b&w and AutoGK

[richarddd]

Anything special one should do to compress a black & white movie with AutoGK?

I've noticed that the compressibility percentage is usually quite low (often 35%-40%) especially for the older b&w movies.

[len0x]

You might want to set resolution to some minimum value to ensure that AutoGK doesn't produce too small videos - for b&w old movies, compressibility around 50% should work OK.

[richarddd]

What would you use as a minimum resolution (all are 2CD)

The Grapes of Wrath:

[10/29/2004 8:15:59 PM] Compressibility percentage is: 36.09
[10/29/2004 8:15:59 PM] Chosen resolution is: 512x384 ( AR: 1.33 )
[10/29/2004 8:15:59 PM] Predicted comptest value is: 68.22
[10/29/2004 8:15:59 PM] Running first pass.
[10/29/2004 10:23:37 PM] Duration was: 2 hours 7 minutes 37 seconds
[10/29/2004 10:23:37 PM] Speed was: 24.38 fps.
[10/29/2004 10:23:38 PM] Expected quality of first pass size: 62.65

or My Man Godfrey

[10/30/2004 1:19:10 AM] Compressibility percentage is: 39.33
[10/30/2004 1:19:10 AM] Chosen resolution is: 528x400 ( AR: 1.32 )
[10/30/2004 1:19:10 AM] Predicted comptest value is: 69.22
[10/30/2004 1:19:10 AM] Running first pass.
[10/30/2004 2:54:00 AM] Duration was: 1 hour, 34 minutes 49 seconds
[10/30/2004 2:54:00 AM] Speed was: 23.59 fps.
[10/30/2004 2:54:00 AM] Expected quality of first pass size: 72.40

or The Big Sleep

[10/30/2004 5:19:28 AM] Compressibility percentage is: 48.65
[10/30/2004 5:19:28 AM] Chosen resolution is: 592x448 ( AR: 1.32 )
[10/30/2004 5:19:28 AM] Predicted comptest value is: 68.19
[10/30/2004 5:19:28 AM] Running first pass.
[10/30/2004 7:17:52 AM] Duration was: 1 hour, 58 minutes 24 seconds
[10/30/2004 7:17:52 AM] Speed was: 23.08 fps.
[10/30/2004 7:17:53 AM] Expected quality of first pass size: 68.43

[len0x]

First one is ok to me. Second can be adjusted by putting width+32. Third width+16 (but since resolution is already quite high I'd leave it as it is).
As a rule I don't like to see resolutions below 512x384, so that should be a minimal one. As long as you got at least 576x***(for 4:3 movie, not widescreen) - you don't have to worry either. What to do with values in between its up to your taste.

[richarddd]

I'm confused.

The three resolutions were
1) 512x384
2) 528x400
3) 592x448

Applying your suggested changes, we'd leave the first alone, even though it's the lowest resolution, add 32 to the second (432, so ~574x432) and perhaps add 16 to the last (464, so ~617x464). If 576 is a good enough minimum to change the second, why leave the first as is?

An alternative would be to go to 3 CDs, but that seems a bit much for a movie well under 2 hours. Or reduce the sound quality (for example, 190 kbps mp3 at mono is only ~95, which seems low, but I should experiment more).

[len0x]

My suggestions came from the fact that I like to see compressibility around 60% for old b&w movies. 70% or more seems a bit like a waste because noise cannot be sharp by definition :)

so
1) already has desired compressibility
2) compressibility can be lowered
3) compressibility can be lowered again

P.S. mono encoding is almost a must because there is no stereo to begin with (2 AC3 channels are the same).

[richarddd]

Compressability: Gotcha.

Sound: fwiw,

1) Grapes of Wrath is stereo (http://us.imdb.com/title/tt0032551/dvd)
2) My Man Godfrey is two channel mono (http://us.imdb.com/title/tt0028010/dvd)
3) The Big Sleep is two channel mono (http://us.imdb.com/title/tt0038355/dvd)

65-95k seems a bit low. Doesn't lame share info between channels for stereo?

Thanks again for a great program.

[manono]

About The Grapes Of Wrath:
Audio:
The sound comes in its original monaural, unfortunately presented in two channels, and in a 2.0 stereo remix. In both instances background noise has been largely eliminated, but from there the choice is yours. The advantage of the stereo is that it spreads out the sound a bit more widely between the front channels, providing a more modern listening experience. With it comes a slight increase in brightness and edginess, however. The original mono appears smoother, if more confined. In any case, whichever choice you make, you're getting a soundtrack that is better than anyone has probably ever heard it before.
From here:
http://www.dvdtown.com/review/Grapes_Of_Wrath_The/12004/2034/
Amazon.com (http://www.amazon.com/exec/obidos/tg/detail/-/B0000DJZ8R/qid=1099360420/sr=1-1/ref=sr_1_1/104-6386676-9394332?v=glance&s=dvd) says the same thing.

