JPS59169284A - Reproducer of digital video signal - Google Patents

Abstract

PURPOSE:To reduce the deterioration of picture quality due to noises even in a variable speed reproduction mode by providing plural different types of correcting circuits to a digital video reproducer and switching these correcting circuits between a normal reproduction and a variable speed reproduction. CONSTITUTION:The video signal which is replaced with a correction signal Sr with a correction control signal Sc by a switch SWD is written to a field memory 3. While the signal Sr is selected by switches SWA and SWB through a memory 3 out of the signals obtained by transmitting the video signal delayed by a field through 1-line memories 1 and 2. The SWB selects and delivers (a) and (b) every field, and the signal Sr obtained by this selection is used for correction in a normal reproduction mode. While the SWA selects (b), (a), (b) and (c) every four fields and delivers them for correction in a variable speed mode. In this case, the signal Sr is reset to its original position every four fields. A selection circuit 4 selects and connects an SWC to the output of the SWB or SWA in response to the normal and variable speed reproductions.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to color image reproduction of digital video signals, and particularly to slow reproduction in digital VTRs.

The present invention relates to image reproduction suitable for variable speed reproduction of still images and the like.

Digital VTRs record and reproduce digitized video signals, but because the number of recording bits increases, multichannel recording is performed in which data is divided into multiple channels and recorded. An example of a recording format on a helical scan type tape is shown in FIG. 1(a).

In this example, the data is divided into 1/3 of the screen and recorded. For example, channel A records data on the left side of the screen, channel B records data on the center of the screen, and channel C records data on the screen cloth. In normal reproduction in which data is reproduced at the same tape speed as during recording, data in the valley channel is reproduced along the solid arrow in FIG. 1(a).

On the other hand, variable-speed playback such as slow, still, and fast-forward playback, where the tape is played back at a different speed than when it was recorded, is problematic.

A signal is played along the line arrow. Therefore, the reproduced image obtained by variable speed reproduction is an image obtained by combining signals of a plurality of fields, as shown in FIG. 1(b). On the image,
The cross-hatched area is an area called a noise band that occurs between tracks, and it is impossible to reproduce images in this area. Therefore, this area is modified to be replaced with a highly correlated signal to reproduce an image with less deterioration in image quality.

In a digital VTR, retouching is performed even during normal playback, but the retouching situations are different between normal playback and variable speed playback. In normal playback, the signal of the entire screen can be played back, so it is extremely rare for the same location to be modified several fields in succession. Since it occurs at a fixed location, it is necessary to modify the same location all consecutively. Therefore, even if a retouching method is effective during normal playback, if the retouching method is applied during variable speed playback, there is a problem in that image quality deterioration due to retouching becomes extremely large.

For NTCS composite format television signals, for example, as shown in Figure 2(a), lines with errors that require correction are corrected using the signal of an adjacent line whose color subcarrier phase matches that of the previous field. For stills during variable speed playback, for example, line 4 of the second field, line 3 of the third field, and line 3 of the fourth field are modified to be replaced with the signal of line 4 of the first field. Therefore, in variable speed playback such as stills,
As shown by the dots in FIG. 2(b), the correction data moves from the bottom to the top on the screen, resulting in extremely large deterioration in image quality. That is, even if the modification causes little deterioration in image quality during normal playback, the modification results in significant deterioration in image quality during variable speed playback. One object of the present invention is to provide means for reducing image quality deterioration due to noise in a digital video signal reproducing apparatus that performs variable speed reproduction during normal reproduction.

In order to achieve the above objects, the present invention provides a digital video signal playback device that performs normal playback and variable speed playback, which includes a plurality of different types of correction circuits for noise band correction, so that the tape speed is the same as that during recording. The plurality of correction circuits are selectively used during normal playback and variable speed playback in which the tape speed is different during recording.

Hereinafter, the present invention will be explained in detail based on Examples.

FIG. 3 is a diagram showing the main part of an embodiment of the present invention.

In this embodiment, the modified signal for normal reproduction is obtained from the output of switch B, and the modified signal for variable speed reproduction is obtained from the output of switch A. Next, the operation of this embodiment will be explained.

