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[_phil_]

Isn't 12xdvd data transfer faster than 2xbr?

a 12x dvd is 12x at max ,and around 5 at min.When you stream ,you do it based on the lower speed.

 

[Arwin]

a 12x dvd is 12x at max ,and around 5 at min.When you stream ,you do it based on the lower speed.

5? I thought more like 8x (at least in the Xbox), i.e. similar transfer rates to BluRay 2x.

 

[TheChefO]

a 12x dvd is 12x at max ,and around 5 at min.When you stream ,you do it based on the lower speed.

Gotcha - so: br streaming @1-1.5x?

 

[_phil_]

BD is said 2x constant.
X360's is a CAV. DATA transfers varies more than double between edge and center.

 

[London Geezer]

BD is said 2x constant.

As explained by yours truly many times, Bluray drives can arbitrarily choose whether to use CLV or CAV at any one time, depending on what would be faster for the task data they need to get from the disc. All Bluray drives are both CAV and CLV and they can switch at any one time depending on the situation.





(*Waits for the kids to ask what CAV and CLV are*)

 

[sonyps35]

The real question though is which is straight up faster in say, an average gaming loading/streaming scenario, 12 DVD or 2X Blu-Ray. We understand the 12X DVD has greater peak speed, while Blu-Ray is said to have certain advantages to overcome this.

My bet is on the 12X DVD though. I'd like to see a real scientific comparison instead of innuendo though.

 

[_phil_]

edit : x360's peek is 15.Lowest should be around 7,rather

 

[London Geezer]

The real question though is which is straight up faster in say, an average gaming loading/streaming scenario, 12 DVD or 2X Blu-Ray. We understand the 12X DVD has greater peak speed, while Blu-Ray is said to have certain advantages to overcome this.

My bet is on the 12X DVD though. I'd like to see a real scientific comparison instead of innuendo though.

As has been explained lots of times, 12x DVD is faster than 2X Bluray, but the problem is that the DVD drive will only reach the full 12x speed in the outer tracks of the disc, whereas on Bluray that's constant when it needs to be, and variable when it needs to be.

 

[TheChefO]

As has been explained lots of times, 12x DVD is faster than 2X Bluray, but the problem is that the DVD drive will only reach the full 12x speed in the outer tracks of the disc, whereas on Bluray that's constant when it needs to be, and variable when it needs to be.

Got it - thanks for clearing that up. So then in streaming applications 2xbr is how much faster than 12x dvd?

 

[Shifty Geezer]

As has been explained lots of times, 12x DVD is faster than 2X Bluray, but the problem is that the DVD drive will only reach the full 12x speed in the outer tracks of the disc, whereas on Bluray that's constant when it needs to be, and variable when it needs to be.

Um, I'm not quite getting this. CLV slows down the disc speed towards the outer edge to match the transfer rate of the inside tracks. If your inside track can manage (pie in the sky figures) 20 MB/s @ 5000 RPM, in CLV you'd slow down the motor so you're reading 20 MB/s at maybe 2500 RPM on the outside, right? But then if you kept the 5000 RPM with CAV, you'd be getting 40 GB/s towards the outside edge. Thus when it comes to varying between CAV and CLV, CAV gives the same minimum transfer rate but higher maximum, no? At which point why bother slowing down the drive for CLV?

 

[London Geezer]

Um, I'm not quite getting this. CLV slows down the disc speed towards the outer edge to match the transfer rate of the inside tracks. If your inside track can manage (pie in the sky figures) 20 MB/s @ 5000 RPM, in CLV you'd slow down the motor so you're reading 20 MB/s at maybe 2500 RPM on the outside, right? But then if you kept the 5000 RPM with CAV, you'd be getting 40 GB/s towards the outside edge. Thus when it comes to varying between CAV and CLV, CAV gives the same minimum transfer rate but higher maximum, no? At which point why bother slowing down the drive for CLV?

there...

