KR0139290B1 - Recording reproduction apparatus for high definition video signals - Google Patents

Abstract

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Description

Video disc recording method and playback device

1 is a main block diagram of a recording system of a high-density video disc recorder to which the present invention is applied.

2 shows a track format of a video disc.

3 and 4 show time charts of video signals showing a recording format.

5 is a main block diagram of a regeneration system.

6 is a time chart of playback processing.

7 is a block diagram showing details of a processing circuit.

8 is a time chart of signal restoration processing.

9 and 10 are time charts of dropout processing.

* Description of the symbols for the main parts of the drawings *

1: Video Disc 10, 11: Photo Detector

21: Dropout detector 42,43,44,45: Line memory

54,56,60,63: Adder

The present invention relates to a disc recording method and a disc reproducing apparatus of a high density (wide band) video signal.

The video recording is divided into two channels alternately by 1H, and recorded on two disc parallel spiral tracks on a disc with a time difference between the channels, so that the dropout process at the time of reproduction is performed strongly and with high precision.

As a method of recording and reproducing a high density (wide band) video signal having a luminance of 20 MHz and a chroma of about 6 MHz on an optical disc, a multichannel method has been considered. In other words, parallel tracks that can be recorded (reproduced) at the same time are provided for the channels, and signals encoded in the channels are distributed to each track for recording and decoded into a single signal during reproduction. According to this method, the recording density of the recording medium is increased even if the running speed is not so high, but the amount of recording and reproducing information per unit time increases by the number of channels. If the recording density is made constant, the recordable time per disc is reduced by the number of channels.

If the number of channels is 2, two parallel tracks are spiraled on the disc. That is, video signals are simultaneously recorded by two optical heads for tracks of individual channels, and video signals are simultaneously reproduced from each track by the two optical heads in the player.

When a signal is dropped out when recording or reproducing a high density video signal, image degradation is more noticeable than when recording and reproducing a normal video signal.

As a method of interpolating a dropout portion, a conventionally widely used method is to set a memory or delay line of 1H (horizontal scanning period), and when a dropout occurs, the signal portion before 1H accumulated in the memory or delay line. This is how you interpolate. This method is relatively simple, but there is a drawback that when the dropout portion is interpolated from the diagonal line part of the image, the diagonal line is not continuous and a discontinuity is generated.

As another interpolation method, when a dropout occurs using the 3H memory, the interpolation is a method of interpolating the average value of the memory contents of the 1H sections before and after the portion. According to this method, the discontinuity point of the oblique line is not so noticeable.

When the latter interpolation method is applied to a video disc device of a two-channel track, signals must be recorded in line sequence (1H, 2H, 3H ...) in each track. Therefore, simultaneous recording (reproducing) of two channel tracks in line sequential format requires simultaneous recording (reproducing) of two fields, and a field memory is required for the recording system and the reproduction system, respectively. This increases the cost.

In view of this problem, the present invention enables simultaneous recording (reproducing) of two channels without using a field memory in the recording system and the reproduction system, and enables the processing of average value interpolation with less image quality degradation for dropout. It aims to do it.

The video disc recording method of the present invention divides a video signal into two channels alternately in units of 1H (horizontal scanning period), and provides a parallel displacement of two channels with a timing displacement of 1H between each channel. I have to record.

The video disc reproducing apparatus of the present invention disregards the video signal in two channels alternately in 1H (horizontal scanning period), and reproduces a disc recorded on two parallel parallel tracks with a time difference of 1H between each channel. A reproducing apparatus comprising: a reconstructing circuit for time-compressing a reproducing signal of each channel, correcting the time difference, and restoring it into one line sequential signal; Dropout correction for detecting an interpolation circuit provided in each channel forming the interpolation signal and a reproduction signal of one channel, and replacing the dropout portion of the line sequential signal with the interpolation signal obtained from the other channel. A circuit is provided.

