JPH0222979A - Video signal recording and reproducing device - Google Patents

Abstract

PURPOSE:To attain the miniaturization and the low cost of a device by using a line memory to compress a video signal when it is recorded and to extend when it is reproduced as an auxiliary memory, and enabling non-segment recording to be performed without accumulating entire picture in the memory. CONSTITUTION:OMEGA winding is realized and the non-segment recording is performed by using a vertical blanking part 7 not being related to a video within one field, and the line memory(RAM)11 to compress the video signal including the video and a horizontal synchronizing signal 10 when it is recorded and to extend the signal when it is reproduced as the auxiliary memory. And it is set as 1.25<=n<m assuming the write clock of a time base compression device at a recording side and the readout clock of a time base expansion device at a reproducing side as (m), and the readout clock of the time base compression device at the recording side and the write clock of the time base expansion device at the reproducing side as (n). In such a way, it is possible to attain the miniaturization and the low cost of the device as a whole.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Field of Application> The present invention relates to a video signal recording and reproducing apparatus (so-called video tape recorder) for magnetically recording and reproducing video signals.

<Prior art> In recent years, the demand for higher quality television images has increased, and various attempts have been made, but one that is attracting attention as one of the most effective means is the high-definition TV system, or high-definition. (hereinafter referred to as HDTV) system. Several attempts have been made to develop a so-called HD-VTR for use with this system.

However, 1 (D-VTR has a larger amount of information than conventional
It is necessary to record and reproduce broadband signals that are approximately twice as large, and a high transfer rate is required, and for this purpose it is necessary to increase the relative speed of the head and the magnetic tape.

As a prior art, for example, 1987 IEEE Vo
l, CE-J3 A3r Wideband Rec
ordingTechnology for High
Definition Ba5ebandVCRs
As seen in J, the luminance signal band is 20MHz.

In order to record and reproduce the color signal band of 5MHz, the rotation speed of the rotating drum is 5400r, which is three times that of a conventional general VTR.
, m, and further divide one frame into, for example, three segments (this is called 3-segment recording).
A method has been proposed in which data is recorded on separate tracks, and the transfer frequency is reduced by increasing the number of tracks recorded at a time to two (this is called 2-channel recording).

FIG. 2(a) shows the configuration of a conventional segment recording type magnetic head. In the figure, a magnetic tape 1 is helically wound around a rotating drum 2 via a supply side guide pole 3 and a take-up side guide ball 4.

Magnetic heads 5 and 6 are attached to the rotating drum 2 adjacent to each other. The drum rotation speed is 5400r, p, mte. The moving directions of the magnetic heads 5, 6 and the magnetic tape 1 are as shown by the arrows. According to the above configuration, the track pattern recorded on the magnetic tape 1 is as shown in FIG. 2(b) K, and the video The signal forms one screen (frame) with three rotations of the drum. This is so-called 2ch, +1 segment recording.

Next, FIG. 3 shows how the screen is divided in comparison with the track pattern described above. In Fig. 3(a), the video input signal is
Figure (b) shows the lct'1VTRK record signal. The video input signal has a part called a vertical blanking part 7 which does not affect the video, and in normal home video, heads are switched in this part. However, H
In segment recording of a D-VTR, the head switching position is located not only in the vertical blanking section 7 but also in the video section in order to divide the screen. Therefore, when recording as shown in FIG. 3(b), the vertical blanking section 7 is divided into three head switching areas, and the video signal is delayed by a time T for each head switching area. It is processed using a circuit. Also, the comparison between the track pattern and the segment in one field is shown in Figures 2 and 3.
It forms a field. Note that during playback, the signal processing is reverse to that during recording.

However, in the above-mentioned conventional technology, since it is divided into segments and combined into 9, an image memory is required to store the information of the image portion in terms of circuit processing. A signal processing circuit is required to process the transitions between screens. For this reason, it has a huge memory capacity, which not only increases the cost, but also inevitably increases the size of the entire device, making it extremely inappropriate as a consumer device.

