JPH1132329A - Encoding device and camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent block-shaped distortion, the increase of a mosquito-noise, and the generation of the difference in level of picture quality by changing each kind of picture quality parameter in a picture signal processing means through a picture signal processing controlling means by a code amount controlling means. SOLUTION: A general gamma correction processing and a picture quality adjusting processing such as outline emphasis is operated to a digital picture signal in a picture signal processing circuit 3. A picture encoder 4 operates the encoding and compressing processing of a picture signal, and converts the compressed data into a bit stream, and outputs it. This signal is temporarily stored in a buffer 5, and the information of code amounts (m) is transmitted to a code amount controlling circuit 6. The target value of code amounts to be generated for the picture of one frame is calculated by a code amount controlling circuit 6 for each frame based on a transmission rate, the code amounts (m) of the encoded data stored in the buffer 5 are always monitored, and a quantization coefficient (q) is changed so that the code amounts (m) can approach the target code amounts, and feedbacked to the picture encoder 4. Thus, the feedback control of the code amounts can be attained, and the transmission rate can be controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an encoding apparatus and a camera, and more particularly to an encoding apparatus for encoding and compressing an image signal and an audio signal to output the encoded image signal and the audio signal. Regarding the camera to play.

[0002]

2. Description of the Related Art In recent years, with the spread of personal computers, various communication media typified by the Internet, intranets, and the like often use expression means using images. This means that the video is not just for viewing but is being treated as one of information data.

In such an environment, techniques such as video signal encoding and compression processing for efficient information transmission are indispensable. In particular, compression encoding of a moving image signal requiring a high compression rate is performed by a combination of a plurality of algorithms such as DCT transform, inter-frame prediction, motion compensation, and the like. This makes it possible to utilize the correlation between the images of adjacent frames and the motion information of the subject,
Efficient compression coding is realized for a subject including motion. These encoding methods include H.264, which is an encoding standard for videophones and communications. 261
In addition, MPEG, which is a moving image storage encoding method, is generally known. These encoding techniques are described in the Journal of the Institute of Television Engineers of Japan, Vol. 45, No7, pp. 793 ~
799 (1991) and ibid. 807-812 and the like.

[0004] Among the data compression methods described above,
One of the most important techniques is code rate control. This is a control for averaging the data rate in consideration of not causing a failure in the buffer on the decoder side.

In order to equalize the code amount, the code amount (number of bits) assigned to each frame is controlled by changing the quantization coefficient. The quantization coefficient is DC
A coefficient for quantizing data that has been arranged and encoded in frequency components by T-transformation or the like, and controls the amount of code generated by dividing the encoded data by the quantization coefficient. For example, when encoding a video signal,
If the subject in a certain frame has many fine parts and the amount of code generated is large, increase the quantization coefficient to reduce the amount of code generated in the next frame. If the amount of code generated is small due to the large number of flat portions, the quantization coefficient is reduced to increase the amount of code generated in the next frame.

However, in general, the larger the quantization coefficient is, the coarser the reproduced image becomes and the larger the error from the original image becomes.

These are described in the Journal of the Institute of Television Engineers of Japan, V
ol. 47, No. 10, p. 1304-1312 (1
993).

[0008] Encoding and compression processing of an image signal are performed in accordance with such a method.
As described in Japanese Patent No. 2853 and Japanese Patent Application Laid-Open No. 7-22048, a method has been proposed to prevent image quality deterioration by performing encoding based on information of a subject, control information of a camera, and the like. I have.

Japanese Patent Application Laid-Open No. 6-292194 discloses an image quality correction circuit for controlling the data amount (code amount) by adjusting the image quality according to a predetermined compression parameter. Automatic image quality adjustment cannot be performed to maintain an optimal state for compression.

Further, Japanese Patent Application Laid-Open No. 4-227185 discloses a coded output data amount control method for adjusting the image quality in units of a plurality of blocks so that the code amount becomes a constant value. However, if the image quality is adjusted in block units, an image quality step may occur between the blocks, and the image quality may be degraded.

[0011]

In the above-described conventional method, the generated code amount increases at a stretch when the screen is a fine subject as a whole or when the motion is irregular. In addition, the code amount control is performed so as to greatly reduce the code amount generated next time. Therefore, an error occurs in the generated code, which appears as block-like distortion or mosquito-like noise.

