Video file sizes

thegoat · Member Joined: 05 Oct 2006 Location: Australia

HI,

I am trying to create a DVD with four different videos, and create a menu to point to each file. The files are around 900mb each, so I should be able to fit at least 4 on each DVD right? The problem is, when I start import the files into my authoring software it seems to only say I can fit 2 files on there.

any ideas why this would be?

Thanks for any help!

guns1inger · Member Joined: 01 Apr 2004 Location: Miskatonic U

Because you don't know what you are doing. The basics : video is compressed by different methods. Each have their strengths and weaknesses, and each compress by different amounts.

AVI is a container format. The contents are compressed by different codecs. The most common at the moment are Xvid and Divx, but there are many different types. Xvid/Divx are part of the mpeg4 family.

DVD requires that it's video be compressed using mpeg compression technology. Specifically mpeg2 for full resolution, although mpeg1 is compliant under certain conditions. (See What is DVD - top left corner - for more details).

Mpeg2 does not compress as much as mpeg4. As a general rule, when converting xvid/Divx to DVD you need to use a bit rate 3 -4 times higher to hold the same quality.

The amount of space a video takes up is equal to the bitrate x running time. Bitrate calculators do the math for you and make it easy to see how much you can fit where. Bitrate also influences quality. Generally, the lower the bitrate, the lower the quality. Down to a point this may not matter, but after that it matters a lot.

Now to your case :

Unless the movies you have already mpeg2 they will have to be re-encoded. If this is the case, the 900MB means absolutely nothing. The true size will be given by running time x bitrate. So get a bitrate calculator and start working it out. You can get a good 2 hours on a single layer disc. You can get 3 hours at a lower quality. Below that you need to start reducing resolution.

You don't say what your authoiring program is, but it sound like a simplistic one which does everything for you but gives you no options to play with yourself. If this is the case, then you are stuck with 2 movies.

However, even if you had better software, chances are you would have to go to VCD (read sub-VHS quality) to get all four on a disc.
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thegoat · Member Joined: 05 Oct 2006 Location: Australia

HI Gunslinger.

Thanks for the reply. Files have already been re-encoded from xvid/divx to mpeg2. Does this still mean I can only fit around 2 files on a disc?

What confuses me, is, I thought adding a menu was just that - adding a menu. I'm assuming the dvd authoring software does something else to the files, as normally I would be able to at least 4 900mb files on a dvd if I burnt them straight to dvd.

Thanks for any help!

guns1inger · Member Joined: 01 Apr 2004 Location: Miskatonic U

Which is why I asked about the authoring program you used.

Also, being mpeg2 does not make them compliant. Again, read What is DVD (top left corner).

If your files do not meet the requirements for compliance, they will be re-encoded.

If you use a rubbish tool like NeroVision or WinAVI, or even Adobe Encore 1.x, your files will get re-encoded, even if they are compliant.

So :
How did you encode them ?
To what specification did you encode them ?
What is your authoring tool ?
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thegoat · Member Joined: 05 Oct 2006 Location: Australia

guns1inger · Member Joined: 01 Apr 2004 Location: Miskatonic U

WinAVI is a poor quality tool known for out-putting non-compliant material. You can use g-spot to verify if it have given you something DVD compliant.

I believe that DVDit PE6 also has a habit of re-encoding compliant material, so even if WinAVI has given you something useful, DVDit will encode again.

Good authoring software doe not need to have a built in encoder, as you should prepare your assets before authoring. Most authoring tools that have their own encoders tend to wield them very badly.
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thegoat · Member Joined: 05 Oct 2006 Location: Australia

HI Gunslinger,

Can you recommend any good encoding/authoring tool/s?

thanks,

guns1inger · Member Joined: 01 Apr 2004 Location: Miskatonic U

ProCoder Express for encoding, Tmpgenc DVD Author for authoring, if you want something simple.

If you want to do it for free, HCenc (although you will need avisynth and FitCD for this), and GuiforDVDAuthor.
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bassualdo · Member Joined: 08 Nov 2009 Location: Brazil

very good topic! thanks!