A team of engineers from the consumer electronics giant's semiconductor division developed the low-power MPEG-4 silicon that handles a low-bit rate video stream for videoconferencing, and also decodes and synthesizes objects for complex, interactive multimedia applications on handheld devices.

Scheduled for sampling in the second quarter, the chip is targeted at both cell phones and PDAs, said Takashi Hashimoto, an engineer at Matsushita's System LSI Development Center. Matsushita, a leading cell phone supplier for NTT Docomo in Japan, hopes the new chip will help Docomo energize MPEG-4-based multimedia applications, starting this spring in Japan's wideband CDMA services.

The chip's claim to fame is that it supports not only MPEG-4 Simple Profile — the encoding/decoding of moving images at up to 386 kilobits per second — but also MPEG-4 Core Profile, which supports the independent manipulation of multiple objects on a screen.

Other companies such as Toshiba Corp. and Qualcomm Inc. also offer system-on-chip devices for handhelds that support low-bit rate MPEG-4 Simple Profile, but Matsushita's new chip is the only design available to decode MPEG-4 Core Profile.

While it's unclear if videoconferencing will become a prevalent multimedia application on handheld units, Matsushita's support for MPEG-4 Core Profile assures the chip of meeting the emerging needs of interactive, object-based Web-browsing applications.

With 20 Mbits of embedded DRAM, the chip integrates a proprietary DSP core, eight dedicated hardware engines, and three interface units, including a video processing unit, a memory interface and a host interface. "This is a hybrid architecture consisting of a programmable DSP and dedicated hardware engines to meet the demands for a lower power and higher performance MPEG-4 solution," Hashimoto said.

The chip's many hardware blocks including DCT, motion estimation and variable length coding engines to support the MPEG-4 Simple Profile codec. Context-based binary arithmetic decoding, padding and composite engines are devoted to MPEG-4 Core Profile decoding.

At 54 MHz, Hashimoto said the MPEG-4 chip consumes as little as 50 mW when encoding and decoding a single stream of moving pictures in QCIF resolution at 15 frames per second. "Its power consumption increases by 20 mW per object, as the chip is tasked to decode more streams," he said.

The low-power consumption is an absolute requirement to get the chip designed into a cell phone, Hashimoto said. "We reduced the chip's power consumption for external I/O circuits by employing an embedded DRAM, while we also incorporated clock gating features in each block to cut the chip's internal power consumption," he said.

The chip can encode up to two streams of moving pictures in QCIF resolution at 15 frames/s, in parallel with decoding four streams of moving pictures in QCIF at 15 frames/s. It is also capable of simultaneously decoding four objects based on MPEG-4 Core Profile in QCIF at 15 frames/s, while encoding and decoding a single stream of moving images compressed in MPEG-4 Simple Profile.

The chip does not handle audio, but supports H.263 and MPEG-4 video coding.

Matsushita engineers said they believe that picture quality is an essential element of the new MPEG-4 chip. Its integrated video processing hardware block captures video input from a CIF camera and outputs display images to an LCD at a maximum 60 frames/s. The same unit also performs pre- and post-filtering for video input/output data, and superimposes graphic data on the video, while supporting such features as picture-in-picture.

To further improve picture quality, the chip comes with its own noise reduction filters and error correction algorithm. In wireless applications, it is essential that the chip detect and recover transmission errors quickly, Hashimoto said. Matsushita has proposed its internally developed error correction algorithm that's now part of the MPEG-4 syntax to the MPEG-4 committee, he added.

Application developers

With a bulk of young cell phone users in Japan, many consumer electronics companies and service providers hold high hopes that teenagers will figure out creative uses of MPEG-4-capable cell phones beyond simple videoconferencing. By leveraging MPEG-4 Core Profile capabilities, a user can download cartoon characters or background images from the Web or from a local flash memory card, synthesize them with a moving picture of the user captured by the cell phone, then send it to a friend, Hashimoto said. The receipt of emerging MPEG-4-based data broadcasts operated by TV networks is another promising application, he said.

Matsushita's initial production of the MPEG-4 chip will be for internal consumption, most likely for cell phones Matsushita will supply to NTT Docomo this year. By 2002, Matsushita said it plans to manufacture one million MPEG-4 chips per month.

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