JPH05176297A - Picture recording device - Google Patents

Abstract

PURPOSE:To facilitate consecutive shot by recording a pattern recorded at first after start of recording to a prescribed position of a track and recording a signal representing the joint of the picture to a prescribed position of a recording medium. CONSTITUTION:Recording of a post-recording picture is started from a track No.6 next to a track No.5 on which data of a final frame of a recorded picture are recorded. Then a mark (n) is added to the frame number. For example, a number 17n indicates it that the frame No.7 of the post recording picture is an I frame. A mark or a signal representing consecutive shot after a frame of the picture recorded already is recorded to a prescribed position of the magnetic tape such as a control track extended in the lengthwise direction of the magnetic tape. At reproduction, the picture of the frame No.7n is reproduced and outputted consecutively after the reproduction output of the picture of the frame based on the mark or the signal representing consecutive shot.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording apparatus, and more particularly to an image recording apparatus for compressing a moving image by variable length coding and recording it on a recording medium.

[0002]

2. Description of the Related Art A digital video tape recorder (VTR) is known as an image recording apparatus for digitally compressing a moving image and recording it on a recording medium such as a magnetic tape. There are two compression methods, one that uses a fixed length coding method and one that uses a variable length coding method.

FIG. 3 is a block diagram showing the configuration of a conventional example of an image recording / reproducing apparatus using a fixed length coding system. Input terminal 10
An image signal of a moving image to be recorded is input to.
The A / D converter 12 digitizes the analog image signal from the input terminal 10, and the fixed length encoding circuit 14 converts the analog image signal into an A / D signal.
The output data of the converter 12 is encoded with a fixed length. The modulation circuit 16 performs low frequency suppression modulation on the output of the fixed length coding circuit 14, and the output is amplified to a predetermined level by the recording amplifier 18. The switch 20 is connected to the a contact at the time of recording, and is connected to the b contact at the time of reproducing, and the output of the recording amplifier 18 is applied to the magnetic head 22 via the switch 20, and the magnetic tape 2 is supplied.
Recorded in 4.

At the time of reproduction, the recording signal of the magnetic tape 24 is reproduced by the magnetic head 22, and the output thereof is the switch 2
It is applied to the demodulation circuit 28 via 0 and the reproduction amplifier 26 and demodulated. The fixed length decoding circuit 30 is a decoding circuit corresponding to the fixed length coding circuit 14, and is the demodulation circuit 2
The output of 8 is decoded and a digital reproduction image signal is output. The output of the decoding circuit 30 is converted into an analog signal by the D / A converter 32, and the analog reproduced image signal is output from the output terminal 34 to the outside.

The fixed-length coding circuit 14 normally employs a coding method in which the amount of data after coding is constant within one screen (one field or one frame). The fixed-length coding method includes pulse code modulation (PC
In addition to the M) system, there are so-called sub-sampling system for digital compression, differential coding (DPCM) system, and the like. The former does not compress image information at all, so there is no deterioration in image quality, but the amount of recorded data is enormous and the recording rate must be increased. Therefore, the hardware and the recording density and recording time of the recording medium are inevitable. There are many problems with such points.

When digital compression is performed by fixed length coding, a compression rate of about 1/4 to 1/6 can be achieved. However, in the case of high definition television signals such as HDTV, the amount of recorded information is still large. Pass. In addition, the image quality is noticeable.

On the other hand, in the variable length coding method using Huffman code or arithmetic code, for example, a high compression rate of about 1/10 to 1/20 can be achieved without deteriorating the image quality. An adaptive discrete cosine transform (ADCT) system is known as such a high-efficiency variable-length coding system (for example, Takahiro Saito et al., "Coding System for Still Images", Television Society Journal, Vol. 44, No. 2 (1990). And Hiroshi Ochi et al., “International Standard Trends in Still Image Coding”, 1988 National Conference of the Institute of Image Electronics Engineers of Japan, etc. 14).

[0008]

However, in the variable length coding system, the amount of recorded information per screen is basically not constant. Therefore, there is a problem that editing, for example, joint photographing (or joint recording) is difficult, and a reproduced image is largely disturbed before and after joint photographing. Such problems are
This is particularly prominent in a digital VTR using a magnetic tape, which is a sequential access medium, as a recording medium.

An object of the present invention is to provide an image recording apparatus which solves such problems.

