Television – Basic receiver with additional function – For display of additional information
Reexamination Certificate
1998-06-02
2001-01-16
Hsia, Sherrie (Department: 2714)
Television
Basic receiver with additional function
For display of additional information
C348S589000, C348S600000, C348S607000
Reexamination Certificate
active
06175386
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method of processing a television picture signal including video and graphic information, said processing comprising the step of storing the television picture in a picture memory. The invention also relates to a television receiver adapted to carry out such a method.
2. Description of the Related Art
Current television receivers show an increased use of digital signal processing circuits for features, such as noise reduction and/or flicker reduction. Generally, the receivers have a picture memory for that purpose. Television receivers also have additional features, such as teletext reception, sophisticated menu-driven control systems, multilingual subtitling, electronic TV-Guide facilities, etc. These additional features require on-screen-display of graphic information. Often, this graphic information is generated by character-based graphics devices which require a moderate memory capacity. However, there is a trend towards enhanced graphics devices which define graphic information on a pixel-by-pixel basis and require a large memory capacity.
Needless to say, that it is important to reduce the memory capacity in such television receivers, for example, by using a shared memory for the various functions. A television receiver having such a shared memory is disclosed in U.S. Pat. No. 5,119,200. This prior art comprises a picture memory for storing the received video signal as well as the locally generated graphics (teletext) signal. The receiver utilizes the fact that a pixel on the screen either represents video information or graphic information. One bit per pixel is stored in the memory to indicate the type of information. The prior-art receiver allows the video information in the memory to be refreshed and processed at the field or frame rate without affecting the stored graphic information.
OBJECT AND SUMMARY OF THE INVENTION
It is an object of the invention to further reduce the memory capacity in such a television receiver.
To that end, a method of processing a television picture signal including video and graphic information is provided, said processing comprising the step of storing the television picture in a picture memory, characterized by compressing the video information and graphic information in accordance with different compression algorithms, and storing the compressed video and graphic information in said picture memory. Preferably, both types of compressed information are stored in the same memory.
The invention will be appreciated if it is realized that applying a certain compression algorithm to video as well as graphic information generally results in different artifacts and compression ratios for the different types of information. The invention is based on experiments which show that a compression algorithm which is adequate for one type of information, in terms of data reduction and coding artifacts, may be disastrous for another type of information. The perception of the signals is totally different. Often, graphic information is text, the legibility of which is of crucial interest. For video, natural behavior of moving objects and a sufficient signal-to-noise ratio are important. For example, MPEG-compression of video information yields satisfactory results because it is based on average video statistics. However, applying the same MPEG-compression to graphics leads to a considerable degradation of the graphic picture quality. This is felt to be unacceptable because consumers have meanwhile become used to very high quality teletext and on-screen-display images.
Preferably, the video information is subjected to a lossy compression algorithm, and the graphic information is subjected to a loss-less compression algorithm. Data reduction of the television signal is achieved herewith while the high quality of the graphic information is preserved in conformity with the consumer's expectations.
The invention is not restricted to receivers in which the graphic information is locally generated, inter alia, in the form of teletext pages or on-screen menus. Video information and graphic information can also be mixed at the transmitter end. Television stations insert their logos in the transmitted picture and use sophisticated graphic devices for program captions and subtitles. Popular quiz programs are based on simultaneously showing the players and the electronically generated game field with the players' scores. Further, with the advance of interactive TV and video-on-demand, video images will often be mixed with graphic menus. In order to also reduce the memory requirements for these television pictures, while maintaining the high quality of the embedded graphic information, an embodiment of the invention further comprises the step of determining the type of information in a given picture area on the basis of a predetermined property of the television picture signal in said picture area. The television receiver now automatically detects whether the information in a picture area (for example, a rectangular block of pixels) is video information or graphic information, and selects the appropriate compression strategy for that area, accordingly. An example of a property of the television picture signal is the amount of uniformity between pixel values in a given image area. The determination of the type of information in a picture area can be improved by taking account of the type of information in adjacent (spatially or temporally) picture areas.
REFERENCES:
patent: 5119200 (1992-06-01), Van Den Hombergh et al.
patent: 5448307 (1995-09-01), Gelissen et al.
patent: 5926611 (1999-07-01), Yang
De With Peter H. N.
Van De Schaar-Mitrea Mihaela
Goodman Edward W.
Hsia Sherrie
U.S. Philips Corporation
LandOfFree
Television picture signal processing in which video and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Television picture signal processing in which video and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Television picture signal processing in which video and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2529642