WO2016161678A1

WO2016161678A1 - Method, device, and processing system for video encoding and decoding

Info

Publication number: WO2016161678A1
Application number: PCT/CN2015/077866
Authority: WO
Inventors: 武晓阳; 浦世亮; 沈林杰; 俞海
Original assignee: 杭州海康威视数字技术股份有限公司
Priority date: 2015-04-08
Filing date: 2015-04-29
Publication date: 2016-10-13
Also published as: CN106162194A

Abstract

A method, device, and processing system for video encoding and decoding. The method comprises: producing background frames for a video sequence to be encoded; encoding image frames and the background frames of the video sequence to be encoded to produce respective video streams; and, inserting into the video streams identifications of whether or not each frame of image is to be displayed when decoded. By producing the background frames for the video sequence to be encoded, encoding the video to be encoded into video streams of the image frames and of the background frames, and adding identifications to the video streams to determine whether or not corresponding images need to be displayed when decoded, non-display frame encoding is supported at a stream layer to support background image reference, encoding efficiency is increased, and display of images that do not need to be displayed is prevented during display, thus increasing display efficiency.

Description

Method, device and processing system for video encoding and decoding

Technical field

The present invention relates to the field of video surveillance technologies, and in particular, to a video encoding and decoding method, apparatus, and processing system.

Background technique

The digital video compression standard began in the 1980s. After more than 30 years of development, the existing standards include ITU-T series H.261, H.263, ISO MPEG-1, MPEG-4, and two organizations. Developed MPEG-2/H.262, H.264/AVC, HEVC (newest release in 2013). There are other standards of organizations, such as domestic AVS, Microsoft's VC-1, Google's VP8 and so on. Similarly, these standards use a block-based hybrid coding framework that combines predictive coding, transform coding, and entropy coding with three large coding techniques to encode equal-blocking of the image.

Predictive coding is an important coding technique for video compression. According to different sources of prediction data, the coded image can be divided into I frames (intra prediction frame, Intra), P frame (inter prediction frame, prediction), B frame (bidirectional prediction frame, Bi-Prediction). As shown in FIG. 1 , when the I frame is subjected to predictive coding, only the data of the current frame is used for prediction, and the decoding can be independently decoded without relying on other frames. When the P frame is used for predictive coding, the reconstructed image of the encoded image of the previous frame is used as a reference. When the P frame is decoded, the image of the reference frame must be decoded before decoding. When predictive coding is performed on a B frame, the previous frame and the subsequent frame can be used as reference at the same time to become a bidirectional reference frame. The B frame decoding needs to be decoded after both the previous reference frame and the subsequent reference frame are successfully decoded. P-frames and B-frames can be used as reference when using other frames instead of other frames. When I frame, the frame data can be used as a reference.

In surveillance video, most of the captured images are fixed scenes. There are many still areas on the screen, called the background; there are few moving parts, called foreground (or target), usually moving objects. On the other hand, with the advancement of technology and the improvement of processor performance, the accuracy of target extraction is getting higher and higher. In order to further improve the compression efficiency of the surveillance video, the target extraction and the video coding may be combined, and the picture to be encoded is divided into a background part and a target part, and the target part is also called a foreground part. For the encoding of the background part, using the background image as a reference can greatly improve the coding efficiency. 2 is an encoding reference relationship based on a background frame reference. The original I frame is changed to an R frame (refresh frame), and no more intra prediction techniques are used. The background frame can be inter-coded with reference to the background frame, and only the background frame can be referred to. . Other P frame and B frame reference relationships are unchanged, and reference frame coding may also be referred to. Generally, G frames (background frames) are widely spaced. In theory, as long as there is no large change in the scene, such as sudden changes in light and pan/tilt conversion, the background frame can be used for encoding. Through such an idea, the compression efficiency of the video can be further improved.

In the background frame reference coding scheme, the background frame (G frame) is different from other frames in that it may not exist in the video sequence, and may be generated by a background generation technique or by selecting a still frame. Such a background frame does not need to be displayed when it is randomly accessed, but only a random access R frame can be displayed. However, in the prior art, the image frames participating in the encoding need to be displayed, and the support cannot be implemented. Displays the encoding of the image.

