The reason for using the DPCM structure is that for most sources of practical
interest, the variance of the prediction error is substantially smaller than
that of the source.
DSM (Digital Storage Media)
A digital storage or transmission device or system.
DVC (Digital Video Cassette)
Tape width is
1/4", metal partical formula. The source and reconstructed video
sample rate is similar to that of
CCIR-601,
but with additional
chrominance subsampling (4:1:1 in the case of 30Hz and 4:2:0 in the
case of 25 Hz mode). For 30 frames/sec, the active source rate is 720
pixels/lines x 480 lines/frame x 30 frames/sec x 1.5 samples/pixel
average x 8 samples/pixel = ~ 124 Mbit/sec.
A
JPEG-like
still image compression algorithm (with macroblock adaptive
quantization) applied with a 5:1 reduction ratio (target bitrate of 25
Mbit/sec) averaged over a period of roughly 100 microseconds (100
microseconds is pretty small compared to MPEG's typical 1/4 second
time average!)
DVI (Digital Video Interactive)
Digital Video Interactive (DVI) technology brings television to
the microcomputer. DVI's concept is simple: information is
digitized and stored on a random-access device such as a hard disk
or a CD-ROM, and is accessed by a computer. DVI requires
extensive compression and real-time decompression of images.
Until recently this capability was missing. DVI enables new
applications. For example, a DVI CD-ROM disk on twentieth-century
artists might consist of 20 minutes of motion video; 1,000
high-res still images, each with a minute of audio; and 50,000
pages of text.
DVI uses the YUV system, which is also used by the European
PAL color
television system.
The Y channel encodes luminance and the U and V channels encode
chrominance.
For DVI, we subsample 4-to-1 both vertically and horizontally
in U and V, so that each of these components requires only 1/16 the
information of the Y component. This provides a compression from the 24-bit
RGB space of the original to 9-bit YUV space.
The DVI concept originated in 1983 in the inventive environment of the David Sarnoff Research Center in Princeton, New Jersey, then also known as RCA Laboratories. The ongoing research and development of television since the early days of the Laboratories was extending into the digital domain, with work on digital tuners, and digital image processing algorithms that could be reduced to cost-effective hardware for mass-market consumer television.