JPH0955937A - Picture transmission method, picture transmission system, picture encoder and picture decoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To transmit a picture in which a moving picture part and a still picture part coexist with a high compression rate without deteriorating picture quality by separately and appropriately compressing and transmitting a moving picture and a still picture without generating a mixed picture on a transmission side. SOLUTION: The transmission side 10 consists of a moving picture information generation means 11 consisting of a video camera and the like, for example, an effector 12, the generation circuit 13 for an external synchronizing signal VH and an encoder 14. In the transmission side 10, at the time of transmitting picture information of the screen on which a moving picture part and a still picture part coexist, moving picture information and still picture information which constitute the screen, are separately compressed and encoded for every one screen, and the moving picture information and the still picture information which are compressed and encoded are multiplexed and transmitted. In a reception side 20, the moving picture information, the still picture information and the synthesized information are separated from reception information by a decoder 21 to expand/decode compressed data. Then, the decoded moving picture information and still picture information are composed, based on composition information.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is suitable for application when, for example, information on a screen in which a moving image portion and a still image portion are mixed in one screen is compression-encoded and transmitted, and decompression-decoded on the receiving side. Image transmission method, image transmission system, and image encoding device and image decoding device used in this method.

[0002]

2. Description of the Related Art In today's broadcasting, there are many programs produced by using DVI (Digital Video Instruments) such as digital switchers. For example, in a sports broadcast program, a still image portion including a score and character information for player introduction is superimposed on a moving image portion such as a game content shot by a video camera to form a mixed screen.

In the case of compressing and transmitting this kind of image information, conventionally, it has been a general practice to compress and code and transmit information for one screen in which a moving image portion and a still image portion are mixed. Target.

[0004]

The MPEG method is well known as a method for compression-encoding image data. This method is a method of temporally compressing data by performing motion compensation processing between frames and one screen horizontally ×
Vertical = 8 pixels x 8 lines, divided into a plurality of small blocks, and each block is subjected to DCT (discrete cosine transform) processing to spatially compress the two compression methods. This is the method to use.

When the information of the screen in which the moving picture and the still picture are mixed is compressed by the MPEG method, the block processing is performed as described above, so that when the compression ratio becomes large, especially the title character appears. The block distortion tends to be noticeable in a portion with many flat portions.

In addition, when a moving image is continuously encoded in an inter mode for transmitting only motion information which is a difference between preceding and following frames, residual errors are accumulated and the S / N is deteriorated. It is necessary to frequently perform intra-coding in which data is directly compressed and transmitted. Therefore, in the case of the information of the image in which the moving image and the still image are mixed as described above, it is necessary to frequently perform the intra coding for the moving image portion.

For a still image only, intra-coding is performed only when the image changes, and for a frame with no image change, the image quality after decoding is sufficient if an ultra low rate signal with zero energy is sent. Is. However, in the case of a mixed image, forced intra-encoding for a moving image is periodically performed for the above reason, but the amount of information of the original image to be intra-encoded increases due to the still image portion, and the compression ratio is increased. Had to be taken large, degrading the image quality.

At present, there is a teletext as a method of separately transmitting only a still image portion although it is only a character. However, in teletext, there is no variation in the character type created by DVI, and still images such as athlete's face photographs in sports programs could not be transmitted in teletext.

In view of the above points, the present invention provides an image transmission method, an image transmission system, and an image transmission system capable of transmitting an image in which a moving image portion and a still image portion are mixed at a high compression rate without degrading the image quality. An object of the present invention is to provide an image encoding device and an image decoding device used in this method and system.

[0010]

The present invention is characterized in that the moving image portion and the still image portion are separately compressed and transmitted in consideration of the following points.

That is, the above-mentioned moving image portion and still image portion mixed in one screen are information that must be transmitted simultaneously as a program in a broadcast program, for example.
It is information of the nature that complements each other, but is a signal of a completely different nature. Therefore, it is not necessary to directly compress and transmit the image data in which the moving image portion and the still image portion are mixed, and separately transmit the moving image portion and the still image portion separately by appropriately compressing them. However, it is sufficient that the receiving side can perform composition.

For the mixed image of the moving picture and the still picture on the broadcasting side, one screen worth of moving picture information and still picture information are prepared in advance, and the mixed picture information is stored in the digital switcher as described above. Are synthesized by. However, if the reception side synthesizes, it is possible to provide the reception side with the function of this digital switcher.

Therefore, on the transmitting side, the moving image information and the still image information are separately appropriately compressed and transmitted without generating the mixed image, and the receiving side synthesizes them. At this time, if the information for synthesizing is also sent from the transmitting side, the image intended by the transmitting side can be generated at the receiving side like a broadcast program.

The present invention realizes the above, and when transmitting image information of a screen in which a moving image portion and a still image portion are mixed, one of the moving image information constituting the screen is transmitted.
For each screen portion and for each screen portion of the still image information that constitutes the screen, compression encoding is separately performed, and the compression encoded moving image information and still image information are multiplexed and transmitted. On the receiving side of the multiplexed information, the compression-coded moving picture information and still picture information are decoded, and the moving picture information and the still picture information are combined by using the corresponding moving picture information and still picture information for each screen, and the moving picture part and the still picture part. The feature is that an image in which and are mixed is obtained.

