Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N5/00—Details of television systems
  • H04N5/76—Television signal recording
  • H04N5/91—Television signal processing therefor
  • H04N5/93—Regeneration of the television signal or of selected parts thereof
  • H04N5/937—Regeneration of the television signal or of selected parts thereof by assembling picture element blocks in an intermediate store

Definitions

• the invention relates to a video recorder according to the preamble of claim 1.
• the video images are recorded field by field in oblique tracks on a video tape.
• Each helical track comprises the picture lines of a field which are joined together.
• the inclined tracks are arranged side by side without any gaps.
• the video tape is wound with a half turn around a head wheel of the video recorder which rotates at a constant speed and which contains two recording and playback heads for recording or scanning the video images.
• a video head is provided alternately for recording a full field. The two video heads have different angles of inclination to each other.
• a video head as a playback head can only scan information from the helical track that was recorded on the tape by a video head with the same slit inclination angle. This assignment reduces when scanning a helical track from the next track to a non-disturbing dimension.
• the display device To reproduce the video images recorded on the video tape, the display device must have the same system properties as the recording device used for recording the video images on the video tape. In addition, the video tape must be moved past the video heads at the same speed as when the video images were recorded on the video tape, so that the video heads remain on the inclined track assigned to them when they are scanned.
• the invention is based on the object of designing a video recorder according to the preamble of claim 1 in such a way that the video images reproduced in a search run are as free of interference as possible. This object is achieved according to the invention by the features specified in the characterizing part of claim 1.
• a video recorder In a video recorder according to the invention, the reproduction of a trouble-free image during a search of the device is achieved almost without additional mechanical means.
• a special electronic program sequence which is contained, for example, in a microprocessor already present in the video recorder, an oscillating transport movement of the video tape is generated, the average tape speed of which is the search speed of the video recorder.
• This oscillating transport movement of the video tape can, for example, due to the mechanical inertia of the
• Belt transport system can be generated by the alternating specification of two different transport speeds. If video playback heads are used whose track height is greater than the track width of the video tracks of the tape, the slower tape speed can be used to scan a complete video field containing a field is provided to be two to three times the recording speed.
• An envelope detector which detects from the bumps of the envelope of the FM-modulated video signal generated by the head amplifier of the video playback heads, an oscillation width of a positive bump that spans the switch-on time of the associated video playback head, allows a relatively short period of the slow tape speed. As a result, a relatively high frame rate can be achieved during the search despite the mechanical inertia of the tape transport system.
• FIG. 1 is a block diagram with the circuit and functional blocks of a video recorder required for trouble-free image reproduction of a search
• FIG. 2a shows schematically juxtaposed tape sections of a video tape with the scanning path of the video heads over the video inclined tracks during an oscillation of the oscillating tape transport movement
• Fig. 2b the duty cycle of the two video heads as
• FIG. 1 shows a block diagram which contains the circuit and drive blocks of a video recorder which are required for interference-free image reproduction of a search run.
• This search run is connected with a fast forward or rewind run of a video tape 1 which is inserted into the video recorder.
• the video tape 1 is pressed by a pressure roller 3 against a capstan 2, which is driven by a motor 4 and transports the video tape forwards or backwards.
• the motor 4 and thus the tape speed of the video tape 1 are regulated by a tape servo circuit 5, to which the necessary control signals are fed from a tape run control circuit 6.
• the tape run control circuit ⁇ is connected to an operating device 7, on the operating elements 8 of which a user of the video recorder carries out the desired operating setting of the video recorder.
• the video tape 1 is guided with half a loop 9 around a head wheel 10 of the video recorder.
• the head wheel 10 contains two video heads K1 and K2, which serve as playback video heads in the playback mode of the video recorder, and is driven by a head motor 11.
• the video heads K1 and K2 are different video tracks on the video tape 1 due to their different gap inclination angle assigned. These video tracks are arranged in an alternating sequence as inclined tracks on the video tape largely next to each other, as shown schematically in Fig. 2a. In Fig. 2a twelve rear interlaced tape sections 12 to 19 of the video tape 1 are shown side by side.
• the non-hatched video tracks 20 are assigned to the video head K1 and the hatched video tracks 21 to the video head K2.
• Each video track has the length of a field, ie the video signals of the lines of a field are recorded in a continuous row.
• a head control circuit 20 regulates the head motor 11 in such a way that the head wheel 10 contains a number of digits determined for normal playback and the video heads K1 and K2 scan the video tracks 21 and 22 assigned to them.
• the video signals sampled by the video heads K1 and K2 from the video tape 1 pass via rotating transmitters 23 and 24 and via a head switch 25 into a head amplifier 26, at the output 27 of which a frequency-modulated video signal S FM occurs.
