AutoGK Auto Width

[indijay]

I was wondering if anybody knows how Auto GK decides its auto width option. I recently ripped 4 DVDs using Auto GK and I got following resolutions 688x304, 640x336, 672x328, 512x384 in the output. All of the source videos were of 720x576.
I am not getting a clue why for every video I rip, I get different resolution if I select Auto width.
Why it is not possible to have resolution of 720x576 or this reduced resolution has something to od with compression?

My ripping procedure involves using DVD decryptor to copy DVD and then loading ifo file to AutoGK and selecting Xvid output equivalent to 2CD (1400mb)

I really appreciate anybody solving my queries.
Thanks in advance

[jimmalenko]

I believe that it does a compressibility test and then decides on the best frame size based on the results of this, whilst considering either the size or quality constraints you have set. This only happens when you choose auto width, mind you.

You should be able to select Fixed Width and it will use the width you specify as well as the correct height in order to maintain the AR.

[desijay]

I guessed that it selects best frame size taking into consideration the constraints that I have offered.

To the best of my knowledge, I can only select fixed width but I don't get an option to select height. I never tried it as it takes about 4 hours on my machine to rip DVD but wondered if anybody managed to get decent ripping at frame size same as the source.

I appreciate any comments on frame size and bitrate selection (I cant find this option as well) as I am planning to watch these movies over 28" 4:3 TV set.

[manono]

Hi Jim-

Yes, he could choose a fixed width in Advanced Settings, but since he hasn't a clue about how the width is chosen in the first place, it'll be easy for him to choose a width too great for his movie, and come up with lousy looking results, or a width too low for his movie, and perhaps not reach his desired file size. I'd suggest that until he has a better understanding of how AutoGK works (hint: read the tutorial) he leave it on Auto.

I can only select fixed width but I don't get an option to select height.

Based on what you said in your first post, you'd only screw it up. If you want a 720 width, then go for Target Quality Mode at 75%. But you'll lose all control over file size. The bonus is that it will run only one pass, and it will take not much more than half the time.

No, you can't choose the bitrate. You choose the filesize. Since they're directly correlated, it's the same thing.

[jimmalenko]

Are desijay and indijay one and the same person ???

[desijay]

Unfortunately Yes,
I had this indijay account long time ago (which I forgot eventually) so I opened new account (while at work and so my mac kept in its mind) When I wanted to post message at home, I searched through all subscription mails and found this old indijay so posted using that one and desijay at work (from mac's memory)

Apologies, I will soon delete one of that.

BTW, Which tutorial Manono is referring to? I went through one on their website and the other on rita.it but I didn't find any explanation on how AutoGK decides frame size, or I missed it somewhere!!

[manono]

Hi-

I was referring to this tutorial:

http://www.autogk.me.uk/modules.php?name=TutorialEN

Is that the same one you saw? Going over it again, I see that len0x (the author of AutoGK) removed my log analysis section where I explain the compression test. I wrote the original guide, but he's modified and added some things, but it's still about 95% mine. You're right that there's no longer anything about how the horizontal resolution is chosen, and I apologize. It used to say:

A Compression test encodes 5% of the movie (15 frames of every 300 frames, so it samples the entire movie) to get an idea of how well it will compress, and to give us an idea if the default parameters (resolution and file size mainly) will give us a good quality movie. The Compress Test is run at a Horizontal Resolution of 640.

And there was more later on about how the resolution, matrix, and resize filter is adjusted if the compress test results are too high or low. The tutorial is also included in the AutoGK package. It does still explain in detail about the Target Quality 1-pass method. Rita also has a very good guide.

[indijay]

Yes, its the same link that I went through. Any chance that I can find that old tutorial of yours where you have explained everything. I am quite curious to know how this thing works

[manono]

Hi-

No, it's only on my computer now, but I'll give you a brief rundown. The figures are for XviD, as the new version of DivX gives different and lower percentage results. And I may have the figures slightly wrong, but you'll get the idea. You can read the results in your log files.

After running the compress test, a percentage figure is returned. AutoGK is looking for a figure between 60 and 75%. Results between these figures will give a good quality movie. Below the figure and the results won't be as good. Very much below and the AVI will look bad. That's one reason why blindly choosing a fixed horizontal width can lead to bad results, although AutoGK will take some steps to improve the results. Above the figure and you either won't be able to achieve the desired file size, or you won't be taking full advantage of MPEG-4 compression.

The default resolution is 640*xxx. If you come out below the percentage spread, it can lower the horizontal resolution, use a softer resizer (Bicubic instead of Lanczos), use a softer matrix (HVS_Better instead of HVS_Best, or if the ESS chipset option is enabled, H.263 rather than MPEG), or all three. Based on the better compressibility of the changes, it first estimates the new percentage, and then after running the first pass gives the actual percentage. The 2 figures are usually pretty close.

If the percentage is too high, as with several of your movies, it raises the horizontal resolution and, if necessary, drops the use of B-Frames (I think).

Much of how AutoGK works is explained in the log. Another of its innovations, and still the only program out there that can do it I think, is to analyze the source to determine if it's interlaced and needs to be deinterlaced for AVI, if it's 23.976fps film (if NTSC), or if it needs to be IVTC'd (if NTSC). It's quite clever and quite good in that respect. That process is also explained in the log.

I won't explain about resizing from DVD resolution to AVI resolution, but there's a very good reason why AutoGK allows you to only choose the horizontal resolution. Trust me, the resulting AVI will have the correct aspect ratio.