Getting supported Read/write speeds

Hi all!

I’m now working on extracting device information, in this case, the read/write speeds supported by the drive.

Reading MMC commands, y supose that i have to use the GET_PERFORMANCE command with “type field” = 0x03 (Write speeds), and, like MMC says…

“This command reports a list of possible Write Speed descriptors. If recordable media is mounted, logical unit shall report the list of speeds that are available for the Blocks of the current mounted medium. If no recordable media is mounted, logical unit shall report the most appropriate list of speeds such as the list for CD-R media or just maximum recording
speed. Logical unit shall report Write Speed descriptors in descending order…”

ok, now, i send the command with a CD-RW, and I get two speed descriptors (each speed descriptor is a pair of read/write speed):
1- write speed = 2X || read speed = 2X
2- write speed = 4x || write speed = 4X
that is more or less a normal result (read speeds… :S)

but if i test with a normal recorded cd (cd-r, cdrom…) i get 8 speed descriptors all with the same values
– write speed = 24X || read speed = 24X (that is the maximun write speed of my drive)
Is this normal??

So, how can i get ALL the supported read/write speeds in a drive?? i’m getting crazy :P.

Thanks for advance!!

PD: I dont want to use the Page 2A information, becouse it’s deprecated and the write speeds information is erroneous in the last dvd recorders.

I had the same problem a while back. I couldn’t find a way around it, so just displayed those values you mentioned. Not much help I know, but it might prevent you going any more crazy!

Ok, i was seening how nero do it.

So, i think it do this: Send a SET_CD_SPEED command, with a write speed value, and then request page 2A (with MODE_SENSE) to see what is the current write speed. This proccess is repeated with all posible write speeds :eek: .The result: too much SET_CD_SPEED and MODE_SENSE commands sended. Is it real?? anybody can confirm this??

Ok, suppose that this method is the correct…or at least the most compatible. We have now all the possible write speeds for this drive. But, what about read speeds??

Arg! i’ll continue looking for it…

Ok, the problem is solved. In the MMC-1, the page 2Ah shows fields (like current write speed, current read speed, etc) that in the next MMC are obsoleted, but it seems to be filled correctily in the next versions