JPH02295392A - Picture coding control method - Google Patents

Abstract

PURPOSE:To allow a receiver side itself to set a subjective quality of a transmission picture mode suitable to the subjectiveness at the receiver side by sending a parameter signal from the receiver side and controlling a coding characteristic of a sender side encoder. CONSTITUTION:A picture data is sent from a sender side coder 1 to a receiver side decoder 2 via a data transmission line 9 and similarly a picture data is sent from a receiver side coder 12 to a sender side decoder 13. Moreover, a parameter signal 22 is sent from the receiver side to a coding section 6 of the sender side coder 1 to control the generated information quantity object value and the coding object range. Thus, the coding characteristic from the receiver side to the sender side is operated to control the subjective quality of the received picture.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image encoding control method, particularly to image encoding transmission.

[Prior art] The image coding transmission method disclosed in Technical Report CS85-3 "Color moving image transmission method for video conferencing" of the Institute of Electronics and Communication Engineers, co-authored by Atsumichi Murakami, Atsushi Ito, and Isao Uezawa, is This is shown in Figure 5.

In FIG. 5, a transmitting side encoding device (1) and a receiving side decoding device (2) are connected by a data transmission path (9),
Receiving side encoding device (12) and sending side decoding device (13)
are connected by a data transmission path (15).

Here, the transmitting side encoding device (1) includes a preprocessing circuit (4) that performs A/D conversion, format conversion, etc., and an encoding section (6).
), a transmission buffer (8), and a transmission side decoding device (1
3) includes a receiving buffer (16), a decoding section (18), and a post-processing circuit (20).

Next, the operation will be explained.

The input video signal (3) on the transmitting side is processed by the pre-processing circuit (4).
/D conversion and format conversion.

This converted digital image signal (5) is subjected to encoding processing in the encoding section (6), and the encoded signal (7
) is temporarily stored in the transmission buffer (8) and transmitted to the receiving side at a constant transmission speed. The decoding device (2) on the receiving side decodes the transmission signal using a method corresponding to the encoding method of the encoding device (1) on the transmitting side to obtain a reproduced video signal (10).

Further, the transmission signal on the receiving side is encoded and transmitted in the same way, and the transmitting side decoding device (13) decodes the digital image signal (17) to obtain a decoded signal (9), and then the reproduced signal ( 21) is obtained.

This image encoding device is for efficiently reducing redundancy in video signals and transmitting images with a small amount of transmitted information. Next, a method for reducing the amount of information will be explained.

One of the methods for reducing the amount of information is an interframe differential encoding method. This encodes only the changed part of the current input frame with respect to the transmitted frame signal.The difference between the current input frame signal and the previous frame reproduction signal is calculated, and the magnitude of this difference is determined by a certain threshold value. Only the part that exceeds this is to be encoded. By the way, since the movement of the subject varies over time, if the threshold value remains constant, a large temporal imbalance will occur in the amount of information generated in the encoded signal (7).
The movement of the reproduced image deteriorates in terms of subjective quality.

Therefore, it is necessary to smooth out the amount of generated information by controlling the threshold according to the amount of generated information.

An example of this threshold control is shown in FIG. This is done by setting a target value BM for the amount of information generated per frame, and if the actual amount of information generated is larger than that, then the next frame will be higher than the current threshold, and conversely if it is smaller, then This is to perform control to lower the temperature. That is, this threshold control can be expressed by the following equation.

T-T-1+ΔT1ΔT-g (B-BM, T-1),
Here, T-1 is the threshold value for the previous frame, and B is the amount of generated information.

FIG. 7 shows the threshold value versus generated information amount characteristic. As can be seen from this figure, by controlling the threshold value to vary according to the amount of movement of the image, the average amount of generated information becomes BM. On the other hand, if the generated information amount target value BM is lowered, the threshold value becomes higher, and as a result, the image quality deteriorates, and if the BM is increased, the image quality becomes higher.

