JPH06315133A - Method and device for recording and reproducing dynamic image signal - Google Patents

Abstract

PURPOSE:To realize a high-speed system capable of obtaining a smooth and low-speed reproducing image for a high-speed motion in common with a usual system in the method and the device for recording and reproducing a dynamic image signal. CONSTITUTION:By a switching signal from a switch control means 8, a clock generating circuit 2 switches a clock signal, an encoding circuit 3' switches an encoding system so as to correspond to a frame rate of a dynamic image signal inputted in an image input means 9, and recording to a recording/ reproducing system 5 is always executed by a prescribed transmission rate. A decoding circuit 6' executes decoding corresponding to the encoding circuit 3', and outputs an image by a reproducing system corresponding to the switching signal from the switch control means 8 in an image display means 10. in such a way, the recording/reproducing method for the dynamic image signal can be switched in accordance with a request without changing a recording medium.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moving picture signal recording / reproducing method and apparatus for recording and reproducing a moving picture signal with high efficiency coding.

[0002]

2. Description of the Related Art In a method of recording and reproducing a moving image signal with a recording / reproducing apparatus such as a digital VTR, the input moving image signal itself has an enormous amount of data. Therefore, data compression is performed by a high efficiency encoding technique. Is common. As such a high-efficiency coding technology, several methods such as a method combining orthogonal transformation and variable length coding, and a method combining inter-frame prediction and intra-frame prediction have been proposed. By using this method, it is possible to efficiently compress and record the moving image signal.

FIG. 2 shows a block diagram of a system for high-efficiency-encoding a moving image signal for recording and reproducing, and its operation will be briefly described below.

First, at the time of recording, the clock signal s output from the clock generation circuit 2 in the image input means 1
1, the moving image signal d1 is input at the normal frame rate N [Hz]. Subsequently, in the encoding circuit 3, the moving image signal d1 is data-compressed into the variable length encoded data d2 by the clock signal s1 at the frame rate N [Hz] using a predetermined encoding method, and the switch 4 It is recorded in the recording / reproducing system 5 via. However, recording / playback system 5
Is usually a fixed transmission rate system, the variable-length coded data d2 is generated at the transmission rate R of the recording / reproducing system 5 by controlling the amount of generated data in the encoding circuit 3.

Next, at the time of reproduction, the variable length coded data d3 is reproduced from the recording / reproducing system 5 via the switch 4 at the transmission rate R and output to the decoding circuit 6. In the decoding circuit 6, the variable length coded data d3 is decoded into a moving image signal d4 by a decoding method corresponding to the encoding method of the encoding circuit 3, and the moving image signal d4 is output by the image display means 7.

In the above system, the moving image signal d4 is displayed at the frame rate N [Hz] when the normal speed reproduction is performed, and the moving image signal d4 is displayed at the frame rate M (M <N) when the low speed reproduction is performed. Display in [Hz]. For example, when the input moving image signal is NTSC and N = 30, in normal speed reproduction, one frame is displayed every 1/30 seconds,
The low-speed reproduction is realized by repeating the same frame, that is, by displaying one frame for 1/10 seconds, for example (hereinafter, this method is referred to as a normal method).

In this normal system, when the input moving image signal is a fast moving scene, there are problems such as deterioration of resolution due to repetition of the same frame at the time of low speed reproduction, and frame skipping in which the motion becomes discontinuous. Therefore, a moving image signal recording / reproducing system (hereinafter, referred to as a high speed system) that can obtain a smooth low-speed reproduced image even for a moving image signal including a high-speed scene has been proposed. In the high-speed method, for example, a moving image signal is input at (n × N) [Hz], which is n (where n> 1) times the normal frame rate, and a reproduced moving image signal is input at a frame rate N [Hz]. It is realized by displaying.