Since the lines are divided into two channels alternately, an interpolation signal approximating the other channel can be made by the average value signal between lines of the reproduction signal of one channel. In addition, since timing displacement is set between the channels, even if a dropout occurs in one channel, the probability that the interpolation signal obtained from the other channel is affected by the dropout is small. Therefore, powerful dropout processing can be performed by signal interpolation. In addition, since interpolation is performed with an average value between channels, discontinuities do not occur in an oblique portion of an image in the interpolation portion, and a high quality reproduction image is obtained.

Fig. 1 shows a main block (encoder) of a recording system of an optical disc recording / reproducing apparatus for high density video to which the present invention is applied, and Fig. 2 shows a track format of a video disc.

The video disc 1 may be optical, and may be recorded, reproduced, erased, recorded only once and not erased, or a commercially available press-only reproduction disc.

In the track, two of the first and second channels CH-1 and CH-2 are formed in parallel spiral form from the inner circumference of the disk 1 to the outer circumference. The track pitch between channels is, for example, 1.5 mu m, and two-channel simultaneous recording is performed by modulating the two-split laser beam into video signals to form a pit corresponding to the FM carrier on the track. One frame of information is recorded in two tracks of each channel. If the angular velocity is constant (CAV, 1800 rpm), one frame is recorded for each disc rotation.

The interval (circle pitch) between the track of the second channel CH-2 and the track of the first channel CH-1 in the next rotation is 1.67 mu m. The spacing of the parallel tracks of the two channels is smaller than 1.5 [mu] m and the pitch of the pitch is because there is little interference due to crosstalk because the video information is correlated between the channels. Therefore, the recording density is higher than when the entire track is formed at the same pitch.

In addition, the track interval between channels can be narrowed down to about 1.1 μm according to the correlation information, thereby extending the recording time by 20%. If the degree of correlation varies greatly in one disc, it is better to change the track interval between channels according to the degree of correlation.

The audio signal is recorded by time-compressing the PCM signal in the vertical blanking period.

On the reproduction side, a laser beam divided by three is used, focusing and tracking are performed by the beam in the center, and two tracks are simultaneously read out by the beams on both sides.

The video signal to be recorded is a luminance Y signal having a bandwidth of 20 MHz and a color difference signal P _R , P _{B having a} bandwidth of 6 MHz, respectively, as shown in the waveform diagram AC of FIG. 3 (hereinafter simply referred to as color C). Signals R, B). Each channel (CH-1, CH-2) on the disk has a time extension of the Y signal by 5/3 times as shown in Figs. 3, D and E, and the odd lines (Y ₁ , Y ₃ ...) are removed. One channel and even lines (Y ₂ , Y ₄ ...) are recorded alternately on each track of the second channel.

Further, the C signals B and R are each time-compressed by 1/2, and time-division multiplexed with the Y signal. At this time, the even lines B ₂ , B ₄ ... and the odd lines R ₁ , R ₃ ... of the B signal are removed, and the odd lines B ₁ , B ₃ ... of the B signal are divided into two channels. In addition, the even lines R ₂ , R ₄ ... of the R signal are recorded in two channels. Therefore, in each track, the C signals are arranged in a color line sequence of R, B, R, and B.

As shown in Fig. 3, 1H on the disc corresponds to 2H of the recording signal. By the time extension (5/3 times) of the Y signal, the baseband recording maximum frequency drops from 20 MHz to 12 MHz. In addition, the C signal increases the compression frequency of the baseband from 6 MHz to 12 MHz by time compression (1/2 times). Therefore, on the disc, Y signals and R and B signals in the 12 MHz band are recorded by FM modulation.

In order to perform the dropout interpolation described later, a time difference of 4H (2H on the disc) is actually provided between the first and second channels as shown in the format of FIG. In this embodiment, the first channel is recorded with 4H delay than the second channel.

