Basics

2.1 Terminology and symbols

(1) Definition of terms

Table 2.1 defines the terms used.

Table 2.1 Definition of terms

term	meaning
sector	A basic unit of data handled in a CD block. (2352 bytes fixed) The sector size and structure follows the CD-ROM format.
stream	A logically continuous flow of data distinguished by sector headers and subheaders.
cd buffer	A buffer within a CD block that stores sector data.
CD buffer size	CD buffer size in sectors.
buffer compartment	A partition of the CD buffer into multiple logical partitions. It can be viewed as a logical element that stores and retrieves streams.
buffer partition size	Size of the buffer partition in sectors.
sector position	The position of the sector within the buffer partition. (position in sector units) Takes a value from 0 to (buffer partition size - 1). Sectors in the buffer partition are accessed using the sector position as a key.
Aperture	A logical element that separates streams according to set conditions.
selector	A logical element that selects streams, consisting of an aperture and a buffer compartment. A stream selection circuit can be constructed using a selector.
device	A logical device that generates and absorbs streams such as CD-ROM and MPEG. Above circuit Stream selection processing is possible by connecting a device to.
connector	Aperture, buffer compartment, terminals for connecting devices.
Frame address (FAD)	The absolute time on the CD, 00:00:00, is set to 0, and each frame is numbered consecutively. Corresponds one-to-one with absolute time. CD blocks are accessed using the frame address as the key, not the absolute time. access. (both CD-ROM and CD-DA)
Logical sector number (LSN)	The absolute time on the CD, 00:02:00, is set to 0, and the numbers are consecutively assigned to each sector (frame). What I attached. Logical sector number = frame address - 150 (2 seconds). Used for information in directory records (ISO9660).
File information	Directory record information maintained for accessing files. FAD at the beginning of the file, file size, unit size, gap size, Contains file number and attributes.
file identifier	Sequential number within the directory to identify the file. Takes a value between 0 and (number of directory records - 1). However, 0: indicates your directory, 1: indicates the parent directory.

(2) List of symbols and abbreviations

Table 2.2 List of symbols and abbreviations

Symbols/abbreviations	meaning	explanation
Adr	address	address
B.C.D.	binary coded decimal	Binary coded decimal number
bn,bufno	buffer no.	buffer partition number
bufnum	buffer numbers	Total number of buffer partitions
CI	coding information	Coding information
CN	channel no.	channel number
Ctrl	control	Control
dst	destination	Copy/move destination
fad	frame address	frame address
fasnum	fad sector numbers	Number of frame address sectors
fid	file identifier	file identifier
fln,filtno	filter no.	Aperture number
FN	file no.	file number
LSB	least significant bit	least significant bit
MSB	most significant bit	most significant bit
ply	play parameter	playback parameters
pos	position parameter	position parameters
SM	submode	submode
sct	sector	sector
ses	session information	Session information
sesno	session no.	session number
snum	sector numbers	Number of sectors (when specifying sector range of partition)
sp,spos	sector position	Sector position (when specifying sector range of partition)
src	source	Copy/move destination
stat	CD status information	CD status information
subh	subheader condition	Subheader conditions for aperture
TNO	track no.	Track number (song number)
toc	TOC information	TOC information
txwnum	transfer word numbers	Number of transferred words (data transfer size in words)
X,idx	index	index number
word	word	word. A unit of length of 2 bytes (16 bits).

(3) Numerical notation

Add "B" to the end of binary numbers. (Example: The decimal number 5 is written as 101B.)
Add "H" to the end of hexadecimal numbers. (Example: The decimal number 255 is written as FFH.)
However, hexadecimal numbers in C language programs are expressed using C language specifications (0x).

(4) Handling of BCD

As a general rule, BCD is not used for parameters etc. All numerical values recorded in BCD on CDs, such as track numbers, are converted to binary values and exchanged.

(5) C language identifier

The CD communication interface uses identifiers that begin with CD or Cd. Applications must be careful not to collide with these identifiers.

2.2 Disk layout

(1) Track layout

Figure 2.1 shows the relationship between the track structure and the access keys that specify locations on the disk.

Figure 2.1 Relationship between track structure and access keys

(2) Multi-session layout

Figure 2.2 Multi-session layout