ISO vs PXI

vbimport

#1

Was just wondering if anyone knows: is there some kind of advantage that PlexTools’ pxi [image] format has over iso (the only other choice in PT)? If they both can hold all the same data… then… ugh… why does every program have to make up a new proprietary format… Bleh.

Okay okay. I shall simmuh den 'n prepare to receive enlightenment.


#2

Anyone? Anyone at all?


#3

Ew. Just realized that iso can only be used for data discs. Interesting. Yeah well.

Sure would be cool if the Alcohol peeps could add support for the pxi format…


#4

Hi,

ISO is the first appearing “file-embedded description” of CD contents.

ISO and PXI (and also other cdrom image files) have some common caracteristics: they contains file names (for plain files and directories), file dates, some others properties (depending on what extension is used (rockridge, joliet, romeo, …)) and of course file data.
Thus they can be burned :slight_smile: or mounted just like regular hard-drives.

A sector on a CD contains 2448 bytes divided into 3 parts:

  1. 2048 bytes for plain data.
  2. 304 bytes for EDC/ECC (error detection/correction),
    which is redundant with 1) (that’s the goal for detecting and correcting some errors not catch during some hardware-level stages (known as C1/C2 errors))
  3. 96 bytes for subchannels (CD-Text, …).

ISO stores only the first part (2048 bytes of data),
so ISO isn’t suitable for usages where others parts are taken into account or used in a different manner, for instance:

  • CD Audio (only audio), Mixed-CD (data+audio), CD-Extra (audio+data) (notice the order), (Super)Video-CD, CD-I, (others ?)
    which use the EDC/ECC part for storing audio or data,
  • some protections which rely on EDC/ECC part which aren’t corresponding to the related plain data part,
  • CD-Text or CD-G (quite useless without audio anyway :slight_smile: ),
  • some other protections which rely on subchannel part,
  • … .

To overcome those limitations, all the copy-CD software (some are although mastering-CD Soft too) have introduced their own format (the vast majority can deal with ISO as well):
PXI for PlexTools, CUE/BIN for CDRWin, CDJ for Discjuggler, CCD/BIN/SUB for CloneCD, BWx for BlindSuite, MDS/BIN/SUB for
Alcohol, NRG for Nero, …

Of course as this isn’t complex enough, you might encounter some other extensions (RAW = BIN, …) or some variants (ISO storing EDC/ECC thus acting like BIN/RAW files, …).

In addition, some file formats are able to store all the sessions, some only the first, some take hybrid CD (MAC and PC data).
I don’t know for sure how qualify ISO and PXI for that.

To re-focus on your question, PXI is able to store data, EDC/ECC and CD-Text, CD-G i.e. some subchannels but I’m not sure if all subchannels are taken into account (there are 8 subchannels named from P to W)).
You can easily notice it. A simple way to do this is making an image out of a CD and doing some maths.

75 sectors are read/burned per second at x1.
75 sectors * 2048 bytes (for data) = 150 ko (1 ko = 1024 bytes !)
75 sectors * 2352 bytes (for audio) = 176400 bytes
(176400 = 44100 Hz * 2 (16 bits) * 2 (stereo))
(2352 = 2048 (plain data) + 304 (EDC/ECC))
Those numbers may ring some bells :slight_smile:

So imagine you make an image of a 74 min 00s CD.
For an ISO, the resulting image size should be near 7460752048 = 681984000 bytes ~ 650 Mb (1 048 576 bytes)
For a BIN (data + EDC/ECC), size near 74
60752352 = 783216000 bytes.
For a PXI (data + EDC/ECC + 96 bytes of subchannel), 746075*2448 = 815184000 bytes.
Some softwares only take the first subchannels (16 bytes instead of the full 96 bytes), PXI may be in this case.
In addition, some file formats store additional information into the image, so there is small “size-overheat”.
The bigger the CD is, the more accurate the calculations are.

Reversing the process may interest you as well.
So you have a data CD with (hum) some files totalizing 521 548 654 bytes (manual random :)), this leads to those results:
521548654/75/2048 (remember: data) ~ 3337 s = 55 min 37 s
ISO size near 512548654 bytes (the actual sum of all file sizes) (plus somewhat 1 Mb, somewhat 10 Mb).
BIN/RAW size near 512548654/20482352 ~ 588 630 095 bytes (quite bigger).
PXI (I assume 96 bytes subchannel) size near 512548654/2048
2448 ~ 612 655 813 bytes (even bigger)
(sorry if this was trivial or borring (or both), I just wanted to make it as clear as possible).

PXI isn’t widely supported. In fact, only PlexTools and ISOBuster which had recently added support for it, know it.
Although PXI is able to store some info for dealing with protections, PlexTools isn’t envisaged to duplicate copy-protected CD, so results aren’t guaranted at all.

All these considerations could lead you to other questions so don’t hesitate, use the search function (first) and post questions not already answered.

Have nice imaging and calculations :slight_smile:


#5

Very detailed info MiRV! Thanks!


#6

Yeah… appreciate the response. Definitely some nice details der… shall file away for safekeeping. :smiley: