Encoding black en white movies

[curna]

Hi, I'm a newbie and I have started encoding with to old black and white films: "Hiroshima mon amour" and "Magnificient Ambersons". Both of them are pal 4:3 films.

I've followed the GKnot method and I changed a little bit the avs script to add some other filters.

The filters I have applied are (that's the case of Hiroshima mon amour, Magnificient Ambersons it's very similar):

greyscale
FieldDeinterlace()
crop(15,0,693,568)
BicubicResize(448,336,0,0.75)
SpatialSoften(2,5,5)


Resolution: 448x336

And I've used divx 5.02 pro codecs with 2 passes with a bitrate of 980.

The options I have checked are:

-GMC
-Bidirectional encoding
-Maximum interval keyfram 60
-Maximum quantizer: I've tried with 8 and 6
-Minimum quantizier: I've tried 2 and 1


With this settings I've come across the following problems:

-With "Hiroshima mon amour" my file is smaller than what it was suposed. I've tried rising the bitrate to 1000 kbps, but the final avi still was 25 MB of what was supposed (although the minimum quantizier I've tried was 1)

-With both films, I get black squares in the image in the dark scenes. That's the BIG problem I have, I don't know how to get rid of them.

Does anybody know how can I reduce the effect of black squares in the image ?? And what's the reason why "Hiroshima mo amour" cannot bigger then 575 MB ??

Thanks for any help.

[N_F]

Some movies just compress very well. I don't know the length of your movies, but old black & white movies are usually quite hard to compress so it doesn't really fit in your case.

Do you have such such low maximum key-frame interval just to increase the filesize? Otherwise I recommend using ~125 with 25 fps movies. In my tests that has been "the magic limit" where size and "searchiblity" comes together.

If you disable B-frames you are quite likely to reach your desired filesize. Also check http://forum.doom9.org/showthread.php?s=&threadid=24584

[manono]

Hi and Welcome to the Forum-

Hiroshima Mon Amour is only 88 minutes long. So I think if you increased the resolution, you'd come up with a larger file size. Next time run a Compress Test first to help choose the proper resolution.

As for the blocks in dark areas, well, welcome to the wonderful world of MPEG4. Not much you can do about them except perhaps to use the MPEG2DEC3.dll with the lumafilter option. You can find more information about the problem and the solutions proposed Here (http://forum.doom9.org/showthread.php?s=&threadid=31301&highlight=black+blocks). Warning-this is a very long thread and some of it applies only to XviD.

[curna]

Thanks for the answer.

About the resolution, using GKnot, I did the compression test and if the resolution was greater I came up with ratios of 50%.

And besides this, if I raise the resolution, wouldn't I have more problems with blocks ??

Right now I'm gonna read this thread. Thanks for the information.

[manono]

OK-so you did run the compression test for that resolution and came up with less than 100%? Then it's not maxing out the file size. And you're right,using a resolution that gives you 50% on the Compress test will give you more blocks. But those are different kinds of blocks. They'll be the kind where it gets blocky during action scenes, and not the so-called "Black Blocks".

I might suggest running a 1 Pass Quality Based at 100% or Quant 2 and see if it comes out undersized that way. By the way-the 2 pass method doesn't use Quant 1, even if you set it to do so. To run a 1 Pass, you'll have to do it directly in VDub, and not through GKnot.

You might open up the analyze.log created at the beginning of the second pass and check the average quant (up near the top) and see if there was room for improvement.

And you're getting the bit rate from the DivX5 setting and not the DivX3 setting of GKnot (with the blue picture at top, and not the red picture)? And you have the Audio File Size filled in correctly?

And N_F's suggestions are good ones. Increase the maximum spread between key-frames, and as a last resort disable B-Frames.

Also, I'm not sure that I'd use a spatial smoother in there. It negates the sharp resizer you used in the first place. You might as well leave off the SpatialSoften and use BicubicResize(448,336,0,0.5) instead. If you want to get rid of some of the noise found in classic movies, you'd be better off using a Temporal Noise Filter.