The video signal, which has been replaced with the modified signal SrK by the switch D in response to the modified control signal SC, is written into the field memory 3. On the other hand, the modified signal Sr converts the video signal delayed by one field in the field memory 3 into one line memory 1.2.
are selected by switch A and switch B. Switch B selects a and b for each field and outputs it, and the modified signal Sr obtained from this is the second
This is explained in the figure and is used for correction during normal playback. On the other hand, switch A has a period of 4 fields, and b
, a, b, and c as output, as shown in Figure 2 (a
) The correction signal shown by the dotted line is used for correction during variable speed playback. In this case, since the modified signal Sr returns to its original position every four fields, the problem of the modified signal moving from the bottom to the top as described above is solved. Then, in the selection circuit 4, the output of the switch CL is selectively connected to the output of the switch B1 or the switch A depending on normal reproduction or variable speed reproduction.

Note that normal playback and variable speed playback can be easily distinguished by, for example, detecting the tape speed.

FIG. 4 is a block diagram of main parts of another embodiment of the present invention. In this embodiment, during normal playback, signals are always written to the field memory 6 with switches G and H' always closed to create a modified signal Sr, and during variable speed playback, for example, the noise band area is switched to switches G and H'. There is no i-cut, and a plurality of types of modification signals are used by generating modification signals from a state in which writing to the field memory 6 is prohibited. Next, the operation will be explained. The output signal of the field memory 6 is a signal whose polarity of the cycloma phase is inverted by the chroma inversion circuit 5, and the signal of the field memory 6, which are selected by a switch E, and the line of the previous field having the same line number as the line number of the current field is output. The signal or the chroma-inverted signal is defined as the modified signal Sr. Switch E
The selection is controlled by the switch control circuit 7, which compares the field information 8f stored in the field memory 6 with the field information of the current image and selects the signal so that the color subcarrier phase matches. It will be done.

In addition, during normal playback and variable speed playback, switch G,
H is controlled by the selection circuit 8, and as mentioned earlier, the switch is controlled to be open in the noise band region during variable speed reproduction.

This is because when the noise band region is fixed, such as in stills, for example, if the switch is closed, the modified signal will become more and more degraded by the chroma inversion circuit each time it passes through the chroma inversion circuit. This is to avoid That is, by passing the information stored in the field memory through the chroma inversion circuit only once at most, a good modified signal that prevents this deterioration can be obtained. Note that the identification R of normal playback and variable speed playback can be easily identified by, for example, the tape speed. Furthermore, since corrections occur in a concentrated manner in the noise band portion, it is possible to determine whether the noise band is a noise band or not by looking at the correction area in units of several lines, for example.

As described above, according to the present invention, it is possible to reproduce an image with little deterioration due to correction in both normal reproduction and variable speed reproduction, and the obtained effects are significant.

Note that in the embodiment described in this text, information on the previous field is used for the modified signal during normal reproduction, but it is clear that this may also be information such as one line or two lines before the current field.

Furthermore, in the present invention, a method has been described in which the correction is switched according to the normal playback mode and the variable speed playback mode. It is also possible to reduce the cost of image quality deterioration by switching and retouching.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the recording format on a tape in a digital VTR and images of variable speed playback, Fig. 2 is a diagram of a correction method using information of the previous field, and Figs. FIG. 2 is a configuration diagram of main parts of an embodiment. 1.2... Erline memory, 3.6... Field memory, 4, 8... Selection circuit, 2... Chroma inversion circuit, 7... Switch control circuit. 1st (θnyn 2) Figure 3 (m) Closed 4- Figure procedure amendment (method) % formula % Title of invention Relationship to case of person who amends digital video signal playback device Patent applicant Name 141 :
! 510) Hayashi Shikikai 11 Hitachi
・Installation Name (542) B Ritsu Denshi Co., Ltd. Representative 1: Address 〒too Marunouchi, Chiyoda-ku, Tokyo-
Chome 5-1 Stock Company IT: +a τshitsui office phone number 11 + 212-1111 (input) 2) (61
) (2)

Claims (1)

[Scope of Claims] 1. A plurality of different types of correction circuits are provided, and all of the correction circuits are selected and used in normal playback where the tape speed is the same as that during recording, and variable speed playback where the tape speed is different from that during recording. Digital video signal playback device. 2. Consisting of at least a field memory and a plurality of line memories, the field memory and the line memo IJ'? 2. The digital video signal reproducing apparatus according to claim 1, characterized in that the correction circuit comprises a selectively selected correction circuit Kanakura. 3. A modification circuit comprising at least a field memory and a chroma inversion circuit, and having means for selecting the outputs of the field memory and the chroma inversion circuit, and inhibiting a write operation to the field memory. The digital video signal reproducing device according to item 1.