However, the high-speed system is intended for a special use at a broadcasting station, etc., and directly records an input moving image signal on a large-capacity recording medium such as a semiconductor memory without considering high-efficiency coding. Since it is configured as described above, it was considered as a system separate from the above-described normal method moving image signal recording / reproducing method. Further, even if the data compression of the moving image signal is performed by the encoding circuit 3 in FIG. 2 in consideration of the high efficiency encoding, the recording / reproducing system is not used because the compression rate is the same as the conventional one and the transmission rate is not compromised. It was necessary to change to a larger capacity and higher transmission rate.

[0009]

As described above, in the method and apparatus for recording / reproducing a high-efficiency-coded moving image signal, the normal system for outputting a low-speed reproduced image by repeating the same frame and the input moving image are used. The high-speed method in which the frame rate of the signal is increased and the low-speed reproduction output is performed at the normal frame rate is configured by different systems, and in order to realize the high-speed method, in comparison with the normal method, It was necessary to set a recording medium having a large capacity or a high transmission rate.

Therefore, an object of the present invention is to provide a moving image signal recording / reproducing method and apparatus capable of realizing the normal system and the high-speed system in one system and recording and reproducing on the same recording medium. It is in.

[0011]

In order to achieve the above-mentioned object, according to the present invention, an image input capable of inputting a moving image signal at a normal frame rate N [Hz] or n times thereof at the time of recording. And the frame rate is (n
In the case of × N) [Hz], there is provided an encoding means capable of further compressing the moving image signal by 1 / n times as much as the conventional one, and a decoding corresponding to the encoding means at the time of reproduction. Means and an image display means capable of switching between low-speed reproduction and normal-speed reproduction methods according to the frame rate. Further, the normal frame rate N [H
z] and the n-fold frame rate (n × N) [Hz], the image input means and the encoding means,
And switch control means for switching the operations of the decoding means and the image display means.

[0012]

The image input means has a frame rate N [Hz],
Alternatively, a moving image signal is input at a frame rate (n × N) [Hz], and the encoding unit has a frame rate (n × N).
In the case of N) [Hz], the moving image signal is data-compressed to 1 / n times the frame rate in the case of N [Hz],
Recording is performed at the fixed transmission rate of the recording / playback system. As a result, the moving image signal can be recorded on the same recording medium regardless of the difference in frame rate.

The decoding means corresponds to the encoding means, and restores the moving image signal from the encoded data reproduced from the recording / reproducing system, and the image display means reproduces the moving image signal according to the frame rate. Outputs a moving image signal. That is, when the frame rate is N [Hz], low-speed reproduction is performed by repeatedly displaying the same frame of the previous startup image signal, and normal speed reproduction is performed by outputting at the frame rate N [Hz]. The frame rate is (n × N)
In the case of [Hz], the pre-start image signal is output at a frame rate N [Hz] to perform low-speed reproduction, and one frame out of n frames is output to perform normal-speed reproduction.

Further, the switch control means switches the operations of the image input means and the encoding means, and the decoding means and the image display means in accordance with the frame rate of the input moving image signal. As a result, the recording / reproducing method of the moving image signal can be switched according to the request.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a moving image signal recording / reproducing method and apparatus according to the present invention. In this embodiment, the frame rate N1 in the normal system is 30 [H].
z], the data rate R1 is 160 [Mbps], and the frame rate N2 in the high-speed system is three times that, that is, 9
The case where the data rate R2 is 0 [Hz] and the data rate R2 is 480 [Mbps] will be described. The parts corresponding to those in FIG. 2 are designated by the same reference numerals.

In FIG. 1, basically, the switch control means 8, the image input means 9, and the image display means 10 are the parts newly proposed in the present invention, and are the encoding circuit 3'and the decoding circuit 6 '. For, the new setting is made as necessary.

First, the recording operation will be described.

The switch control means 8 outputs a switching signal s2, and the clock generating circuit 2 outputs a clock signal s1 corresponding to the switching signal s2. The image input means 9 receives 30 [Hz] or 9 depending on the clock signal s1.
The moving image signal d1 'is input at 0 [Hz], and the encoding circuit 3'also compresses the moving image signal d1' into variable length encoded data d2 at the frame rate according to the clock signal s1. The variable length coded data d2 is
Recording is performed on the recording / reproducing system 5 at a fixed transmission rate via the switch 4.

