Re: DVD-Video compatibility

Hi Roadkill,

I don't know much about this, frankly. But I think that you're correct that a lot of players won't read the flag. For sure, the older players won't know what DVD-R is, as this book wasn't specified until over a year after the first players shipped. That's why the bit setting on the +R format works so dramatically; but that's for the lead-in, which all players must read.

The Spec says:

"VOBU_IDP_ID -
Adapted Disc Type: Describes the type of a disc to which this Part 3: VIDEO SPECIFICATIONS is adapted"

It goes on to describe "identifiers" in the main VMG IFO files and in the Navigation Packs in the VOB, that are supposedly there to tell the player what kind of platter is playing in it.

Since I replied to you, I checked a DVD Studio Pro written DVD-R in TFDVDEdit 1.0 (our first version of the app was like IFOEdit, showing all the gory details) and it did not set this field to identify the disc as a recordable. I don't know if any other app does.

My theory now (uh, oh :-), is that since DVD-R first came out with a 3.95 disc size, which has the same data holding pit length and width (and data capacity) as one of the layers on a dual layer disc, and the two also have the same reflectivity rating, that a flag was introduced in the spec to compensate for the smaller pit and larger data size DVD R General disc, when it was introducted later, and to tell the player...to slow down it's spin!

Right now (with the current level of our DVD spec knowledge) we have to lower the bit rate because of the smaller data pit sizes on DVD-+R (4.7GB), because it's harder for the player to pull data off the platter with smaller data pit sizes (to jump from a capacity of 3.95G to 4.7G over the same surface area) with the less reflective DVD recordable disc (both + and - R).

What leads me to this conclusion, is if you check the specs for DVD-R, it has the same "channel bandwidth" capacity (ability to be read by the player) as a more reflective replicated DVD-ROM! But we know in the real world, that the lower the bit rate, generally the higher the percentage of compatibility is had. So I couldn't figure out for the longest time what was up; why didn't the specs of the DVD-Recordables state this reality; the need for lower bit rates on them?

So unless Pioneer and the gang is pulling another fast one on us, these identifiers must slow down the velocity of the rotation of DVD-recordable in the newer players, just a tad; to make it easier for the player to read the data of the more data compacted, LESS REFLECTIVE, recordable with 4.7 G of data (not a problem getting data off the same data pit size of the ultra reflective replicated disc).

My next experiment after we get '3 out of beta, is to write a +R disc with the compatibilty bit set (that will get playback started on the older players), still with a moderate bit rate (keep compatibilty with older players)...and to flag the DVD +R disc as a DVD-Recordable; this might be the margin that makes some borderline players compatible!

We'll see, huh? (the risk of a blown beaker on this one doesn't dissuade me one bit :-),

Take care,

Trai