The problems of block-like distortion and mosquito-like noise are the most serious problems that affect the reproduction image quality of a compressed moving image. In particular, audio signals are simultaneously encoded and multiplexed by synchronizing with the image. In such a system, in order to synchronize the two, the control of the code amount of the image signal must be stricter, and coding noise is more likely to occur.

In the image quality adjustment control for each block,
There is a possibility that a difference in image quality occurs between blocks and a step occurs.

An object of the present invention is to generate a moving image signal when an irregular motion such as a camera shake occurs or when a subject containing many high frequency components is photographed. It is an object of the present invention to provide an encoding apparatus and a camera capable of preventing an increase in block-like distortion and mosquito-like noise and occurrence of a step in image quality.

[0015]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an encoding apparatus comprising: (1) an image signal processing means for processing an input signal; Image signal processing control means for controlling various image quality parameters such as frequency characteristics and linearity; (3) coding means for coding an image signal output from the image signal processing means; and (4) coding means. And a code amount control unit that calculates a quantization coefficient based on the code amount generated in and controls the encoding unit, wherein the image signal processing control unit performs the image signal processing in accordance with the value of the quantization coefficient. The frequency characteristic and the linear response of the image signal in the processing means are changed.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG.
This will be described with reference to FIG. The present invention has a large effect when applied to encoding of a moving image.

FIG. 1 is a block diagram showing an embodiment of the encoding apparatus according to the present invention. An analog image signal input from an input terminal 1 is converted into a digital image signal by an image A / D converter 2. The image signal processing circuit 3 applies an image signal processing control circuit 7 to the digital image signal.
Under the control of, image quality adjustment processing such as general gamma correction processing and edge enhancement is performed.

The image encoder 4 encodes and compresses image signals according to algorithms such as DCT transform, quantization, frame prediction, and motion compensation. Further, the image encoder 4 converts the compressed data into a bit stream including various types of coding information in accordance with the standards such as MPEG and outputs the bit stream. Since the encoded signal (encoded data) must be output at a constant rate,
The information is temporarily stored in the buffer 5 and the information of the code amount m is sent to the code amount control circuit 6. The encoded data once stored in the buffer 5 is output from an output terminal 8.

The target value of the generated code amount for one frame image is calculated by the code amount control circuit 6 for each frame based on the transmission rate. The code amount control circuit 6 constantly monitors the code amount m of the encoded data stored in the buffer 5,
By changing the quantization coefficient q so that the code amount m approaches the target code amount and feeding it back to the image encoder 4, feedback control of the code amount is performed to control the transmission rate.

FIG. 2 is a functional block diagram of the code amount control circuit 6 in the encoding apparatus shown in FIG. Buffer 5
Is compared with the target code amount set in the target code amount setting unit 12 by the code amount comparator 11. The code amount comparator 11 obtains a difference between the target code amount and the code amount m in this comparison processing. The quantization coefficient calculation unit 13 calculates the quantization coefficient q based on the difference with respect to the target code amount. The target code amount is obtained for each frame, but is determined by the initial value for the encoding of the first frame, and from the subsequent frames, the overall transmission rate is kept constant in consideration of the previously encoded code amount. The target code amount calculation section 14 calculates the value so as to keep the same.

When the code amount m is larger than the target value, the quantization coefficient calculator 13 increases the quantization coefficient q so as to reduce the code amount m, and conversely, the code amount m is smaller than the target value. At times, the quantization coefficient q is reduced so as to increase the code amount m. Therefore, in the case of a subject whose code amount m suddenly increases, if the target code amount for the next encoding is suddenly decreased, the encoding efficiency is reduced and the block size is reduced at the time of encoding. Shape distortion and mosquito noise increase.

Therefore, in the coding apparatus according to the present invention, the quantization coefficient information output unit 1 sends the information q ′ about the quantization coefficient q to the image signal processing control circuit 7 to the code amount control circuit 6.
5 are provided. The image signal processing control circuit 7 updates the image quality control coefficient for the strength of contour enhancement, linearity, and the like given to the image signal processing circuit 3 based on the quantization coefficient information q ′ provided from the quantization coefficient information output unit 15.