Here, assuming that the transmission rate of the recording / reproducing system 5 is R3 = 16 [Mbps], R is R in the case of the normal system.
It is necessary to compress the data by 3 / R1 = 1/10 times. On the other hand, in the case of the high speed method, a compression rate three times that in the case of the normal method is required, such as R3 / R2 = 1/30 times. For this reason, the encoding circuit 3 ′ uses the switching signal s 2
Accordingly, the compression rate is simply increased by using the conventional encoding method, or the encoding method is switched.

Therefore, as a specific example of the method of increasing the compression rate in the encoding circuit 3 ', the case of using the conventional encoding method will be described in detail.

FIG. 3 shows a frame structure of a high-efficiency coding system for moving picture signals, which is being studied by the International Organization for Standardization (ISO), as an example of a conventional coding system. This method is an encoding method that combines inter-frame prediction, orthogonal transformation, and variable length encoding,
Each box shape in the upper half of FIG. 3 represents a frame, and the lower half schematically represents the amount of generated data after coding corresponding to each frame. Each frame is divided into three modes according to the prediction method, and as indicated by an arrow indicating the prediction direction in the figure, I1 and I2 are frames (I frames) whose encoding is completed within the frames, and P1 to P3. Is a frame in which only prediction in the forward direction is temporally performed (P frame), and B1 to B10 are frames in which prediction in both the front and rear directions is performed (B frame). The generated data amount for one frame in each prediction mode has a relation of I frame> P frame> B frame, and basically, good image quality also has the same order relation. That is, the image quality is maintained by periodically inserting I frames, and a group of a fixed number of frames including only one I frame (here, 12 frames) is called a group of pictures (GOP).
The amount of generated data is controlled in units of OP.

From the above, for example, the number of constituent frames of the GOP is increased, and the I-frame insertion period is set to be one frame for every 36 frames, which is three times as large as that in the conventional case. The rate can be tripled. In this case, the image quality may be deteriorated by extending the I frame period, but since the frame rate is increased, it is possible to perform encoding without changing the I frame period in real time. The difference in the pattern between the frames is also small and the prediction efficiency is improved.
The amount of data generated in a frame can be suppressed to some extent. However, if it is possible to simply reduce the amount of data assigned to the GOP without changing the number of frames constituting the GOP and increase the compression rate without degrading the image quality, the above process is not necessary.

Next, the operation during reproduction will be described.

Variable length encoded data d3 from the recording / reproducing system 5
Is reproduced at a transmission rate of 16 [Mbps] via the switch 4 and output to the decoding circuit 6 ′. Decoding circuit 6 '
Is the switch control means 8 as in the case of the encoding circuit 3 '.
The switching system s2 switches the decoding system as necessary, and the variable length coded data d3 is decoded into the moving image signal d4 'by the decoding system corresponding to the coding system of the coding circuit 3'. . The image display means 10 switches between the normal system and the high speed system by the switching signal s2,
The moving image signal d4 'is output.

A specific example of the high-speed image display method will be described. FIG. 4 shows a method of outputting frames for low speed reproduction and normal speed reproduction in the high speed system.
The decoding system corresponds to the above-mentioned encoding system. First, in the case of low-speed reproduction, the decoded moving image signal d
The frame rate is 30 [H
z] to output. Since the input moving image signal d1 'is input at a frame rate of 90 [Hz], it is possible to grasp fine movement even in a fast-moving scene by the low-speed reproduction. For normal speed playback, one frame is output for every three frames and the frame rate is 30 [H
z]. In this case, I frame except B frame,
A high-quality reproduced image can be obtained by selectively outputting only P frames.

As described above, according to this embodiment, in the method and apparatus for recording and reproducing the moving image signal encoded with high efficiency, the switch control means for switching between the normal system and the high speed system is provided, and the image input and By switching the encoding / decoding and the image display according to the frame rate, the normal system and the high-speed system can be realized in the shared system without changing the recording medium.