FIG. 8 shows the frame rate (number of transmitted frames per second) versus image quality characteristics. Here, since the frame rate is proportional to the reciprocal of the generated information amount, if the generated information amount target value BM is set to a certain value, the average image quality will be the value Q corresponding to BM. becomes. Which point in this frame rate vs. quality characteristic is targeted is determined subjectively at the design stage, and is set as a fixed value within the device.

[Problems to be Solved by the Invention] The conventional image encoding control method has the above configuration, and in addition to selecting the frame rate versus image quality characteristics based on the subjectivity of the designer, Since it operates with fixed parameters regardless of the installation situation, there is a problem in that the subjective quality on the receiving side is not necessarily appropriate.

The present invention has been made in order to solve such problems, and it is an object of the present invention to enable the receiving side to manipulate the subjective quality characteristics of the transmitted image.

[Means for Solving the Problems] An image encoding control method according to the present invention includes transmitting a control parameter signal from the receiving side to the transmitting side encoding device, manipulating the transmitting side encoding characteristics from the receiving side, This allows the subjective quality of received images to be controlled.

[Operation] The image encoding device according to the present invention sends a parameter signal from the receiving side to control the target amount of information generated in the transmitting side encoding device, and the transmitting side encoding device receives the control signal sent from the receiving side. The encoding process is performed by changing the encoding characteristics based on the parameters, and the encoded information is transmitted. Thereby, subjective quality control of the received image can be achieved from the receiving side.

[Example] Next, the present invention will be explained in more detail with reference to the example shown in FIGS. 1 to 4.

In FIG. 1, image data is sent from a transmitting side encoding device (1) to a receiving side decoding device (2) via a data transmission path (9), and similarly, image data is sent from a receiving side encoding device (12). Image data is sent to the side decoding device (13) via the data transmission path (15), and in particular in this invention, the encoding unit ( A parameter signal (22) is sent to 6) to control the target amount of generated information and the encoding target range.

Next, the operation will be explained.

On the receiving side, the generated information amount target value BM is set to a specific point in the frame rate versus image quality characteristics of the reproduced image. When trying to increase the frame rate (corresponding to motion), set the target value BM small,
In order to improve the image quality, the target value BM may be increased. In this way, in order to change the target value BM depending on the subjectivity of the receiving side, the transmitting side encoding device changes the value of the target value BH or the parameter signal (22) which is the target value BM control information regarding increase/decrease from the current value. (1). The parameter signal (22), which is this control information, can be transmitted in addition to the encoded image information transmitted from the receiving side, and no new transmission line is required.

FIG. 2 shows the internal configuration of the encoding unit (6) of the transmitting side encoding device (1), which includes a decoder (23) that decodes the parameter signal (22), a decoded signal (24), and a feedback signal. (11) is input manually; a valid/invalid judgment circuit (27) into which the threshold value (26) output from the threshold control circuit (25) is input; A valid/invalid information table (29) that stores one frame of /invalid information (28) and an image signal (
5) based on the stored valid/invalid information (30),
It also includes an encoding/decoding circuit (31) that performs encoding processing.

Here, the parameter signal (22) transmitted from the receiving side
Based on this, the encoding unit (6) of the transmitting side encoding device (1) decodes it in the decoder (23), and uses the decoded signal (24) to determine the amount of generated information used in the threshold control circuit (25). The target value BM is changed and the threshold value (26) is controlled.

As a result, the amount of information generated per frame on the transmitting side encoding device is equal to the target value BM of generated information set on the receiving side.
converges to.

With such a configuration, it becomes possible to set arbitrary frame rate versus image quality characteristics from the receiving side according to the characteristic curve as shown in FIG.

In the above embodiment, an example of setting the frame rate versus image quality characteristics by controlling the generated information amount target value BH has been shown, but the receiving side can also set the encoding target range in the screen. FIG. 4 shows an example of a range specification method. In the figure, the encoding target range can be set using two-dimensional coordinates of two points.

