Network broadcast system using low bit-rate audio coding technology

The VQVision network broadcast system, which can issue and distribute signals of high-fidelity music and video images in real time based on the use of best-effort networks that do not guarantee the transmission bandwidth of a LAN or the Internet, has been developed. Streaming signal distribution without sound interruptions has been realized by reducing the amount of data transmitted to about 1/18 to 1/88 of the original sound, without degrading the quality of music, by incorporating the TwinVQ low-bit-rate audio coding technology. This technology has been adopted as an ISO/IEC MPEG-4/Audio International standard for compressed transmission processing of music. In addition, the speed of the music encoder has been increased by the newly developed multithreaded high-speed encoder processing technology, and a self-synchronizing scheme for renewing received images in synchronization with audio data packets has been designed and loaded. On the basis of these features, scheduled broadcasting or multicast live broadcasting of images and high-fidelity music at bandwidths up to stereo CD bandwidth is performed by software developed without using dedicated encoder hardware and the like. Evaluations of the performance of this network broadcast system show that an encoder speed increase by a factor of up to 1.5 to 2 can be achieved by multithreading, and that high performance allowing simultaneous compression coding and transmission of a signal to a server in real time can be obtained even in live broadcasting in CD-bandwidth stereo if dual CPUs operating at a clock frequency of 300 MHz are used. In addition, it has been found that network broadcasting signals composed of images at 15 frames/s and CD-bandwidth stereo audio of a quality close to that of the original audio on a 512 kbit/s network band can be received without interruption, with a very small delay time of about 0.7 s from the time of its transmission. In addition, the reproduction timings of audio and images coincide exactly, even 24 hours from the beginning of signal reception.