1998-03-03 , E/IC-1004/54

MPEG2 video encoding can now be done inexpensively on a home PC

Philips Semiconductors, the largest European semiconductor company, has solved the problem of analog videotape not being a very robust medium with its announcement today of a low-cost way to store video in a digital form on various media, such as CD or DVD, using a home PC. Until now, expensive professional equipment was needed to transform analog video into a digital signal and then compress it to fit onto a disk.

The company has shrunk all the complex hardware needed to perform the transformation onto a single silicon chip. The  SAA6750H, as it is known, is an example of the company's pioneering work of creating complete systems on a single IC. It also draws on Philips' many years of experience as leaders in the development of video compression and decompression hardware and software for professional and business use.

"Analog tape is the most common media for video recording today," explained G¸nther Dengel, Managing Director of Consumer Systems at Philips Semiconductors. "But, the problem with analog videotape is that it is very fragile. And irreplaceable shots of a wedding, a new baby or a birthday party can be lost forever. Furthermore, duplicating an analog home video conventionally from tape-to-tape leads to annoying signal distortions. A digital storage medium, such as a Hard Disk (HD), Recordable CD (CD-R), ReWritable CD (CD-RW) or Digital Versatile Disc (DVD), is a much more robust way of storing and duplicating video."

The actual technique used in this case is called MPEG2 video encoding, where MPEG is short for Motion Pictures Experts Group, an international committee set up to standardize compression, decompression and transfer of compressed video data. MPEG2 has become the new main standard for high-quality digital video and provides video quality that is better than S-VHS (Super-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 or DVD players.

With just a few more components, a manufacturer can create an add-in 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.

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

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

It uses motion estimation algorithms that were specially developed in the Philips Research Laboratories to achieve both a high-quality and a high-compression factor at very low cost. By using only I and P frames (B frames are not used), a significant reduction in overall system build cost is achieved, e.g. only 2MB of DRAM is needed compared to at least 4MB for IPB coding, and editability of the compressed streams is improved. High picture quality (much better than S-VHS) can be reached at around 4-8Mbit/sec.

Another refinement of Philips Semiconductors' 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, as compression algorithms by nature tend to enhance the disturbing effects of noise. The SAA6750H is the first device to use a patented, motion-compensated temporal noise filtering technique, which 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 20KB of on-chip microcode in RAM. This approach of using programmable microcode software provides considerable flexibility to customise and adapt the functionality of the chip.

Other applications include using the chip to encode broadcast-quality video for storage on disc or encoded transmission.

The SAA6750H is priced in the region of $38.50 when purchased in volumes of 100 000.

PC add-in card design
For this application, the SAA6750H has been optimised to work with two other ICs from Philips Semiconductors. The SAA7111 family of ICs that convert analog TV signals into a digital format and the  SAA7146 PCI bridge master IC that transfers the data from the card into the PC.

Philips Semiconductors, a division of Philips Electronics NV, headquartered in Eindhoven, The Netherlands, is the ninth largest semiconductor supplier in the world and the fourth largest supplier of discretes in the world. Philips Semiconductors' innovations in digital audio, video, and mobile technology position the company as a leader in the consumer, multimedia and wireless communications markets. Sales offices are located in all major markets around the world and are supported by systems labs.