Error Recovery Parameters/interleaving questions

vbimport

#1

Hello everyone,

I have been collecting some info about reading ‘bad’ (damaged in any way, not copy protected) CD/DVD’s for some time. Few questions related (and not) to this:

  1. Suppose I sent to my drive a MODE SELECT command with Error Recovery Parameters (Page 1) set to read sectors regardless of errors (RC/TB as 1).
    Are there any situations when READCD command will return me check_condition and no data anyway (I am thinking specifically about errors in sector header/synchronization bytes)?

  2. Is there any way to determine whether a CD/DVD supports mode select parameters mentioned above other than testing it empirically? Does any specs/drive reviews on the web include such info? (I am asking beacuse none of the drives i have access to support those. I would be thankful for suggesting at least one DVD-RW which is buyable at the moment and can do this for sure). Is a sheep-test related to this in any way?

  3. I am also interested in the interleaving mechanism in both CD and DVD. From what i read, on a CD each sector is being spread over 108 other sectors. Sector is made of 98 24-byte ‘blocks’ + 98 byte subchannel data (why is it 108 sectors then? Did I miss something?). Suppose we are looking at sector 100 - is it physically stored through sectors 100-208, 46-154 or differently? What is the sequence of the 24-byte blocks - 1,2,3,… or is it shuffled somehow?
    On how many sectors is the data spread on a DVD (when 16 ‘frames’ are coded together)?

Thanks for any responses.


#2

Hi,

From tests I’ve made in the past, I can tell you:

1)Seems it only affects ECC/EDC in sector for CD-ROM (data) CDs. This means C1/C2 are not affected and it does mean that it has no effect on CDDA (audio) CDs.

2)I have only seen Plextor drives support the parameter, and drives I’ve had success (and own) are:

  • Plextor W8432T
  • Plextor Premium
  • Plextor 755A
    I’ve tried my friend’s Plextor Premium 2 which also supports it too.

#3

For DVD you want to look at the spec here: http://www.ecma-international.org/publications/files/ECMA-ST/Ecma-267.pdf

And start at section 21 Physical Sectors and work back through 19 Recording Frame. And the ECC block “Figure 20” shows the arrangement of the 16 sectors of data with the PI and PO ECC bytes before being interlieved into recording frames.

Basically you need 16 recording frames to build the ECC block in order to start checking and correcting errors. Hence 16 sectors is the smallest amount of data a DVD mech reads and 16 sectors is your answer to “how many sectors is the data spread on a DVD”.

And there are 619008 clocks of EFM data making up the 16 recording frames. As in an SY0 sync mark being either the EFM/laser pattern “11000111000011111111111111100001” or “00111000111100000000000000011110” is just 32 clocks. So if you look up the length of one clock (see 10.6.4 Channel Bit Length) and multiply it by 619008 you should get the approximate length of the 16 recording frames on the surface of the DVD.