This coordinate information is transmitted to the transmitting side encoding device (1), and the encoding device (1), as shown in FIG.
By rewriting the contents of the invalid information table (29) and invalidating all the valid/invalid information (30) of the part corresponding to the non-encoding target range, that part is frozen and the encoding range is limited. I can do it. That is, by limiting the encoding target range to only the desired portion, image quality can be improved at a constant transmission rate.

As described above, according to the present invention, the amount of information generated per frame of a video input signal is determined to be larger than the target value according to the amount that is different from the preset target value. When the threshold value is small, the threshold value is increased, and when the threshold value is small, the threshold value is changed to converge the generated information amount to the target value. In encoding control, a parameter signal is transmitted from the receiving side to the transmitting side encoding unit, and the target value is changed to converge the amount of generated information to the changed target value, and if necessary, stranded information is By configuring an image encoding control method characterized in that the encoding target range is specified and the encoding process is performed, the transmitting side can be controlled from the receiving side,
An image suitable for the subjectivity of the receiver can be obtained.

[Effects of the Invention] As explained above, the present invention has a configuration in which parameter signals are transmitted from the receiving side and the encoding characteristics of the transmitting side encoding device can be controlled, so that it is possible to select the transmitted image that is most suitable for the subjectivity of the receiving side. This has the effect of allowing the receiving side to set the subjective quality themselves.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an image encoding transmission method according to an embodiment of the present invention, FIG. 2 is an internal configuration diagram of the encoding section of a transmitting side encoding device according to the present invention, and FIG. 3 is a frame rate diagram according to the present invention. Fig. 4 is an explanatory diagram of the encoding target range setting method according to the present invention, Fig. 5 is an explanatory diagram of the conventional image encoding transmission method, and Fig. 6 is an explanatory diagram of the conventional threshold value. FIG. 7 is an explanatory diagram of the control method, FIG. 7 is a characteristic diagram of the threshold value versus the amount of generated information, and FIG. 8 is an explanatory diagram of the conventional setting of the frame rate versus image quality characteristic. In the figure, (1) is a transmitting side encoding device, (2) is a receiving side decoding device, (3) is a transmitting side input video signal, and (4) is a receiving side decoding device.
is a preprocessing circuit, (5) is a digital image signal, (6) is an encoding unit, (7) is an encoded signal, (8) is a transmission buffer, (9) is a data transmission path, and (10) is a reproduced video. signal,
(11) is a feedback signal, (12) is a receiving side encoding device, (13) is a sending side decoding device, (14) is a receiving side input video signal, (15) is a data transmission path, (16)
is the reception buffer 7, (17) is the digital image signal, (1
8) is a decoding unit, (19) is a decoded signal, (20) is a post-processing circuit, (2l) is a reproduction signal, (22) is a parameter signal, (23) is a decoder, (24) is a decoder signal,
(25) is a threshold control circuit, (26) is a threshold, (
27) is a validity/invalidity determination circuit, (28) is validity/invalidity information, (29) is validity/invalidity information table, (30) is stored validity/invalidity information, (31) is an encoding/decoding circuit. It is. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Agent Patent attorney Masuo Oiwa (2 others) Fig. 4 Transmission control information (ao-bo)-(at-t)l) Generated information amount target value BM image quality control characteristics Fig. 3 Threshold control Method example Figure 6 Figure 7 Figure z/BM Framereto image quality characteristics

Claims (1)

[Claims] Depending on the amount of deviation of the amount of information generated per frame in the video input signal from a preset target value, the threshold value is increased when the amount of information generated is larger than the target value, and the threshold value is increased when the amount of information generated is smaller than the target value. In interframe coding control in which coded information obtained by converging the generated information amount to a target value by changing a threshold value so as to decrease the amount of information is transmitted to the receiving side, transmits a parameter signal, changes the target value, converges the amount of generated information to the changed target value, and specifies coordinate information as necessary to limit the encoding target range and perform encoding processing. An image encoding control method characterized by performing the following steps.