CD-ROM-XA (Bridge)
12 messages in this thread
Your explanation of CD-XA was in line with what I have always heard, but
somehow I am still confused about why then a CD-ROM XA player can't play a CD-I
disk. Any explanation of that would be most appreciated. Thanks.
Peter
There are anumber of subtle differences between CD-I format and
CD-ROM XA format:
1. The first track (Track 0) of any Compact Disc contains a table
of contents. This table lists all the tracks on the disc. On a
CD-I disc, the data tracks are omitted from the table of contents. This can
prevent a CD-ROM XA player from being able to read the data
tracks of a CD-I disc.
2. The table of contents also contains a flag that says whether a disc is an
ordinary CD (CD-DA or CD-ROM), a CD-I disc, or an CD-ROM XA disc. A CD-ROM XA
drive can check this flag and refuse to play a CD-I disc.
3. The directory tree of a CD-ROM XA disc is stored in an ISO 9660 compatible
format. The directory tree of a CD-I disc uses a mutated
version of ISO 9660 that breaks some of the ISO rules. This can
prevent an XA compatible driver from reading a CD-I disc.
4. The CD-I format defines an additional audio file format that CD-ROM XA
drives are not required to support.
That's all I can think of off the top of my head. There may be others.
Matt,
How about the whole issue of CD-I Graphics, DYUV, 555, CLUT 4,7, and 8. just
for formats of graphics.
Then there is the problem of Multiple overlayable and transparent graphics
planes in different formats.
Then there is the whole issue of the Line and field special effects table.
At one point I thought I knew how a lot of it could be done, but then got to
thinking about what the Philips and Sony lawyers might have to say about doing
it !
Glen Chapman
You're absolutely right. CD-I graphics format is from different from XA
graphics format.
Matt,
Was there ever a real XA graphics format? I thought its was sort of "heres a
sector type, put stuff in it, and good luck when it comes off the disc.
Glen
Glen:
And they accuse publishers of putting out "shovelware?" Seems to me Philips et
al have been shovelling a bit for quite a while! International standard,
right!
Best – Rich
<<International standard, right! >>
Right, just like flying a flag upside down and sending . . . – – – . . . in
morse code!
Glen
There are specific video formats defined within the sub header. 8 bit CLUT
640*480 and 320*200 etc. There is also a user defined bit if the user wants to
do his own thing.
These are all in the Yellow book ISO 9660 extension.
<Entering Nit Pick mode>
I think your reference to the CD-ROM XA spec as "the Yellow book ISO 9660
extension" may confuse people into thinking XA is the one and only Yellow Book
and ISO 9660 extension. While CD-ROM XA is an extension to both the Yellow
Book and the ISO 9660 spec., there are many others. XA is simply one Yellow
Book and ISO 9660 extension.
As long as picking nits, the term Yellow Book is really obsolete. The Yellow
Book was Philips's and Sony's original proprietary proposal for a CD-ROM
format. It is superseded by the newer international CD-ROM standard, ISO/IEC
10149. Yellow Book is sort of like the High Sierra directory format: the
original draft proposal by the industry leaders. ISO/IEC 10149 is like ISO
9660; it's the final, open, international standard. However, ISO/IEC 10149 is
much closer to the draft Yellow Book standard than ISO 9660 is to the draft
High Sierra standard.
Early draft versions of the XA spec. did not define a video data format. The
current May 1991 version does include a graphics standard.
Matt,
Is this still the raw bit stream that Sandy mentioned, or has something
worthwhile been added?
Partial apologizes to Sandy and others, some of my last few comments have been
in jest. A "REAL" XA would be superb, especially the audio. If SONY would
have completed it, and the XA spec had encompassed a more comprehensive
graphics set, like the Green Book did, we would have something worth using.
Since I seem to be in semi-FLAME mode tonight, Why does Phillips and Sony let
the XA name/logo, whatever, be associated with what vendors today are calling
XA compatable. To me XA compatable should imply an ADPCM decoder somewhere in
the data path, and the hardware level flags to triage a CD Data stream. Kodak
will/may be real XA some day, but excluding multi-session stuff, they are still
doing 2048 reads via the normal IOCTL interface.
FLAME OUT..
Glen Chapman
Yep, this is the CLUT bitmap bitstream. None of the fancy video effects of
CD-I.