摘要:
This invention concerns a method of reproducing, at a selectable magnetic tape speed different from that used during the recording, a video signal stored in a plurality of separate tracks inclined to the center line of the magnetic tape by means of a head wheel carrying peripherally arranged magnetic heads, wherein the addresses of reproduced lines of picture information are derived solely from the composite signal reproduced from the magnetic tape, wherein useful lines are read into respective locations of a picture store in accordance with these line addresses, and wherein the stored lines are read out from the store in a predetermined sequence.In the embodiment described the line addresses are derived by a counter to the counting input of which are delivered pulses which correspond to that of the horizontal synchronizing pulses taken from the magnetic tape, to the resetting input of which are delivered pulses which correspond to the vertical synchronizing pulses taken from the magnetic tape, and to a third input of which are delivered pulses the frequency of which corresponds to the frequency of cross modulation disturbances and each of which causes a change in the registered count by an amount which is determined by the registered count itself and whether the tape reproduction speed is greater or less than the recording speed.
摘要:
A method and apparatus for representing the amplitude curve of a selected portion of a video signal upon the picture screen of a video display device, at least the selected portion being in digital form and not requiring conversion to analog form prior to such representation.This is achieved by using the line structure of the line raster produced on the picture screen of the video display device as a digital-analog converter. The range of possible digital values for the individual picture elements of the selected line of the video signal are allocated as reference values to respective lines of the line raster, and during each line period of the line raster the digital values of the elements are compared in succession with the appertaining reference value. When during any line period of the line raster the compared values agree the picture screen is momentarily brightened, so that each picture element of the selected line is represented on the screen with a vertical displacement determined by its digital value, so that an amplitude curve similar to an oscillogram is produced having a horizontal time axis.In a further embodiment of the invention, arranged to display the amplitude curve of selected picture elements each taken from a respective line of the video signal, the reference values are allocated to respective columns of the line raster of the display device. The result is the production of an oscillogram on the picture screen having a vertical time axis.
摘要:
A complete analog color-T.V. signal is separated into a luminance component and a color component. Each component is digitalized and then written into an RAM sequentially using a first addressing schedule for the write-in. The information is then read-out using a different addressing schedule for the read-out. The thusly read out digitalized components are converted back into analog form and combined to form another complete analog color T.V. signal. This technique makes possible a variety of special effects, including horizontal and/or vertical image compression, the display of a half image and alongide it a mirror-symmetrical version thereof, the storage of four color T.V. images in a manner which is interleaved in both the x and y directions of the memory, and others.
摘要:
An analog PAL color television signal which is to be encoded is passed through a comb filter to separate the signal into a chrominance component and a luminance component each having a carrier frequency. Each signal is then separately scanned at a rate which is directly related to the color carrier frequency (4.43 MHz) of the signal. The luminance signal is fed to a scanning and holding circuit which scans it at a rate of twice the color carrier frequency or 8.86 MHz. The chrominance signal is fed to a scanning and holding circuit which scans it at a rate which is one-half the color carrier frequency of 2.21 MHz. This scanning and holding of each component signal converts the signals into a corresponding PAM signal. Each PAM signal is then quantized and encoded in a PCM coder. The resulting signals are applied to a digital combiner which thereby produces a digital color video signal.
摘要:
A digital main store having a capacity of one field and a buffer store of much lower capacity upstream of the main store are so arranged that the buffer control controls the buffer store to compensate frequency differences between an input television signal and a reference signal. An address generator controls the main store to compensate phase differences between the two signals.
摘要:
A head wheel is rotated at a predetermined, essentially constant speed within a tape cylinder over which a tape is guided in a spiral path, on which video signal tracks are recorded in inclined track portions. The instantaneous position of the head wheel is determined, for example by a tacho generator applying signals to a counter, phase-synchronized by the outputs from the head wheel tacho generator. The instantaneous position of the tape is determined, for example from sensing the cross modulation of signals derived from the head as the head crosses from one track portion to another, or by sensing the phase jump of the pulse sequence of the horizontal synchronization signals; the two position signals are combined in a logic stage so that a line address can be derived of a signal transduced at any one instant by said head from an incremental area of the tape, the signal being associated with the line address for storage, for example in a memory for subsequent re-recording or reproduction at a time relation (slow motion or fast motion) differing from the original recording speed.