Summary of the invention

It is an object of the present invention to provide a video encoding and decoding method, apparatus and processing system for encoding a video to be encoded into two video streams, an image frame and a background frame, by generating a background frame for the video sequence to be encoded. The code stream adds an identifier to confirm whether the corresponding image needs to be displayed during decoding, and supports non-display frame coding at the code stream layer to support background image reference, improve coding efficiency, and avoid displaying unnecessary display images during display.

In order to achieve the above objectives, the following technical solutions are specifically adopted:

The first aspect adopts a video encoding method, including:

Generating a background frame for the video sequence to be encoded;

Encoding the image frame and the background frame of the encoded video sequence to generate a video code stream;

An identifier for displaying whether each frame image is displayed at the time of decoding is inserted in the video code stream.

The identifier for inserting each frame image in the video code stream to be displayed during decoding is specifically:

In the header information of the NAL unit of the video code stream, the type of the frame corresponding to the NAL unit is identified by 2 bits, wherein the identifier is not displayed when the frame is displayed as a background frame.

The image frame and the background frame of the video sequence to be encoded are respectively encoded to generate a video code stream, specifically:

The image frame and the background frame of the video sequence to be encoded are divided into corresponding strips to encode respective generated video streams;

Adding a syntax element to the strip header information or modifying the semantics of the original syntax element to identify whether the stripe is displayed when decoded.

A Picture Header carrying background frame header information is inserted at the front end of the video stream corresponding to the background frame.

The image frame is encoded with reference to the background frame.

The added syntax element includes is_output, and the type is u(1). When u(1) is 0, it is not displayed, and when u(1) is set to 1, it is displayed.

The second aspect adopts a video encoding device, including:

a background frame generating unit, configured to generate a background frame for the video sequence to be encoded;

a code stream generating unit, configured to respectively encode an image frame and a background frame of the encoded video sequence to generate a video code stream;

An identifier insertion unit is configured to insert, in the video code stream, an identifier of whether each frame image is displayed at the time of decoding.

The identifier insertion unit is specifically configured to:

The code stream generating unit is specifically configured to:

The identifier insertion unit is specifically configured to:

The identifier insertion unit is specifically:

The image frame is encoded with reference to the background frame.

The third aspect adopts a video decoding method, including:

Obtaining a video code stream, where the video code stream is encoded by an image frame and a background frame, and the video code stream is inserted with an identifier of whether each frame image is displayed at the time of decoding;

Decoding an image frame of the video code stream based on the background frame;

An image of the corresponding frame is displayed based on the identification.

The identifier is set in the NAL unit header information of the video code stream, the header information of the corresponding stripe of each frame, or the Picture Header of the video stream stream front end.

The identifier corresponding to the background frame is not displayed, and the identifier corresponding to the image frame is displayed.

The fourth aspect adopts a video decoding device, including:

a video code stream acquiring unit, configured to obtain a video code stream, where the video code stream is encoded by an image frame and a background frame, and the video code stream is inserted with an identifier of whether each frame image is displayed when decoding;

a decoding unit, configured to decode an image frame of the video code stream based on the background frame;

And a display unit, configured to display an image of the corresponding frame based on the identifier.

A fifth aspect of the invention provides a video processing system, comprising the video encoding device according to any one of the preceding claims, and the video decoding device according to any one of the preceding claims.

The invention has the beneficial effects that: by generating a background frame for the video sequence to be encoded, the video to be encoded is encoded into two video code streams of an image frame and a background frame, and an identifier is added to the video stream to confirm whether the corresponding image needs to be displayed during decoding. Support non-display frame encoding at the code stream layer to support background image reference, improve coding efficiency, and avoid displaying unnecessary images during display.

DRAWINGS

1 is a schematic diagram of an inter-frame reference relationship in block-based hybrid coding in the prior art;

2 is a schematic diagram of a background frame reference relationship;

3 is a flowchart of a method of a first embodiment of a video encoding method provided in an embodiment of the present invention;

4 is a flowchart of a method of a second embodiment of a video encoding method provided in an embodiment of the present invention;

FIG. 5 is a schematic structural diagram of NAL header information in a second embodiment of a video encoding method according to an embodiment of the present invention; FIG.

6 is a structural block diagram of a first embodiment of a video encoding apparatus provided in an embodiment of the present invention;

FIG. 7 is a flowchart of a method of a first embodiment of a video decoding method according to an embodiment of the present invention; FIG.

