UDF or ISO? Is one "better"?

Very good topic. I’m going to burn a few identical dvds with a bunch of tv episodes. One with ISO, other with UDF, and the 3rd with ISO+UDF system. I will report on their size and more important on compatibility, in my case with Philips DVP 642.

OK here are the results.
I used ImgBurn2.1.0.0. in build mode to record 15 video files: 14 avi and one mpg.
The sizes of the discs (checked as well after burn):

UDF1.02: I 11:17:35 Image File Size: 2,807,496,704 bytes

ISO:9660: I 11:24:06 Image Size: 2,806,972,416 bytes

ISO+UDF: I 11:35:59 Image Size: 2,807,496,704 bytes

As you can see, aprox 0.5 MB difference

there are no typos here as udf and iso+udf turned out to be identical.
All 3 discs played fine but the ISO had file names screwed up as well as their order.

I didnt use any directory structure. So it is not now clear to me why one should use ISO+UDF over UDF. Does ISO part provide for better PC compatibility?

Almost forgot. Recognition times in Philips (from the moment ‘close’ is pressed)

UDF - 16 sec
UDF+ISO - 16sec
ISO - 12 sec


Yes, better backwards compatibility. :wink:

Thanks chef . Udf1.02 works fine under wXP. Perhaps things are different in DOS…

I believe some operating systems (such as windows/DOS predating XP) can not read UDF formatted discs (it is possible there is third party software), which is why UDF+ISO is a better choice.

FidelC, even different in 16-bit windoozes, eg. w9x.

astonished by [B]taylormade[/B]!!! only registered in the site to post one great answer :)!!!
thanx taylor :slight_smile:

still hoping for UDF 2.60 support, and hoping for a WINXP patch that contains all the fixes and includes UDF 2.60 support and MountRainier or Packet Writing native support… we deserve a SP3!!!

and as i can still see… Vista still sucks!!!

i might be sticking to UDF or ISO+UDF and a linux for future compatibility…

THX for this thread - great reading!! I see nothing “lame” in the original question ;), quite the contrary i think a lot of users which aren´t so familiar yet with the whole burning stuff, might have asked themselves more than one time what the difference is. But out of habit and thx to the “time-saving-automatic-software” they have always clicked the big red button “BURN, BABY BURN - DON´T THINK, DON´T ASK - JUST BURN” :bigsmile:
P.S.: Could be me, too :wink:

Was the ISO burn ROM Form1 or Form2? And which UDF version was the UDF burn?

UDF1.02 - you already quoted it.

:eek: :o

thanks, that was totally stupid… :doh:

Is there any useful redundancy provided by creating a UDF+ISO hybrid?

For example, the disc becomes damaged and the UDF TOC becomes trashed, but the ISO one is still readable, thus allowing the discs contents to be saved. Is this type of situation a realistic possibility?

I think probably not.

Your example is theoretically possible, but the TOC is such a small part of the disc that you’re very unlikely to damage only the UDF (or ISO 9660) TOC and not any part of the data or the rest of the TOC.

But it could happen.

Compatibility with as many operating systems as possible is the major reason for choosing a UDF+ISO hybrid.

Seriously… I read through the messages here and NO-ONE seems to know ANYTHING about what they’re talking about. Some of the babbling nonsense it just laughable.

Okay… let’s get some things crystal clear for people. Firstly, people NEED to understand that an .iso file has nothing and I mean NOTHING to do with whether it contains ISO or UDF structures. So given any .iso file, you cannot tell, unless you know what you’re looking for, whether it contains a ISO, UDF or both filing systems. (And mixing ISO and UDF, which some of the people above are calling “Hybrid” is technically incorrect. It’s actually part of a standard and isn’t some hybridized thing)

