Television – Image signal processing circuitry specific to television – Special effects
Patent
1997-11-24
2000-06-27
Tung, Bryan
Television
Image signal processing circuitry specific to television
Special effects
345472, 345141, 348600, H04N 974
Patent
active
060813008
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method and apparatus for generating On-Screen-Display (OSD) messages using stored bitstreams. More particularly, this invention relates to a method and apparatus that extracts and concatenates a plurality of stored "character bitstreams" to construct a valid OSD message bitstream that represents a screen of OSD messages.
BACKGROUND OF THE INVENTION
On-Screen-Display messages play an important role in consumer electronics products by providing users with interactive information so as to guide them through the usage and configuration of the product. The increasing development of digital video technology presents an ever increasing problem of generating OSD messages which are compatible with the various commercially available digital video decoders. These decoders are generally designed to decode bitstreams with a specific format such as the ISO/IEC international Standards 11172 (1991) (generally referred to as MPEG-1 format) and 13818 (1995) (generally referred to as MPEG-2 format).
Although the MPEG standards specify a general coding methodology and syntax for generating a MPEG compliant bitstream, many variations are permitted, thereby supporting a broad range of applications such as desktop video publishing, video conferencing, digital storage media and television broadcast.
In effect, MPEG does not define a specific algorithm needed to produce a valid bitstream. Thus, MPEG encoder designers are accorded great flexibility in developing and implementing their own MPEG-specific algorithms.
This flexibility fosters development and implementation of various MPEG-specific algorithms. However, a common goal of MPEG encoder designers is to design a MPEG-specific algorithm that operates within a prescribed bit rate and operating delay constraint. As such, before an image is encoded, a MPEG-specific algorithm must execute a complex process of balancing numerous factors such as coding mode decisions, picture type, rate control, coarseness of the quantization scale, motion estimation, scalability, detection of distortion, effect of scene cuts and the nature of the signal within the macroblock. Without knowing in advance as to the nature of the images that are to be encoded, an encoder must spend many computational cycles to determine the optimal values for various parameters to properly encode an image.
In the field of OSD message generation, a frame of OSD messages is generally encoded in the same manner as other images without special treatment. However, unlike other images, OSD messages contain repetitively used components, i.e., the basic set of font characters (letters, numbers and other special characters). This prior knowledge of the nature of the input images can be used to improve the efficiency of the encoding method for a frame of OSD messages. Thus, a need exists for a method and apparatus for generating a valid bitstream of a frame of OSD messages by exploiting the repetitive nature of OSD messages.
SUMMARY OF THE INVENTION
The invention concerns an apparatus and concomitant method for constructing a valid OSD message bitstream from a plurality of stored character bitstreams.
More specifically, in accordance with the invention, each character of the OSD font set is initially scaled into a fixed block size, e.g., a block size of 16.times.16 pixels. Thus, each OSD character is enclosed within a block size that is smaller than or equal to the size of a macroblock used by a MPEG-specific encoder. Each character is then encoded into a MPEG-compliant bitstream using the intra macroblock coding syntax. The "character bitstream" which represents each character is stored within a storage medium. When a frame of OSD messages needs to be encoded, the character bitstreams are read from the storage medium and cascaded to form a valid MPEG bitstream which represents the frame of OSD messages.
These and other aspects of the invention will be described with respect to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the Drawings:
FIG. 1
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patent: 3911420 (1975-10-01), Lampson
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4th International Online Information Meeting, London, Dec. 1980, pp. 67-77.
GLOBECOM '92, vol. 1/3, Dec. 6, 1992, Shae et al. "Mixing and Playback of JPEG Compressed Packet Videos", pp. 245-249.
Beyers, Jr. Billy Wesley
Lam Wai-Man
Emanuel Peter M.
Kiel Paul P.
Thomson Consumer Electronics Inc.
Tripoli Joseph S.
Tung Bryan
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