Evidently you have your choice. Personally, I don't have much use for Mono remixed to Stereo, and would definitely go with the dual channel Mono, and then convert it to true one-channel Mono. By doing that you'll free up quite a few bits to improve the video quality. I like my Mono between 70 and 80 or so. So, maybe choose 160 in AutoGK, make sure it's set for Mono, and the bitrate will be cut in half.

[richarddd]

Another question: Rules of the Game (2cd, mono)

[11/2/2004 6:22:45 AM] Compressibility percentage is: 33.05
[11/2/2004 6:22:45 AM] Using softer matrix.
[11/2/2004 6:22:45 AM] Chosen resolution is: 512x384 ( AR: 1.33 )
[11/2/2004 6:22:45 AM] Predicted comptest value is: 62.49

Any suggestions?

manono: That'll teach me to trust IMDB :(

What bit rate do you like for stereo?

[manono]

I'd make sure the sharp matrix is used, even if it then takes the percentage down to the mid-fifties at 512x384. Nothing wrong with that for old grainy/noisy movies. For Rules Of The Game, there's no longer a negative to use for the source. They (Criterion) had to use a 35 mm film source, and the picture is kind of soft to begin with, along with being fairly grainy.

For stereo audio, I usually try to get something in the 140-150 range, if I'm not using the AC3. It's a matter of taste, though.

[richarddd]

What would you recommend I read to get a better understanding of these issues?

[manono]

Which issues? The quality of the DVD and its source material(s)? I like to hit the Reviews (http://www.dvd-basen.dk/uk/home.php3?search=rules+of+the+game&mvis=ok&region=1&land=%25&ok=go) first, to learn what I can. However, very few reviewers have the knowledge and ability to take apart DVDs to go over them frame-by-frame and field-by-field the way we here at Doom9 can.

If he has a review or DVD comparison of the movie you're looking for, then the DVD Beaver Site (http://www.dvdbeaver.com/film/DVDCompare6/rulesofthegame.htm) is an invaluable resource.

You have good taste in films. A man after my own heart. :)

[richarddd]

I meant issues such what the best settings for compression might be, the relation between compressibility, resolution, etc. Sorry for not being clear.

I was about to make the same comment on your taste in film :)

[manono]

Oh, my mistake.

I have nothing on which to base my beliefs but my eyes. I don't know of any real studies, or sites focusing on your questions (except this one). But from experience I'd say that the "dirtier" the source, the noisier and grainier it is, the lower you can let the compression percentage go. Or to put it another way, the higher you can let the average quant go. With older movies I don't mind at all letting the average P-Frame quant get up to around 4, whereas for the recent and real clean Hollywood movie DVDs, I'd much prefer to get the average P-Frame quant below 3.

Of course, the lower you let the resolution go, the softer the picture becomes. So, at some point you have to set some sort of a minimum resolution. For me, for full screen movies, it's 512x384. But you can decide for yourself at what point you won't let the resolution drop any further. I'll keep it at 512x384, even if it means a lower compressibliity, or a higher average quant.

But these are things you'll have to decide for yourself, and with the experience of doing more rips, comes the knowledge of what kinds of limits you'll accept.

[richarddd]

Experimentation is no doubt the way to go, although that seems contrary to the spirit of AutoGK :)

Alas, I need more basic information, such as what "P-Frame quant" means and how to manipulate it. Maybe I should start with the xvid FAQ at http://ronald.vslcatena.nl/docs/xvidfaq.html

[manono]

By P-Frame quant getting up to 4 I was saying in really general terms that under some circumstances it's OK to let the compressibility percentage get down to as low as 50. The noise and grain will hide a lot of problems. There are those that even believe in adding noise, either before the encoding (the Blockbuster plugin, and others), or with postprocessing at playback.

I work a lot with silent films, and I've seen first pass sizes at 512x384 (not 720x480, mind you) that were larger than the original vobs. Talk about hard to compress! And it's not all that uncommon.

And yes, Cruncher's FAQ is an excellent place to learn all about XviD, and even MPEG-4 in general.

[len0x]

AutoGK still does quantizer limitation, so manual intervention is not necessary (max quantizer is controled by the quality).

[richarddd]

Results for Rules of the Game with 1.73, .sharpmatrix and .mono, 2CD

[11/5/2004 4:45:53 AM] Compressibility percentage is: 36.32
[11/5/2004 4:45:53 AM] Chosen resolution is: 512x384 ( AR: 1.33 )
[11/5/2004 4:45:53 AM] Predicted comptest value is: 68.66
[11/5/2004 4:45:53 AM] Running first pass.
[11/5/2004 6:35:38 AM] Duration was: 1 hour, 49 minutes 44 seconds
[11/5/2004 6:35:38 AM] Speed was: 23.28 fps.
[11/5/2004 6:35:38 AM] Expected quality of first pass size: 71.02