FIG. 3 shows this state. When the generated code amount m is large and the quantization coefficient q is large,
As shown in (A), an instruction to cut the small amplitude input signal by weakening the filtering and contour emphasis or intentionally distorting the linearity of the signal response as shown in (B) is given as an image. By outputting the signal from the signal processing control circuit 7 to the image signal processing circuit 3, the information amount of the image signal is reduced. By doing so, even if the quantization coefficient q is a large value, the information amount itself of the input signal to be compressed decreases, so that the generated code amount m is reduced, and the encoding process is not performed. This can be performed efficiently within each coding unit block. Therefore, block-like distortion and mosquito-like noise seen in the range of the coding unit block are reduced. In addition, since such an increase or decrease in the information amount is performed before a coding block for coding processing is determined, there is little possibility that a sharp change in image quality occurs between adjacent blocks.

This is an operation to reduce blur and detail in the image in terms of the actual image quality, but it also has the effect of reducing block-like distortion and mosquito-like noise. An apparatus capable of providing a small number of compressed images can be realized.

Conversely, when the generated code amount m is small and the quantization coefficient q is small, even if the band of the high frequency component is widened with respect to the input image data, the same applies.
Since the encoding can be efficiently performed within each encoding unit block, the image quality can be improved by encoding up to a small portion.

Next, another embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. In this embodiment, an example will be described in which an actual moving picture compression apparatus is configured using the encoding apparatus according to the present invention described in the above embodiment.

FIG. 4 is a block diagram of a video camera having a moving image compression function according to the present invention. C which is an imaging means
The CD sensor 16 converts the subject image into an analog image signal, and the amplifier 17 amplifies the analog image signal. The subsequent signal processing system is configured in the same manner as in the above-described embodiment, is converted into a digital image signal by the image A / D converter 2, and executes image quality adjustment processing by the image signal processing circuit 3. The image quality setting parameters of the image signal processing circuit 3 are given from a control microcomputer constituting the image signal processing control circuit 7.
The encoding circuit 18 includes the image encoder 4 and the buffer 5 described above.
The image signal is encoded under the control of the control microcomputer constituting the code amount control circuit 6 and recorded by the recording device 19. As the recording device 19, an IC memory device, a DVD recording device, a magnetic disk or a magnetic tape recording device can be used.

FIG. 5 is a block diagram of an image compression processing board having a moving image compression function according to the present invention. The image compression processing board is a device for generating a compressed bit stream from an incoming analog video signal, and is often used as a computer expansion board.

The synchronization processing circuit 20 generates an image signal obtained by removing the synchronization signal from the analog video signal input via the amplifier 17. After that, an encoding process is performed in the same manner as in the above-described video camera to generate a compressed bit stream.

In these embodiments, a dedicated IC is used for the image signal processing circuit 3 and the encoding circuit 18, and the code amount control circuit 6 and the image signal processing control circuit 7 for controlling these are used.
Use a microcomputer. Information including the coding coefficient q is
The code amount is transmitted from the code amount control circuit (control microcomputer) 6 to the image signal processing control circuit (control microcomputer), and the image quality setting parameters such as frequency characteristics and linearity are updated. When the encoding circuit 18 has a function of performing an encoding process by obtaining an encoding coefficient q, the code amount control circuit (control microcomputer) 6
May be obtained by acquiring the encoding coefficient q from the encoding circuit 18 and transmitting it to the image signal processing control circuit (control microcomputer).

According to these embodiments, the quantization coefficient q
When the value of is large, for example, the amount of information itself of the input signal of the encoding circuit 18 is reduced by lowering the frequency characteristic, so that the generated code amount is also reduced, and the encoding process is performed one by one. It can be performed efficiently within a unit block. Therefore, block-like distortion and mosquito-like noise seen in the range of the coding unit block are reduced.

FIG. 6 is a block diagram showing an embodiment of a video camera using the encoding device according to the present invention.

The video camera according to this embodiment uses a lens 21 to transmit an optical signal of a subject image to a sensor 2 such as a CCD.
2 is imaged. The sensor 22 converts the formed optical signal into an analog image signal. Image A / D converter 2
Converts an analog image signal obtained from the sensor 22 into a digital signal and outputs it as a digital video signal. Hereinafter, the configurations and operations of the image signal processing circuit 3, the image encoder 4, the buffer 5, the code amount control circuit 6, and the image signal processing circuit 7 are the same as those of the above-described embodiment, and thus the duplicated description will be omitted.

Also, the audio signal is encoded in synchronization with the image signal encoding process. The audio signal acquired by the microphone 23 is digitized by an audio A / D converter 24 and sent to an audio encoder 26 via an audio signal processing circuit 25. The audio signal encoded by the audio encoder 26 is
The image signal output from the buffer 5 is multiplexed with the image signal by the system signal multiplexing circuit 27, and is recorded in the recording device 19 as compressed and encoded data.

