Technology: Interactive video gets the full motion treatment

2019-02-26 02:10:00

By BARRY FOX THE DUTCH electronics giant Philips is developing a new technology that could greatly enlarge the applications for interactive video. The company has demonstrated a compact disc that can store 72 minutes of moving video pictures in digital format, something made possible only by using data compression techniques. Researchers appear to have overcome the technical problems that hampered the recording of video on compact discs in digital format – that the rate at which data stream off the disc is simply too slow. The system demonstrated was a ‘full motion video’, or FMV, version of Philips’ interactive compact disc system, known as CDI. FMV/CDI can store its 72 minutes of moving video on a 12-centimetre disc along with sound, still pictures, graphics, cartoon animation and computer software. A CDI player can read all types of data from the disc. The system can be used in multi-media publishing such as in games, video encyclopaedias, and interactive training systems. Philips stresses that FMV is not intended to replace the 30-centimetre video discs that store moving pictures as analogue signals. These are popular in the US and Japan for watching feature films in the home. Philips’ researchers embarked on a crash programme to develop FMV/CDI in 1987 after the David Sarnoff Research Center in the US demonstrated its Digital Video Interactive (DVI) system. DVI records an hour of video on a 12-cm disc. Intel, the American chip manufacturer, later bought the rights to DVI and is producing a set of chips which will enable a personal computer to produce moving video pictures from a CD player. Intel and the American computer giant IBM have now said they will work together to sell DVI boards for personal computers which are built round Intel’s 386 processor chip and either incorporate or are connected to a CD-ROM player or drive. The DVI boards that plug into the back of a PC cost $2000. The total outlay for a DVI system will be at least $5000, five times the promised price for a CDI player. A 12-cm CD can store 600 megabytes of digital code and the data stream off the disc at a fixed speed of 170 kilobytes per second. This is far too slow for digital video. FMV works in stages to compress the data. First, all the pictures (25 per second for European video, 30 for the US and Japan) are converted into digital code. But only the code for alternate pictures is recorded. Also, the number of bits needed for each picture is drastically reduced by breaking each picture down into blocks, comparing the blocks and recording only how they differ. If a face, for instance, is moving across the screen, then only the direction and speed of motion are coded. The digital code adapts itself to the amount of information to be recorded, with the size of the coding steps changing according to the content of the picture. Taken together, these methods reduce the data rate by a factor of 144 to 150 kilobytes per second, which leaves around 20 kilobytes for compressed sound. On replay, the coded pictures are reconstructed from this difference and motion information. Then the missing alternate pictures are interpolated from information culled from the pictures that came just before and just after. Motorola in the US and Matsushita in Japan are working with Philips on chip sets for the new system. Domestic CDI players, costing $1000 and looking like a music CD player, will go on sale in the US and Europe in 1991. When connected to a hi-fi system and domestic TV set they will play music CDs,