1 is a block of an encoder for converting an input video signal in accordance with the recording format (channel distribution, channel time difference and time extension compression). The Y signal of the input is distributed to the first channel (Y ₁ , Y ₃ ...) and the second channel (Y ₂ , Y ₄ ...) by the branch switch SW-1 which is switched every 1H. Inputs are made to the memory memories 2 and 3. The contents of each memory (2) and (3) are read out over time by a read clock of 3/5 times the frequency of the input clock.

On the other hand, the R signal and the B signal of the input are supplied in parallel to the selection switch SW-2 switched in the 1H alternation, and the B signal of the odd line and the R signal of the even line are selectively outputted alternately in line, and B ₁ R ₂ B ₃ Serialized as R ₄ ... The serial signal of this line sequence is distributed to the first channel (B ₁ R ₂ ...) and the second channel (B ₃ R ₄ ...) by the branch switch SW-3 which is switched every 2H. Inputs are made to the memory memories 4 and 5. The contents of each of the memories 4 and 5 are time-compressed and read out by a read clock of twice the frequency with respect to the input clock.

The read timing of each of the memories 2 to 5 is controlled to have a time division relationship shown in Figs. D and E, and the first channels are the mixers 6, or the second channels are the mixers 7. Are mixed into B ₁ Y ₁ , R ₂ Y ₃ ... and B ₃ Y ₂ , R ₄ Y ₄ .

The memories 2 and 4 of the first channel have a function of channel skew, and output the luminance signal and the color signal of the first channel by 4H delayed from the second channel, respectively. As a result, a wideband video signal is recorded on the disc 1 in the format shown in FIG.

5 shows a block diagram of the reproduction system, and FIG. 6 shows a time chart of the reproduction processing.

As already explained, the parallel tracks on the disc 1 are read simultaneously by the parallel beam pickup. The reproduction signals obtained from the photo detectors 10 and 11 of each channel are supplied from the RF amplifiers 12 and 13 to the FM demodulators 14 and 15, and the demodulated video output is converted into an A / D converter. 16) and (17) are converted into digital signals. Hereinafter, signal processing is performed by digital signals.

The digital video signals A and B of each channel shown in FIGS. 6A and 6B are time-base corrected by TBCs 18 and 19, and the mixer 20 is corrected by the line sequential serial signal i as shown in FIG. Lose. In addition, the mixer 20 has a function of compressing the time axis of the signal of each channel by 1/2, correcting the time difference, and restoring line sequentiality. Since this function is realized by the memory for several lines, the function of the mixer 20 may be provided in the line memories of the TBCs 18 and 19.

In addition, the mixer 20 has a dropout compensation function using a line memory. The dropout of the disc reproduction signal is detected for each channel by the dropout detector 21 in accordance with the outputs of the RF amplifiers 12 and 13. The dropout detection signal is given to the mixer 20 as an interpolation control signal via a suitable delayer 22. In the dropout period, the average interpolation signal formed by the output of the line memory is derived instead of the missing reproduction signal.

The line sequential signal i of the output of the mixer 20 is divided into the Y signal and the C signals R and B by the separator 23, and the Y extender 24 and the C expander 25 are respectively used in FIG. It is time-extended so as to become the signals W and X of the shown normal time base. The extension ratio of the Y extension 24 is 6/5 times, and the extension ratio of the C extension 25 is 4 times. The outputs of each of the expanders 24 and 25 are subjected to frequency-amplification processing and the like in the Y signal processor 26 and the C signal processor 27. Further, in the C signal processor 27, as shown in Figs. 6, Y and Z, the line sequential signals B and R are decomposed and parallelized, and the R signals of odd lines and even lines of missing lines at the time of writing are removed. Processing is generated by interpolation by lines before and after each.

The outputs of the signal processors 26, 27 are provided to the D / A converters 28, 29, 30, and the luminance signals Y, the color difference signals B, R are obtained.

In the audio system, first, the PCM audio signals in the vertical blanking period are output by the separators 31 and 32 from the outputs of the FM demodulators 14 and 15. The separated audio signal is subjected to time axis correction and time extension processing by the TBCs 33 and 34, and digital signal processing such as PCM decoding, deinterleaving, error detection, correction, interpolation, etc. by the decoding and error correction circuit 35. Receive.