[0010]

An image recording apparatus according to the present invention is an apparatus for performing variable length coding of image information and recording it on a recording medium, and a screen to be recorded first after starting recording is set at a predetermined position of a track. In addition to recording, a signal indicating the seam of the image is recorded at a predetermined position on the recording medium.

[0011]

According to the variable-length coding method, the recording data amount varies depending on the screen and the recording position on the recording medium is not constant. However, by the above means, for example, in the case of joint shooting, the recording start position of the post-recorded image is clearly defined. Become. Further, the presence of the data portion that does not need to be reproduced becomes clear by the signal indicating the seam of the image, and this can be ignored. Therefore, the images before and after the joint shooting can be reproduced and output without the disturbance of the reproduction screen.

[0012]

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

FIG. 1 shows a schematic block diagram of a digital VTR which is an embodiment of the present invention.

An image signal of a moving image to be recorded is input to the input terminal 40. The A / D converter 42 digitizes the analog image signal from the input terminal 40. The variable-length coding circuit 44 has the A / D converter 12 before recording starts.
Output data of the A / D converter 1 is encoded in the frame, and the A / D converter 1 receives the recording start instruction from the operation switch 46.
The variable-length coding of the second output data is started within the frame and between the frames, and the variable-length coding within the frame and between the frames is stopped in response to the recording stop instruction. Details of the variable length coding circuit 44 will be described later.

The modulation circuit 48 performs low frequency suppression modulation on the output of the variable length coding circuit 44, and the output is amplified to a predetermined level by the recording amplifier 50. The switch 52 is connected to the a contact for recording and the b contact for reproducing, and the recording amplifier 5
The output of 0 is applied to the magnetic head 54 via the switch 52 and recorded on the magnetic tape 56.

At the time of reproduction, the recording signal of the magnetic tape 56 is reproduced by the magnetic head 54, and the output thereof is the switch 5.
2 and the reproduction amplifier 58, and is applied to the demodulation circuit 60 and demodulated. The variable length decoding circuit 62 is a decoding circuit corresponding to the variable length coding circuit 44, and includes the demodulation circuit 6
The output of 0 is decoded and a digital reproduction image signal is output. The output of the decoding circuit 62 is converted into an analog signal by the D / A converter 64, and the analog reproduced image signal is output from the output terminal 66 to the outside.

FIG. 2 is a block diagram showing the configuration of the variable length coding circuit 44 which is a characteristic part of this embodiment, and particularly shows the quantization and prediction coding unit in detail. 70 is A / D
An input terminal to which an output of the converter 42 is input, 72 is a raster scanning image data from the input terminal 70 for horizontal i pixels ×
It is a blocking circuit that blocks into blocks of vertical j pixels. i and j are usually about 8 to 16. A delay circuit 74 delays the output of the blocking circuit 72 by 3 frames.

Reference numerals 76, 78, and 80 are subtractors for calculating a prediction error for predictive differential encoding. The subtractor 76 subtracts the locally decoded value three frames before from the output of the blocking circuit 72 and subtracts it. 78 subtracts from the output of the 3-frame delay circuit 74 the image data obtained by interpolating and synthesizing the locally decoded values of 1 frame before and 4 frames before, and the subtracter 80 outputs the image data of 2 frames before from the output of the 3-frame delay circuit 74. And the image data obtained by interpolating and combining the locally decoded values 5 frames before are subtracted.

A switch 82 selects the output of the blocking circuit 72 (a contact), the output of the subtractor 76 (b contact), the output of the subtractor 78 (c contact), or the output of the subtractor 80 (d contact). Is.

Reference numeral 84 is a DCT circuit for performing a discrete cosine transform on the data selected by the switch 82, and reference numeral 86 is a DC
A quantizing circuit that quantizes the output (frequency coefficient) of the T circuit 84 with a different quantizing step for each frequency coefficient, and 88 is an inverse quantizing circuit that dequantizes the output of the quantizing circuit 86. The quantization step size in the quantization circuit 86 has a great influence on the compression rate of information. The characteristics of the quantizing circuit 86 and the inverse quantizing circuit 88 can be changed by the control coefficient from the input terminal 90. Normally, the control coefficient is determined according to the occupation rate of the data buffer in the subsequent stage, and the quantization characteristics of the quantization circuit 86 and the inverse quantization circuit 88 are feedback-controlled.