FIG. 7 is a block diagram showing an embodiment of a video camera with a recording / reproducing function using the encoding device according to the present invention. This video camera is different from the video camera described with reference to FIG. 6 in that the video camera is provided with a playback system for compressed and encoded data of audio and image signals stored in the video camera.

The recording / reproducing device 31 records and reproduces the compressed and coded data output from the system signal multiplexing circuit 27. The compression-encoded data read from the recording / reproducing device 31 is separated into an image portion and an audio portion, and the image portion is
2 and decodes it into a digital image signal, and the audio section inputs it to an audio decoder 34 and decodes it into a digital audio signal. Thereafter, the image D / A converter 33 and the audio D
A / A converter 35 converts the analog signal into an analog signal and
Output as an analog video signal.

[0037]

As described above, according to the present invention, the level of the image signal at the preceding stage of the encoding processing unit is adjusted in accordance with the level of the quantization coefficient calculated based on the code amount generated by the encoding processing unit. Since the frequency characteristics are controlled, efficient coding processing can be realized even when a subject whose code amount significantly increases or decreases is imaged, and further, occurrence of a step in image quality can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an encoding device according to the present invention.

FIG. 2 is a block diagram showing a specific example of a code amount control circuit in the encoding device shown in FIG.

FIG. 3 is a characteristic diagram showing a state of image quality control in the encoding device according to the present invention.

FIG. 4 is a block diagram of a video camera having a moving image compression function according to the present invention.

FIG. 5 is a block diagram of an image compression board having a moving image compression function according to the present invention.

FIG. 6 is a block diagram showing an embodiment of a video camera using the encoding device according to the present invention.

FIG. 7 is a block diagram showing an embodiment of a video camera with a recording / reproducing function using the encoding device according to the present invention.

[Explanation of symbols]

2 image A / D converter, 3 image signal processing circuit, 4 image encoder, 5 buffer, 6 code amount control circuit, 7 image signal processing control circuit.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hirotaka Kobayashi 1410 Inada, Hitachinaka-shi, Ibaraki Pref.Hitachi Ltd. (72) Inventor Junji Shiokawa 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Visual Information Media Division of Hitachi, Ltd.

Claims (6)

[Claims] 1. An image signal processing means for generating a digital image signal, an image signal processing control means for controlling various image quality parameters such as frequency characteristics and linearity in the image signal processing means, and encoding the digital image signal And a code amount control means for controlling a code amount generated by the image coding means, wherein the code amount control means is provided via the image signal processing control means. An encoding device, wherein various image quality parameters in the image signal processing means are changed. 2. The apparatus according to claim 1, further comprising: means for generating a digital audio signal from the audio signal; audio encoding means for encoding the digital audio signal; and a signal encoded by the audio encoding means and the image code. An encoding device comprising signal multiplexing means for multiplexing a signal encoded by the encoding means. 3. The image signal processing control means according to claim 1, wherein said image signal processing control means includes a frequency characteristic and a linear characteristic of said digital image signal in said image signal processing means based on quantization coefficient information calculated by said code amount control means. An encoding device characterized by controlling the sex and the like. 4. An image pickup means for converting a subject image into an analog image signal, a signal conversion means for converting the analog image signal into a digital image signal, and a digital image signal to be recorded based on the digital image signal. Image signal processing means, image signal processing control means for controlling various image quality parameters such as frequency characteristics and linearity in the image signal processing means, image encoding means for encoding the digital image signal to be recorded, In a camera including a code amount control unit that controls a code amount generated by an image encoding unit and a recording unit that records the encoded signal, the code amount control unit includes the image signal processing control unit. An image signal processing means for changing various image quality parameters via the image signal processing means. 5. A digital audio signal generating means for generating a digital audio signal from an audio signal, an audio encoding means for encoding the digital audio signal, a signal encoded by the audio encoding means and the image code Signal multiplexing means for multiplexing the signal encoded by the multiplexing means, the recording means,
A camera characterized by recording a multiplexed signal. 6. The image signal processing control means according to claim 4, wherein said image signal processing control means calculates a frequency characteristic and a linear characteristic of said digital image signal in said image signal processing means based on quantization coefficient information calculated by said code amount control means. A camera characterized by controlling gender and the like.