Optical discs, such as Compact Discs and Digital Versatile Discs, are formatted in a contiguous spiral of blocks (or sectors). Following is an overview of the storage capacity of these formats available in DiscJuggler.

Compact Discs

A Compact Disc contain blocks (or sectors) of 2352 bytes each, going from the center hole to the outer diameter. The block at logical address 0 (beginning of the disc) is located near the center of the disc; the last addressable block (end of the disc) is located near the outer edge of the disc.

The common unit of measurement for CD capacity is time. Following are some basic formulas to convert time in blocks.

Blank discs are usually available in the following sizes (block sizes approximated).

The size of the block is a direct consequence of the way the analog audio signal is converted in digital samples. The audio data is sampled at 44.1 kHz, 16 bits, 2 channels (Stereo).

(44.1 x 1000) x 16 x 2 = 1,411,200 bits/sec

1,441,200 / 8 = 176,400 bytes/sec

176,400 / 75 = 2352 bytes

The physical block size on the CD is actually 2448 bytes divided into the following.

The additional 96 bytes are also known as sub-codes. The P and Q sub-codes are used for control purpose, storing information about the type, relative and absolute position of the block on the disc. The R-W sub-codes are normally used to store auxiliary user data such as the graphic portion of a CD+G Karaoke disc.

Digital Versatile Discs

Much like Compact Discs, Digital Versatile Discs are comprised of a continuous spiral of blocks (or sectors) starting from the center hole ending at the outer rim of the disc. The blocks are only of size 2048 bytes, making the format less complicated.

Blank discs are usually available in the following sizes (block sizes approximated).