Reference numeral 92 denotes an entropy coding circuit for performing entropy coding (for example, Huffman coding) on the output of the quantization circuit 86 using the statistical property of zero continuous data, and 94 denotes the output of the entropy coding circuit 92. It is an output terminal supplied to the modulation circuit 48 of FIG.

Reference numeral 96 is an inverse DCT circuit for inverse discrete cosine transforming the output of the inverse quantization circuit 88, and 98 is an inverse DCT circuit 96.
Adder that adds zero or a predetermined prediction value to the output of
00 is a delay circuit for delaying the output of the adder 98 by 3 frames, and 102 is a product-sum operation of performing output multiplication of the output of the adder 98 and output of the 3-frame delay circuit 100 with predetermined weighting and outputting interpolated combined data. A circuit, 104 is a delay circuit that delays the output of the product-sum operation circuit 102 by one frame, and 106 is a delay circuit that delays the output of the delay circuit 104 by another frame.

Reference numeral 108 denotes a zero (a contact), a delay circuit 10.
A switch for selecting the output of 0 (contact b), the output of the delay circuit 104 (contact c), or the output of the delay circuit 106 (contact d), and 110 is an operation signal input from the operation switch 46 via the input terminal 112. Switch 82,1
08 is a control circuit for controlling 08. Switches 82, 108
Is connected to the a contact regardless of the frame before the recording is started, but from the start of the recording, it is switched frame by frame in the switching sequence shown in FIG.

The switches 82, 108 will be described in detail later.
Is connected to the a-contact, intra-frame coding is used, when connected to the b-contact, inter-frame coding with a difference of 3 frames is used, and when connected to the c-contact or d-contact, the frame is composed of the interpolated composite value of the two preceding and following frames. Inter-coding (bidirectional coding) is used.

The operation of the circuit of FIG. 2 will be described with reference to FIG. 5A shows the frame order of the image data input to the input terminal 70, and FIG. 5B shows the frame order of the image data recorded on the magnetic tape 56.

Frame # immediately after switch operation for starting recording #
7, the switches 82 and 108 are connected to the a contact as shown in FIG. The blocking circuit 72 converts the raster scan image data from the input terminal 70 into a block row of i × j pixels, and the output thereof is applied to the a contact, the subtractor 76 and the delay circuit 74 via the switch 82. .. At the stage where the block circuit 72 outputs the image data of frame # 7,
The delay circuit 74 outputs the image data of frame # 4, which is three frames before.

The DCT circuit 84 transforms the image data blocked by the blocking circuit 72 into a frequency domain by discrete cosine transform, and outputs transform coefficients. The quantization circuit 86 quantizes the output of the DCT circuit 84 with a different quantization step size for each transform coefficient. The quantization step size of the quantization circuit 86 is controlled by the control coefficient from the input terminal 90.

The entropy coding circuit 92 entropy codes the output of the quantizing circuit 86, and the output is supplied to the modulating circuit 48 of FIG. The image at this time is an intra-frame coded frame (hereinafter referred to as an I frame) that is compression-coded within one frame.

The inverse quantization circuit 88 inversely quantizes the output of the quantization circuit 86, and the inverse DCT circuit 96 inversely DCT-transforms the output of the inverse quantization circuit 88. Since the switch 108 is connected to the a contact, the adder 98 outputs the output of the inverse DCT conversion circuit 96 as it is. The output of the adder 98 is applied to the 3-frame delay circuit 100 and the product-sum operation circuit 102.

At this point, the output of the delay circuit 100 is the locally decoded image data of frame # 4, and the product-sum operation circuit 102 is the interpolated composite image data by the weighted product-sum operation of frame # 7 and frame # 4. Is being output.

At the time point when the second frame # 8 is input, the switches 82 and 108 are connected to the c-contact as shown in FIG. That is, the switch 82 selects the output of the subtractor 78. At this point, the delay circuit 74 is in the frame # 5
Image data is output, and the delay circuit 100 outputs the frame # 5.
The local decoding data of the intra-frame coding is output, and the delay circuit 104 outputs the interpolated combined data of the frame # 7 and the frame # 4. The subtractor 78 subtracts the interpolated combined data (bidirectional predicted image data) of the frame # 7 and the frame # 4 from the image data of the frame # 5, and the output thereof is applied to the DCT circuit 84 via the switch 82. ..

