Can anyone tell me how the sub-headers are written in the CD-XA form 1 and form 2 is written? I know so far that the sub-header is in fact only 4 bytes long and that the next four bytes are duplicates… but what information does it hold? how can I distinguish a mode 2 form 1 sector from a mode 2 form 2 sector without having to analyze the sectors structure to do it?

Can anybody help me out with this?


As far as I know the only way is to analyze the sector to tell a “form 1” from a “form 2”. Lucky for us the MMC2 draft (pg 47) has a brief specification of the subheader. In particular bit 5 of the sub-mode byte will tell you that.


where can I find the mmc2 draft? from t10?


well… I found a website that seems to have the description of what the sub-headers are used for, it’s in German though, but I did the best translation that I could, here is the translated text:

Byte		Use
 1 	Identification of interlocked files (00 when not interleaved) 
 2 	Channel Number
 3 	Submode Byte
		BIT 7: Signals End of File (EOF)
		BIT 6: Signals if Data is dependent on time
		BIT 5: Signals if sector is Form 1 or Form 2
		BIT 4: Type on (depends on the Operating System)
		BIT 3: Data Sector		-\
		BIT 2: ADPCM Audio Sector	- |--> Identification for the type of data found in the sector
		BIT 1: Video Sector		-/
		BIT 0: Signals End of Record (EOR)
 4 	Type of Coding for the Video and Audio data (00 when data sector)
 5-6	Copy of the last 4 bytes (for data security)

I’m not quite sure about what the first byte does, that frase is taken directly from babelfish, without any editing done by me, becuase I am not sure what it is trying to say, BIT 4 is also a translation done by altavista’s babelfish and I am not sure of what it is supposed to mean… Can anyone shed some light on this subject?

btw, here is the site that i got the info from:


and go into SCSI-3 architecture.

But it’s pretty much what you have found in the German.


what’s the difference between the final drafts that they have on the site and the final documents that they publish? are there that many differences to the standard?


I’m not sure myself, I don’t have the final standards. The draft seems to be adequate for making a working tool.