JP2510658B2 - Recording and playback device - Google Patents

Description

The present invention relates to a digital signal recording / reproducing apparatus,
Especially, it relates to the dubbing.

[Conventional technology]

2. Description of the Related Art In recent years, a so-called high-definition digital VTR, which records and reproduces a video signal by converting it into a digital signal, has been attracting attention as one that enables high-quality image reproduction. In such a high-quality digital VTR, a dubbing function is also provided. During dubbing, a reproduction signal is output as a digital signal, and the other VTR records the reproduction output signal as it is as a digital signal.

3 (A) and 3 (B) are conventional VTR recording systems,
FIG. 1 is a block diagram showing an example of a reproduction system, where 1 is an A / D (analog / digital) converter, 2 is a dubbing interface circuit consisting of a switching switch, 3 is a front filter,
4 is a sampling circuit, 5 is a recording signal processing circuit, 6 is a reproduction signal processing circuit, 7 is an interpolation filter, and 8 is D / A (digital /
Analog) converter.

 First, the recording system shown in FIG. 3A will be described.

The dubbing interface circuit 2 is closed on the side a during recording of a normal analog signal and closed on the side b during dubbing.

Assuming that a normal analog signal is recorded, this input analog signal is converted into a digital signal by the A / D converter 1 and supplied to the front filter 3 via the dubbing interface circuit 2. The pre-filter 3 and the sampling circuit 4 at the next stage perform processing for preventing aliasing interference due to A / D conversion. The digital signal processed by these is a recording signal processing circuit. In step 5, recording processing is performed and recording is performed on a recording medium (not shown).

Here, the operation of the front filter 3 and the sampling circuit 4 is
It will be described with reference to the drawings.

In the figure, a circle frame and a square frame represent pixels (sample data) of the replacement digital signal. Further, here, the row of pixels ▲ Z ⁱ ₊ ▼ arranged in the horizontal direction in the uppermost row is the row of pixels on the scanning line having the first field, and the row of pixels ▲ Z ⁱ ₀ ▼ placed in the horizontal direction in the middle row. this scanning line adjacent the next second pixel row scan lines of the field, the pixel ▲ Z ⁱ which is arranged in the horizontal direction of the lowest stage _- ▼ first field pixel column further the following ▲ Z ⁱ ₀ It is a pixel column on a scanning line adjacent to the scanning line having ▼.

By the way, when the analog signal is A / D converted, a part of the sideband of the obtained digital signal enters the baseband of the input analog signal, and it becomes difficult to separate the input analog signal. When a digital signal in which a part of the input analog signal is mixed in the sideband is converted into an analog signal, the input analog signal is mixed as noise in this analog signal, and the S / N is significantly deteriorated.
This is a turnback obstruction.

The pre-filter 3 and the sampling circuit 4 suppress the diagonal component of the analog signal mixed in the digital signal in order to prevent the aliasing interference. That is, in FIG. 4, when focusing on the pixel Z ₀ in the ○ frame, this pixel Z ₀
, That is, vertically, horizontally, diagonally □ Pixel of the frame ▲ Z ⁺² ₊ ▼, Z ₊ , ▲ Z ^-2 ₊ ▼, ▲ Z ⁺¹ ₀ ▼, ▲ Z ^-10 ₀ ▼, ▲
^{_{Z +2 - ▼, Z -,}} ▲ Z -2 - ▼ respective predetermined weighting to create a line of connexion new pixel Z ₀ to which a replacing the original pixel Z _0.
This processing is carried out for every other pixel in the O frame of each scanning line of each field.

The above is the operation of the front filter 3, but by this,
The pixels in the ◯ frame have an average value of the pixels in the □ frame, so that the pixels of the input analog signal mixed in the pixels in the ◯ frame are also averaged and suppressed.

The sampling circuit 4 extracts from the output digital signal of the prefilter 3 only the pixels in the ◯ frame shown in FIG. That is, the pixels in the □ frame that are not processed by the front filter 3 are thinned out. As a result, the sampling circuit 4 can obtain a digital signal in which the mixed input analog signal is sufficiently suppressed.

 Next, the reproducing system shown in FIG. 3 (B) will be described.