Next, let’s talk filing systems that your CD/DVD .iso file can contain. The most basic of them being ISO 9660. The inherent problem with ISO9660 is that it limits filenames to 8 characters, plus 3 additional ones for an extension, rather like MS-DOS did. It also limits the characters in those filenames to be uppercase characters only and has a distinct limit on how long a path can be, (so deep directories are not allowed). Having an ISO9660 fully compliant filing system also means that these character set restrictions apply to the Volume Name and other info format fields. If you write a CD/DVD that is ISO9660 compliant and contains long filenames, they will be converted to uppercase and have their filenames truncated like this… HelloWorld.txt becomes HELLOWOR~1.TXT

Now the ISO filing system format can have its restrictions relaxed and allow the use of lowercase filenames and long filenames and this relaxation is called Joliet. Due to the way the TOC (Table Of Contents) is identified, it actually is possible to have long filenames without Joliet, but this can lead to all sorts of problems. So, for the sake of this explanation, long filenames and lowercase characters I’m going to assume are Joliet. The one thing that Joliet doesn’t allow is Unicode, as it limits the character set to 110 characters. Another huge issue is that ISO9660/Joliet doesn’t support file sizes greater than 4GB.

Then there came UDF, which again is filing system and therefore is also stored in an .iso file format. What is different about UDF is that it supports Unicode, large directory depth and removed many of the restrictions imposed by ISO9660 and Joliet, especially the file size restriction. The problem for UDF was how to keep compatibility with older systems that don’t understand UDF. So how does this work? Well, UDF has it’s own TOC with it’s own format, BUT a CD/DVD can also be written with a ISO9660/Joliet TOC as well. You can therefore make a CD/DVD as a ISO9660 only, ISO9660/Joilet, UDF only or ISO9660/Joilet/UDF. If your operating system supports UDF, it will use that TOC as opposed to the ISO9660/Joliet TOC and if it doesn’t support UDF, then it will use the ISO9660/Joliet TOC and completely disregard the UDF TOC.

Now someone above suggested that if you damaged the UDF TOC, then the ISO9660/Joliet TOC could be used as a backup… Well unfortunately, that’s not how the operating system works! Firstly, the TOC is miniscule portion of the CD/DVD layout and the ISO9660/UDF TOC’s are adjacent so the chance of damaging one without the other, is extremely remote. Secondly, if the .iso image contains a UDF TOC, it will use that one, irrespective of whether the ISO9660 one is present, even if it is undamaged.

The important thing to understand here is that you can have multiple filing systems on a CD/DVD and your operating system will pick one that it supports and use that. These filing systems are actually identified by a “magic number” that defines how the TOC is formatted. Another important things to understand is that by filing system, I do NOT mean that the data is stored any differently, it’s NOT. The TOC’s are different, the data placement MAY be different (too complex to explain why this is), but usually it is not, but the data is exactly the same. So depending on the Mode the CD/DVD is written as, the data is exactly the same.

I also saw someone saying the wrote UDF disc because pressed DVD’s are UDF etc etc. This isn’t true at all. In actual fact, most DVD’s are ISO9660/UDF in format, especially films. You can actually see this yourself if you look at the contents of the DVD. You’ll notice that VIDEO_TS and all of the .VOB files are uppercase and 8 characters long and don’t exceed the maximum 4GB limit. (Although as I’ve explained, just because the filenames are ISO9660 compliant, doesn’t mean the DVD isn’t still UDF only)

Now if you’re making your own .iso images the best and most compatible way to create a ISO9660/UDF disk. This will mean your image will be compatible with just about any system. You will have to ensure that the files you include in your image do not exceed 4GB and use short uppercase filenames, but that’s the price you pay for compatibility. If you need files larger than 4GB, you’re limited to the UDF filing system only.

Since someone mentioned “Hybrid” images, in actual fact, the CD/DVD format does actually support Hybrid images where you have two completely separate filing systems that have differing files and different TOC’s. That’s how HFS+ CD/DVD’s work, that contain an Apple Mac filing system and an ISO9660 one, but that’s beyond the scope of this explanation. Hope everyone learned something…?