em8471 ETC-unknow, em8471 Datasheet - Page 3

• Manufacturer Part Number: em8471
• Description: Mpeg Decoder Set-top Streaming Applications
• Manufacturer: ETC-unknow

MPEG-1 and MPEG-2 Huffman Decoder
The MPEG Video Decoder engine uses the Huffman
Decoder as its front end. It can decode either a MPEG-1 or
MPEG-2 formatted data stream. The Huffman Decoder is
commanded directly from the RISC processor. It extracts
fixed-length, variable-length or start codes from the bitstream
and returns the value to the RISC processor or passes it
directly to the Inverse Quantizer. The Huffman Decoder can
also do tasks such as decode the macroblock increment
address, get the macroblock type, get coded block pattern,
get motion vector codes and decode a delta motion vector.
MPEG-4 Huffman Decoder
The MPEG-4 Huffman Decoder is the front-end to the
MPEG-4 engine. It provides specialized instructions to the
RISC processor to enable the decoding of Simple Profile
MPEG-4 streams. These instructions are of three different
kinds: get or view a fixed-length bit field, get an individual
variable length code and get the DCT coefficients for the
whole macroblock. Additionally, the Huffman Decoder pro-
vides support for the error-resiliency features of MPEG-4. It
can be used to read data-partitioned Video Object Planes,
with or without Reversible Variable Length Codes (RVLCs). It
cannot, however, read RVLCs backwards.
Video Decoder Block Diagram
355 Fairview Way • Milpitas, CA, USA 95035 • Tel: [phone] • Fax: [phone]
R-BUS
R
MPEG MISC
IRQ C
ESET
RBUS I
DRAM
T
I
IMER
PCI BUS
NTERFACE
PCI BUS
C
www.sigmadesigns.com • [e-mail]
NTRL
NTRL
NF
.
.
.
ACDC
ACDC
_
MPEG-1&2
_
IN
H
OUT
UFFMAN
Sigma Designs, Inc.
RISC C
P
16-
REDICTOR
Z
AC/DC
IG
BIT
Z
ORE
AG
H
MPEG-4
UFFMAN
AC/DC Predictor
If the input stream is MPEG-1 or MPEG-2, the AC/DC predic-
tor passes through. Otherwise, it receives data from the zig-
zag through a 19-bit stream interface. A predictor is added to
the incoming AC/DC coefficients. The result is saturated and
output to the inverse quantizer through a similar interface.
This result will also be used as future predictors. For predic-
tion, this block must save an entire macroblock line of infor-
mations. This module supports MPEG-4 simple profile.
Inverse Quantizer
The Inverse Quantizer block resides between the AC/DC
predictor block and the inverse DCT block. Its primary func-
tion is to receive coefficients from the AC/DC predictor, scale
them and send them to the IDCT. It supports the MPEG-1,
MPEG-2 MP@ML and MPEG-4 simple profile.
Inverse DCT
The IDCT (Inverse Discrete Cosine Transform) module is a
hardware implementation of the DCT/IDCT of an 8x8 pixel
block used in MPEG compression/ decompression. The DCT
transforms a block of 8x8 pixels into a block of 8x8 trans-
formed coefficients. The IDCT transforms a block of 8x8
transformed coefficients back into a block of 8x8 pixels.
D-BUS
PMEM
DMEM
Q
I
UANTIZER
NVERSE
IDCT
SDRAM C
C
OMPENSATION
M
OTION
ONTROLLER
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