• This frequency-modulated video signal S FM is converted in an image signal processing arrangement 28 into a standard-compliant video signal S N , which is fed via a first playback transmission path 29 to a video output 30 of the video recorder for transmission to a display device (not shown).
• the Belt run control switch 6 set in the operating state of a fast forward or rewind. In. this
• the program sequence is switched on, in a sequential order and alternately in succession in a first one
• Time period T1 a reference signal S r1 for a high
• Time period T2 a second reference signal S r2 for a low tape speed, for example twice the recording speed, to the
• the frequency-modulated video signal S FM sampled in the tape section 12 by this video head K1 and amplified by the head amplifier 26 has a envelope curve, the course 31 of which is shown for the tape section 12 in FIG. 2c in accordance with the course of the scanning path 32 and which is generated by an envelope demodulator 40 connected to the output 27 of the head amplifier 26 as an envelope signal HS.
• the scanning path of the second video head K2 which is then switched on begins in the next band section 13 with the offset of a video track in a video track 21 not assigned to the video head K2 and then crosses two video tracks assigned to it and two video tracks not assigned to it. This creates two bumps 41 and 42 in the envelope of the frequency-modulated output signal of the head amplifier 26, which indicate the presence of a video signal sufficient for image reproduction.
• the scanning path 34 of the first video head K1 switched on for scanning the tape section 14 crosses five video tracks 21 assigned to this video head K1 and thus generates at the output of the head amplifier 26 five bumps 43 of the envelope 31 of the frequency-modulated video signal scanned in this tape section, which in FIG Band section 14 are shown.
• the video head K2 connected in this band section crosses four video tracks 22 assigned to it, so that the envelope signal HS corresponding to the envelope of the frequency-modulated video signal at the output 27 of the head amplifier 26 has four bumps 44.
• the video head K1 switched on there crosses three video tracks 21 assigned to it, what results in three cusps 45 of the enveloping curve in band section 16.
• the scanning path 37 of the video head K2 switched on in the next band section 17 lies essentially only in the region of a video track 21 not assigned to this head, so that this video head K2 only generates sufficient frequency-modulated video signals of the two neighboring tracks for transmission at the beginning and at the end of its scanning path 37.
• the video head K1 thereby generates a frequency-modulated video signal sufficient for transmission in the band section 18 at the output 27 of the head amplifier 26 the full length of the video track scanned in this band section 18.
• the associated section of the envelope signal HS of this video signal thus forms a single bump 46 which spans the entire turn-on time T K1 of the video head K1 in the band section 18.
• the scan in band sections 18 and 19 corresponds to the scan in band sections 12 and 13.
• Envelope demodulator 40 each the time range in which the head amplifier 26 has a frequency-modulated video signal S FM at its output 27 with one for the
• Image signal processing provides sufficient amplitude.
• the envelope curve demodulator 40 which generates the envelope curve signal HS shown in FIG. 2c at its output 47, is followed by an envelope curve detector 48, which in the switched on state, the envelope signal HS compares with the switch-on signals S1 and S2 of the two video heads K1 and K2 and which, from the shape and arrangement of the bumps 41 to 45 of the envelope signal HS, recognizes a bump 46 whose vibration range completely spans the switch-on time TK1 of the associated video head K1 .
• the envelope detector 48 also transmits the switch-on signal S1 for the video head K1, which is connected to the head amplifier 26 during this bump 46, as a read-in signal Sw (FIG.
• This playback transmission path 50 is switched on during the search mode of the tape control circuit 6 via switches 51 and 52 instead of the normal playback transmission path 29 and contains an analog-digital converter 53, a read-in register 54 and a read-out register 55 of the field memory 49 and a digital-analogue Converter 56.
• the field memory 49 is continuously read out during the entire search operation by a read command R, regardless of a read operation into the field memory 49 possibly carried out via the read-in register 54.
• fields scanned from the individual video track in the band sections 12 and 18 are read into the field memory 49 via the read-in register 54 and the field previously contained in the field memory is overwritten. In between five scans by the video heads K1 and K2, in which 35 fields are not processed. Thus, in the exemplary embodiment shown, every 36th field is read into the field memory 49 and read 6 times therefrom for image reproduction at a search speed which is 6 times the recording speed.

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• Engineering & Computer Science (AREA)
• Multimedia (AREA)
• Signal Processing (AREA)
• Television Signal Processing For Recording (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

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ID=6349190

Family Applications (1)

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Citations (4)

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• 1988
  • 1988-03-09 DE DE3807630A patent/DE3807630C1/de not_active Expired
• 1989
  • 1989-03-06 WO PCT/EP1989/000227 patent/WO1989008965A1/de not_active Ceased
  • 1989-03-06 EP EP89903472A patent/EP0362335B1/de not_active Expired - Lifetime
  • 1989-03-06 DE DE89903472T patent/DE58906883D1/de not_active Expired - Lifetime
  • 1989-03-06 JP JP1504473A patent/JP2987164B2/ja not_active Expired - Lifetime

Patent Citations (4)

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