DVD specs
use red laser, allows for smaller tracks;
pitch meaning more data can be fit in the same surface area,
capacity 4.7 GB, data rate is variable
Dual layers
essentially two disks on top of one another, two different lasers, one passes through top, only sees bottom
DVD-9
2 layer, single sidded
dvd-18
2 layer dvd double sided
dvd 9
single sided single layer
dvd 14
double sided, 1 layer 1 sided (players switch from layer to layer… slight pause) but does not switch sides
dvd video
2 chanel pcm
audio- 16 bit 96khz
only supports 48 and 96k, not 44.1 or 88.2
-dolby digital ac-3 soundtrack containing 1 to 1.5 channesl up to 44.8 kbps bit rate
optionally can contain DTS sumend up to 1.4 mbps
video
rests of the bit rate dedicated only to video, the increasted audio quality = the decreased pic quality
meridian lossless packing (mlp)
an optional lossless data compression must be used for 24 bit/96khz 5.1 can be used to increase playing time or other formats (roughly 2.1 compression)

7mbps with MLP=420mb per min or 52 MB per minute.
(90 minute playing time)

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**most dvd single layer**

SuPER audio CD (SACD)
dvd based created by sony/phillips as a proposal for dvd-audio
stereo for 5.1 usually single layer and cd layer hybrid;
contains no video content at all, not even menus. encoded in direct streams digital or DSD, direct recording of the output of sigma delta modulation converter
-1 bit sampling at 1.8mhz
-sigma/delta modulation converter
optical storage
process of using reflected light to read data off a surface usually a disk
-not limited to digital data only
-refelcted light from the source returns at varying intensity due to changes in the surface. these different intensities are converted to a varying voltage.
to store digital data..
two different light intensities are needed.
laser disks
optically stored analog video/audio later adapted for digital audio with analog video
cd was designed to be analog..
but was switched to the digital design.
wavelegnth of the laster
determines the data rate bandwidth. smaller wavelenght lasers can focus on a smaller area allowing data to be closer together on the disc.
Rayleigh Critera
Cds- green lasers- 750mB
dvds- red lasers- 4.7 gb
blu-ray-blue lasers – 50 gb
cd developed by sony/phillips in late 1970s, phillips developed optical storage system.
in late 1970s, phillips developed optical storage system.. sony developed digital pcm audio system
track pitch
width of the track of data running spirally from the center out. standard 1.6 micrometers
linear velocity
how fast the track passes over the laser as if the track were in a straight line
constant linear velocity (clv)
the linear velocity remains constant throughout the entire disc to accomplish this the disc needs to spin slower when the laser is reading the outer edge
prerecorded discs…
are stamped mechanically so the data track is physically created in a material
recordable/rewriteable discs
data is contained in a layer of material that can be altered by applying a laser to it creating two different reflections mimicing pits/lands
magneto optical storage minidiscs
combines laser and magnetic recording, level of mag. field needed to change a mag. medium is temporary dependent. a material only magnetically coered at high tempurature is placed in the constant mag field. a laser is used to raise the temp. of a small area in the medium until it reaches the temp. where it can be magnetically altered. accidental erasure nearly impossible . can hold more data than magnetic medium