On the other hand, segment one frame as shown above.

There is also non-segment recording, in which recording is performed without dividing into segments. With this non-segment recording, the proposal for 0HD-VTR is the so-called 1-inch C format.
Realized by TR, drum diameter φ13511111%
Drum rotation speed 360 Or, p, m, tape wrapping angle 346
It has the following specifications.

FIG. 4 shows the configuration of a conventional non-segment recording type magnetic head. In the figure, the rotating drum 2 and the supply side pole 32
The arrangement of the balls 4 on the winding side is shown in FIG. 5, where the gaps 9 between the rotating drum 2 and each ball and between the poles are Gtpm,
The relationship is shown when the tape winding angle is θ degrees.

Each pole 3, 4 is attached obliquely to the rotating drum 2 so that the tape 1 is wound around the rotating drum 2 at a predetermined lead angle in order to perform helical recording.

Here, as shown in Fig. 5, for example, considering the miniaturization of the device for consumer use, the drum diameter is set to φ761°, and the ball diameter is set to φ4.
■If we obtain a wrapping angle similar to the above C format,
To achieve non-segment recording, the gap 9 is physically small and unrealistic. Of course, a certain amount of gap can be obtained by reducing the ball diameter, but
For the reliability of magnetic tape, the ball diameter should be as large as possible (
The radius of curvature should be increased). In the example of the C format mentioned above, the drum diameter is large, and because it is for professional use, tape loading is done manually, so there are few problems, but in the case of a consumer-use device that is equipped with an automatic tape loading mechanism, the above explanation is not necessary. As such, its feasibility is difficult.

<Means for Solving the Problems> The present invention aims to improve the drawbacks of the above-mentioned prior art and provide an HD-VTR that is low-cost and highly reliable. To achieve this, a line memory is used to compress the video signal when it is recorded, and to expand it when it is played back.
This allows the tape to be wrapped almost all the way around the rotating drum.
It embodies the so-called Ω winding. Also, in order to lower the data transfer frequency per track, two channels are recorded. With this configuration, so-called non-segment recording is performed.

Effect> Due to the above configuration, ■ Because of non-segment recording, the circuit system is not complicated and a huge amount of image memory is not required.

(2) The capacity of the line memory for compressing and decompressing data on the time axis is only about 5 to 15% that of segment recording, and the cost of the entire device can be reduced.

(2) Furthermore, even during double-speed search, one screen is formed in one scan, resulting in a good search image without image distortion.

<Example> Examples according to the present invention will be described below.

FIG. 1 is an explanatory diagram showing the operation of an apparatus according to an embodiment of the present invention.

FIG. 1(a) shows a recording signal of one revolution (one field) of the rotary drum, and this signal includes a vertical blanking section 7 not related to the image, an image, a horizontal synchronizing signal 10, etc. When recording this signal, the magnetic tape 1, magnetic helad 5,
The timing when 6 does not make contact, the so-called head blanking part, corresponds to the vertical blanking part 7 of the video signal,
Video signals and recording signals must correspond in real time.

However, when performing non-segment recording, interference occurs between the poles as described above, and the ball diameter must be made very small (below φ, θ), which is difficult. Therefore, as shown in Figure 1(b), this device uses a RAM (Random Access M
memory)+1 is prepared and written to this RAM 11 at a writing speed fscI. When recording onto a tape, the data stored in the RAM 11 is read out at a reading speed ZSC2 and recorded onto the tape using the signals shown in FIG. 1(c). At this time, if the relationship is fscI<fsc2, then the video data has been compressed at a ratio of fSCI<fSC2. Furthermore, RAM1
In terms of the number of lines, the capacity of 1 is (Hl-8 in Figure 1).
2) is sufficient, there is no need to memorize the entire screen, and only a small amount of memory is required.

