摘要:
In order that one clock signal generator in a digital video signal processing circuit comprising a line-coupled clock signal generator and using, for example one or more field memories is sufficient for writing and reading these memories and can still process a signal from a video recorder, the control loop of the clock signal generator uses a comb filter circuit which rapidly corrects regular variations in an output signal of a phase detector of the control loop, which variations are caused by the head drum of the video recorder, without having to adapt the proportioning of a conventional loop filter circuit.
摘要:
The invention relates to a memory device of the charge-coupled shift register type which is subdivided into four sections each of which has a storage capacity of, for example 208,800 bits and which can operate in different modes: parallel-in/parallel-out (as background video memory); 2.times.2 parallel-in, demultiplex/multiplex mode, for example for 100 Hz TV; scan mode; parallel-in-recirculation mode; "shortened" memory, for example for 525-line system, etcetera. Control is realized via a decoding and timing block in which a multi-bit control word is serially input and decoded. In a scan mode (for example, as a teletext memory), the memory sections are scanned one-by-one under the control of a separate scan register in which a scan bit (logic 1) is step-wise shifted until all sections have been read. Via a data output, the scan bit is transferred, for example to the scan register of a further memory device (via its serial data input) which is connected in series with the former memory device.
摘要:
In a digital chrominance signal processing circuit for a chrominance signal which is sampled at a frequency equal to a number of times the chrominance subcarrier frequency, this frequency can be made variable, without switching to a different crystal frequency, by using a clock signal produced by a crystal oscillator (65) and a digital oscillator (71) which is controlled via a digital number (at 73) and whose quiescent frequency can be changed by changing a number to be applied to an input (95) of an adder circuit (85). Additionally, the adder circuit (85) is supplied with a number representing a control signal (at 88) and applies via its output (83) the frequency-determining digital number to an input (73) of the digital oscillator (71).
摘要:
A device is described for electronically executing a mathematical operation, being Z=KA+(1-K)B. It is also described how this device or how several of such devices can be used for the design of a number of realizations, such as a recursive filter, a digital mixer etc. The basic idea is the electronic implementation of a mathematical function for binary variables.
摘要翻译:描述了用于电子地执行数学运算的装置,即Z = KA +(1-K)B。 还描述了该设备或者这些设备中的几个可以用于多个实现的设计,例如递归滤波器,数字混频器等。基本思想是用于二进制变量的数学函数的电子实现 。
摘要:
Continued circulation of residual signal values in a recursive first order digital video signal filter, in which a truncation circuit (37) is used for eliminating a portion of the least significant bits in the feedback signal path (31, 37, 43, 11) of the filter, is prevented by adding (19, 47, 51) before the trucation circuit a logic one value to the feedback signal path at the level of the least significant bit of the bits remaining after the truncation circuit. Video signal filters of such a type are frequently used as noise suppression circuits.
摘要:
In a digital demodulation circuit for a chrominance signal of a color television signal having a first digital oscillator (35) for producing reference signals and a phase control loop (29, 17, 19, 49, 43) therefor, there is added in the phase control loop a signal combination (at 56) which is obtained from a phase control loop (67, 63, 59) of a second digital oscillator (77). This second digital oscillator derives the sampling frequency for sampling the chrominance signal from a signal source (83) of a constant frequency and couples this sampling frequency to the horizontal deflection frequency. By the addition in the phase control loop of the first oscillator, variations in the horizontal deflection frequency cannot lead to the undesired phenomenon of the first digital oscillator being pulled to a side-band frequency of the color subcarrier wave.
摘要:
An output timebase corrector converts orthogonal sampled video (VS) into asynchronous sampled video (VOS) with asynchronous sample values occurring at clock instants (TC) of a clock signal (CLK). The asynchronous sampled video (VOS) is displayed on a display screen of a display device (DD). A discrete time oscillator (DTO) of a time-discrete phase-locked loop (PLL) supplies a time base signal (OS). The time-discrete phase-locked loop (PLL) determines a phase difference (PE) between the time base signal (OS) and reference instants (FB) indicating a timing of a line deflection of the display device (DD) to obtain the time base signal (OS) being locked to the reference instants (FB). The time base signal (OS) controls a sample rate converter (SRC) such that the asynchronous video values (VOS) which occur at the clock instants (TC) are interpolated from the orthogonal sampled video (VS) by the sample rate converter (SRC) such that the video signal is displayed on the correct position on the display screen. In the output timebase corrector according to the invention all circuits are clocked by clock signals (CLK) originating from one and the same clock generator (OSC).
摘要:
A line synchronizing circuit for a picture display device comprising a control loop for controlling a line oscillator. An incoming line synchronizing signal and also a reference signal generated by the oscillator are applied to a phase discriminator circuit. The output signal of the phase discriminator circuit is smoothed to obtain the control voltage for the oscillator. Pull-in of the control loop is established by means of a coincidence detector. Prior to that, an edge of the reference signal is compared with the center instant of a line synchronizing pulse. When the control loop is in the pulled-in state, it is changed by the coincidence detector to compare the leading edge of a line synchronizing pulse to the center instant between the said edge of the reference signal and its first preceding edge.
摘要:
A time-discrete signal is delayed by a selectable fraction (.delta.) of a sampling period of the time-discrete signal. First (F1) and second (F2) differential signals having mutually different phase characteristics are derived from the time-discrete signal and are subsequently combined (MIX) dependent upon the selectable fraction (.delta.) to obtain a phase-adjusted correction signal. The product of the selectable fraction (.delta.) and the correction signal is added to the time-discrete signal to obtain a time-discrete signal which has been delayed by the selectable fraction (.delta.). The second differential signal is obtained by means of a differentiator with asymmetric coefficients in order to optimise the transfer characteristic for .delta.=0.5.
摘要:
A non-integral delay circuit for delaying a digital signal by a selectable fraction (.delta.) of a sampling period of the digital signal includes a first differentiator (S3) to obtain a first differential signal (F1) having a first phase characteristic with respect to the digital signal, a second differentiator (D) to obtain a second differential signal (F2) having a second phase characteristic with respect to the digital signal, the first and second phase characteristics differing from each other, a mixer (MIX) for combining the first (F1) and second (F2) differential signals in dependence on the selectable fraction (.delta.) to obtain a phase-adjusted correction signal, and an adder (A9) which adds a product (M3) of the selectable fraction (.delta.) and the phase-adjusted correction signal to the digital signal, to obtain the digital signal delayed by the selectable fraction (.delta.) of the sampling period of the digital signal.