We all know the bad sectors which appear on every SafeDisc(2) CD. If a drive reaches such a sector, it reports "unable to read sector" to the application and the sector is filled up with zeroes, or whatever. CloneCD uses the HEX-value 55, I think (image scanned with CDmage). A long time ago, BlindRead introduced a great method to avoid the slow-down of CD-ROM drives, while encountering bad sectors. The data is read as audio, which has the same sector-size as a raw Data-Track (2352 bytes/sector).
If have read Rayman 2 (SDv1) for testing:
First with the UltraPlex 40max, alternative read method, enabled.
Second with CloneCD, fast error skip, enabled (disabling shouldn't give any differences).
The resulting images are different. All bad sectors of the CloneCD image are filled with "55", while the BlindRead image seems to have always different values in every bad sector.
OK, next I created a very strange disc!
I used a regular wave music file, cutted it to be a multiply of 2352 bytes and removed the wave header to get a RAW-PCM file.
I burned this file with CDRWIN as a Mode1 disc.
file test.raw binary
track 01 mode1/2352
index 01 00:00:00
The final CD is pretty "cool".
It runs in a regular cd-player as an audio-CD, but at the end a VERY SHORT click noise will appear. I have no idea why this occurs. Almost none CD-ROM will be able to read such a CD again. Nice copy protection, BTW .
But the disadvantage is that "new" cd-players won't recognize the CD as audio because of the DATA flag in the subchannels.
The UltraPlex is one of the rare drives which can read such a CD again (Toshiba SD-M1401 and PlexWriter failed both) because the Mode1 Track gives no sense as audio.
If you read the DATA Mode1 Track containing audio with CDRWIN (only read sectors works) as Mode1/2352 you'll get garbage, but if you read it as audio, you'll get the whole file (with that annoying click at the and :-[).
It would be interesting to know: When is a sector unreadable? Because if you read the CD as audio, ALL sectors are readable, no matter if the CRC is OK, or not. So the sectors stay unchanged.
Maybe BlindRead reads the CD without correcting the bad sector in opposite to CloneCD.
It would be nice, if anyone could give me additional infos about the topic "unreadable secotrs, CRC, etc".
Thanks in advance