摘要:
The invention provides an apparatus for producing video frequency color value signals which correspond to a desired arrangement of vertical or horizontal color bars on a television screen. In the case of vertical color bars the apparatus derives during each line period an identical series of pulses having a multiple of the line frequency. Each series of pulses is applied to a binary counter which provides as output a sequence of sets of binary signals. This sequence of sets of binary signals is translated by a pre-programmed store into a further sequence of sets of binary signals, these latter sets of signals being applied to a digital-to-analogue converter adapted to derive therefrom corresponding sets of color value signals. Each set of color value signals defines a differently colored line segment. The effect of this operation over a plurality of successive line periods is to build up a number of vertical color bars each composed of vertically adjacent line segments of the same color derived from identical sets of color value signals occurring in successive line periods.In the case of horizontal color bars the apparatus operates in a similar manner except that the series of pulses initially produced is at a fraction of the line frequency and is derived once for each field period rather than once for each line period.
摘要:
In playback scanning of oblique tracks the jumps of velocity errors in the transition from one head to another are found to be substantially constant, but the magnitude of the velocity error as a whole is subject to statistical fluctuation and the like. Within a track a velocity error determined for one line is used for correction in the following line, while for the first line the magnitude of a jump from a previous magnetic head changeover in the same sense is utilized. With the help of a value from the last line or next-to-last line of the earlier track, a correction value is provided for the first line of the after next track. A ramp signal is inserted in each horizontal blanking interval ahead of the color synchronization signals, raising the latter to the top of the ramp level. The inserted signals are digitized along with the video signal. Samples of the digital ramp signal which pass through a magnitude window (70-73), which is set for passage of not more than two samples in a narrow range symmetrical with respect to the ramp midpoint, address a PROM which converts those magnitudes into timing error values of the pulse generator which provides sampling rate pulses for the converter that digitizes the video signal. The timing error values are used to correct the phase of that pulse generator.
摘要:
The rotary headwheel device for scanning oblique tracks on an advancing magnetic tape is provided with normal playback heads which follow the recording heads and trace the path of the same oblique tracks and also with auxiliary playback heads which trace the path of the respective tracks which the normal playback heads trace but do so 6 and 1/2 revolutions in advance. In order to improve display of the content of recorded digital television signals in a slowed down or accelerated motion mode, the auxiliary playback heads are shifted axially to offset them by a half track width from their position useful for audio processing, whenever the magnetic tape playback speed is off-normal. At such times the outputs of the several normal playback heads are evaluated as to error rate and if any of these outputs exceeds a reference error rate, a switchover unit on the rotary scanning device switches the rotary transformers, which carry the playback outputs to processing channels, from the normal playback heads to the auxiliary playback heads. The error rates are then measured and evaluated for the auxiliary playback heads, and when one of them shows an error rate exceeding the reference error rate, the rotary transformers are switched back to the normal playback heads and so on. The mechanical shift of the relative offset between auxiliary playback heads and normal playback heads is made and maintained electromagnetically for the duraton of off-normal tape speed operation in playback.
摘要:
The head wheel of a video recorder-reproducer is equipped with a set of four advanced read heads, in addition to the usual sets of four read and write heads, so that each advanced read head can read the contents of an oblique track on a magnetic tape on which one of the write heads will be able to record thereafter and which will be read still later by one of the normal read heads. The advanced read heads are so located that while one of them is reading a track, one of the normal read heads is out of contact with the tape. The advanced read heads are used for reading out audio sections of video tape tracks for processing and rerecording in accordance with a previously known processing procedure used in editing newly recorded video tapes for better audio recording. The normal read heads are available for an after-check of the rerecorded audio. A switching system timed by the rotation of the head wheel disconnects each of the normal read heads in a sequence during the periods in which they are respectively out of contact with the tape and at the same time the switches in one of the advanced read heads for scanning the mid-portion of the recorded tracks where the audio sections of the recording are located.