Further, the composite information for combining the moving image information and the still image information on the receiving side is further multiplexed with the moving image information and the still image information and transmitted.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an overall outline of an embodiment of an image transmission system to which an image transmission method according to the present invention is applied, which is applied to a television broadcast.

In this system, the transmitting side 10 is composed of, for example, a video camera or a VTR, and comprises a moving picture information generating means 11 for generating a moving picture video signal MV and a moving picture information for generating a still picture video signal SV. An external device for synchronizing the effector (special effect device) 12 that generates the composite information Cs for composition, the video signal MV of the moving image from the moving image information generating unit 11 and the video signal SV of the still image from the effector 12. It comprises a synchronizing signal VH generating circuit 13 and an encoder 14 for performing compression coding of image information and processing for generating transmission information.

In this case, for example, in the case of a sports broadcast program, the moving image information expresses the appearance of a moving player or the like, and the still image information includes various data related to the game such as the score of the game, a face photograph of the player, or the like. Introductory character information.

The output information of the encoder 14 is transmitted to the transmission line 15
Is transmitted to the receiving side 20 through the. The transmission line 15 is not limited to a wireless communication line such as terrestrial broadcasting or satellite broadcasting,
It may be a wired communication path for transmission through a predetermined communication cable, or recording / reproduction on a magnetic tape or disk.

The receiving side 20 comprises a decoder 21, a composite image display signal forming circuit 22 and an image display monitor 23.

The decoder 21 separates the moving image information, the still image information, and the combined information from the received information, and decompresses and decodes the compressed data. Then, the decoded moving image information and the still image information are combined based on the combination information.

The synthetic image display signal generation circuit 22 is configured to include an image display controller and a D / A converter,
The composite image information from the decoder 21 is converted into a display image signal and output to the image display monitor 23. The image display monitor 23 displays the composite image on its screen.

The effector 12 is a video telop,
It is a device also called a scroller or the like, and a video SV of a still image from this is displayed on a part of the moving image screen, as described above, or by switching to a part thereof, for example, a character or figure pattern, a photograph, etc. The content is a still image of. Also, the synthetic information C from the effector 12
s determines, on the receiving side 20, at which position on the screen the still image output from the effector 12 is to be displayed, and in what method and mode, a combination method for displaying the still image mixed with the moving image and the like. It is for.

In the case of this embodiment, the method of synthesizing the moving image and the still image is predetermined, and the synthesizing information Cs from the effector 12 has the structure shown in the table of FIG. The composition information Cs is determined for each frame.

That is, in this case, as the composition mode,
There are three modes of “no combination”, “composition required”, and “adaptive combination”, and the mode identification information indicating the combination mode is included in the combination information Cs. Therefore, the synthesis mode identification information is composed of 2 bits for one frame.

Then, in the case of the two modes of "combination required" and "adaptive composition" with composition, information indicating a composition information compression algorithm, information indicating a composition method, and composition control means will be described later. The synthesis information Cs includes the synthesis control information indicating which of the first synthesis control means and the second synthesis control means is used.

In the case of this embodiment, there are two kinds of synthesizing methods: "switching" and "superposition". The information indicating the synthesizing method is information indicating which of these is adopted in the frame, and is composed of 1 bit for 1 frame. The "switching" synthesis method replaces a part of the moving image with a still image, and the "superimposition" superimposes the still image on the moving image so that the still image is transparently displayed.

There are two kinds of composition control means, that is, the first composition control means and the second composition control means in each of the case of "switching" and the case of "superposition" of the composition method. Is information on which one is to be adopted on the receiving side. Therefore, the synthesis control information is composed of 1 bit for one frame.

Then, the effector 12 outputs the first synthesis control signal KY when the first synthesis control means is adopted as the synthesis control means and outputs the first synthesis control signal KY when the second synthesis control means is adopted. The second synthesis control signal LS is output.

First when the composition method is "switching"
The synthesizing control means of is within one frame, that is, within one screen,
The moving image is designated to be replaced with a still image at an arbitrary screen position determined by the effector 12, and the first composite control signal CT1 in this case is the key signal KY.

This key signal KY, as shown in FIG.
The signal is a signal synchronized with the still image video signal SV from the effector 12, and a 1-bit signal (binary signal) is superimposed in the horizontal scanning period so as to indicate a period in which a still image should be displayed.

That is, when the effector 12 generates the still picture video signal SV as shown in FIG. 3A, the key signal KY as the first composite control signal CT1 is displayed on the screen as shown in FIG. 3B. It becomes active level (high level) in the area where the image is to be displayed (still image effective area), and becomes low level in other areas. Then, on the receiving decoder side, the still image signal is replaced with the moving image signal in the active level section.

Second when the composition method is "switching"
The composite control signal CY2 of is a switching level LS that is fixed within one frame.

When the effector 12 produces a still picture, the switching level LS is the video signal SV of the still picture.
Is a reference level when switching to a still image instead of a moving image at that position on the screen when the level exceeds a certain level.

