I compared the extracted images but each time the subchannel data varies somewhat.
They’re random errors:
…because of pre-mastering faults, random
defects originated between mastering and pressing,
or burning or readout errors by the drive. Of course
scratches, dust and fingerprints play a role here too.
Spec establishes a limit for random errors: the BLER
(BLock Error Rate) averaged over any 10 s shall be
less than 3 x 10^-2. BLER is measured at the input
of C1 decoder, blocks are erroneus when at least a
symbol is erroneus and symbols are erroneus when
at least a bit is erroneus. All this happens at main
channel and unfortunately I see no spec for subs,
but you can understand now that random errors
aren’t necessarily an indication of a faulty drive.
How can you extract the subchannel data accurately if possible?
Listing the different protection schemes for the 8 subcoding channels…
Channel P: no protection, Channel Q: 16-bit CRC, Channels R to W:
[FONT=Arial][SIZE=2][SIZE=2][FONT=Arial][SIZE=2][FONT=Arial]To protect the data in the subcoding channels R to W, a (24, 20) Reed-Solomon error correction code is used. To improve the burst error correction capability, 8 times interleaving is added to this error-correction system. The first two symbols in a PACK have additional protection with a (4, 2) Reed-Solomon error correction code.
[SIZE=2][FONT=Arial]Only a packed mode reading drive (100b) can make a difference [/FONT][/SIZE][SIZE=2][FONT=Arial]by decoding[/FONT][/SIZE]
[SIZE=2][FONT=Arial]subchannels R to W, “cleaning” them from reasonable amounts of random errors.[/FONT][/SIZE]
Is there another program that does a better job?
[SIZE=2][FONT=Arial]The rest of the job (P and Q) can only be carried out by software, like in CDGTool.[/FONT][/SIZE]
As you can see, the R-W subchannels are basically filled with “FF” bytes. A standard audio cd should not have data in R-W subchannels.
That’s correct, but unfortunately this practice is frequently performed by the industry.
This is the reason behind the insane amount of time it takes to dump these subcodes.
The 100b decoder just has a hard time trying to process so much nonsense information.
I’m no programmer so I can’t really fix them unless I do it manually which would take forever. Are they really errors? Do they all need to be corrected to “FF” bytes? Any software available? I’ve been looking everywhere. Thanks in advance.
Yes, random errors to be corrected to “FF” bytes, I selected this thread to release
Truman’s R2WFill, a proggie to fill channels R to W with any value, keeping P&Q.
R2WFill.zip (2.73 KB)