The output of the subtractor 78 is discrete cosine transformed and quantized by the DCT circuit 84 and the quantization circuit 86. The entropy coding circuit 92 entropy codes the output of the quantizing circuit 86, and the output is supplied to the modulating circuit 48 of FIG. 1 via the output terminal 94. The image at this time is differentially encoded with the combined value of the frame # 4 and the frame 7 sandwiching the frame of interest # 5 as the predicted value,
Hereinafter, this is referred to as a bidirectional prediction / interpolation frame (abbreviated as B frame).

The bidirectional predictive coded data of the frame # 5 is inversely transformed by the inverse quantizing circuit 88 and the inverse DCT circuit 96, and the adder 98 interpolates and synthesizes data of the frame # 7 and the frame # 4 (bidirectional predictive data). (Image data) is added and decoded. The decoded image data of frame # 5 is applied to the delay circuit 100 and the product-sum operation circuit 102.

At the time when the third frame # 9 is input, the switches 82 and 108 are connected to the d-contact as shown in FIG. That is, the switch 82 selects the output of the subtractor 80. At this point, the delay circuit 74 has the frame # 6.
Of the frame # 6 and the delay circuit 100 outputs the frame # 6.
The local decoding data of the intra-frame coding is output, and the delay circuit 106 outputs the interpolated combined data of the frame # 7 and the frame # 4. The subtractor 78 subtracts the interpolated combined data (bidirectional predicted image data) of the frame # 7 and the frame # 4 from the image data of the frame # 6, and the output thereof is applied to the DCT circuit 84 via the switch 82. ..

The output of the subtractor 78 is supplied by the DCT circuit 84, the quantization circuit 86 and the entropy coding circuit 92.
It is processed in the same manner as the previous frame, and is supplied from the output terminal 94 to the modulation circuit 48 in FIG. The image at this time is differentially encoded with the combined value of the frame # 4 and the frame 7 sandwiching the frame of interest # 6 as the predicted value, and the bidirectional prediction
It is an interpolation frame (B frame).

The bidirectional predictive coded data of frame # 6 is processed by the inverse quantization circuit 88, the inverse DCT circuit 96 and the adder 9.
Decrypted by 8. The decoded image data of frame # 6 is applied to the delay circuit 100 and the product-sum operation circuit 102.

At the time when the fourth frame # 10 is input, the switches 82 and 108 are set to b as shown in FIG.
Connect to contacts. That is, the switch 82 selects the output of the subtractor 76. At this point, the delay circuit 100 outputs the locally decoded data of the intraframe coding of the frame # 7.
The subtractor 78 subtracts the locally decoded value (inter-frame predicted image data) of the frame # 7 from the image data of the frame # 10, and the output is the DCT circuit 8 via the switch 82.
4 is applied.

The output of the subtractor 78 is compression-encoded by the DCT circuit 84, the quantization circuit 86 and the entropy encoding circuit 92, and is supplied from the output terminal 94 to the modulation circuit 48 of FIG. The image at this time is the frame # 1 of interest.
Difference-coding is performed with the decoded value of frame # 7, which is three frames before 0, as a prediction value, and is hereinafter referred to as an inter-frame coded frame (hereinafter, abbreviated as U frame).

The inter-frame coded data of frame # 10 is the inverse quantization circuit 88, the inverse DCT circuit 96 and the adder 9.
Decrypted by 8. The decoded image data of frame # 10 is applied to the delay circuit 100 and the product-sum operation circuit 102.

Thereafter, the B frame is twice, the U frame and the B frame are twice, and the I frame is formed. Then, the I frame, the U frame and the B frame are formed by the same repetition.

Next, the operation when recording is stopped will be described. In the present embodiment, it may be necessary to record the frame after the recording stop instruction time point due to the presence of the bidirectional prediction / interpolation frame. For example, in FIG. 5, frame # 1
It is assumed that the recording stop is input by the operation switch 46 between 5 and frame # 16. In this case, frame # 15
Is a bidirectional prediction / interpolation frame, the data of frame # 16 is required to restore. Therefore,
Frames # 16, # 14, 15 and so on
Record up to 16.

