kaching said:
Like I said above. nondescript is trying to compare BRD to HD DVD using a rule of thumb that assumes everything else is constant besides numerical aperture and cover layer thickness.
I think it would be more accurate to say that what
he did was provide a baseline for comparison on top of which other factors could be added as appropriate. Doesn't mean they belong in the baseline formula representing what is absolutely possible with optical media.
Thus he gets nonsensical statements like "BD should theoretically allow 71% more data than HD-DVD, but that is clearly not the case. This may reflect a more conservative design."
I guess I'm not seeing why this is nonsensical since it's basically just a different way of saying what you're saying: theory of what's absolutely possible shows one thing while practical implementation shows another, so there must be other contributing factors.
Separate from this specific statement he has also acknowledged it at least two other times, once before you challenged and once after in response to your challenge.
Thanks kaching. You said it better (and probably more politely) than I could have said it myself. In any case, the problem has been reduced from "DVD forum engineer says I'm clearly missing several things" to "significant digits" and "the specs on BR may have changed."
For anyone who is wondering, this are some of those statements:
nondescript said:
These are (apparently) pretty standard "rule-of-thumb" metrics [...]
I got these equations in the proceedings of a optical storage symposium (forgot the year and title), and the paper was by Phillips. I can`t say I understand it fully (for example, I don`t see why disk flatness tolerance is inversely proportional to the cube of numerical aperture, I think it should only be inversely proportional to the square of numerical aperture), but I understand enough to know what`s going on.
nondescript said:
The system with a thinner cover layer will have better performance, unless there are other factors to counteract it. But the relation between thinner cover layer and data density holds true regardless. And since I haven`t seen any "other factors" published yet (nor have you mentioned any) I can`t make comparisons based on those other factors.
nondescript said:
If he says the percentages are off, fine - these are just rule-of-thumb calculations based on optics only, and were never meant to be precise. However, if there is something fundamentally wrong, I would like to know. I highly doubt he will deny the benefits of a thinner protective layer and higher numerical aperture, but I freely admit that might not be the whole picture.
The "he" in this quote being the uber-engineer that has enough time to tell aaaaa00 that my equations are clearly missing several things, but unfortunately, not enough time to tell exactly what those things are.
Yeah! Well, I read a paper instead, but I'm sure Phillips presenters were just lazy and based the slides off the paper. (Or the paper was a summary of the presentation similar to the link). Like I said, these are rule-of-thumb metrics, so it's not surprising that they would show up in multiple places.
It's like arguing that Car A is faster then Car B because Car A can combust more fuel and air per second than Car B.
Sure in theory that means Car A can extract more power, and thus should be able to accelerate faster and reach a higher top speed... but what if the engine for Car A also weighs twice as much, because the increased forces inside it require the engine components to be stronger?
In theory a car that consumes more gasoline per unit time releases more energy per unit time and generates more power(=energy/time). Sounds pretty reasonable to me. To consider acceleration(=distance/time^2), you obviously need to consider mass, even from a theoretical perspective. Even with a completely theoretical (and very simple) model, you still need to be careful (or, at the very least, dimentionally correct). Try not to equate the equations I posted (which could be off due to other factors not considered in the model) with the car model you proposed (which is fundamentally inconsistent).
Anyways, enough hair-splitting - I understand your point - to make a complete comparison, we need to consider everything - from the DSP algorithms to the chemical composition of the mascara the factory worker was wearing when she walked by the assembly line. My point, which as kaching says, I have stated several times both before and after your objection, is that, espically as outsiders, we cannot know everything, and so we use physical models to provide baseline comparisons, which, while obviously not perfectly accurate, nonetheless provide useful insight.
............heh isn't Samsung co-operating with Sony on TV's... that mistake must'vebeen the Sony funboi in me messing with my mind again 
