DE2608240A1 - Video disc player audio cutout - senses when signals are repeated using memory system and comparator - Google Patents

Abstract

The video disc player, for spiral track discs has a picture detector (6-11) detecting when the same track is scanned several times (due to radial jumping) and automatically producing a signal (Us) that cuts out the audio channel (2, 4) to prevent the audio signals being repeated as well as the video signals. The absence of sound is regarded as less disturbing than repeated sound. Two memories (9, 10) alternately retain codes ('1', 'O') representing picture-signal sequences. The alteration depends on the number of rotations made by the disc. A comparator (11) compares the outputs of the memories and produces the sound-blocking signal when they are the same.

Description

Video record player

There is a video disc player known (DT-AS 20 29 909), in which the The scanner is mechanically guided through a spiral groove and is resilient in the process is attached to a carriage which is moved radially over the optical disc. The sled carries out a so-called forced feed, while the groove fine-tunes the Carries out sampler, which is made possible by the resilient storage. On the image plate an image sequence of an integer number of images is recorded on each circumference, in particular a complete picture, i.e. two interlaced fields.

When playing, the pickup follows the spiral groove so that the image sequences are played back one after the other, together with the at the same time recorded audio signal. In practice it happens that the scanner on a Point of the circumference jumps in the radial direction into an adjacent groove section. Since an image sequence consisting of an integer number of images is recorded on a perimeter is, the scanner jumps to the corresponding pixel of a previous or the following picture, so that no disturbance occurs in the picture. It will then only the same sequence of images, e.g. the same image, reproduced several times. These Repetition of the same picture is eventually made by the so-called forced feed ends again, which causes a forced movement of the scanner in the radial direction.

While with the mentioned jumping the image reproduction is not essential is impaired, however, there is a disturbance in the sound reproduction, because a short section of the audio signal is played back repeatedly. At a Image plate with a whole image per revolution is e.g. a segment of 40 ms of the tone repeated at a frequency of 25 Hz. That means an annoying rattle in tone.

The invention is based on the problem of this disturbance in the sound reproduction to eliminate.

This object is achieved by the invention described in claim 1 solved. Advantageous further developments of the invention are specified in the subclaims.

The invention is based on the consideration that a gap in the sound reproduction much less disturbing than the additional signal that occurs during the repetition. Therefore, the sound channel becomes each time the pickup jumps in the radial direction and the sound would be disturbed, temporarily switched off. Criterion for this Shutdown is always that an image sequence assigned to a circumference of the optical disc has been scanned several times in succession.

The invention is based on the drawing of an exemplary embodiment explained. FIG. 1 shows a block diagram of the invention and FIG figure 2 curves to explain the mode of operation. The small letters show which ones Points in Figure 1 are the signals according to Figure 2.

Figure 1 shows a video disc player 1 with a sound channel 2, a Video channel 3, a loudspeaker 4 and a picture tube 5.

The sound interference suppression circuit includes a switch 6, a generator 7, a switch 8, two memories 9, where, a comparator 11 and a gate 12.

The mode of operation is explained with reference to FIG. On a perimeter a whole image with a duration of 40 ms is recorded on the optical disc. Every second image is identified by an identification signal "1" according to FIG. 2a.

This signal is during a blank line of the vertical blanking time recorded and is closed with the generator 7 during this blank line Switch 6 given to switch 8. The switch 8 is from the generator 7 with a Switching voltage b of 12.5 Hz switched before the beginning of each picture, so that the memory 9,10 each store the identification signals of two successive images.

These characteristic signals are compared in the comparator 11.

If the scanning is done correctly, one picture at a time is scanned, the identification signals lllft and "0" are always in the memories 9, 10. saved. In the case of such different signals, the comparator 11 generates an output 12 a voltage, which is however not used.

The comparator does not generate a manipulated variable at output c. Gate 12 thus remains permeable, so that the sound can be heard in the desired manner with the loudspeaker 4 is played. So long so at the outputs of the switch 8 the identification signals ~ 1 "and and 0 appear alternately from picture to picture, so one If the image plate is scanned undisturbed, the gate 12 remains transparent.

According to Figure 2a 'is now by jumping the scanner into a adjacent groove section during revolution No. 2 that during revolution l scanned image scanned again so that at the beginning of rotation no. as with correct sampling, the identification signal "0", but the identification signal 1 occurs. The comparator 11 now receives two identical signals at its two inputs, namely 1. It then generates a manipulated variable Us at its output c, which is more desirable Way, the gate 12 locks and interrupts the sound reproduction. At the beginning of the revolution No. 3 the same image is scanned again by jumping the scanner again, so that the comparator 11 again receives two identical identification signals "1". Gate 12 thus remains blocked in the desired manner and the audio channel is interrupted. At the beginning of rotation no.4, the scanner scans the next image sequence again, so that now the identification signal "0" occurs again. The comparator 11 now receives again two different characteristic signals, so that the manipulated variable U5 on line c ceases to exist. The gate 12 is permeable again and the sound reproduction is more desirable Way turned on.

In the example shown, the sequence of images consists of one revolution the image plate from an image. If several images are recorded per revolution, the circuit is to be modified accordingly, in such a way that each of the identification signals after the sequence of images assigned to one rotation has elapsed, e.g. after three or vir pictures, can be compared with each other. At four frames per revolution it would then switch 8 to the other after each four images have elapsed position be switched. In the case of an optical disc with no recorded identification signals the memories 9,10 constantly receive the signals "0", ie the same values, and the Block the audio channel in an undesired manner. Therefore it is convenient to use the circuit to train so that it is ineffective per se and only effective if the circuit detects the presence of a recorded identification signal. Then there is compatibility guaranteed with plates without identification signals. The circuit is designed, for example, that it is only effective and the manipulated variable Us can generate if for a a certain time of e.g. l s a regular pattern e.g. 0 - 1 - 0 - 1 - 0 - l im sampled signal during the corresponding time, e.g. a blank line during the vertical blanking time is determined. With consecutive numbering of all image sequences the circuit can be activated, i.e. the blocking of the audio channel, once a frame sequence number has been recognized, i.e.

if it is an appropriately marked image plate.

L e r s e i t e

Claims (7)

Claims with video disc player with a through a spiral 1. Optical disk player groove of the optical disk guided scanner, being along the A sequence of images including a sound signal is recorded on each groove circumference is characterized by an image recognition circuit (6-11) which, when the Image sequence of the same groove circumference is scanned several times in direct succession, a manipulated variable (Us) blocking the audio channel (2,4) is generated. 2. Player according to claim 1, characterized in that two memories (9,10) are provided, which alternate with the number of revolutions of the optical disc different image sequence identification signals (11111, "O") fed from image sequence to image sequence are, and that at the outputs of the memory (9,10) a comparison circuit (11) is connected, which, if the stored values match, the manipulated variable (Us) generated. 3. Player according to claim 1, characterized in that at one Image plate, the image sequences of which are continuously numbered by a digital identification signal are evaluated in the detection circuit (6-11) only the last bit of the identification signal will. 4. Player according to claim 1, characterized in that the circuit for generating the manipulated variable (U5) in itself ineffective and only by one of the image plate scanned identification signal for the image sequences is effectively controlled. 5. video disk for a player according to claim 1, characterized in that that the image sequences assigned to a groove circumference alternate from image sequence to image sequence are provided with different identification signals ("1", "0 '). 6. Plate according to claim 5, characterized in that every second Image sequence is marked with a pulse (Fig. 2a). 7. Plate according to claim 5, characterized in that the identification signals are recorded during the blank lines of the vertical blanking period.