DSP: XL2 = 8 bit, DVX = 12 bit

Re: DSP: XL2 = 8 bit, DVX = 12 bit

Slapdragon: Great point
Kidster: I agree

Good news: Someone got back to me quickly!
Bad news: I'll have to dig further (wrong channel, my fault)

Reply...

"Thank you for contacting Canon product support.

Decisions are made by our engineers and product designers in Japan,
based on a number of factors. Consumer demand, technological
limitations, and customer feedback are all taken in to consideration.
Unfortunately, I am unable to provide you with an exact reason why this
particular feature is what it is on the new XL2.

Thank you for choosing Canon.

Sincerely,

Johnny
Product Support Representative

Special Note: Certain issues are very difficult to resolve via e-mail. If your question remains unanswered after you have received this e-mail, the direct assistance of a Canon telephone support representative may be required."

I'll call then. (I'm an info geek)
 
Re: DSP: XL2 = 8 bit, DVX = 12 bit

Dear Johnny,

Unfortunately, certian purchase choices are made elsewhere than in the frontal lobe of my brain.  If your organization wont let the sales guys talk to the engineer guys, my organization wont let my payment guys talk to my camera buying guys.

Thanks for nothing,
A consumer.
 
Re: DSP: XL2 = 8 bit, DVX = 12 bit

Hi all.

This is my first post on this forum, and it just happens to fall well within
my range of knowledge, as I am an engineer (h/w, s/w, f/w and a struggling filmmaker), and do have some knowledge of DSP and microprocessor architectures. Finally, a question I might be able to help with.

In general, a 12-bit DSP can be considered a "better" DSP than an 8-bit DSP if what you are talking about is the "width" of its instructions path, that is, the width in bits of the numbers used to represent its instruction set. I say in general, as in the end, it all boils down to the software that was written to run on the device and how good it is at crunching the incoming digital video data. In many cases, it is possible to write code that performs a set of algorithms well on a DSP or processor of any instruction width, that is to say, that depending on the requirements of the algorithm, one might be able to write code that will run equally well on an 8-bit, 12-bit, 16 bit, or 32-bit architecture. In those cases, the additional instruction width doesn't gain you much. The algorithm being implemented just doesn't need to make use of the extra bits.

So, why the additional bits? Often times it boils down to running those instructions more quickly, by packing more information into each instruction. At other times, having the additional bits means that you can have access to additional instructions to implement algorithms that would be prohibitively difficult to manage in a smaller architecture. I would venture, that the engineers at Canon decided that they could get all they're algorithmic processing needs met at an acceptable level with a smaller, cheaper architecture, and thus spend the engineering dollars on something that would have a greater marketing impact like a better, more expensive lens. Usually, there is a trade-off with speed, and power, and heat dissipation in this kind of decision as well. But you can rest assured, that if the engineers didn't feel that their s/w could run effectively on a smaller DSP, they would have argued for a bigger, "better" one.

As for the anecdotal evidence that a bigger DSP means a better picture, that isn't always the case. Again, it boils down to the software -- what you do in code with that extra instruction width. With a bigger DSP you might be able to write a finer, faster piece of code that implements a better imaging algorithm, and therefore, get a better picture, but you could also just take the same code that ran well on a lesser DSP, and find that it now just runs a little bit faster. Again, it depends on the algorithm being implemented, and the constraints of that algorithm.

More important than the DSP alone, is the width of the Analog-to-Digital Convertor, and the complexity of the algorithms you want to use. A wider ADC bus generally means more accurate sampling, and better dynamic range. Coupled with efficient visual processing algorithms, and you can get a pretty nice picture, processed quickly.

All things then considered, the DVX is an extraordinary piece of hardware, and I would venture, so is the new Canon.

Just my $.02.

-Omar Green
 
Re: DSP: XL2 = 8 bit, DVX = 12 bit

Hi Auteur0,

12 bits means nothing if you don't precise 12 bits of what...

It could be the address bus, the size of registers or even the size to code the instructions.

For example, the good old motorola 68000 had a 24 bit adress, 32 bits registers and a 16 bit alu and data bus.

---

btw, keep on struggling for film making...
 
Re: DSP: XL2 = 8 bit, DVX = 12 bit

Agreed.

that's exactly what I meant, and why I limited myself to talking about instruction width, and data bus width. Because we're talking about an embedded DSP, post 2K, chances are the engineers at Canon aren't describing the address bus width -- memory is pretty cheap these days.

Even though in general, the marketing departments of electronics firms like to confuse people (to sell more products), 12-bits of anything doesn't mean much, even after it's specified. What they should really be talking about is which DSP algorithms they've implemented, what the dynamic range of the ADC is, and what they're doing to eliminate noise.

They might also want to specify how much of the data captured from the CCD is really used in the algorithms. Anything less than that is just marketing fodder -- no disrespect to marketing folks, I'm soon to be one myself (in my day job).

BTW -- thanks for the encouragement. I did the starving artist thing in NYC for 4 years after 10 years in Engineering, only to leave that town with a manager, a couple of short films, and a couple of semi-successful rewrite jobs. Been in the Boston area for 18 months writing code, and now I'm off to Cambridge in the UK for 2 years. Better film center there than in Boston, and I'll finally be able to crew up like I want and shoot some off-kilter stuff with my DVX.

Any UK folks on this forum?

-Omar
 
Re: DSP: XL2 = 8 bit, DVX = 12 bit

Shane Carruth was a software engineer before he said STOP.

He wrote his screenplay, shoot it (s16 color) and sent it to Sundance. He won.

Of course, things as not as simple as just saying : He sent it...

There is a lot of work, talent, a strong will behind his success.

But, this is a message of hope for all people trying to escape from
real world to live with an for their passion.

:)
 
Re: DSP: XL2 = 8 bit, DVX = 12 bit

as long as we're talking about bits not meaning much unless they're in a very specific context, I'd like to point out that the Atari Jaguar was the first 64 bit console, and had two processors. It also had crappy games, weird color problems, and I'm pretty sure the people who made the games and the people who made the hardware weren't on speaking terms.

that said, I own two, and about 20 games... sigh... classic gaming junky.
 
Re: DSP: XL2 = 8 bit, DVX = 12 bit

Just to be clear, maybe simplify:

I assume that 12-bit DSP implies 12-bit sampling.

Gamma curves map CCD-sampled intensity levels to 8-bit DV intensity levels.

With selectable Gamma curves, there's much more flexibility and accuracy if you are downsampling from 12 bits than if you are distorting 8 bit samples.

Somewhere someone posted pictures comparing gamma curves on DXV100P vs. A... this clearly showed the differences in both highlight and shadow detail, which is what you'd expect from the 4-fold DSP resolution jump. Some of this may have to do with soft knees, too, but the pictures are compelling.
 
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