FIG. 6 shows a track on the magnetic tape 56 of the image data of each frame which has been variable length coded as described above.
An example of the pattern is shown. Since each frame is variable-length coded, the amount of recording data differs for each frame, and the data of one frame often spans multiple tracks. A frame number is added after B, U, and I indicating B frame, U frame, or I frame, respectively, and when a plurality of tracks are straddled, child numbers are further added.

It is assumed that another image is to be jointly shot after frame # 15 in the pattern shown in FIG. In this case, in this embodiment, the user returns the magnetic head to the track # 1 which is the first recording track, reproduces and outputs frames # 8, # 9 and # 10 in order from frame # 7, and then frame # 15.
When the image is reproduced and output, the recording start switch of the operation switch 46 is operated. In response to this, the variable length coded data of the post-recorded image is sequentially recorded from the beginning of the track next to the track on which the image of frame # 15 is recorded (track # 6 in FIG. 6).

FIG. 7 shows a recording track pattern after this joint shooting. To facilitate understanding, it is assumed that the post-recorded image starts recording from the frame # 7, and n is added to the frame number. That is, I7n indicates that the frame # 7 of the post-recorded image is the I frame.

A mark or a signal indicating that the recorded image is continuously shot after frame # 15 is recorded on a predetermined portion of the magnetic tape 56, for example, a control track extending in the longitudinal direction of the magnetic tape 56. deep.

During reproduction, the image of frame # 7n can be continuously reproduced and output after the image of frame # 15 has been reproduced and output by the above-described mark or signal for joint shooting.

In the above description, the coding is performed on a frame-by-frame basis. Further, the arrangement and number of intra-frame encoded frames, inter-frame encoded frames, and bidirectional prediction / interpolation frames are not limited to the above example. Further, it goes without saying that the variable length coding system is not limited to the system of the above embodiment.

Further, the case where the intra-frame coding, the inter-frame coding and the bidirectional predictive coding are mixed has been described.
The present invention can of course be applied to the case where one or two of these are used.

Although the example in which the magnetic tape is used as the recording medium has been described, it goes without saying that the case of using other recording medium such as a magnetic disk, an optical disk, a magneto-optical disk is also included in the scope of the present invention. ..

[0050]

As can be easily understood from the above description, according to the present invention, since the recording of the image is started from the predetermined position (usually the beginning) of the track, the reproduced image is not reproduced even if the splicing is performed. It becomes easy to control the reproduction operation so as not to disturb, and continuous reproduced images can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration block diagram of an embodiment of the present invention.

FIG. 2 is a circuit example of a variable length coding circuit 44.

FIG. 3 is a configuration block diagram of a conventional example.

FIG. 4 is a table showing a switching sequence of switches 82 and 108.

FIG. 5 is an explanatory diagram of an input image and a recorded image.

FIG. 6 is an example of a recording track pattern.

FIG. 7 is a recording track pattern after joint shooting.

[Explanation of symbols]

10: Image input terminal 12: A / D converter 14: Fixed length coding circuit 16: Modulation circuit 18: Recording amplifier 2
0: Switch 22: Magnetic head 24: Magnetic tape
26: Reproduction amplifier 28: Demodulation circuit 30: Fixed length decoding circuit 32: D / A converter 34: Reproduction image output terminal 40: Image input terminal 42: A / D converter 44: Variable length encoding circuit 46: Operation Switch 48: Modulation circuit 50: Recording amplifier 52: Switch 54: Magnetic head 56: Magnetic tape 58: Reproduction amplifier 60: Demodulation circuit 62: Variable length decoding circuit 64: D / A converter
66: Reproduced image output terminal 70: Input terminal 72: Blocking circuit 74: Delay circuit 76, 78, 80: Subtractor 82: Switch 84: D
CT circuit 86: Quantization circuit 88: Inverse quantization circuit 9
0: Control coefficient input terminal 92: Entropy coding circuit 94: Output terminal 96: Inverse DCT circuit 98: Adder 100: Delay circuit 102: Sum of products arithmetic circuit 104,
106: Delay circuit 108: Switch 110: Control circuit 112: Operation signal input terminal

Claims (1)

[Claims] 1. A device for variable-length-coding image information and recording it on a recording medium, wherein a screen to be recorded first after recording is started is recorded at a predetermined position of a track, and a signal indicating a joint of images is recorded on the recording medium. An image recording apparatus for recording the image at a predetermined position.