EM8475 查看數據表（PDF） - Unspecified

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EM8475

MPEG-4 Decoder for Set-top, DVD and Streaming Applications

Unspecified 

EM8470, EM8471, EM8475, EM8476

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.

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.

Video Decoder Block Diagram

DRAM

MPEG MISC

TIMER

IRQ CNTRL.

RESET CNTRL.

RBUS INF.

ACDC _OUT

ACDC _IN

AC/DC

PREDICTOR

ZIGZAG

MPEG-1&2

HUFFMAN

MPEG-4

HUFFMAN

SDRAM CONTROLLER

IDCT

INVERSE

QUANTIZER

MOTION

COMPENSATION

R-BUS

D-BUS

PCI BUS

INTERFACE

16-BIT

RISC CORE

DMEM

PMEM

PCI BUS

Sigma Designs, Inc.

355 Fairview Way • Milpitas, CA, USA 95035 • Tel: 408.262.9003 • Fax: 408.957.9740

www.sigmadesigns.com • sales@sigmadesigns.com

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