Here, the relationship between the drum diameter and the wrapping angle will be explained with reference to FIGS. 1(a) and 1(e). Tape wrapping angle θl, drum diameter θD
1 (Fig. 1(d)), assuming that the recording length on the tape is fixed, non-segment recording can be achieved by using one part of memory (RAM) from the compression ratio fscl/fsc2 mentioned above. However, as shown in FIG. 1(e), the tape winding angle can be slightly reduced, the tape guide ball diameter can be increased, and interference between poles can be reduced.

FIG. 6 shows a system schematic block diagram of an embodiment of a video signal recording/reproducing apparatus according to the present invention.

The video inputs include a luminance signal (Y) and a wideband color signal (Cw
), a narrowband color signal (Cn), and R, G, B signals.
It is converted into Cw and Cn signals. After selecting Y, Cw, Cn or R, G, B by the selector circuit 13, the video signal is converted into a digital signal by the A/D converter 14, the Y signal is passed through as is, and the color signal is recorded. After separating the Cw and Cn signals by a filter 15 to narrow the signal band, they pass through a line j@order circuit 16 for line sequential processing.
□ TCI (Ti
meCompressed Infgration
) The encoder 17 compresses the luminance signal and color signal in the time axis,
They are superimposed and are usually converted into TCI at a ratio of 3:1.

The TCI signal is converted back to an analog signal by the D/A converter 18, FM modulated by the FM modulator 19, and recorded on the magnetic tape 1 by the recording amplifier 20 via the magnetic heads 5 and 6.

On the other hand, the reproduction signals from the magnetic heads 5 and 6 are transmitted to the reproduction amplifier 2.
2, TBC (Time Ba5eCorr
ector) 2B, and time axis jitter correction is performed. The signal from TBC23 is TCI decoder 2
The luminance signal is sent to a synchronization addition circuit 25 to obtain a synchronization signal for signal processing, and the color signal is sent to a line alternation circuit 26 to return the line-sequential signal to its original state.゜ and Cw thinned out due to TCI,
The Cr1 signal is passed to a linear interpolation circuit 27 for linear interpolation using, for example, signals before and after IH. These Y, Cw
, Cn signals are converted into analog signals by the D/A converter 28 and output as video. The inverse matrix circuit 29 is R
, G, and B signals.

In the above system configuration, the HD-TV double signal, that is, l
The degree of data compression described above (see FIG. 1) when recording and reproducing an I252 in/frame signal will now be explained, taking into account the transfer lock of the signal processing circuit.

Let fy be the video signal sampling frequency (MH2), η be the effective video ratio between IH of the video signal, N be the sampling clock frequency after TCI, and K be the sampling clock frequency including horizontal synchronization, color phase burst, etc. At this time, the total number of clocks allocated for one line (IH) is 4/3, which is the data compression ratio of TCI.

On the other hand, recording by the apparatus according to the present invention is non-segment recording, and physically there is no recording area (head blanking area).
There is. Considering signal synchronization, it is necessary that the number of lines (H number) in one rotation of the drum is an integer, and the number of lines in one rotation of the drum is calculated as follows.

Here, when the data compression method of the device according to the present invention described above is applied, if the data compression rate = - (m, n are integers), the master clock frequency at the time of recording becomes ft = fyX-, and the formula Expression must be an integer.

Further, if H is the number of effective lines per frame and θ is the effective wrapping angle, the following relational expression holds true.

If we find the condition that the above formulas (1) and (2) and fy have a factor such as 48KHz, which is the sampling frequency of PCM audio, then for example, fV=51.840MH2, n=13. m=l0. ni=
85°Ne=1872. H=+052 Rai:/, Hd=
There are 600 lines and θ=815.6°.

Here, the relational expression between the drum diameter and the wrapping angle is as follows.