The switching level LS is, for example, 256.
When it is possible to specify a step level, the video information of one frame is represented by 8-bit level information, and the effector 12 uses the switching level LS.
Is output as a second combined control signal CT2.

When the composition method is "overlap", the composition control means is a mixture of a still image and a moving image. Then, in this case, the mixing ratio k (k ≦ 1 and the ratio of the still image to the screen) is changed in one frame in the first combining control means, and in the second combining control means, Mixing ratio k
Is constant within one frame.

Then, in the case where this combining method is "superposition", when the first combining control means is adopted,
The effector 12 outputs a signal as the first combined control signal CT1 that is synchronized with the still image video signal SV as with the key signal KY, and has a mixing ratio k that changes within one frame.
The information of is output. Further, when the second synthesis control means is adopted, the effector 12 outputs, as the second synthesis control signal LS, information in frame units in which the mixing ratio k is constant within one frame.

As described above, the first combined control signal CT
1 requires information for each horizontal section of one frame, like the key signal KY in FIG. 3B, so in this embodiment, information is compressed and transmitted. On the other hand, since the second synthesis control signal CT2 has a very small amount of information such as several bits per frame, the second synthesis control signal LS is required.
Are transmitted without being compressed in this embodiment.

Regarding the information of the composite information compression algorithm of the composite information, whether the method of "compressing with the same compression algorithm as the moving image" is adopted as the compression method of the first composite control signal CT1 or "the original compression algorithm This is an indication of whether or not the method of “compressing with” has been adopted. In this embodiment, as will be described later, for a still image as well, a method of "compressing with the same compression algorithm as the moving image" and a method of "compressing with a unique compression algorithm" are selectively used. Since it is possible to adopt any one of them as the compression algorithm for the still image information, the information of the combination information compression algorithm is selected as the compression algorithm for the still image information. It will also indicate whether or not.

The information of this synthetic information compression algorithm is
It is not included in the combined information Cs from the effector 12, and is added in the encoder 14 as described later.

In this embodiment, the encoder 14 has a concrete structure as shown in FIG.

That is, the video signal MV of the moving picture from the moving picture information generating means 11 is supplied to the compression encoder 31.
Each frame is sequentially compression-coded. The compression encoder 31 uses, for example, hybrid encoding using DCT (discrete cosine transform) and motion compensation, for example, MPEG.
1 is used. In this case, the intra coding for the frame is performed at a constant cycle with the scene change portion. The compressed video data from the compression encoder 31 is supplied to the multiplexing circuit 37.

The still picture video signal SV from the effector 12 synchronized with the moving picture video signal MV by the external synchronizing signal VH generation circuit 13 is supplied to the compression encoder 32a and the compression encoder 32b. Supplied.

The compression encoder 32a performs compression encoding using the same algorithm as the moving image information. In this example, the still image video signal SV is compression encoded by MPEG1. Intra coding of frames is performed at the transition of still images.

The compression encoder 32b performs a unique compression encoding different from the compression encoding of the moving image information. As the compression coding method, a method using run length coding and Huffman coding or a method using run length coding and arithmetic coding is adopted. The compression is performed for each frame as one unit, as described above.

The compressed still image information from the compression encoders 32a and 32b is supplied to one input end a and the other input end b of the switch circuit 35. The switch circuit 35 includes a constant rate controller 39 described later.
It is switched to either one input end a or the other input end b by the switching signal from. Then, the compressed still image information from the switch circuit 35 is transferred to the multiplexing circuit 3
7 is supplied.

Of the first and second combined control signals CT1 and CT2 from the effector 12, as described above, the first combined control signal CT1 to be compressed.
Is supplied to the compression encoder 33a and the compression encoder 33b.

The compression encoder 33a performs the same compression encoding as the moving image information, and in this example, compresses the still image video signal SV by MPEG1. Further, the compression encoder 32b performs original compression encoding,
For example, the compression encoder 32b is configured by using the same encoding method.

The compressed first synthesis control signal CT1 from the compression encoders 33a and 33b is supplied to one input end a and the other input end b of the switch circuit 36. The switch circuit 36, in conjunction with the switch circuit 35, is switched to either one of the input terminals a or the other input terminal b by a switching signal from a constant rate controller 39 described later. Then, the compressed first combined control signal CT1 from the switch circuit 36.
Are supplied to the multiplexing circuit 37.

On the other hand, the second synthesis control signal CT2 and the synthesis information Cs, which do not require compression, from the effector 12 are supplied to the delay circuit 34, and the compression codes of the moving image information, the still image information and the first synthesis control information are compressed. It is synchronized with the moving image information, the still image information and the first combined control signal CT1 that are delayed and compressed for a time corresponding to the conversion processing time. And
The second synthesis control signal CT2 and the synthesis information Cs delayed by the delay circuit 34 are supplied to the multiplexing circuit 37.

As described above, the composite information Cs from the effector 12 and the first and second composite control signals CT1 and CT2 are data in frame units.

In the multiplexing circuit 37, the compressed moving image information from the compression encoder 31, the compressed still image information from the switch circuit 35, and the compressed first composite control signal from the switch circuit 36. CT1, the second synthesis control signal CT1 from the delay circuit 34 and the synthesis information Cs are multiplexed. The multiplexed data from this multiplexing circuit 37 is
It is sent to the transmission line 15 through the constant rate buffer 38.

