You are burning the latest song you bought on ITunes to a disk. The song is 3 minutes, 23 seconds long and was sampled as a stereo signal (two sides, left and right) at 44.1 kHz using 16- bit encoding. How much space on the disk does this one track take up? If your CD is 640MBytes, how many songs of this size can you fit on one disk (assume 1 byte is 8-bits in length)? Remember, you don’t want fractional songs! How many songs could be saved on this same CD if the sampling rate was 128kHz using 32 bit encoding? Solution A) This stream of audio frames, as a whole, is then subjected to CIRC encoding, which segments and rearranges the data and expands it with parity bits in a way that allows occasional read errors to be detected and corrected. CIRC encoding also interleaves the audio frames throughout the disc over several consecutive frames so that the information will be more resistant to burst errors. Therefore, a physical frame on the disc will actually contain information from multiple logical audio frames. This process adds 64 bits of error correction data to each frame. After this, 8 bits of subcode or subchannel data are added to each of these encoded frames, which is used for control and addressing when playing the CD. CIRC encoding plus the subcode byte generate 33-bytes long frames, called \"channel-data\" frames. These frames are then modulated through eight-to-fourteen modulation (EFM), where each 8-bit word is replaced with a corresponding 14-bit word designed to reduce the number of transitions between 0 and 1. This reduces the density of physical pits on the disc and provides an additional degree of error tolerance. Three \"merging\" bits are added before each 14-bit word for disambiguation and synchronization. In total there are 33 × (14 + 3) = 561 bits. A 27-bit word (a 24-bit pattern plus 3 merging bits) is added to the beginning of each frame to assist with synchronization, so the reading device can locate frames easily. With this, a frame ends up containing 588 bits of \"channel data\" (which are decoded to only 192 bits music). The frames of channel data are finally written to disc physically in the form of pits and lands, with each pit or land representing a series of zeroes, and with the transition points—the edge of each pit—representing 1. A Red Book-compatible CD-R has pit-and-land-shaped spots on a layer of organic dye instead of actual pits and lands; a laser creates the spots by altering the reflective properties of the dye. The audio data stream in an audio CD is continuous, but has three parts. The main portion, which is further divided into playable audio tracks, is the program area. This section is preceded by a lead-in track and followed by a lead-out track. The lead-in and lead-out tracks encode only silent audio, but all three sections contain subcode data streams. The lead-in\'s subcode contains repeated copies of the disc\'s Table Of Contents (TOC), which provides an index of the start positions of the track.

1. You are burning the latest song you bought on ITunes to a disk. The song is 3 minutes, 23
seconds long and was sampled as a stereo signal (two sides, left and right) at 44.1 kHz using 16-
bit encoding. How much space on the disk does this one track take up? If your CD is
640MBytes, how many songs of this size can you fit on one disk (assume 1 byte is 8-bits in
length)? Remember, you don’t want fractional songs! How many songs could be saved on this
same CD if the sampling rate was 128kHz using 32 bit encoding?
Solution
A)
This stream of audio frames, as a whole, is then subjected to CIRC encoding, which segments
and rearranges the data and expands it with parity bits in a way that allows occasional read errors
to be detected and corrected. CIRC encoding also interleaves the audio frames throughout the
disc over several consecutive frames so that the information will be more resistant to burst errors.
Therefore, a physical frame on the disc will actually contain information from multiple logical
audio frames. This process adds 64 bits of error correction data to each frame. After this, 8 bits
of subcode or subchannel data are added to each of these encoded frames, which is used for
control and addressing when playing the CD.
CIRC encoding plus the subcode byte generate 33-bytes long frames, called "channel-data"
frames. These frames are then modulated through eight-to-fourteen modulation (EFM), where
each 8-bit word is replaced with a corresponding 14-bit word designed to reduce the number of
transitions between 0 and 1. This reduces the density of physical pits on the disc and provides an
additional degree of error tolerance. Three "merging" bits are added before each 14-bit word for
disambiguation and synchronization. In total there are 33 × (14 + 3) = 561 bits. A 27-bit word (a
24-bit pattern plus 3 merging bits) is added to the beginning of each frame to assist with
synchronization, so the reading device can locate frames easily. With this, a frame ends up
containing 588 bits of "channel data" (which are decoded to only 192 bits music).
The frames of channel data are finally written to disc physically in the form of pits and lands,
with each pit or land representing a series of zeroes, and with the transition points—the edge of
each pit—representing 1. A Red Book-compatible CD-R has pit-and-land-shaped spots on a
layer of organic dye instead of actual pits and lands; a laser creates the spots by altering the
reflective properties of the dye.
The audio data stream in an audio CD is continuous, but has three parts. The main portion, which
is further divided into playable audio tracks, is the program area. This section is preceded by a
lead-in track and followed by a lead-out track. The lead-in and lead-out tracks encode only silent

2. audio, but all three sections contain subcode data streams.
The lead-in's subcode contains repeated copies of the disc's Table Of Contents (TOC), which
provides an index of the start positions of the tracks in the program area and lead-out. The track
positions are referenced by absolute timecode, relative to the start of the program area, in MSF
format: minutes, seconds, and fractional seconds called frames. Each timecode frame is one
seventy-fifth of a second, and corresponds to a block of 98 channel-data frames—ultimately, a
block of 588 pairs of left and right audio samples. Timecode contained in the subchannel data
allows the reading device to locate the region of the disc that corresponds to the timecode in the
TOC. The TOC on discs is analogous to the partition table on hard drives. Nonstandard or
corrupted TOC records are abused as a form of CD/DVD copy protection
The audio data stream in an audio CD is continuous, but has three parts. The main portion, which
is further divided into playable audio tracks, is the program area. This section is preceded by a
lead-in track and followed by a lead-out track. The lead-in and lead-out tracks encode only silent
audio, but all three sections contain subcode data streams.
The lead-in's subcode contains repeated copies of the disc's Table Of Contents (TOC), which
provides an index of the start positions of the tracks in the program area and lead-out. The track
positions are referenced by absolute timecode, relative to the start of the program area, in MSF
format: minutes, seconds, and fractional seconds called frames. Each timecode frame is one
seventy-fifth of a second, and corresponds to a block of 98 channel-data frames—ultimately, a
block of 588 pairs of left and right audio samples. Timecode contained in the subchannel data
allows the reading device to locate the region of the disc that corresponds to the timecode in the
TOC. The TOC on discs is analogous to the partition table on hard drives. Nonstandard or
corrupted TOC records are abused as a form of CD/DVD copy protection