Television – Bandwidth reduction system – Data rate reduction
Patent
1996-08-29
1998-11-03
Tung, Bryan
Television
Bandwidth reduction system
Data rate reduction
H04N 732
Patent
active
058316779
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a system for and a method of inter alia capturing and compressing video in real time, and/or for replaying compressed video. The video can either be stored on a computer storage medium such as, but not limited to, a hard disc for future use, or can be transmitted through a communications channel to a receiving station.
EXAMPLE APPLICATIONS
In the digital domain, any application which can make use of video will be enhanced by the ability to process compressed video. Efficient compression and decompression is important in a number of applications, for example those outlined hereunder. Provided below are some descriptions, by way of example only, of how the invention in some of its various forms could be applied.
In one version, the invention can be used to provide the video processing required for a video telephone through PSTN (analog) telephone lines. In this case, the video is compressed in real time for transmission. Because of the constraints on bandwidth, the quality is not expected to be very high. For example, 160*120 pixel resolution, 10 frames per second and 32 intensity levels would be one example of image quality. At this frame rate, there is considerable processor time both to improve compression (cf section on learning) and playback (cf section on playback). Typical data rates are between 9.6 kb/s and 30 kb/s. In this case, a hardware based solution such as MPEG would be uneconomical, and current standard alternatives cannot deliver the required compression rates.
In another implementation, the invention can be used to produce higher quality images and higher frame rates than before. These pictures may include colour, and will be at higher frame rates than the PSTN version. Typical data rates are between 38.4 kb/s and 128 kb/s. Other solutions exist to this problem (for example H.261), but they are typically much more costly to implement.
In a further implementation of the invention, data rates of around 256 kb/s could be transmitted by radio to a receiving station. Because the codec can be implemented in software on a low cost computer system, it is relatively straightforward to add extra features, such as error correction, which may be needed over a noisy radio link. The radio communications could be used, for example, for live news or live sport transmissions to an aircraft. Hardware based solutions would not prove as easy to maintain as this invention, as any chances to the specification of the equipment on the aeroplanes could lead to problems with approval on radio emissions.
In a further example of the invention, video data can be compressed and stored on to a computer disc, such as a CD-ROM, for playback in software or hardware on a microcomputer. In this case, data rates of up to about 2 Mb/s are acceptable, although the invention here may need as little as 400 kb/s at the required quality.
The invention allows the manipulation of large quantities of video data on a computer, and as such can be used for making a digital off line video editing system. In an off line system, the video quality does not have to be as high as broadcast quality, and as such lower data rates could be used. For the professional market, all frames must be captured (for example 25 frames per second in PAL).
In another implementation, the invention allows videos of approximately VHS quality to be edited and shown on a microcomputer. This could be used, for example, to make corporate videos. The efficient compression of large quantities of video is vital in this case.
DISCLOSURE OF THE INVENTION
According to the present invention there is provided a method of processing digital video information in an adapted format for real time transmission or storage after compression, said method comprising: video image frame as a series of binary coded words, describing first and second blocks or groups of pixels of which the second group is a sub-set of the first group and includes a representation of the luminance of 2.times.2 pixel blocks, corresponding portions of one frame
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"Linear Filtering for Reducing Blocking Effects in Orthogonal Transform Image Coding" by Avril et al. Paper No. 92-001, Journal of Electronic Imaging Apr. 1992.
"Adaptive Dynamic Range Coding Scheme for Future HDTV Digital VTR" by Kondo et al, Proceedings of Fourth Intl. Workshop on HDTV and beyond, Italy, Sep. 1991.
"Codeword-Dependent Post-Filtering for Vector Quantization-Based Compression" by Ashok K. Rao, 1993 IEEE Intl Symposium on Circuits and Systems, Mar. 1993.
Eidos PLC.
Tung Bryan
LandOfFree
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