Audio Video News

Last week, Philips Semiconductors announced the first single-chip MPEG2 video encoder for home PCs. Dubbed the SAA6750H, this chip provides a low-cost way to store analog (VCR) video in a digital form on various media, such as CD or proposed recordable forms of DVD. Previously, consumers had to rely on expensive professional equipment that could easily run into thousands of dollars.

"Analog tape is the most common medium for video recording today, but it is very fragile," explains Gunther Dengel, managing director of Consumer Systems at Philips Semiconductors. "Irreplaceable video of a wedding, a new baby, or a birthday party can be lost forever. Signal distortions resulting from tape-to-tape duplication techniques further exacerbate these limitations. Transferring data to a digital storage medium, such as a hard disk, CD-R, or CD-RW, is a much more robust way of storing and duplicating video."

MPEG, the Motion Pictures Experts Group, is an international committee set up to standardize the compression, decompression, and transfer of video data. The MPEG2 compression algorithm has become the primary standard for high-quality digital video, providing video quality that is better than S-VHS. Low-cost MPEG2 decoders, which are necessary to play back the recorded video, can already be found in a large number of products, including set-top boxes, PC cards, and new generations of Video-CD and DVD players. With the new chip, manufacturers can now create an MPEG2 encoder card for a home PC for a few hundred dollars---far below the cost of similar MPEG2 systems that have been produced so far.

"An analog video signal contains masses of information," adds Dengel. "By turning this into a digital signal, the information can be easily handled electronically and compressed to a fraction of its former size so it fits comfortably onto the hard disk of a PC without taking up the whole disk. It can then be sent as an e-mail attachment or transferred to a recordable CD. It's also very easy to make extra copies of the CD for all members of the family."

The SAA6750H takes PAL or NTSC video signals and generates an MPEG2 Elementary Stream (ES) that is compatible with MPEG2 Main Profile @ Main Level (MP@ML) encoding. This output is fully compliant with the MPEG2 standard (ISO 13818-2), and it is compatible with a 16-bit parallel interface using Motorola (68xxx-like) or Intel (xxx86-like) protocol style.

The SAA6750H uses motion-estimation algorithms that were developed in the Philips Research Laboratories to achieve high quality and high compression at very low cost. High picture quality (much better than S-VHS) can be achieved with a bit rate around 4-8 megabits/sec.

Another refinement of Philips Semiconductors' new design is a sophisticated algorithm that reduces noise in the input video before it is compressed. This is particularly important for home recordings, which are usually noisy, because compression algorithms tend to enhance the disturbing effects of noise. The SAA6750H is the first device to use a patented, motion-compensated, temporal noise-filtering technique that Philips developed for professional equipment to get rid of any noise and deliver a picture quality that can be even better than the original.

The software algorithms all run on a specially developed, on-chip, high-performance processor accompanied by over 20 KB of on-chip microcode in RAM. This approach of using programmable microcode software provides considerable flexibility for customizing and adapting the functions of the chip.

In addition to home-video applications, the chip can be used to encode broadcast-quality video for storage on disc or encoded transmission.