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Advanced Television at Low bitrates And Networked Transmission over Integrated Communication systems

Exploitable results

Summary: IMAGE (Integrated MIMD Architecture for Generic Motion Estimation) is a VLSI integrated circuit for incorporation into MPEG2 video coders. Its function is to perform motion estimation, vector refinement and mode selection within the coder. Other applications based on block matching, such as post-processing of motion vectors, computation of dual prime vectors for low delay coding or the selection of the macroblock prediction mode, can be developed by exploiting the programmability of IMAGE. Specific interfaces enable several IMAGE circuits to be linked seamlessly together, to obtain increased processing power.
An important factor in containing the costs and maintaining the technical quality of future television (TV) production will be the ability to handle and process the video and audio signals as much as possible in compressed form. This is already happening using a chaotic assortment of different compression systems. The bridge from one compression system to the next makes decoding and recoding obligatory, leading to a progressive loss of signal quality. The only solution with current technology is to use many more bits than strictly necessary in the earlier part of the chain, which provides sufficient 'headroom' but removes most of the advantages of compression. Server and network capacities are forced to be up to ten times higher than they need to be. In this context, the project develops the technology which will enable the signal to be kept in compressed Moving Picture Expert Group (MPEG)-2 format throughout the complete broadcast chain and quality between each stage of the programme chain is largely avoided. The project has found effective solutions to the two fundamental difficulties standing in the way of the entirely MPEG2 programme chain: switching of bit-streams and bit-rate changing. Real-time and software bit-stream switching can now be implemented to frame accuracy in video and audio without perceptible distortion. Off-line and on-line editing can now be used to assemble programmes from MPEG-2 coded bit-streams stored on a standard PC hard disk. The ability to transcode from a higher to a lower bit-rate while maintaining a quality equal or better than coding only once at the lower rate, means that the bit-rate used in earlier parts of the chain need only be equal to or a little higher than that anticipated for final delivery. Storage and network costs are reduced as statistical multiplex can be used on previously compressed material with quality loss.
Summary : It has been shown that transparent cascading of MPEG-2 video coders and decoders is possible by ensuring that the same coding decisions are used in each generation. This is the basis of the Mole. The Mole has been shown to be invisible, even on the most critical picture material. Algorithms for transparent switching of MPEG-2 video bitstreams have been developed. These allow full flexibility for positioning of the switching point in the bitstream. Algorithms for bit-rate changing of MPEG-2 bitstreams have been developed. These give substantially higher picture quality than is possible with conventional decoding and re-coding. Loss of sound/vision synchronisation can occur as a result of restrictions imposed on switching times by audio and video frame structures. A means has been devised which can minimise the accumulation of synchronisation error. Constraints on the positioning of switching and editing points within the MPEG Layer II audio bitstreamhave been eased by the development of a signal processing technique for repositioning frame boundaries. Higher quality re-coding of previously encoded audio signals can be achieved by deducing information about the previous encoding from the signal itself. A method for transmitting audio frame synchronisation information and hidden data has been devised. Signal processing techniques have been developed for the manipulation of MPEG layer II coded audio signals to produce a seamless programme from a number of individual source items.
Summary: video The distributed programme acquisition and editing system is a network of IT file servers and workstations interconnected with ATM. The system is configured by software to allow broadcast quality MPEG signals to be stored and retrieved, converted into low resolution versions for browsing and edited together to make finished programmes. Interesting aspects of this system are the use of novel MPEG bit stream processing techniques and CORBA controlled streaming interfaces. The novel MPEG bit stream processing techniques permit high-quality frame-accurate manipulation of even the most compressed streams with a long Group of Pictures. The use of highly compressed MPEG streams allows broadcast quality video to be handled by relatively inexpensive IT platforms. The CORBA controlled streaming interfaces provide flexibility in setting up connections within the system and ease the integration of new services. Demonstrations were given during the last year of the project at EXPO'98 and IBC'98. The result owners intend to license the technology.
Summary: The result consists of production hardware to generate the video MoleTM signal from an MPEG2 bitstream and to re-encode a video signal with or without Mole to an MPEG2 bitstream with minimal quality loss.The re-encoding hardware incorporates a very high quality encoder for first-time encoding of video signals.The result also includes SMPTE Standards covering the technology and the offer of licence agreements for its exploitation, audio The result consists of hardware, which has been developed to implement techniques for decoding and re-coding MPEG audio without noticeable loss in quality.By transmitting a "Mole" along with the decoded audio, the subsequently coded bitstream is nearly identical to the original bitstream.This means that conventional digital audio systems not employing compression can be used with MPEG audio without the quality loss normally introduced on re-coding.The hardware units are prototypes to demonstrate that the techniques developed in this project are realisable. The hardware is fully functioning and was demonstrated as part of a combined audio/video demonstration at IBC98. Assistance would be given to enable a licensee to implement these techniques in their decoders or encoders.