(Do is the diameter after data compression) For example, if DQ=φ76m, the diameter of the drum before data compression is D=φ71.25m, and the physical compression ratio is α=0.9375. Further, the winding angle at this time is θ=θX−=336.64° due to the inversely proportional relationship as described above. When these numerical values α are applied to FIG. 5, it is recognized that the interference between the balls is clearly reduced, the ball diameter can be increased, tape damage is small, and non-segment recording can be easily realized.

Furthermore, when finding the limit point of n7m, when m=1.2, f
y=45.36MHz, Ni=37, Ne=1600
, Hd=567, the wrapping angle is θ#334. Further, if the physical overlap is made by wrapping 5 extra wraps on the inlet and outlet sides of the tape, that is, 10 extra wraps, the total wrapping angle becomes 344 degrees. In Fig. 5, the above numerical values are in the range of ball diameters φ1 to φ6 and the gap amount is 0, 1 y
It is close to m and is unrealistic. In the case of m=1.25, fy=56.16MHz, ni=64, Ne
=2000°Hd=585, the effective wrapping angle is θ
= 323.7°, and with the extra winding for the above-mentioned overlap, the angle is 333.7°. In Fig. 5, the gap amount is 0.3 to 0.6 in the range of ball diameters φ1 to φ6, and there is at least no physical interference between the balls or between the drum and the balls, and a realistic ball arrangement is possible. .

Therefore, the condition is -≧1,25. Increasing the compression rate of n7m reduces mechanical constraints as mentioned above, but as the compression rate increases, the amount of line memory increases, leading to an increase in cost, so the benefits of the present invention are not achieved. Ha-≦! , about 4 is preferable.

FIG. 7 shows the physical dimensions of this example. θ=315.
6°, θ3=5°, tape feed speed Vt=47.680
rrw's,) rack pitch Pt=0.0381m,
Drum rotation speed = 360 Or, pom. Further, FIG. 8 shows the relative dimensions of the CHA head and CHB head.

The azimuth angles of the head gaps of the CIA head and COB head are opposite to each other, and have an appropriate angle θ4 to reduce adjacent crosstalk during reproduction. In the above explanation, normal recording patterns such as PCM audio, control track, time code track, etc. are not mentioned, but it goes without saying that these are added.

<Effects of the Invention> As described above, according to the present invention, when recording a video signal, the signal is slightly compressed, and when playing back, the signal is slightly expanded, so that the memory is used auxiliarily, and the entire screen is stored in the memory. As a result of being able to easily perform non-segment recording without storing data in the memory, the entire device can be made smaller and less expensive, making it possible to provide it as a consumer device.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the operation of an embodiment of the video signal recording and reproducing apparatus according to the present invention, FIG. 2 is an explanatory diagram of the configuration of a conventional magnetic head, FIG. 3 is an explanatory diagram showing how the screen is divided, and FIG. 5 is a graph showing the relationship between the wrap angle of the gap, FIG. 6 is a schematic system block diagram of an embodiment of the device according to the present invention, and FIG. 7 is a diagram illustrating the structure of a conventional magnetic head. FIG. 8 is an explanatory diagram of the configuration of a magnetic head of an embodiment of the apparatus according to the invention, and FIG. 8 is an explanatory diagram showing the positional relationship of the magnetic head. In the figure, I: magnetic tape, 2: rotating drum, 3: supply side ball, 4: take-up side ball, 5: magnetic head, 6: magnetic head, 7: vertical blanking section, 10: video, horizontal synchronization signal . Agent: Patent Attorney Takeshi Sugiyama (and 1 other person) 1st Doctor Diagram 115 No.

Claims (1)

[Claims] 1. In a helical scan rotary head type video signal recording and reproducing device that compresses the time axis of a video signal and records it, and expands the time axis and demodulates it during playback, the recording side includes a time axis compression device. On the playback side, the read clock of the time axis expansion device is m, on the recording side, the read clock of the time axis compression device, and on the playback side, the write clock of the time axis expansion device is n, then two clocks are used. A video signal recording/reproducing device characterized in that the ratio n/m is 1.25≦n/m.