SERVICE MANUAL
Document No
Date of Origin
Date of REV
51-L-DSR004
98-10-21
PAGE REV.
0
PAGE
15 /102
S-00-005(96.03.27)
REV.1
4-5. DEMUX
& CPU
A Transport
Demultiplexing
integrates
all audio, video, and data service
MPEG-2
transport
layer functions,
the DEMUX's
principle
operation
is straight
forward:
4-5-1. A stream of data packed in transport
layer format 188 bytes per packet
enters the DEMUX IC through
its channel
decoder
interface.
The DEMUX system or IC detects
the sync byte, which is the first byte of
every transport
packet header.
Once in sync, byte, byte-aligned
data is
posted to the next stage of processing.
4-5-2. The DEMUX parses the incoming
data using its Packet ID(PID)
processor.
Upon user programming
the DEMUX extracts
the user selected
program,
audio, and video Packetized
Elementary
Stream(PES)
data, Program
Specific
Information(PSI),
Service
Information(SI),
and Private
Data.
4-5-3. The selected
audio and video PES layer encoded
data stream is output
through
the DEMUX.
4-6. A/V DEC O D I N G
Video Compression
& Decompression
Concepts
The MPEG standards
define a format
for compressed
digital
video.
Encoders
designed
to work within the confines
of the standard
compress
video
information,
and decoders
decompress
it. The MPEG algorithms
for video
compression
and decompression
are flexible,
but generally
fit the
following
criteria.
4-6-1. Data rates are about 1 to 1.5Mbit/sec
for MPEG-1 and up to 15Mbit/sec
for MPEG-2.
The MPEG-2 A/V Decoder
used in DRX100 is capable
of
supporting
data rates up to 15Mbits/sec.
4-6-2. Resolution
are about 352 pixels horizontal
up to about 288 lines vertical
for MPEG-1 and 720 x 576 for MPEG-2(main
profile).
The A/V Decoder
used
in DRX100 is capable
of resolution
up to 720 x 576 for either MPEG-1 or
MPEG-2.