Automatic CAV/CLV selection:
"Professional Disc for DATA" drives support both CAV (constant angular velocity) and CLV (constant linear velocity) transfer modes when reading and writing data. In CAV mode the disc rotates at a constant speed, meaning that the transfer rate slows as the pickup approaches the center of the disc, but seek operations are fast (110ms average). In CLV mode the speed of the pickup is constant, so although seek operations take longer, the maximum transfer rate of 11MB/s is maintained at all times. The drive firmware automatically selects the Optimum mode to ensure the best overall performance. For example, if accessing a series of relatively small text files, CAV is used for fast seek times, but when reading large music or video files, CLV is employed to ensure the maximum transfer rate. The factory setting ensures that the drive automatically selects the optimum transfer mode. But if necessary the user can select the transfer mode: DIP switches allow selection of either CAV or Optimum mode, while any one of the three modes (CAV, CLV or Optimum) can be specified by a mode select command.*

In the end it's all about seek times... Oh and i think you got CAV and CLV mixed up...

 

[Shifty Geezer]

In the end it's all about seek times... Oh and i think you got CAV and CLV mixed up...

Muchas gracias. And I haven't got the terms mixed up. If I have, it's not me that's mixed up but the people who coined the terms

 

[Powderkeg]

As has been explained lots of times, 12x DVD is faster than 2X Bluray, but the problem is that the DVD drive will only reach the full 12x speed in the outer tracks of the disc, whereas on Bluray that's constant when it needs to be, and variable when it needs to be.

You are sort of neglecting to mention that a 12X DVD MINIMUM speed is about the same as 2X Bluray constant, aren't you?

2X Bluray read speed = 8MBps
12X DVD read speed = 8.2-16.5 MBps

 

[London Geezer]

You are sort of neglecting to mention that a 12X DVD MINIMUM speed is about the same as 2X Bluray constant, aren't you?

2X Bluray read speed = 8MBps
12X DVD read speed = 8.2-16.5 MBps

I said that when the DVD drive actually reaches 12X, it is always faster than 2X Bluray, unless i got my numbers wrong... I'm just not sure what the minimum speed of the DVD drive is, that's why i never mentioned it.

 

[Robert.L]

2X blu ray is 8.58 megabytes

 

[_phil_]

You are sort of neglecting to mention that a 12X DVD MINIMUM speed is about the same as 2X Bluray constant, aren't you?

2X Bluray read speed = 8MBps
12X DVD read speed = 8.2-16.5 MBps

x360 12x dvd read spead 7 -15 mbs.Not exactly sure on the lowest speed ,but the hight figure is acurate.

 

[scooby_dooby]

So anytime the BR drive is accessing a "series of relatively small text files" it actually runs in CAV mode just like 360's DVD drive, meaning read speeds lower than 2x?

Very interesting, so the BR drive is not infact a 2x CLV drive as many have argued, but alot of the time will in fact run in CAV mode with throughput considerably less than the peak 9MB/s.

What would be very interesting to find out is the actual difference in seek times between CAV and CLV, anyone know? I wonder how big the difference is.

 

[Titanio]

So anytime the BR drive is accessing a "series of relatively small text files" it actually runs in CAV mode just like 360's DVD drive, meaning read speeds lower than 2x?

Very interesting, so the BR drive is not infact a 2x CLV drive as many have argued, but alot of the time will in fact run in CAV mode with throughput considerably less than the peak 9MB/s.

Where are you getting that from?

If it's CLV, then it'd be a constant 9MB/s. If it's CAV, 9MB/s is either the peak or the minimum. I believe it's supposed to be CLV though.

 

[scooby_dooby]

Where are you getting that from?

If it's CLV, then it'd be a constant 9MB/s. If it's CAV, 9MB/s is either the peak or the minimum. I believe it's supposed to be CLV though.

LB's quote. And I'm assuming 72mbps is the peak for a 2xBR drive, is it not?

 

[Titanio]

LB's quote. And I'm assuming 72mbps is the peak for a 2xBR drive, is it not?

Sorry, I see that now, but that says it can be either - 9MB/s constant, or a varying rate to improve seeks.

Then again, that quote refers to the "Professional Disc for DATA" range from Sony, which I think is based on Blu-ray, but it doesn't seem clear to me that the exact same thing will apply for regular Blu-ray drives. That comment also refers to a max CLV rate of 11MB/s, not 9, so I'm not sure if it's all the same?