In this embodiment, the constant rate controller 39 causes the transmission rate of the data sent to the transmission line 15 to fluctuate when viewed microscopically, but becomes constant when viewed macroscopically. Controlled as.

That is, the compression encoders 31, 32a, 3
2b, 33a, and 33b are associated with variable-length coding (entropy coding), and have a function of controlling the generated code amount.

Then, these compression encoders 31 and 32
a, 32b, 33a, 33b generate information on the generated code amount, and the information on the generated code amount is supplied to the constant rate controller 39. Further, the constant rate buffer 38 sends information on the buffer occupancy at that time to the constant rate controller 39.

The constant rate controller 39 is a compression encoder of a compression algorithm of the same compression algorithm as the compression encoder 31 of the moving image information, generated from the compression encoders 32a and 33a, and a compression encoder of a unique compression algorithm different from that of the moving image information. 32b, 3
The switch circuit 3 is configured to compare the generated code amount from 3b and select the compression encoder having the smaller generated code amount.
The switching signals of 5 and 36 are formed.

In this case, when the switch circuits 35 and 36 are switched in conjunction with each other, the generated code amount is the generated code amount of the still image information compression encoder and the compressed code of the first synthesis control information CT1. It will be compared with the total amount of code generated by the digitizer.

Then, the constant rate controller 39 supplies the multiplexing circuit 37 with information as to which of the compression encoder having the same compression algorithm as the moving image information and the compression encoder having the unique compression algorithm is selected. Multiplexing circuit 37
This information is included in the composite information Cs as the information of the composite signal compression algorithm and multiplexed.

The constant rate controller 39 also compresses the buffer occupancy rate from the constant rate buffer 38, the compression encoder 31 for moving image information, one of the selected compression encoders 32a and 32b, and the compression encoder. Encoder 33a,
Each of the compression encoders 31 and 32a or 32b and 33b, based on the information of the generated code amount from one of 33b.
The target amount (target amount) of the generated code amount for a or 33b is determined, and the information of the target amount is sent to the corresponding compression encoder.

A compression encoder 31, one of the selected compression encoders 32a and 32b, and a compression encoder 33.
In one of a and 33b, the encoding process is executed so that the generated code amount becomes the target amount. As described above, the above-described constant rate control is performed.

By the way, if the composition mode is "composition is essential",
When the synthesizing method is “switching”, it is meaningless to transmit the moving image portion of the area replaced with the still image as it is. Therefore, in this embodiment, when the synthesizing method is “switching”, the processing for reducing the code amount is performed, such as not transmitting the moving image information in the area replaced with the still image.

That is, as shown in FIG. 4, the composite information C
While s is supplied to the compression encoder 31, the still image video signal SV and the switching level LS as the second synthesis control signal CT2 are supplied to the comparison circuit 40.

In the comparison circuit 40, the switching level L
S is compared with the video signal SV of the still image to detect a region where the moving image replaces the still image, and the region detection signal is supplied to the compression encoder 31.

The compression encoder 31 detects whether "switching" is designated as the synthesizing method from the information of the synthesizing method. Then, if “switching” is designated as the combining method, the compression encoder 31 detects which of the first combining control means and the second combining control means is used from the combining control information, The first combination control means detects the area replaced with the still image from the key signal KY, and the second combination control means detects the area replaced with the still image from the output of the comparison circuit 40.

Then, the compression encoder 31 replaces the moving image information in the detected area with a dummy DC signal. Therefore, the moving image information of this area is the DCT
By this, compression coding is performed as information of only the DC component, and the code amount is reduced.

It should be noted that instead of replacing with a dummy DC signal, the compression ratio of the moving image information in the area portion is increased, or in the case of the inter coding mode, a code amount reduction such as a macroblock skip is generated. You may make it process.

As described above, the moving picture information is compressed and multiplexed at a high rate, and the still picture information is compressed at a low rate and multiplexed, and the image information is transmitted.

The multiplexed information which has been compression-encoded as described above and transmitted through the transmission line 15 is separated into moving image information, still image information and composite information in the decoder 21 on the receiving side 20, and is also compressed. The data that had been
Decrypted. Then, the decoded moving image information and the still image information are combined based on the combination information and the first or second combination control signal.

FIG. 5 shows a concrete configuration example of the decoder 21 in this embodiment. That is, the multiplexed information from the transmission line 15 is input to the buffer 51. Then, the compressed moving image information, the compressed still image information, the combined information, and the first and second combined control signals are read out at high speed from the buffer 51 for each frame, and the separation circuit 52 synchronously separates them.

The compressed moving picture information thus separated is supplied to the decompression / decoding circuit 53, where it is subjected to MPEG1 decoding processing and expanded / decoded into the original moving picture information. And
The decompressed and decoded moving image information MVd is supplied to the image combining circuit (switcher) 70.