The digital signal reproduced from the recording medium (not shown) is processed by the reproduction signal processing circuit 6, supplied to the interpolation filter 7, and thinned by the sampling circuit 4 (FIG. 3 (A)). Interpolated pixels are interpolated. In other words, in FIG. 4, the pixels in the □ frame are thinned out by the sampling circuit 4, but the interpolation filter 7 is similar to the front filter 3 in that the pixel position to be interpolated is Predetermined weights are added to the surrounding pixels in the ∘ frame to add them, and the pixels in the □ frame are formed and inserted at this position.

The digital signal processed by the interpolation filter 7 can be directly output as a digital signal, or can be converted into an analog signal by the D / A converter 8 and output. In the case of dubbing to another VTR, the output digital signal of the interpolation filter 7 is directly supplied to another VTR.

When dubbing a signal recorded on another VTR recording medium, in the recording system shown in FIG.
The dubbing interface circuit 2 is closed on the b side and other VT
The digital signal from R is processed by the front filter 3, the sampling circuit 4, and the recording signal processing circuit 5 via the dubbing interface circuit 2 and recorded on the recording medium.

[Problems to be Solved by the Invention]

As described above, in the above-described conventional technique, it is possible to output and input a digital signal during dubbing, and D / A conversion and A / D conversion of the signal to be dubbed are not performed. It is possible to avoid image quality deterioration and S / N deterioration.

However, the digital signal to be dubbed is already processed by the pre-filter 3 and the sampling filter 4 when recording this in the VTR which outputs this digital signal.
The frequency characteristic is deteriorated by the averaging effect, and the frequency characteristic is deteriorated by the averaging function of the interpolation filter 7 during reproduction. Moreover, even in a VTR for dubbing and recording this digital signal, the digital signal is further processed by the pre-filter 3 and the sampling circuit 4, and the frequency characteristics are further deteriorated.

As described above, the conventional technique has a problem that the frequency characteristic of the signal is deteriorated by repeating the dubbing.

It is an object of the present invention to provide a recording / reproducing apparatus which solves such a problem and is capable of preventing characteristic deterioration due to dubbing.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a dubbing interface circuit between a prefilter and a sampling circuit in a recording system, and a dubbing recording digital signal from another recording / reproducing apparatus is provided in the dubbing interface circuit. The digital signal for dubbing recording to another recording / reproducing apparatus is a digital signal in which pixels are interpolated by an interpolation filter of the reproducing system, and The sampling circuit thins out pixels for which interpolation processing has been performed by an interpolation filter for digital signals for dubbing recording to the other recording / reproducing apparatus.

[Action]

When dubbing the recording signal of another recording / reproducing apparatus, this recording signal is input to the sampling circuit from the dubbing interface circuit and does not pass through the front filter,
The frequency characteristics are recorded without deterioration.

In the reproducing system, the reproduced digital signal subjected to the pixel interpolation processing by the interpolation filter becomes the digital signal for dubbing recording to another recording / reproducing apparatus. In this case, the sampling circuit thins out the pixels interpolated by the interpolation filter. For this reason, even if the dubbing is repeated, when the digital signal pixel-interpolated by the interpolation filter is recorded again, the interpolated pixels of the digital signal are thinned out by the sampling circuit, and always The digital signal composed of the original pixels will be recorded. Therefore, even if it passes through the interpolation filter, the frequency characteristic is not deteriorated by this.

〔Example〕

First, the basic concept of the present invention will be described with reference to FIG. In FIG. 1, 9 is a switching switch, 10 is a dubbing digital signal input terminal, 11 is a dubbing interface circuit, and 12 is a dubbing digital signal output terminal. The same code is attached.

 First, the recording system of FIG. 1A will be described.

A switching switch 9 is provided between the A / D converter 1 and the front filter 3. This switching switch 9 is on the d side when the input signal is an analog signal, and e when it is a digital signal.
Close to the side. These input signals are an analog video signal from an analog signal source such as a video camera and a tuner, a digital video signal from a digital signal source such as a computer, and the like. A dubbing interface circuit 2 is provided between the sampling circuit 4 and the recording signal processing circuit 5. The dubbing interface circuit 2 is closed on the side a during normal recording and on the side b during dubbing.

