Those ICs integrate video encoding functions compliant with the Main Profile at Main Level (MP@ML) of the
MPEG2 standard into a microchip.
At least eight semiconductor makers will start mass producing the ICs by the first quarter of 1999,
targeting consumer products such as home video recorders and digital cameras.
C-Cube Microsystems Inc. of the United States, Digital Media Lab Inc. (DML) and Toshiba Corp. already
started sampling MPEG2 video encoder microchips for business-use products such as encoders to be installed
at a digital broadcasting station and digital video disk (DVD) drives.
NEC Corp., Sony Corp., Fujitsu Laboratories Ltd. and Matsushita Electric Industrial Co., Ltd. are
developing MPEG2 video encoder ICs for consumer-electronics use. Each group will start mass production in
1998: Fujitsu Laboratories and Matsushita Electric Industrial are only in charge of the product
development, while the former's parent company, Fujitsu Ltd., and the latter's subsidiary, Matsushita
Electronics Corp., will be in charge of mass producing MPEG2 video encoder ICs on behalf of the groups.
Mitsubishi Electric Corp. will start producing MPEG2 video codec (coder-decoder) ICs in 1999 that also
integrate MPEG2 audio encoding and decoding functions.
Cutthroat Competition to Reduce Power Consumption
Semiconductor makers are competing with each other for the reduction of power consumption in MPEG2 video
encoder microchips. Their target is 1.5W at present. Less than 1.5W of power consumption will enable them
to use plastic packages instead of ceramic ones, which can reduce the packaging cost by more than
nine-tenths at the stage of mass production.
But 1.5W is only the first step of development because this consumption level is
still too high for mobile devices. Consumer-electronics makers request that the power consumption be
reduced to the level of encoder ICs based on the MPEG1 standard or DV format, and semiconductor makers are
working toward that target.
The power consumption of MPEG2 video encoder ICs has been almost halved each year (See
chart). A dozen or so watts of power consumption in the first half of 1996 was reduced to about 3W in
1997.
Most of the consumer-use MPEG2 video encoder ICs to come on-stream in 1998 will clear the ceiling of 1.5W.
The target will be reduced further to 0.5W from 1999 through 2000. Sony, for example, will start sampling
MPEG2 video encoder ICs using 0.25-micronmeter process technology in 1999, which will reduce 1.2W of
current power consumption by around a half.
Architecture Divided Into Three Categories
MPEG2 video encoder ICs can be divided broadly into three categories of architecture based on the
configuration of circuits that execute functions such as discrete cosine transformation (DCT) and motion
compensation.
A common target is the reduction of power consumption. The three are:
(1) Hard-wired-logic type, in which almost all arithmetic is processed through hard-wired-logic circuits.
(2) Processor type, in which most of the arithmetic is processed by a built-in microprocessor such as
reduced instruction set computer (RISC) chip, and
(3) Hybrid type, in which functions such as encoding control are processed by a built-in microprocessor
and other functions such as motion vector search (motion compensation) and DCT/inverse DCT are processed
through hard-wired-logic circuits.
The hard-wired-logic type needs fewer transistors, and accordingly, it can reduce power consumption. But
it lacks programmability for encoding functions and customer specifications. Microchips from NEC and
Fujitsu belong to this category, which respectively need 3.8 million and 2.5 million transistors, while
microchips belonging to other categories use 4.2-5.5 million transistors.
By contrast, the processor type is programmable. But this type consumes 2.5-4W, so it needs ceramic
packages. Microchips from C-Cube, DML and Toshiba belong to this category. In either case, motion vector
search is processed through hard-wired-logic circuits and other functions are processed through a RISC
processor or a digital signal processor (DSP).
The hybrid type unites programmability and power saving features. It does not require the large amount of
time for programming as does the hard-wired-logic type. Microchips from Sony, Matsushita and Mitsubishi
belong to this category. Input-data-preprocessing and encoding control functions are processed through a
built-in microprocessor.
Original Technologies Emerge to Further Reduce Power
To cut power consumption, semiconductor makers have developed technologies that can reduce arithmetic for
motion search. Each maker has applied its original technologies for this purpose, although they had to
trade off the search accuracy of motion vector against the reduction of arithmetic volume.
Sub-sampling methods are applied to reduce the search area for motion vector. And also, to avoid
deterioration of image quality, original technologies have been used to define the search area and its
shape.
Sony, Matsushita and Fujitsu have increased microchips' search efficiency with a method to change the
search area automatically after referencing the motion vector of the previous frame.
Matsushita changed the sub-sampling ratio and arithmetic capability for horizontal direction based on the
magnitude of the images' motion. That has reduced average power consumption to 0.95W.
NEC has decreased arithmetic volume using a diamond-shaped search area for the motion vector. Other makers
use a rectangular search area.
In addition, Sony, NEC, Matsushita and Fujitsu have used automatic clock-control and
operating-voltage-reduction methods to reduce power consumption.
DML and Mitsubishi are studying to integrate a next generation MPEG2 video codec circuit and 32Mb DRAM
circuit into a chip. This will eliminate interface circuits for synchronous DRAM and reduce the power
consumption by several-hundred mW.
Codec Microchips for Consumer Products Go On Sale
Codec ICs also will be put onto the market. Mitsubishi plans to start producing one-chip MPEG2 video codec
ICs for consumer products. C-Cube already has started sampling the one-chip MPEG2 video codec ICs for
consumer products. DML, in 1999, and Matsushita, within a year, will start sampling products.
One-chip MPEG2 video codec ICs can eliminate an external 16Mb DRAM for application where encoding and
decoding jobs do not overlap at all times. Other competitors assume, however, that an independent,
external encoder IC system exceeds any integration from the viewpoint of total cost.
DML produced an MPEG2 encoder board for personal computers on an experimental basis. It has sound
functions for playing music in game software. The price is about US$200. Modem and graphics accelerator
functions will be added to it in 2000, company officials said.
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Chart: Power consumption of MPEG-2 video encoder ICs has been halved yearly
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(Nikkei Electronics)
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