The compressed still picture information from the separation circuit 52 is expanded and decoded by the switch circuit 54 by the decompression decoders 55a and 55b.
Is supplied to. The decompression decoder 55a includes the encoder 14
Of the compression encoder 32a expands and decodes the data encoded by the compression encoder 32a, and the expansion decoder 55b expands and decodes the data encoded by the compression encoder 32b of the encoder 14. is there. These decompression decoder 55
decompressed still image information SV from a and 55b
d is supplied to the image synthesis circuit 70 via the switch circuit 56.

The switch circuits 54 and 56 are switched to the decompression decoder side corresponding to the compression algorithm adopted by the encoder 14 according to the information of the combined information algorithm in the combined information from the separation circuit 52. However, the decompression decoding circuit 55 outputs the information of the combined information algorithm as the switching signal to the switch circuit 56.
The signal is delayed by the delay circuit 60 at a time corresponding to the processing time at a and 55b and supplied.

First compressed state from separation circuit 52
The composite control signal of 1 is supplied to the decompression decoders 58a and 58b via the switch circuit 57, respectively. The decompression decoder 58a is the compression encoder 33a of the encoder 14.
There is one that decompresses and decodes data compressed and encoded by
The expansion decoder 58b expands and decodes the data compression-encoded by the compression encoder 33b of the encoder 14. The decompression-decoded first synthesis control signal CT1d from the decompression decoders 58a and 58b is supplied to the image synthesis circuit 70 via the switch circuit 59.

The switch circuits 57 and 59 interlock with the switch circuits 54 and 56 to perform decompression / decoding corresponding to the compression algorithm adopted by the encoder 14 based on the information of the combined information algorithm of the combined information from the separation circuit 52. It can be switched to the vessel side.

The combined information from the separation circuit 52 is supplied to the image combining circuit 70 as the information Csd delayed by the delay circuit 60 described above. Furthermore, the separation circuit 5
The second synthesis control signal CT2 from 2 is also delayed by the delay circuit 60 to be the signal CT2d, and the image synthesis circuit 70
Is supplied to.

The image synthesizing circuit 70 usually has a function similar to that of a switcher provided in the DVI on the broadcasting station side, and the moving image information and the still image information are combined with the combining information and the first or second combining control. It synthesizes according to the signal.

FIG. 6 shows an example of a concrete configuration of the image synthesizing circuit 70. The image synthesizing circuit 70 of this example includes a synthesizing circuit 71 when the image synthesizing method is “switching” and a synthesizing circuit 72 when “superimposing”, and output synthetic image signals of these synthesizing circuits 71 and 72. Is the switch circuit 73
Is supplied to one and the other input ends of the composite information Csd
One of the combined image signals is output according to the combining method specified by the effector 12 according to the information about the combining method.

The synthesis circuit 71 is composed of two switch circuits 71.
1 and 712 and a comparison circuit 713. Then, the decompressed and decoded moving image information MVd and still image information SVd are supplied to one and the other input ends of the switch circuit 711, respectively. This switch circuit 71
1 is switched by the output signal of the switch circuit 712, and the output signal of the switch circuit 711 is supplied to the switch circuit 73.

Further, the decompressed and decoded first combined control signal CT1d is supplied to one input terminal of the switch circuit 712, and the output signal of the comparison circuit 713 is supplied to the other input terminal of the switch circuit 712. To be done. Then, the switch circuit 712 is switched by the synthesis control information of the synthesis information Csd.

The still image information SVd and the second synthesis control signal CT2d are supplied to the comparison circuit 713. Then, the still image information SVd and the combining method are "switching".
The second combining control signal CT2 is compared with the switching level LS, and the comparison circuit 713 obtains a signal indicating a region in which the level of the still image information SVd is higher than the switching level LS.

The synthesis circuit 72 includes coefficient multiplication circuits 721 and 722, a switch circuit 723, and a subtraction circuit 724.
And a mixing circuit 725. Then, the decompressed and decoded moving image information MVd is supplied to the coefficient multiplying circuit 721, and the decompressed and decoded still image information SVd is supplied to the coefficient multiplying circuit 722.

Further, the first and second combined control signals CT
1d and CT2d are supplied to one and the other input ends of the switch circuit 723. This switch circuit 723
Are switched by the synthesis control information of the synthesis information Csd. The first and second combination control signals are information of the mixing ratio k of the moving image and the still image when the combining method is “superimposition”, and therefore, from the switch circuit 723,
Information on the mixing ratio k is obtained.

The information on the mixing ratio k from the switch circuit 723 is supplied to the coefficient multiplication circuit 722, and at the same time,
It is supplied to the subtraction circuit 724. Information of k = 1 is supplied to the subtraction circuit 724. Therefore, the subtraction circuit 724 outputs "1-" as information on the mixing ratio.
Information of “k” is obtained and is supplied to the coefficient multiplication circuit 721.

The outputs of the coefficient multiplying circuit 721 and the coefficient multiplying circuit 722 are supplied to the mixing circuit 725 and mixed, and the mixed output is supplied to the switch circuit 73.

Since the image synthesizing circuit 70 is configured as described above, "switching" is designated as the synthesizing method on the transmitting side 10, and the synthesizing control means is the key signal which is the first synthesizing control signal. When the one by KY is designated, the switch circuit 73
Is switched to a state in which the output of the combining circuit 71 is selected.