In this embodiment, IS is used as an encoding method.
Although the high-efficiency coding method studied in O is used, this is not limited to this coding method, and as a method of increasing the compression rate using the coding method, GOP
I described how to increase the number of frames that make up
There is no particular problem even if another method is used as long as the compression rate can be increased without deteriorating the image quality.

Further, in the present embodiment, the method of outputting one frame at a constant interval for the normal speed reproduction of the high speed method has been described, but an image can be output at a high frame rate depending on the display means.

[0030]

As described above, according to the moving picture signal recording / reproducing method and apparatus of the present invention, the normal method of outputting a low speed reproduction picture by repeating the same frame and the frame rate of the input moving picture signal are increased. A switch control means is provided for switching between a high-speed system for performing low-speed reproduction output at a normal frame rate, and switching is performed by appropriately switching between a moving image signal input means, an encoding means, a decoding means, and a display means. It can be realized in a shared system without changing the medium. Thereby, it is possible to switch the recording / reproducing method of the moving image signal according to the request.

[Brief description of drawings]

FIG. 1 is a block diagram showing a moving image signal recording / reproducing method and apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a moving image signal recording / reproducing method according to a conventional example.

FIG. 3 is a diagram for explaining the relationship between the frame structure and the amount of generated data in the moving picture coding system according to the embodiment of the present invention.

FIG. 4 is a diagram for explaining a reproducing method in a high speed method as a recording / reproducing method of a moving image signal.

[Explanation of symbols]

1, 9 ... Image input means, 2 ... Clock generation circuit, 3,
3 '... Encoding circuit, 4 ... Switch, 5 ... Recording / reproducing system,
6, 6 '... Decoding circuit, 7, 10 ... Image display means, 8 ...
Switch control means, d1, d1 ', d4, d4' ... moving image signal, d2, d3 ... variable length coded data, s1 ... clock signal, s2 ... switching signal

Claims (3)

[Claims] 1. A switching control means for outputting a switching signal for switching a frame rate of an input moving image signal in a moving image signal recording apparatus for highly efficiently encoding a moving image signal and recording it as encoded data on a recording medium. And an image input means for inputting a moving image signal by switching a frame rate with a clock according to the switching signal, and an encoding method for changing a data compression rate according to the switching signal to change the moving image signal. And a coding means for compressing data up to a fixed transmission rate of the recording medium regardless of the frame rate. 2. A moving picture signal reproducing apparatus which decodes a moving picture signal which is highly efficient encoded and recorded as encoded data on a recording medium by a predetermined decoding method and outputs it as a moving picture signal at a normal speed reproduction. And a switching control means for outputting a switching signal for switching the low-speed reproduction method, and a decoding system for changing encoded data reproduced from a recording medium at a fixed transmission rate so as to change the data expansion rate according to the switching signal. A decoding means for switching to a moving picture signal of a desired frame rate and a picture display means for outputting the moving picture signal by switching between normal speed reproduction and low speed reproduction according to the switching signal. A moving image signal reproducing apparatus characterized by comprising. 3. A moving image signal is highly efficiently encoded and recorded as encoded data on a recording medium, the encoded data is reproduced from the recording medium, decoded by a predetermined decoding method, and output as a moving image signal. In the moving image signal recording / reproducing method, a frame rate is switched by a clock according to a switching signal for switching between normal speed reproduction and low speed reproduction, a moving image signal is input, and a compression rate is changed according to the switching signal. Switching the encoding method like this,
It is assumed that the moving image signal is compressed and recorded up to a fixed transmission rate of a recording medium and the encoded data reproduced from the recording medium at the fixed transmission rate is changed in data expansion rate according to the switching signal. A moving image characterized in that the decoding method is switched to and decoded into a moving image signal of a desired frame rate, and the moving image signal is output by switching between normal speed reproduction and low speed reproduction methods according to the switching signal. Image signal recording / reproducing method.