JPH10191251A - Video signal recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a video signal recording/reproducing device recording video data obtained by image-compressing a video signal within prescribed time. SOLUTION: A bit rate detection means 4 detecting the bit rate of video data compressed by an image compression circuit 2 and a control circuit 5 for thinning video data supplied to an accumulation device 10 in a frame unit when the bit rate detection means 4 detects the bit rate for not less than prescribed quantity are provided. Video data whose bit rate is set to be constant is supplied to the accumulation device 10 while picture quality is kept to be constant. Even if the bit rate of compressed data changes by screen information in the frame, the video signal within prescribed time is always recorded and reproduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording apparatus for recording a video signal composed of a video signal, an audio signal, and the like. The present invention relates to a video signal recording / reproducing apparatus employing a large-capacity recording medium capable of reading this at any time.

[0002]

2. Description of the Related Art Conventionally, images supplied from many television sources are recorded at a predetermined time by using a rotating drum, and are reproduced later.
However, such a recording method consumes a large amount of magnetic tape, and when reproducing the location of a program desired to be viewed from among a large number of recorded signals, the time required to access the screen becomes long. Is difficult to perform.

On the other hand, for example, a video signal is input as a digital signal, and the digital video signal is applied to various kinds of image compression techniques to reduce the amount of data to be recorded. Since the access time when editing the recorded contents or playing back only the necessary parts becomes extremely short, by securing the capacity of the recording medium to some extent,
An extremely effective recording / reproducing system can be provided.

[0004]

However, a compression circuit that compresses an image at a fixed ratio generally changes the bit rate of the compressed image data depending on the content of the input video. On the other hand, the frame rate of the compressed image data is high in a frame with a fine screen configuration with extremely high frequency components.
On a video screen having a relatively large pattern, the bit rate of the output image data is low. By the way, in a device in which a hard disk or an optical disk is used as a storage medium for video data, the data transfer rate is controlled to be constant.For example, when transferring high-quality compressed data having a high bit rate, With a recording medium of a fixed capacity, there is a problem that the recording time is reduced and a video program in a desired time zone cannot be recorded.

Therefore, if the compression rate is increased to some extent and the amount of data to be recorded is reduced, the transfer rate can be lowered and all video information in a certain time zone can be recorded reliably. However, in this case, there is a problem that the resolution of the recorded video signal is reduced. Therefore, when recording compressed video data on a hard disk, optical disk, etc., in extreme cases,
There is a problem that the recordable time varies depending on the program, and the time management becomes considerably complicated.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems by setting a transfer rate at which all video information at a desired time can be recorded and reducing the deterioration of image quality. In order to provide a recording / reproducing apparatus, when recording an input video signal, the video data compression means for compressing the input video signal, and the video data output from the video data compression means are stored. Memory means readable at the timing of
A bit rate detection means for detecting a bit rate of data output from the video data compression means; and a video data stored in the memory means when a detection value of the bit rate detection means exceeds a predetermined value. Thinning control means for thinning out in frame units. Then, the video frame which has passed through the thinning-out control means is recorded, and a data storage means comprising a reproducible hard disk or optical disk or the like is used.

At the time of reproduction, the video data output from the recording medium as described above is expanded, and the transmission timing is controlled so as to make up for the video frame lost by the thinning-out. Even in such a case, an uncomfortable feeling is minimized.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing an outline of a video recording / reproducing apparatus according to the present invention, wherein 1 is an A / D converter for converting an input video signal into digital data, and 2 is a digital signal. This is an image compression circuit that compresses the video data converted into. In this embodiment, the image compression circuit 2 employs, for example, JPEG standard compression means for compressing a still image in frame units, but may compress the data amount by another compression technique. Reference numeral 3 denotes memory means for temporarily storing the compressed video data, and reference numeral 4 denotes bit rate detection means for detecting the bit rate of the video data compressed. Reference numeral 5 denotes a thinning-out control unit which can output the video data compressed in the memory unit 3 to the subsequent storage device 10 while thinning out the image data in units of frames. The thinning-out rate is determined by the detection result of the bit rate detecting unit. Controlled to be controlled. Also, it is recorded together with the video data thinning information as the signal S _1.