In addition, the switch circuit 7 is selected according to the synthesis control information.
12 is a key signal K as the first combined control signal CT1d
The state is switched to select Y. Then, the switch circuit 711 is switched to a state of selecting the still image information SVd in the still image information area designated by the key signal KY and to a state of selecting the moving image information MVd in the other areas. Therefore, from the switch circuit 711,
A composite image signal in which the moving image is replaced with a still image is obtained in the area designated by the key signal KY, and this is the switch circuit 7
3 is output as an output signal of the image synthesizing circuit 70.

Next, when "switching" is designated as the synthesizing method at the transmitting side 10 and the synthesizing control means is designated by the switching level LS which is the second synthesizing control signal, the synthesizing method is selected. Based on the information, the switch circuit 73 is switched to a state in which the output of the synthesis circuit 71 is selected.

Further, the switch circuit 7 is selected according to the synthesis control information.
12 is switched to a state in which the output from the comparison circuit 713 is selected. As described above, from the comparison circuit 713,
At this time, a signal indicating a region in which the level of the still image information SVd is higher than the switching level LS is obtained, and this is supplied to the switch circuit 711 as a switching control signal.

Therefore, the switch circuit 711 switches to a state where the still image information SVd is selected in a region where the level of the still image information SVd is higher than the switching level LS, and to a state where the moving image information MVd is selected in other regions. To be Therefore, the switch circuit 711 obtains a composite image signal in which the moving image portion is replaced with the still image in the area corresponding to the switching level LS, and this is output as the output signal of the image combining circuit 70 through the switch circuit 73. .

When "superimposing" is designated as the synthesizing method on the transmitting side 10, the switch circuit 73 is switched to the state of selecting the output of the synthesizing circuit 72 according to the information of the synthesizing method.

Then, at the time of this "superposition",
The first combined control signal is one in which the mixing ratio k changes within a frame, and the second combined control signal has a fixed value k within the frame. When the switch circuit 723 is the first combining control means according to the combining control information, the mixing ratio k that changes in the frame is changed to the second according to the combining control information.
In the case of the synthesizing control means, the fixed mixing ratio k in the frame is obtained.

Then, in the coefficient multiplying circuit 721, the moving image information is multiplied by the coefficient (1-k), the still image information is multiplied by the coefficient k, and the mixing circuit 725 mixes both multiplication results. . Then, the output of this mixing circuit 725 is
The combined image signal is output as an output signal of the combining circuit 70 through the switch circuit 73.

In the example of the synthesizing circuit 70 of FIG. 6, two synthesizing circuits are provided in accordance with the two synthesizing methods, but by synthesizing the synthesizing circuit 70 as shown in FIG. The combining circuit can be made into a single circuit for the method.

That is, in the example of FIG. 7, coefficient multiplication circuits 741 and 742 and switch circuits 743 and 74.
4, 745, a subtraction circuit 746, a mixing circuit 747,
It comprises a generation circuit 748 having a coefficient k = 1 and a comparison circuit 749.

Then, the decompressed and decoded moving picture information MVd
Is supplied to the coefficient multiplying circuit 741 and the decompressed and decoded still image information SVd is supplied to the coefficient multiplying circuit 742. The output signal of the switch circuit 743 is the information of the coefficient k as described later, and the coefficient multiplication circuits 741 and 74 are provided.
2 is supplied. The switch circuit 743 is switched according to the information of the combining method of the combining information Csd.

The first and second combined control signals CT1d and CT2d are supplied to one and the other input ends of the switch circuit 744, respectively. The switch circuit 744 is switched according to the synthesis control information of the synthesis information Csd. The first combined control signal CT1d is also supplied to the k = 1 generating circuit 748, and the second combined control signal CT2d is supplied.
Are supplied to the comparison circuit 749. This comparison circuit 749
Is also supplied with still image information SVd.

The output signal of the generation circuit 748 and the output signal of the comparison circuit 749 for k = 1 are supplied to one and the other input ends of the switch circuit 745, respectively.
This switch circuit 745 is also switched by the synthesis control information of the synthesis information Csd.

Then, the switch circuits 744 and 745.
Of the switch circuit 743 are supplied to one and the other input ends of the switch circuit 743, respectively.

In the case of the synthesizing circuit having the configuration shown in FIG. 7, one in which "switching" is designated as the synthesizing method on the transmitting side 10 and the synthesizing control means uses the key signal KY which is the first synthesizing control signal When it is designated, the switch circuit 743 is switched to a state in which the output of the switch circuit 745 is selected according to the information of the combining method.

Then, the switch circuit 745 is switched to a state in which the output signal of the generating circuit 748 having the coefficient k = 1 is selected by the synthesis control information. At this time, the generation circuit 748 is supplied with the key signal KY, and k = 1 information is output in the period corresponding to the area designated by the key signal KY. Then, the information of k = 1 is supplied to the coefficient multiplication circuit 742 through the switch circuits 745 and 743, and is also supplied to the subtraction circuit 746. Therefore, in the period corresponding to the area designated by the key signal KY, the coefficient multiplied by the coefficient multiplying circuit 741 is k = 0, and the combined image signal in which the moving image in that area is replaced with the still image is added by the adding circuit 747. Obtained from.

