Television – Image signal processing circuitry specific to television – Chrominance-luminance signal separation
Reexamination Certificate
2000-03-13
2001-10-09
Hsia, Sherrie (Department: 2614)
Television
Image signal processing circuitry specific to television
Chrominance-luminance signal separation
C348S669000, C348S670000
Reexamination Certificate
active
06300985
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to an apparatus for decoding of composite video to provide high quality serial digital output and, more particularly, to a combination of unique circuits including a three-dimensional comb filter for providing better separation of composite video into luminance and chrominance components, and an optional interpolation circuit for removing any time-base errors on the composite video input.
During the transition to digital television (DTV) production and broadcasting, high quality decoding of composite video signals to produce a serial digital signal is essential to produce digital signals that are comparable to those that originate as digital signals. For signals that originate as composite video, the quality of the DTV signal at the end of the transmission system is only as good as the initial conversion to serial digital interface (SDI). Improper decoding can leave artifacts which, although normally masked in the current National Television System Committee (NTSC) and Phase Alternating Line (PAL) standards, show up as visible errors when viewed on digital television sets. Decoded composite signals may have vertical smear, color errors at vertical transitions, grainy noise, loss of horizontal resolution in both the luminance (luma) and chrominance (chroma) signals, and contouring effects. Also, once a composite signal is decoded incorrectly it may be impossible to fix the problems that are created.
SUMMARY OF THE INVENTION
This invention is a composite video decoder that produces a higher quality digitization, separation of the digitized composite video signal into luminance and chrominance, demodulation of the chrominance signal to its R-Y and B-Y components, removal of time base errors, synchronization of the output to the station reference signal and conversion of the three parallel digital signals to a serial digital signal conforming to International Radio Consultative Committee (CCIR) 259 specifications. A number of unique circuits are made to work together to achieve this improvement in video performance. The innovations consists of the following unique circuits: a three dimensional digital comb filter, an interpolation circuit for time base correction, a sync error detector circuit, a noise measurement circuit and a means of using the noise measurement level to adapt the other circuits for best operation at various noise levels of the video input signal. A unique digital line recursive filter is also used to extract the horizontal synchronizing signal whether the signal is clean or masked by a very high noise level riding on the video signal, which occasionally occurs on poor satellite or microwave links.
The unique circuit designs in the composite video decoder are designed to work together to provide a very high quality translation from a composite video input to a serial digital interface output (SDI). However, many of these circuits may be used in combination with other prior art to improve the operation of other products. Therefore, each unique circuit is described separately with an explanation of how it works with the other circuits.
The combination of circuits makes a much better video decoder. The three dimensional comb filter with the burst locked clock, chroma demodulator, the sync error detection, the interpolation time base error correction circuits, noise measurement circuits and noise immunity circuits work together to achieve a much better digital video output than possible with previous techniques.
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Curtis John W.
Lowe Virgil L.
Fortel DTV
Hsia Sherrie
Womble Carlyle Sandridge & Rice PLLC
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