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Old 19th March 2002, 15:27   #1  |  Link
skaven
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A few questions in Doom9's DivX 5 guide

Ok... I finally got my first rip to work (for the most part). I tried to follow Doom9's DivX guide to the letter. But a few questions remain. I installed the most recent GKnot 'package' for all of the programs that are used in the guide.

First of all, when selecting resolution in GKnot - I can't seem to get the 'autocrop' feature to work. I have loaded the .av2 file and the window is open in the background. But for some reason the 'autocrop' button never shows up. I ended up selecting smartcrop anyway - but I'm not confident of the results. Whats the best option if I can't use 'autocrop'?

Also, when using DivX5 in 2-pass mode, I end up with 2 .avi files. The first file is about 5mb and the second is ~550mb. When using Nandub to mux the .avi and .mp3 it doesn't say what to do with the two files (both passes) from the DivX encoding. I assumed to just use the bigger file - and it seems to have worked. But then I question why the two passes? Just want to make sure I'm doing it right.

Finally, I can't seem to get the final file size right. My first rip/encode ended up being 650mb - a good deal less than the 700mb I was shooting for. Yes I selected the actual MP3 file after the encoding was done. I then typed in the bitrate that the calculator indicated in the DivX5 config. I'd like to get as much bitrate out of the movie as possible and fill up the CD to the max. Any suggestions?

One more quick question. I'm not sure I understand the Bits/Pixel values - and the resolution slider. I just followed his 'hints' and got it as close to .20 as possible. It seems to me that the lower the resolution slider the higher the Bits/Pixel number is. That seems contrary to what is written in the guide:

"If you go for 1 CD stay close to 0.20
If you go for 2 CDs stay around 0.27"

At ~.27 the resolution is actually smaller than at .20! Am I missing something here?

Sorry about all the questions. I am happy to say that the encoding seemed to work well - the audio and subtitles were in sync! I'm getting closer at least!
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Old 19th March 2002, 15:41   #2  |  Link
jggimi
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Quote:
I can't seem to get the 'autocrop' feature to work.
Install the GKnot upgrade, you need to move from 0.21 to 0.23.
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Also, when using DivX5 in 2-pass mode, I end up with 2 .avi files.
Ignore the first, small file.
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Finally, I can't seem to get the final file size right. My first rip/encode ended up being 650mb - a good deal less than the 700mb I was shooting for.
If you want "accurate" size, use SBC (DivX3) or DivX4 with the DivX4Log add-on tool, or XviD.
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I'm not sure I understand the Bits/Pixel values
It's bits / (pixels * frames) and all three impact the final result. If you're using SBC or DivX4 compression tests, you can ignore the number once the compression test has been run. I understand a DivX5 compression test is also possible ... there's a thread in the DivX5 forum.
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Old 19th March 2002, 16:59   #3  |  Link
ffroms
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quote:
-----------------------------------------------
One more quick question. I'm not sure I understand the Bits/Pixel values - and the resolution slider. I just followed his 'hints' and got it as close to .20 as possible. It seems to me that the lower the resolution slider the higher the Bits/Pixel number is. That seems contrary to what is written in the guide:

"If you go for 1 CD stay close to 0.20
If you go for 2 CDs stay around 0.27"

At ~.27 the resolution is actually smaller than at .20! Am I missing something here?
------------------------------------------------

Bits/(Pixel*Frame) show you how many bits will be used per frame . When you change bitrate you'll see that this number changes too. As you set higher resolution that number will change again , because it will use less bits at that bitrate. This value is needed only to set right resolution so stick to Doom9's numbers.
For 1 CD I use 0.22 and for 2 CDs 0.28 , so if number is higher/lower I just change resolution or if that don't help I change bitrate.

FFS
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Old 19th March 2002, 22:34   #4  |  Link
Buggerlugs
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I`m glad i`m not the only one who`s confused by the bitrate in gordian knot ffrom. I know exactly what you mean about the guide contradicting itself. You should try doing a PAL dvd, its even more complex and the guides pretty unhelpful.