Next, when "switching" is designated as the synthesizing method on the transmitting side 10 and the synthesizing control means is designated by the switching level LS which is the second synthesizing control signal, the synthesizing method is selected. Based on the information, the switch circuit 743 is switched to a state of selecting the output of the switch circuit 745.

Then, the switch circuit 745 is switched to a state in which the output signal of the comparison circuit 749 is selected by the synthesis control information. At this time, the switching level LS is supplied to the comparison circuit 749, and this level LS is compared with the still image signal SVd. The comparison circuit 749 outputs the still image information S based on the switching level LS.
Information with a coefficient k = 1 is obtained in a region where the level of Vd is high.

The information of the coefficient k = 1 is supplied to the coefficient multiplying circuit 742 through the switch circuits 745 and 743 and the subtracting circuit 746. Therefore, in the period corresponding to the region where the coefficient k = 1,
The coefficient k to be multiplied by the coefficient multiplying circuit 741 becomes 0, and a composite image signal in which the moving image in the area is replaced with a still image is obtained from the adding circuit 747.

When "superimposition" is designated as the combining method on the transmitting side 10, the switch circuit 743 is switched to the state of selecting the output of the switch circuit 744 according to the information of the combining method.

In the case of this "superposition", at one and the other input ends of the switch circuit 744, the information and the second combination control signal in which the mixing ratio k changes in the frame as the first combination control signal CT1d. Information of a fixed value k in the frame is supplied as CT2d. According to the synthesis control information, the switch circuit 744 outputs the signal CT1d in the case of the first synthesis control means, that is, the information of the mixing ratio k changing in the frame, and the signal CT2d in the case of the second synthesis control means. That is, the information of the fixed mixing ratio k in the frame is output.

Since the output signal of the switch circuit 744 is supplied to the coefficient multiplying circuit 742 and the subtracting circuit 746 through the switch circuit 742, the configuration is exactly the same as that of the synthesizing circuit 72 of FIG. As described above, the combined image signal in which the moving image information and the still image information are mixed according to the value of the coefficient k is obtained from the mixing circuit 747.

As described above, a moving image and a still image are separately compression-encoded and transmitted together with information for combining, and the receiving side displays a screen in which the moving image and the still image are combined using the information for combining. Since it is formed, the moving image information and the still image information can be compressed by appropriate compression encoding, and the image information can be transmitted at a high compression rate without degrading the image quality.

In particular, when the motion compensation method using inter-frame correlation is used as the compression encoding, the intra-coded areas having a large code generation amount are separately provided for the moving image information, the still image information, and the information for synthesis. Since it can be set to, it is possible to reduce the amount of transmitted information. That is, when the moving image information, the still image information, and the information for composition are mixed and compression-coded, when intra-coding is necessary for some information, other information that does not need intra-coding is also used. It is necessary to perform intra-coding at the same time, but if compression coding is performed separately as in the present invention, intra-coding can be performed for each piece of information when necessary, thus degrading image quality. Therefore, the amount of transmitted information can be reduced.

In particular, for still image information and information having extremely strong frame correlation such as the key signal KY, intra-encoding is performed on a frame-by-frame basis only when the image changes (during a scene change). , Others, if necessary for decoding, select a small area in a frame at regular intervals with a considerably long repetition period, for example, in macroblock units, and select intra-encoding. As a result, it is possible to further reduce the code generation amount.

Since the compression control according to the moving image and the still image can be performed, the visual
It is possible to reduce the block distortion that appears in characters that have many flat parts that are easily noticeable. [Modification] In the example of the encoder 14 of FIG. 4, a compression encoder having the same compression algorithm as that for moving image information and a unique compression encoder are provided in parallel for still image information and information for synthesis, respectively. , Either one is selected, but only the compression encoder of the original compression algorithm may be used.

Further, in the above example, the transmission is carried out by the communication of the constant rate data, but the data is divided into packet units and the packet transmission is carried out in bursts.
Data may be transmitted.

Further, in the above example, the decoder on the receiving side synthesizes the moving image and the still image in the synthesizing mode defined on the transmitting side, but the decoder side controls the synthesizing mode of the user. When an input operation unit is provided and the user operates this input operation unit, the switch circuit 73 of FIG. 6 is switched, for example, in accordance with the operation input of the user instead of the combined information from the transmitting side, and only the moving image is displayed. Alternatively, it is possible to obtain a still image only.

Furthermore, by providing a switch for controlling whether or not a still image is to be combined with a moving image, and controlling this switch according to a user's operation input, a still image is displayed on the moving image only when the user wants to see it. The images can be combined and displayed.

Further, by providing a means for designating the switching level and a means for designating the mixing ratio k as the user's input operation means, the composition mode can be changed by the user's manual operation. ,
A new display effect can be expected.

In the image synthesizing circuit 70 shown in FIG. 5, the image synthesizing is performed by digital processing. However, after the still image information and the moving image information are D / A converted, the image synthesizing is performed in the state of the analog signal. But of course it's good.

