Television – Format – Including additional information
Reexamination Certificate
1998-10-13
2001-07-03
Hsia, Sherrie (Department: 2614)
Television
Format
Including additional information
C348S468000, C348S475000, C348S589000, C348S486000
Reexamination Certificate
active
06256070
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The invention relates generally to video image encoding and more particularly to the encoding of raster images with closed captioning.
BACKGROUND OF THE INVENTION
Conventional television receiving systems conform to standards, such as NTSC and PAL, which have evolved since the initiation of television broadcasting. Since these standards evolved over time, they include, for example, modulation schemes that allow for the transmission of color images without adversely affecting the reception and reproduction of these images on televisions that are only capable of displaying images in black and white. These standards also include the encoding of closed caption information within each frame, also formatted so as not to adversely affect the reception and reproduction of images on televisions that are not capable of displaying closed caption text.
Standards, such as SMPTE
125
and CCIR
601
, have been developed for the digital production, storage, and display of images that are substantially compatible with the display of images using NTSC and PAL rasterizing techniques, albeit at higher resolution. These standards address the number of lines per screen image (vertical resolution), the number of digital samples per line (horizontal resolution), and the number of bits per digital sample. The encodings provided by these standards are baseband encodings, and do not include, for example, the modulations that are applied for conventional NTSC or PAL raster encodings with embedded closed caption information. To communicate a digital encoding of image data to a conventional television receiver, the image data must be modulated to conform to the conventional television broadcast conventions, as defined for example by the FCC. That is, the FCC has allocated a maximum of 6 MHz for a television channel transmission and has requested the color information, or chrominance, to be quadrature-phase modulated about a chrominance subcarrier frequency at 3.58 MHz. The FCC has also requested the audio information to be frequency modulated about a sound center frequency at 4.5 MHz and the closed caption information to be contained on lines
21
and
284
of the channel transmission, preceded by a clocking signal of approximately 500 kHz. These frequencies are specific for the North American NTSC standard and are different for other standards and countries.
FIG. 1
illustrates a prior art technique for encoding image data
101
, closed caption data
102
, and other signals
143
for communication to a conventional raster television
160
. In this example, an image processing system (not shown) creates digitally encoded image data
101
. The image processing system may be, for example: a computer graphics system that is used to create images; a computer system that receives images from other sources, such as the world-wide web; a digital video disc player; and the like. The aforementioned digital image standard, CCIR
601
, specifies an interface clock rate of 27 MHz for the communication of image data, corresponding to the sample rate of the image data, which consists of a luminance component at 13.5 MHz, and two chrominance components at 6.25 MHz each. The video encoder
130
encodes these samples for transmission to a raster television using conventional television broadcast encoding techniques, common in the art. The video encoder
130
produces raster encoded sample data
131
that is converted into analog form by a digital to analog converter
140
to form an analog video raster signal
141
.
The closed caption encoder
132
separately processes the closed caption data to form a closed caption raster signal
142
that conforms to the particular rasterization standard used. For example, in accordance with FCC standards, lines
21
and
284
of the conventional NTSC television broadcast are allocated to closed caption. The closed caption information consists of two bytes per television frame; the two bytes of closed caption information must be preceded by a 500 kHz sinusoidal clock signal. The c losed caption encoder
132
provides the 500 Hz clock signal followed by two bytes of the closed caption data
102
as the closed caption raster signal
142
.
The sync control
150
mixes the analog video raster signal
141
, the closed caption raster signal
142
, and any other raster signals, such as modulated audio information, teletext encoded messages, and the like. The sync control
150
identifies, for example, each 21
st
and 284
th
line of the composite raster image, and inserts the closed caption raster signal
142
at each such line. In addition, the sync control
150
adds the appropriate synchronization signals, such as the horizontal and vertical sync pulses, to form the composite raster television signal
151
that is communicated to a conventional raster television
160
.
Conventionally, the processing of each form of data
101
,
102
to form components
141
,
142
,
143
of the raster television signal
151
is performed independently, because each form of data
101
,
102
has specific and independently formulated rules and standards. For example, the processing of image data is performed on discrete data samples of the image data
101
, and produces modulated samples of the raster encoded data
231
. The processing of closed caption data
102
, on the other hand, is primarily the appending of an analog sinusoidal signal (not shown) to a subset (two bytes) of the closed caption digital data
102
. This independent processing, however, results in redundancies in the development and production of the components in each of the independent processes, thereby decreasing the efficiency of the system and increasing the costs of devices and systems used to process image data
101
and closed caption data
102
.
Consequently, there exists a need for an encoding system that combines the processing of closed caption data with image data to allow for a reduction in the size or cost and improved efficiency of such a system. In particular, a need exists for the concurrent processing of closed caption data with image data to allow for the time-shared use of a discrete time oscillator (DTO) for providing the closed caption clocking signal as well as the subcarrier signal that is used to modulate the chrominance components of the image data.
REFERENCES:
patent: 5801782 (1998-09-01), Patterson
ATI International SRL
Hsia Sherrie
Vedder Price Kaufman & Kammholz
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