The output of the decode error correction circuit 35 is band-limited by the filter 36, and is then decomposed and output into two channels of analog audio signals L and R by the separator D / A converter 37.

FIG. 7 is a block diagram showing details of the mixer 20 in FIG. This circuit is composed of a line memory and a delay, and performs time compression, array restoration of a two-channel distributed signal, time difference correction, and generation of a dropout interpolation signal, respectively. The line memory and the delay can be realized by the RAM and the address controller, and the line memory in the TBCs 18 and 19 can also be used.

The reproduction signals a and b (TBC outputs) of the respective channels shown in time charts A and B in FIG. 8 are provided to the Y / C separators 40 and 41, respectively. Are separated. Each separated component is input to the line memories 42-45 each having a length of 2H on the disk, and is read out by time compression at 1/2 by a read clock of twice the frequency of the input clock. 8 shows time compression output. In addition, in these figures, although Y and C (B, R) are not shown separately on account of the circumstances, they may be processed separately according to the signal path of FIG. 7, or may be separated after time compression without separating Y / C.

In the first channel, the B signal section of the output of the line memory 42 is derived through the 3H delay unit 46, the R signal section is derived through the 2H delay unit 47, and recombined as shown in FIG. . In addition, these 2H and 3H delays can be actually realized by the control of the read timing of the line memory 42. Further, the Y signal at the output of the line memory 43 is derived via the 3H delay unit 48 (Fig. 8E).

Similarly, in the second channel, the B signal section of the output of the line memory 44 is derived through the 9H delay unit 49, and the R signal section is derived through the 8H delay unit 50, and recombined as shown in FIG. do. Further, the Y signal at the output of the line memory 45 is derived via the 8H delay unit 51 (Fig. 8H).

The outputs d, e, g and h of the retarders 46-51 are given to the U contacts of the changeover switches SW- 11, 12, 13 and 14, and the respective switches are operated again. It is synthesized by common coupling of the contact outputs, and is derived as the reproduction main line signal i in the line sequence shown in FIG. Each of the delayers 46 and 51 is provided with a delay amount for correcting the skew amount of the two-channel parallel signal and serializing them in line order.

The outputs of the line memories 42-45 are also given to the average value interpolation circuit. That is, the B signal section of the output of the line memory 42 of the first channel is delayed by 1H in the 1H delay unit 52, and is combined with the non-delayed R signal section as shown in FIG. The combined signal j is supplied to the 4H delay 53, and the delayed output K (Fig. 9 k) and the input j are added to the adder 54 and down to 1/2, so that the delayed signal K is shown in Fig. 9L. The average value signal l is formed.

Then, the Y signal of the output of the line memory 43 of the first channel is delayed by the 2H delay unit 55 as shown in FIG. 9M, and the input C and the output m are added to the adder 56 and averaged. As a result, an average value signal n of FIG. 9 is formed. This signal n is delayed back to the 2H delay unit 57 (Fig. 9 O).

Each interpolation signal l and O formed by the average value processing is applied to the D contact of the changeover switch SW- 11 and SW- 12, respectively. At the time of dropout, dropout detection pulses are applied to these switches SW- 11 and 12 as switching signals, and average interpolation signals l and O are derived from each switch in place of the main line signal i.

As shown in the time chart of dropout interpolation in FIG. 9, when the reproduction signals R (52) and Y 52 (FIG. 9 B) of the second channel are missing, the reproduction signal R (50) of the first channel axis is lost. ), The missing portions are interpolated by the average interpolation signals R (52) and Y (52) formed in the average value circuit according to R (54), Y (51), and Y (53) (Fig. 9). 9 degrees I). Since the channel skews for 4H displace the corresponding portions of each channel in the track length direction, dropout of one channel is reliably interpolated by the normal reproduction signal of the other channel.