The front filter 3 and the sampling circuit 4 are respectively connected to the third filter.
It has the same functions as the front filter 3 and the sampling circuit 4 described with reference to FIGS.

In the case of normal recording, the dubbing interface circuit 2 is closed to the side a, and the A / A selected by the switching switch 9 is selected.
The output digital signal of the D converter 1 or the digital signal from the digital signal source is supplied to the pre-filter 3 so that every other pixel is generated from the peripheral pixels as described with reference to FIGS. 3 and 4. . Hereinafter, this pixel is referred to as a calculation generation pixel. Now, as shown in the figure, every other pixel of each field of the input digital signal of the front filter 3 is selected as ◎.
If the other pixels are indicated by marks and the other pixels are indicated by marks x, in the output digital signal of the front filter 3, as shown in the figure, the ∘ marked pixels of the input digital signal are the operation-generated pixels indicated by ∘ marks. Has been replaced.

The output digital signal of the pre-filter 3 is a sampling circuit 4
, And every other operation-generated pixel indicated by a circle is extracted. That is, the original pixels marked with X are thinned out. In the output digital signal of the sampling circuit 4 shown in the figure, the crosses represent thinned pixels. The output digital signal of the sampling circuit 4 passes through the dubbing interface circuit 2, is processed by the recording signal processing circuit 5, and is recorded on the recording medium.

During dubbing recording, the dubbing interface circuit 2 is closed on the b side. A reproduction digital signal of another recording / reproducing apparatus is input from the input terminal 10, passes through the dubbing interface circuit 2, is processed by the recording signal processing circuit 5, and is recorded on the recording medium.

In this way, since the recording digital signal for dubbing does not pass through the front filter 3, it is recorded without deterioration of the frequency characteristic.

 Next, the reproducing system of FIG. 1 (B) will be described.

A dubbing interface circuit 11 is provided between the reproduction signal processing circuit 6 and the interpolation filter 7. The dubbing interface circuit 11 is closed on the h side during normal reproduction for supplying a reproduction signal to a display device or the like, and closed on the i side during dubbing reproduction for dubbing to another recording / reproducing device.
The interpolating filter 7 has the same function as the interpolating filter 7 described with reference to FIGS.

During normal reproduction, the reproduction digital signal is processed by the reproduction signal processing circuit 6 and then supplied to the interpolating filter 7 through the dubbing interface circuit 11. The interpolation filter 7 interpolates the pixels marked with X thinned by the sampling circuit 4. In the output digital signal of the interpolation filter 7 shown in the figure, The mark represents this interpolated pixel. This output digital signal may be directly output to a display device, D /
It may be output after being converted into an analog signal by the A converter 8.

Dubbing interface circuit during dubbing playback
Reference numeral 11 is closed on the i side, and the reproduction digital signal processed by the reproduction signal processing circuit 6 passes through the dubbing interface circuit 11 and is supplied from the output terminal 12 to another recording / reproducing apparatus.

In this way, since the reproduced digital signal for dubbing does not pass through the interpolation filter 7, the frequency characteristic does not deteriorate.

As described above, since the front filter and the interpolating filter do not operate during dubbing, the frequency characteristics are not deteriorated by these, and the image quality is not deteriorated even if the dubbing is repeated.

Needless to say, other recording / reproducing for dubbing with the recording / reproducing apparatus shown in FIG. 1 also has the configuration shown in FIG.

By the way, in FIG. 1A, since it is the front filter 3 that deteriorates the frequency characteristic, the dubbing interface circuit 2 may be provided between the front filter 3 and the sampling circuit 4. Become. In this case, the sampling circuit 4 extracts and records the O-marked pixels, and at the time of dubbing reproduction, a reproduction digital signal consisting of only the O-marked pixels is output from the output terminal 12 of FIG. 1 (B). It is supplied to another recording / reproducing apparatus. In this recording / reproducing apparatus, the first
As in the case of FIG. 9A, a recording system is provided, and this digital signal is processed by the sampling circuit 4 so that the pixels marked with a circle are extracted. That is, the sampling circuit 4 thins out pixels in the same pattern for each frame.