I couldn`t get the crop to work properly either, no matter what I did it looks pre-cropped but when i come to playing back my pityful quality divx later it appears to have encoded the film with the borders.

What minimum resolution should you aim for anyway when encoding an average 1hr 30min film? I know its different for each film but surely theres a ballpark figure.

It amazes me no one has come out with a single application that can rip,crop,encode to specified size and burn to cdr yet. Its the one thing holding back divx from becoming mainstream. At the moment its a mishmash of unstable apps thrown together to achieve a final product which at the end of the day is more trouble than the effort you end up going too.

Is it just me who`d like to see a "working" one application program for divx, because from the tone of Doom9 I get the impression that they prefer the method to stay complex and continue to lurk in the underground. Sadly I don`t think its the way forward.
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Old 19th March 2002, 22:41   #5  |  Link
Asmodian
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@skaven
The first pass avi is just a dummy avi (not sure why it is actually created or at least not deleted at the end) created when the codec compresses the entire movie to determine the best compression ratio to use (and where to put key frames - and bunches of other stuff, I am sure) per frame (or macro block in xvid) based on motion, scene changes and er... stuff
You can just set the first and second pass output file to the same name so first pass avi is overwritten by the second.

The bits/(pixel*frame) is just an approximate quality indicator, the reason one should have it higher for 2CD encodes is because one usually wants better quality when using multiple CD's. Appropriate values for this are very source dependent, I have gotten very good quality (good enough for a 2CD rip if the movie was that long) with a bits/(pixel*frame) value of .17 but that was with xvid and a smoothed anime (ninja cadets) at 640x480 (I have also gotten poor quality with a bits/(pixel*frame) of ~.24 but that was with un-smoothed noisy monty python episodes). I would usually recommend (if you are only willing to try it once ) that you stick to Doom9's or ffroms suggested values.

As for file size accuracy I always set the bitrate at ~25kbps above what gordian knot calculates (as divx 4 but I am using divx 5) for a file size closer to what I wanted.

Hope this clears things up a little skaven.

ps. @ Buggerlugs
I do currently like the way I compress, I like having so much control over way everything is done (I only use G-knot for the resolution/bitrate settings) and I am not sure a one step app would be very easy to get to actually work with all DVD's (with multiple languages, subtitles and such) the variations in DVD's are fairly extreme, and they are designed to be hard to copy. Who are you suggesting write this miracle program? I don't think DivXNetworks wants to make it very easy to copy DVD's, how would they make any money off of that? What do you see as "forward"? I think the money in divx lies in streaming video on the web but I am not really sure...

Last edited by Asmodian; 19th March 2002 at 23:08.
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Old 20th March 2002, 22:33   #6  |  Link
skaven
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Thanks Asmodian! That pretty much answered my questions! My computer is encoding away... should be done by the time I get home from work. Upgrading the GKnot version solved almost ALL of my problems. The 'Autocrop' feature works now, and all of it makes alot more sense. The rip looks good so far, I'm excited to see the final results!

One more question though. Does the encoding process support SMP? I've got a Dual system (1200mhz combined) without a DVDrom drive... if any of this is supported in SMP - it might be worth getting a DVDrom drive for it!


My next project? 2CD DivX5 rip with Dolby Digital!!
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Old 21st March 2002, 04:31   #7  |  Link
Asmodian
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SMP

I have tried using avisynth (with mpeg2dec.dll) to frame serve to virtual dub on a dual P3 600 box, both processors were used but the encode was limited by memory bus speed (neither processor was at 100% - damn shared memory architecture). If you have something better then a single channel of pc100 SDRAM on your dual box it might be useful.
I am not sure if some of the utilities are SMP capable or if my CPUs were both just used by different processes (though their total CPU usage was very similar - obviously doing different things but both ~80%)

Last edited by Asmodian; 21st March 2002 at 04:38.
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