The above is the case where the transmission method is broadcasting.
It can be applied to any of terrestrial broadcasting, satellite broadcasting and cable broadcasting. Further, it is of course applicable to a case where image information is transmitted by wire or wirelessly instead of broadcasting.

The present invention can also be applied to the case where the transmission path is constituted by means for recording / reproducing via a recording medium. In that case, the transmission side becomes the recording system and the reception side becomes the reproduction system.

[0118]

As described above, according to the present invention, moving image information and still image information can be compressed by appropriate compression encoding, and the amount of transmission information can be reduced and optimized. At the same time, it is possible to reduce the block distortion that appears in characters with many flat parts that are visually noticeable.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an image transmission system to which an image transmission method according to the present invention is applied.

FIG. 2 is a diagram for explaining composition information used in the embodiment of the present invention.

FIG. 3 is a diagram for explaining a combination control signal used in the embodiment of the present invention.

FIG. 4 is a block diagram showing an embodiment of an image encoding device according to the present invention.

FIG. 5 is a block diagram showing an embodiment of an image decoding apparatus according to the present invention.

6 is a block diagram showing a configuration example of a part of the image decoding device in FIG.

7 is a block diagram showing another example of the configuration of part of the image decoding apparatus in FIG.

[Explanation of symbols]

 10 transmitting side 11 moving picture information generating means 12 effector 14 encoder 15 transmission path 20 receiving side 21 decoder 31 moving picture information compression encoder 32a, 32b still picture compression encoder 33a, 33b compression encoder for combining information 37 Multiplexing circuit 52 Separation circuit 53 Video information decompression decoder 55a, 55b Still image decompression decoder 58a, 58b Information decompression decoder for synthesis 70 Image synthesis circuit

Claims (9)

[Claims] 1. When transmitting image information of a screen in which a moving image portion and a still image portion are mixed, one screen unit of moving image information forming the screen and one screen portion of still image information forming the screen are transmitted. The unit and the compression encoding are separately performed, and the compression-encoded moving image information and the still image information are multiplexed and transmitted. At the receiving side of the multiplexed information, the compression-encoded moving image information and the still image information are transmitted. Image transmission characterized by decoding still image information and performing composition using corresponding moving image information for each screen and still image information to obtain an image in which moving image portion and still image portion are mixed Method. 2. The image transmission method according to claim 1, wherein
An image transmission method, wherein composite information for composite processing of the moving picture information and still picture information on the receiving side is further multiplexed and transmitted to the moving picture information and still picture information. 3. A system for compressing and transmitting image information of a screen in which a moving image portion and a still image portion are mixed in an image encoding device and expanding the image information in an image decoding device on the receiving side. The apparatus includes a first compression encoding unit that compresses and encodes moving image information that forms the screen in units of one screen, and a second compression encoding unit that compresses and encodes still image information that forms the screen in units of one screen. A compression encoding unit; and a multiplexing unit that multiplexes the compressed data from the first and second compression encoding units, wherein the image decoding device includes the moving image information from the received multiplexing information. Separation means for separating the still picture information and the information to be combined, a first decoder for decompressing and decoding the moving picture information from the separating means, and decompressing and decoding the still picture information from the separating means. Second
And the moving picture information from the first decoding device and the moving picture information from the second decoding device are combined to form image information of the screen in which the moving picture and the still image are combined. An image transmission system comprising a synthesizing means. 4. The multiplexing unit of the image coding apparatus also multiplexes information for synthesis for synthesizing the moving image information and the still image information to form image information for one screen, In the decoding device, the separating means separates the combining information, and the combining means has a function of combining the moving image and the still image using the combining information. Item 3. The image transmission system according to Item 3. 5. A first compression encoding section for compressing and encoding moving image information, a second compression encoding section for compressing and encoding still image information related to the moving image information, and the first and second sections. And a multiplexing unit that multiplexes compressed data from the compression encoding unit, wherein the moving image information is multiplexed at a high rate and the still image information is multiplexed at a low rate, and the multiplexed information is used as output information. Image encoding device. 6. The multiplexing unit is configured to further multiplex composite information for combining the moving image information and the still image information to form one screen with the compressed data. The image coding device according to claim 5. 7. A third compression coding section for compressing and coding the composite information is provided, and the data-compressed composite information is multiplexed by the multiplexing section. The image encoding device according to 1. 8. A screen image of moving image information and one of still image information.
Each screen portion is separately compression-encoded, and the moving image information and the still image information are separated from the transmission information in which the compression-encoded moving image information and the still image information are multiplexed. Separation means, a first decoder for decompressing and decoding the moving image information from the separating means, and a second decoder for decompressing and decoding the still image information from the separating means.
Decoder, and the moving image information from the first decoder and the moving image information from the second decoder are combined to form image information of a screen in which the moving image and the still image are combined. And an image decoding apparatus including: 9. The multiplexing information includes synthesis information for synthesizing a moving image based on the moving image information and a still image based on still image information, and the separation means performs the synthesis from the multiplexing information. 9. The image decoding apparatus according to claim 8, further comprising a function of separating information, wherein the combining unit is controlled by the combining information from the separating unit to control the combination of the moving image and the still image.