However, when pixels are thinned out by the sampling circuit 4 in this manner, the digital signal for dubbing input to the sampling circuit 4 may or may not have pixels between the pixels marked with a circle. . That is, even if the output digital signal of the interpolation filter 7 shown in FIG. Pixels marked with are thinned out, and only pixels marked with ◯ are extracted.

An embodiment of the recording / reproducing apparatus according to the present invention based on the above points is shown in FIG. In the figure, the parts corresponding to those in FIG. 1 are designated by the same reference numerals. Also, normal recording,
Since the reproducing operation is the same as that of the recording / reproducing apparatus shown in FIG. 1, its explanation is omitted.

In the recording system of FIG. 2 (A), during dubbing recording, the reproduction digital signal of another recording / reproducing apparatus input from the input terminal 10 is extracted by the sampling circuit 4 every other pixel marked with a circle. The signal is processed by the recording signal processing circuit 5 and recorded on the recording medium.

In the reproducing system shown in FIG. 2B, even during dubbing reproduction, the reproduction digital signal processed by the reproduction signal processing circuit 6 is subjected to pixel interpolation processing by the interpolation filter 7 and output terminal, as in the normal reproduction. It is supplied from 12 to other recording and reproducing devices.

According to this embodiment, even if the reproduced digital signal passes through the interpolation filter 7 during dubbing, the deterioration of the frequency characteristic due to this is prevented by the thinning operation of the sampling circuit 4, and the dubbing interface circuit in the reproducing system is prevented. Is unnecessary, and the circuit configuration can be simplified.

Further, since the reproduced digital signal obtained from the output terminal 12 is a digital signal in which all the pixels are present after the pixel interpolation processing by the interpolation filter 7, it is provided with a prefilter, a sampling circuit and an interpolation filter. However, the structure is different from that of this embodiment, and not only a conventional recording / reproducing apparatus in which a digital signal for dubbing recording is inputted from a prefilter but also a conventional recording / reproducing apparatus for recording / reproducing a digital signal. On the other hand, a digital signal for dubbing recording can be supplied from this embodiment to perform dubbing recording.

〔The invention's effect〕

As described above, according to the present invention, it is possible to prevent the deterioration of the frequency characteristic due to the front filter and the interpolating filter at the time of dubbing, and the image quality does not deteriorate due to the repeated dubbing. Even for a conventional digital signal recording / reproducing apparatus having a different configuration from the above, the digital signal for dubbing recording can be supplied for dubbing recording.

[Brief description of drawings]

FIG. 1 is a block diagram showing the basic concept of the present invention, FIG. 2 is a block diagram showing an embodiment of a recording / reproducing apparatus according to the present invention, and FIG. 3 is a block diagram showing an example of a conventional recording / reproducing apparatus. FIG. 4 is an explanatory view showing the operation of the front filter, the sampling circuit, and the interpolation filter. 1 ... A / D converter, 2 ... dubbing interface circuit, 3 ... front filter, 4 ... sampling circuit, 7 ... interpolation filter, 8 ... D / A converter, 10 ... Digital signal input terminal for dubbing, 11 …… Dubbing interface circuit, 12 …… Digital signal output terminal for dubbing.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 61-2482 (JP, A) JP 61-18277 (JP, A)

Claims (1)

(57) [Claims] 1. A prefilter for arithmetically generating every other pixel of an input digital signal, and a sampling circuit for extracting the arithmetically generated pixel of an output digital signal of the prefilter to obtain a recorded digital signal. And a reproducing system having an interpolation filter for interpolating pixels thinned out by the sampling circuit in the reproduced digital signal, between the prefilter and the sampling circuit. A dubbing interface circuit is provided, and the dubbing interface circuit selectively supplies the output digital signal of the prefilter and the digital signal for dubbing recording from another recording / reproducing device to the sampling circuit. , A digital signal for dubbing recording the reproduced digital signal output from the interpolation filter to another recording / reproducing apparatus. The sampling circuit extracts a pixel of the digital signal for the dubbing recording supplied from another recording / reproducing device which is not interpolated by the interpolation filter. A recording / reproducing apparatus characterized by using the recorded digital signal.