Similarly, the dropout of the first channel is interpolated in accordance with the reproduction signal of the second channel. That is, in FIG. 7, the B signal section of the output of the line memory 44 of the second channel is delayed by 1H by the 1H delay unit 58, and the non-delayed R signal section is combined with FIG. The combined signal, p, is supplied to the 4H delay 59, and the delayed output q (Fig. 10) and the input p are added to the adder 60 and leveled down to 1/2, as shown in Fig. 10R. An average value signal r is formed.

Further, the Y signal of the output of the line memory 45 of the first channel is delayed by the 2H delay 62 as shown in FIG. 10T, and the input f and the output t are added and averaged by the adder 63. Thus, the average value signal u of FIG. 10 is formed. This signal u is delayed again to the 7H delay unit 64 (Fig. 10V).

Each interpolation signal s and v formed by the average value processing is applied to the contact D of the switching switches SW-13 and SW-14, respectively, and at the time of dropout, the average interpolation signals s and v are substituted for the main line signal i. Derived from each switch.

Therefore, as shown in the time chart of FIG. 10, when the reproduction signals R (46) and Y 47 (FIG. 10 A) of the first channel are missing, the normal reproduction signals R (44) and R of the second channel are lost. The missing portions are interpolated as the average value signals R (46) and Y (47) formed in accordance with (48) and Y (46), Y (48).

7 shows that the switches SW- 11 and 12 of the first channel of the changeover switches SW- 11 and 14 are controlled by the dropout detection pulses of the second channel, and the switches of the second channel. (13) and (14) are controlled by the dropout detection pulses of the first channel. Each dropout detection pulse is given an appropriate delay time and time width, respectively, and is then given to each switch as a switching control signal.

As described above, the present invention divides and records video signals into two channels alternately in a line of parallel spiral tracks in two channels. Thus, even in simultaneous recording (channel), field memory is unnecessary for both recorder and playback system. The recording and reproducing signal processing can be performed by the memory. In addition, an interpolation signal approximating the other channel can be generated by the line-to-line average of one channel.

In addition, since a time difference (skew) is recorded between the channels, even if a dropout occurs in the reproduction signal of one channel, the probability that the interpolation signal of the part obtained in the other group channel is damaged by the dropout is small. Therefore, strong and reliable dropout compensation can be performed by signal interpolation from one channel to the other channel.

In addition, since the average value is interpolated, the hatching of the image becomes discontinuous in the interpolation part, so that it is not noticeable and the image quality deteriorates little.

Claims (3)

A dropout correction circuit for video signals reproduced simultaneously from first and second tracks of a recording medium, wherein the first track includes a first video signal having alternating video lines of the original video signal, and the second track is an original video. A correction circuit comprising a second video signal having residual video lines positioned so as to differ by an integer multiple of the time difference of one recording video line with respect to a first video signal of the signal, A first correction signal generation circuit for receiving the reproduced first video signal; A second correction signal generating circuit including time difference correction means for receiving the reproduced second video signal and repositioning the original video signal line positioned so as to be different by an integer multiple of the time difference; First switch means coupled to the first video signal and the second correction signal generation circuit to correct a dropout video signal of the first video signal to an output of the second correction signal generation circuit; Second switch means coupled to the second video signal and the first correction signal generation circuit to correct a dropout video signal of the second video signal to the output of the first correction signal generation circuit; Dropout correction circuit comprising a. The method of claim 1, Coupled to a first video signal reproduced from the first track to generate a first dropout detection signal supplied to the first switch means, Coupled to a second video signal reproduced from the second track to generate a second dropout detection signal supplied to the second switch means; Dropout correction circuit further comprises a dropout detection means. The method of claim 2, The first correction signal generation circuit includes a first mixing circuit for mixing two continuous video lines of the first video signal, and the second correction signal generation circuit generates two consecutive video lines of the second video signal. And a second mixing circuit for mixing.

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