That is, the bit rate detecting means 4 outputs, for example, a data amount (for example, Start Of Image and End Of Image) of one frame unit of data output from the image compressing means 2.
Is measured, and when the bit rate exceeds a certain value, the thinning control means 5
, A thinning rate is set, and control is performed to limit the amount of video data supplied to the storage device 10 in frame units. The storage device 10 is, for example, a hard disk (HDD)
A data storage using a recording medium such as an optical disk (DVD) or the like, and in the case of the present invention, is expected to have a capacity capable of recording compressed video data for several tens of hours.

Next, a reproduction system will be described. Reference numeral 6 denotes an image expansion circuit that expands compressed video data output when the storage device 10 is read and controlled by operating means (not shown), and 7 stores video data expanded by the image expansion circuit 6 in frame units. It is a memory means. Also, the 8 sets the timing of the video data read from said memory means 7 on the basis of the thinning information S _2, which is thinned in the recording system, the storage device 1
0 shows a transmission timing control circuit for making a read request Q with respect to 0. The transmission timing control circuit 8 outputs a continuous video signal from the A / D converter 9 while supplementing the video time zone of the decimated frame. It is the control that is performed.

FIG. 2 is a block diagram of a JPEG encoding circuit showing a specific example of the image compression circuit 2. The input image data is divided into, for example, 8 × 8 blocks, and a two-dimensional DCT ( (Discrete Cosine Transform) 11 to convert to an 8 × 8 cosine transform coefficient matrix corresponding to the spatial frequency component. Then, the low-frequency component coefficients that greatly affect the image quality are finely quantized by the scalar quantization circuit 12, and the high-frequency component coefficients that have a relatively small effect on the image quality are roughly quantized. After that, the DC component and the AC component are converted into a binary sequence via the inter-block DC difference circuit 13 and the zigzag scan circuit 14, respectively, and the Huffman coding circuit 15 performs Huffman coding.

16A and 16B are tables of coefficients to be divided for Huffman coding. The tables 16A and 16B are in conflict with each other by the quantization table 16C for setting the number of quantization levels and the Huffman coding tables 16A and 16B. A certain compression ratio and image quality are controlled. That is, when a video frame signal having a fine-grained pattern is compressed, the bit rate of a compressed image of the frame output from the byte conversion circuit 17 is increased, and a video frame having a relatively small space portion is converted into a byte. The bit rate output from the conversion circuit 17 decreases.

The JPEG system of the international standard, which encodes color still images with high efficiency, has a lower compression ratio than the MPEG system which is suitable for compressing moving images, but has a relatively low cost of one chip. Simple circuits can be used.
However, the bit rate of the video data compressed as described above greatly changes depending on the content of the image before compression. Therefore, in the case of the present embodiment, this changing bit rate is detected by the bit rate detecting means 4, and when a frame with a high bit rate continues, the video supplied to the storage device 10 is thinned out on a frame basis, and at least The bit rate is set so that the input video program to be recorded is not missed. Also, by simultaneously recording the information S ₁ of the thinning rate of the video data and reading this information to the transmission timing control means 8 at the time of reproduction,
While adjusting the output timing of the video data stored in the memory means 7 and monitoring the video data in the memory means 7, a request Q for reading the next video data from the storage device 10 is made, and the D / A converter 9 so as to obtain a continuous video signal at a predetermined cycle.

FIG. 3, FIG. 4, and FIG. 5 conceptually show how the image data is thinned out as described above. FIG. 3 shows an input video frame in the time axis direction. In this case, each frame F1, F2, F3 still picture indicates a continuous time axis direction of the video frame period t _1. FIG. 4 shows video frames output at a normal bit rate as F1 and F2, and frames at which a high bit rate is detected are shown as F3 to F7. In this period, data is selected in units of frames by the thinning-out control unit 5 at frame periods t3, t4, and t5 longer than the periods indicating the normal frame periods t1 and t2, and are supplied to the storage device 10. Thus, a frame having a high bit rate, for example, F ₃ to F ₈ are recorded in a state of being thinned out.

FIG. 5 shows a case where video data recorded in the recording device 10 is output by the transmission timing means 8 as frame data having a predetermined cycle. Frames F4, F6, inputted as shown in this figure
Although the video data of F8 is lost at the time of reproduction, the bit rate supplied to the storage device 10 within a specific time period and the total data amount are fixed, so that the desired length of video data is independent of the content of the program. Therefore, it is possible to achieve the object that the video signal can be always recorded.

