RU2054822C1 - Digital device for separation of brightness and color signals in pal and ntsc decoders - Google Patents

Abstract

FIELD: TV devices. SUBSTANCE: device has analog-to-digital converter 1, two delay units 2 and 5, subtracter 3, low-pass filter 4, two tracing band-pass filters 6 and 9, two control signal generators 7 and 12, frequency detector 8, amplitude detector 10, differentiating unit 11. EFFECT: decreased distortions of brightness and color. 2 dwg

Description

 The invention relates to television and can be used in monitors of analog-to-digital hardware-studio complexes of television broadcasting and in television broadcast receivers.

 A digital device for separating luminance and color signals in decoders of PAL and NTSC systems is known, which contains a series-connected analog-to-digital converter (ADC), the input of which is the input of the full color video signal (PCVS), the first delay unit and subtractor, the output of which is the output of the digital brightness signal , and a high-pass filter (HPF), the input of which is connected to the output of the ADC.

 A disadvantage of the known device is the presence of distortion of the luminance signal resulting from the notch of the spectrum in the region of deviation of the color subcarrier, and distortion of the color signal due to the superposition on the spectrum of the color signal of the spectrum of the luminance signal.

 The aim of the invention is to reduce the distortion of luminance and color signals.

In FIG. 1 is a structural electrical diagram of a digital device for separating luminance and color signals in decoders of PAL and NTSC systems; figure 2 shows a graph of the function F [g (t)]
The device comprises, an ADC 1, a first delay unit 2, a subtractor 3, an HPF 4, a second delay unit 5, a first servo bandpass filter (SPF) 6, a first driver 7 of the control signal, a frequency detector 8, a second SPF 9, an amplitude detector 10, a block 11 differentiation and the second driver 12 of the control signal.

 The device operates as follows.

, состоящая из высокочастотной составляющей сигнала яркости и сигнала цветности. Этот сигнал подвергается обработке с помощью первого и второго СПФ 6 и 9, центральные частоты которых определяются текущей частотой сигнала цветности, а полосы пропускания скоростью изменения фазы и амплитуды цветовой поднесущей, причем законы изменения полос пропускания в каналах яркости и цветности могут отличаться.PCVS using ADC 1 is converted to digital form, in which all subsequent processing is carried out. Using the high-pass filter 4, the high-frequency part of the digital PCVS is allocated

consisting of the high-frequency component of the luminance signal and the color signal. This signal is processed using the first and second SPFs 6 and 9, the central frequencies of which are determined by the current frequency of the color signal, and the passband by the rate of change of phase and amplitude of the color subcarrier, and the laws of change of passband in the luminance and color channels can differ.

где Φ (t) текущая фаза цветовой поднесущей. Сигнал с выхода амплитудного детектора 10 и блока 11 дифференцирования Y(t) c₂

где с₂ константа; а(t) текущая амплитуды цветовой поднесущей, несет информацию о скорости изменения амплитуды. Первый 7 и второй 12 формирователи управляющего сигнала служат для формирования сигналов, характеризующих одновременно проявление быстрого изменения амплитуды и фазы цветовой поднесущей, и могут иметь характеристики преобразования, например, определяемые законами
в канале яркости
Δf_y c_yg(t)|
в канале цветности
Δf_c F[g(t)]
где g(t)

F[g(t)] функция, вид которой соответствует, например, фиг.2;
с_y константа.The color subcarrier in PAL and NTSC systems is modulated in amplitude and phase, while the phase change can be considered as a frequency change according to the law of the derivative of the phase. Therefore, the signal x (t) c ₁ f (t), where c _{1 is a} constant; f (t) the current frequency of the color subcarrier, at the output of the frequency detector 8 is simultaneously information about the change in frequency and rate of change of phase: x (t) c ₁

where Φ (t) is the current phase of the color subcarrier. The signal from the output of the amplitude detector 10 and block 11 differentiation Y (t) c ₂

where c is ₂ constant; and (t) the current amplitude of the color subcarrier, carries information about the rate of change of the amplitude. The first 7 and second 12 control signal conditioners serve to generate signals characterizing simultaneously the manifestation of a rapid change in the amplitude and phase of the color subcarrier, and may have conversion characteristics, for example, determined by laws
in brightness channel
Δf _y c _y g (t) |
in the color channel
Δf _c F [g (t)]
where g (t)

F [g (t)] a function whose form corresponds, for example, to FIG. 2;
with _y constant.

 Thus, the larger the derivative of the phase and / or amplitude of the color subcarrier, the wider the passband of the first SPF 6. The passband of the second SPF 9 in the case of using the law expressed by the dependence F [g (t)] can be significantly narrowed when the color transition signal small enough, and thus it is advisable to suppress noise. For color transitions of medium and small contrast, which are most common, the bandwidth can be maximum. For the most contrasting transitions, the band can be narrowed, for example, by 30% since the color transitions in the image are masked by the brightness component. Thus, the passband of the SPF is consistent with the spectral width of the envelope of the color subcarrier. Thus, the object of the invention is achieved.

Claims (1)

 DIGITAL BRIGHTNESS AND COLOR SIGNALING DIGITAL DEVICE IN PAL AND NTSC SYSTEM DECODERS, containing a serial-connected analog-to-digital converter (ADC), the input of which is the input of the full color video signal, the first delay unit and the subtractor, the output of which is the output of the brightness signal, high-pass filter ( HPF), the input of which is connected to the ADC output, the first and second detectors and the first band-pass filter, characterized in that the first detector is made frequency, the second detector is amplitude, and the band-pass filter is driving, a second delay block is introduced, the input of which is connected to the input of the frequency detector, the amplitude detector and the high-pass filter output, a second servo-pass filter, the first input of which is connected to the first input of the first servo-pass filter and the output of the second delay block, and the output is the output of the color signal, a differentiation unit, the input of which is connected to the output of the amplitude detector, and two drivers of the control signal, while the first inputs of the first and second drivers of the control signal are connected to the output the differentiation unit, the second inputs — with the second inputs of the first and second servo bandpass filters and the output of the frequency detector, the output of the first driver of the control signal is connected to the third input of the first servo-filter, the output of which is connected to the second input of the subtractor, and the output of the second driver of the control signal is connected with the third input of the second servo bandpass filter.

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