bitrate but fixed quantizer (compression) and all frames are compressed same. Of course there is still question about B-frame (it's compressed 2x then other frames) so I guess it's better without B frame but you can expect higher file size.

When you were doing 2pass encoding did you change mQ and MQ (by default it's 2 and 12) ? Try to set them both to 2. That way you will have fixed quantizer.

FFS

[DJ Bobo]

I don't use the PRO version of DivX5. I use the normal version and it's 100% predictable. When you get an undersized movie, that means that it is already saturated, no matter how much you make the bitrate higher, it won't get any bigger. If you wanna a bigger size, you gotta higher the resolution.

@ffroms
setting both quantizers to 2 is equivalent to quality based 100%
IT's USELESS & TIME WASTING then to use 2-pass encoding!

[ffroms]

I'm new at divx so correct me if I'm wrong.
Here what I think.
Let say you set bitrate at 1000kbps and both quant at 2 (in 2pass) . This will give you file with fixed quant but codec will try to stay close to given bitrate.
If you try to do same movie with 1pass-quality and quant at 2 will give file with only compression at 2 without thinking about bitrate so you probably end with bigger file.
There is still matter with B-Frame.

FFS

[DJ Bobo]

If you set both quantizers to the same setting, DivX will IGNORE the bitrate! you set 0 or 10Mbps, you'll get the same size!

[ffroms]

Thanks for clearing that up to me. I wasn't sure . Anyway , I'll do some testing.

[dragoman]

@tripnotik

Yes, I know exactly what turning b-frames off would do, however he was asking how to get a predictable filesize. Turning off b-frames is the only way to do this in DivX 5 Pro

@ffroms

How do you know that the codec doubles the quantizer for b-frames? Where did you get this information?

@bobonts

Yes, you are correct if you want the best quality, but your filesize will be very large and you cannot predict it.

dragoman

[DJ Bobo]

@ dragonman
http://forum.doom9.org/showthread.php?s=&threadid=22011

[jonny]

If you don't want to go undersized:

1) Use compressibility test: http://forum.doom9.org/showthread.php?s=&threadid=19927
2) If you get more that 80% you'll probably get undersized avi... so try to increase the resolution or decrease number of cds or play with bicubic methods
3) If you get 95%-100% or >100% you can go with a costant quality encoding with quantizers = 2 (without changing setting)

[theReal]

Turning off b-frames is the only way to do this in DivX 5 Pro dragoman, this sounds like you could NEVER get the right filesize with b-frames, and that's not true. If the quality is not saturated (i.e. for most one-cd rips), you can also reach the desired filesize exactly.

[dragoman]

@bob - thanks for the thread reference....just proves I am right in what I said :)

@theReal

You are correct sir, I should have said "only way to do this 100% of the time" - if you are using b-frames and the quality is maxed, then it doesn't work.

dragoman

[theReal]

@dragoman, I know you knew it - but there seems to be a lot of confusion about b-frames amongst newbies, what they do, if they make files smaller or better, or both.
I thought I needed to add that to prevent threads like "is there a bitrate calculator for b-frames??" ;)

[ffroms]

@bobotns
I've done some testing and here are results.
I've done 1pass-quality and 2pass with Divx 4 and 5. Settings for 2pass were bitrate 1000kbps mQ/MQ =2 and everything else was default , and 1pass-quality was 100%. Clip was taken from movie Jurassic Park 1 and scenes are mostly bright with low motion and length of clip is 8:12 min at resolution 704x368 @25fps(PAL).
1pass-quality
Divx4 - 253.677.568 bytes (241,93MB)
Divx5 - 252.899.328 bytes (241.18MB)
2pass
Divx4 - 65.904.640 bytes (62.85MB)
Divx5 - 61.851.648 bytes (58.99MB)

According to this CODEC obey bitrate even thou quanta was set at 2. I check logs from both divx and quanta was 2 for all frames.

FFS

[theReal]

I think in 2-pass encoding, the second pass obeys the bitrate regardless of your quantizer settings (probably that's why the quantizer options in Divx4 were called "1-pass encoding parameters")

For the first pass (that is for a comp. check), the bitrate doesn't matter, though. I tried it on a comp. check in GKnot. If I chose a bitrate of 780 or 1, the results were exactly the same.

btw.: using your bitrate (1000) and length (00:08:12) and no audio, Gknot calculates a size of 59MB for the clip. That shows again Divx 5 is more accurate on the final filesize than Divx 4.

[ffroms]

I didn't calculate the size 'couse I just wanted to see if 2pass with quanta 2 is same as 1pass-quality like bobotns said. What you did is just extra bonus about divx5 :) .
I'll try to do encoding with MPEG4 stuff on and same settings.

FFS

[rui]

I just wanted to share with you guys my experiments. I used divx5 pro with b-frames and GMC.
I believe that divx5 is a lot more accurate than divx4 ever was.
I tried to encode a movie called The Replacements, which i now it to be a hell of a dificult movie to encode. First i tried to encode at a resoluion of 640xXXX aiming for 2 cd's. The final file size was exactly 1400MB.
Then i tried to encode the movie for 1 cd, using the same resolution. I was expecting that, being this a dificult movie and the resolution the same, i would get a file size bigger than 700, but no, my final file was 700MB!

Then i tried another movie, called The Haunting. This movie has a lot of slow motion scenes. I tried to do a 1 cd encode, and my final file size was 670MB. This by using a resolution of 640xXXX. It's clear that if i wanted to reach the 700MB for this movie i would have to choose a resolution bigger than the 640.
So i believe that if one chooses the correct resolution for each movie, divx5 will have no problem in reaching the final size you want.

But my tests only make even more clear that we need a comp check for divx5 to know what resolution to use for a particular movie.

[jonny]

@rui

YES YES YES, with DivX5 i can encode alot of movie at 704x432!!! (instead of 704x304) and comp check is still high (60%-80%)

@all: USE COMP CHECK!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[theReal]

But my tests only make even more clear that we need a comp check for divx5 to know what resolution to use for a particular movie.Using the comp check with Gordian Knot is not that difficult (of course I'd prefer it all automated because I'm lazy, but I can wait). From my limited experience with the comp. check and divx5 I can say that, using b-frames and no other pro-features, 59% doesn't result in undersized files and yields a very good quality.

[rui]

theReal, for now i am using Jonny's way of doing the comp check.
But your values are like main, i am doing a new encoding of the movie The Haunting, and trying a resolution that reaches those percentages, so i can get a perfect file size.

[rui]

Well, I just tried to do a new encoding of the movie "The Haunting".
This time I choose a resolution of 720xXXX, instead of 640xXXX.
The comp check indicated a percentage of 67,9%. I aimed for 1 cd, and voila, a 700MB final file size.
So, concluding, if one does a comp check to determine the movie's compressibility and so choose the correct resolution, we can have a perfect file size.

So, judging by my tests, Jonny's info, and all you guys posts (like TheReal), I can say that if the comp check of a particular movie, taken in consideration the audio and credits size, is between 55% and 70%, we can almost always get our desired file.
If it is above 70%, you can increase the resolution. If it is below 50%, it can still look good, depending on the movie (I'm not certain of the low values, I have to test more in this cases). My worst case scenario was the movie The Replacements, that had a comp check of 27%, and looked like shit, in spite of having reached exactly 700MB.

I would like to read other peoples opinions, please :), that’s the only way to evolve ;)