An inter-frame interpolation circuit is provided after the memory means 7, and the frames F3 and F5 (or F5
5, F7 frame), a predicted frame F4′F6 ′ having pixel data predicted from the pixel data of the preceding and following frames may be created and output.
Further, image data can be handled on a field basis.

[0017] Note that this embodiment the video data captured in the storage medium 10, but thinning rate corresponding to the bit rate was made to change, be recorded in advance how much of the video frame by program to be recorded There are things that can be predicted if their contents can be understood. For example, in the case of news programs, the announcer speaks for a relatively long time,
Recording this portion for each frame may not be very meaningful. Therefore, in the case of such a program, a method of setting in advance so as to increase the thinning rate of the compressed video data can be adopted. Further, since the drama is a program in which the ratio of scene change is large due to the development of the story, the thinning rate may be set to be small. Further, when the thinning rate is set according to both the genre of the broadcast program and the detection result of the bit rate detection means, the recording / reproducing system can be used sufficiently to provide a more practically effective recording / reproducing apparatus. be able to.

[0018]

As described above, the video signal recording / reproducing apparatus according to the present invention is provided with the bit rate detecting means for monitoring the bit rate of the image signal compressed by the digital signal. Based on the result,
Since the thinning control of the video frame to be recorded is performed, especially when recording a video signal formed by a long-time compressed digital signal on a hard disk or an optical disk, the video for a certain amount of time is recorded. It is easy to design to record the contents without omission, and at this time, there is an effect that the recording can be performed without deteriorating the image quality.

When the genre of the video to be recorded can be specified in advance by the program contents, the thinning rate of the video frames to be transferred to the recording device is set in accordance with the contents of the program, so that the recording medium of the same capacity can be recorded. On the other hand, a fixed amount of video can be recorded without lowering the image quality.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an outline of a video signal recording / reproducing apparatus of the present invention.

FIG. 2 is a block diagram illustrating a specific example of an image compression circuit.

FIG. 3 is an explanatory diagram showing a frame configuration of an input video signal.

FIG. 4 is an explanatory diagram of a frame structure of a thinning control recorded on a storage medium.

FIG. 5 is an explanatory diagram of a frame-structured video signal output as a reproduced video signal.

[Explanation of symbols]

1 A / D converter, 2 image compression circuit, 3 memory means, 4 bit rate detection means, 5 thinning control means, 6
Image expansion circuit, 7 memory means, 8 transmission timing control means, 9 D / A converter, 10 storage device

Claims (6)

[Claims] 1. A video data compression means for compressing an input video signal, a memory means for storing video data output from the video data compression means and being readable at a predetermined timing, A bit rate detecting means for detecting a bit rate of data output from the data compressing means; and when the detected value of the bit rate detecting means exceeds a predetermined value, the video data stored in the memory means is converted into a frame unit. A video signal recording / reproducing apparatus, comprising: a thinning control means for thinning out a video frame; and a data storage means for recording and reproducing a video frame passed through the thinning control means. 2. The video signal recording / reproducing apparatus according to claim 1, wherein said thinning-out control means supplies thinning-out information of the thinned-out video frames to said storage means for storage. 3. The video signal recording / reproducing apparatus further comprises transmission timing means for expanding the reproduced video data and processing the reproduced data so as to form a predetermined periodic frame. 2. The video signal recording / reproducing device according to 1. 4. A video data compression means for compressing an input video signal, a memory means for storing video data output from the video data compression means and capable of being read at a predetermined timing; Thinning-out control means for thinning out video data stored in the memory means on a frame basis based on the genre of the video signal obtained, and a video frame passing through the thinning-out control means is recorded and reproduced. A video signal recording / reproducing apparatus, comprising: 5. The video signal recording / reproducing apparatus according to claim 4, wherein said thinning-out control means supplies thinning-out information of the thinned-out video frames to said storage means for storage. 6. The video signal recording / reproducing apparatus according to claim 1, further comprising transmission timing means for expanding the reproduced video data and processing the reproduced data so as to form a predetermined periodic frame. 5. The video signal recording / reproducing device according to 4.