Television – Format conversion
Reexamination Certificate
1999-03-31
2002-03-05
Lee, Michael (Department: 2614)
Television
Format conversion
C348S445000
Reexamination Certificate
active
06353459
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to video data processing. More particularly, the invention relates to real time conversion of video data.
BACKGROUND OF THE INVENTION
Video data encoded according to National Television Standards Committee (NTSC) standard in the United States has a frame size of 720 pixels wide by 480 pixels high and a frame rate of 30 interlaced frames per second. Other video data encoding formats exist, for example, Phase Alternation Line (PAL) and Séquentiel Couleurs à Mémoire (SECAM). These formats are sometimes referred to as standard definition (SD) formats.
High definition (HD) television video data is encoded in a format that provides higher resolution than standard format video. For example, HD formats include 1280 pixel by 720 pixel progressive frames, 1920 pixel by 1080 pixel interlaced frames, or 720 pixel by 480 pixel progressive frames. HD formats are described in greater detail in “ATSC Digital Television Standard” available from Advanced Television Systems Committee (September 1995).
Video decoding hardware such as televisions, video cassette recorders (VCRs) and other devices designed to operate with SD video data generally cannot decode HD video data. Because a large base of SD devices are currently in use and many users are unable or unwilling to upgrade SD devices to HD devices, conversion devices have been developed.
FIG. 1
is a block diagram of one conversion of high definition video data to standard definition video data. In general, conversion according to
FIG. 1
is performed on frames stored in memory and the converted frames are returned to memory prior to output.
High definition video frame
110
is stored in memory
100
. High definition video frame
110
can be decoded and transferred to memory
100
in any manner. Conversion circuitry and/or software
150
reads high definition video frame
110
from memory and converts the high definition frame to a standard definition frame. Conversion circuitry and/or software
150
returns standard definition video frame
120
to memory
100
. Video driver
170
reads standard definition video frame
120
from memory
100
to generate output to a display device (not shown in FIG.
1
).
However, the conversion of
FIG. 1
requires storage of a complete HD frame in memory. If the memory is external to the conversion circuitry, each conversion incurs additional latency to access memory twice (one read and one write). If the memory and the conversion circuitry are included on the same integrated circuit chip, the cost of the integrated circuit is increased. What is needed is an improved method and apparatus for conversion of video data.
SUMMARY OF THE INVENTION
A method and apparatus for conversion of video data is described. A stream of video data encoded according to a source format is converted to a stream of video data encoded according to a destination format. The video data encoded according to the destination format is stored in a buffer. An output stream of video data is generated from data stored in the buffer, wherein access to the data in the buffer is triggered when the data stored in the buffer reaches a threshold value.
In one embodiment, the threshold value is determined based, at least in part, on a horizontal scaling factor and a vertical scaling factor from the source format to the destination. In one embodiment, the threshold value is determined based, at least in part, on a vertical region of interest within the video data encoded according to the source format.
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Unirted States Advanced Television Systems Committee Ghost Canceling Reference Signal for NTSC—ATSC STD Doc. A/49 Aug. 14, 1992, May 13, 1993 pp. 1-6.
United States Advanced Television Systems Committee ATSC Digital Television Standard—ATSC STD Doc. A/53 Apr. 12, 1995, Sep. 16, 1995 pp. 1-64.
Auld David
O-Yang Hsiang
Yeh Gerard K.
Blakely , Sokoloff, Taylor & Zafman LLP
Desir Jean W.
Lee Michael
Teralogic, Inc.
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