FIG. 8 is a structural block diagram of a first embodiment of a video decoding apparatus according to an embodiment of the present invention; FIG.

9 is a block diagram showing the structure of a first embodiment of a video processing system provided in an embodiment of the present invention.

detailed description

The present invention will be further described in detail below with reference to the specific embodiments thereof and the accompanying drawings. It is to be understood that the description is not intended to limit the scope of the invention. In addition, descriptions of well-known structures and techniques are omitted in the following description in order to avoid unnecessarily obscuring the inventive concept.

Please refer to FIG. 3, which is a flowchart of a method of a first embodiment of a method for video coding provided in an embodiment of the present invention. The method in this embodiment is mainly used for various video storage, in particular, storage of monitoring video with a single scene structure in a video image. As shown, the method includes:

Step S101: Generate a background frame for the video sequence to be encoded.

In the process of video coding, the background frame may not exist in the video sequence, but an image frame generated from the video sequence by a certain technical means does not exist independently in the video sequence, and may be generated by background generation technology. A background frame is extracted from the video sequence; or a still frame is selected from the video sequence as a background frame.

Step S102: encoding the image frame and the background frame of the coded video sequence to generate a video code stream.

The image frame and the background frame in the video sequence are separately encoded, and the image frame is selected according to the encoding requirement whether to refer to the background frame, and the background frame is also encoded, because each frame of the background frame is the same, so the encoding of the background frame is compared. easily. After the encoding is completed, each of the video streams is generated.

Step S103: insert an identifier of whether each frame image is displayed at the time of decoding in the video code stream.

According to the prior art solution, video stream decoding will display all images, but in this solution, for the actual display requirement of the image frame, a logo will be added to the video stream in which no display is required to indicate the corresponding image. Whether you need to decode the display.

In summary, by generating a background frame for the video sequence to be encoded, the video to be encoded is encoded into two video code streams of an image frame and a background frame, and an identifier is added to the video stream to confirm whether the corresponding image needs to be displayed during decoding. The code stream layer supports non-display frame coding to support background image reference and improve coding efficiency.

Please refer to FIG. 4 , which is a flowchart of a method for a second embodiment of a method for video coding provided in an embodiment of the present invention. As shown in the figure, the method includes:

Step S201: Generate a background frame for the video sequence to be encoded.

Step S202: Dividing the image frame and the background frame of the video sequence to be encoded into corresponding strips to encode respective generated video streams.

In H.264, the image is divided into strip slices for encoding. Each slice contains Slice Header information, that is, strip header information, and Table 1 is a strip header information part syntax element.

Table 1

Step S203: Add a syntax element in the strip header information or modify the semantics of the original syntax element to identify whether the stripe is displayed when decoding.

In this way, you can add syntax elements to the slice header or modify the semantics of the original syntax elements to express whether the slice needs to be displayed. For example, add the is_ouput syntax element before if(IdrPicFlag), the type is u(1). u(1) is not displayed when the value is 0, and is displayed when the value of u(1) is 1.

For the background frame, the corresponding image does not need to be displayed, so the identifier of the strip header corresponding to the background frame should be added.

It can also be based on the coding method, corresponding to the identification method of the appropriate operation selected. For example, the code stream organization in H.264 and H.265 is NAL, and each NAL unit contains one NAL header information. In H.264, the header information is 1 byte; in H.265, the header information is 2 bytes. Figure 5 is a component of the H.264 NAL header, where R is 2 bits. At this time, a G frame can be represented by R=11b, R=10b represents an R frame, and R=01b represents another P frame and a B frame. Thus, when decoding, if R=11b is encountered, it means that the frame image is a background frame, and no display is needed.

In predictive coding, the coded picture is divided into an I frame, a B frame, and a P frame; in this solution, in addition to the above three frame types, there is a background frame, and the corresponding I frame in this solution is not in an absolute sense. I frame, I frame can provide reference for P frame, but I frame can not achieve intra prediction, that is, can not be independently decoded, must refer to the background frame, in order to reflect the difference, in this scheme, the functional frame corresponding to the I frame is called R Frame, meaning to refresh the frame.

In the AVS1-P2 standard, there is header information before image encoding, and i_picture_header is in front of the I frame, as shown in Table 2.

Table 2

i_picture_header(){I_picture_header(){	描述符Descriptor
i_picture_header(){I_picture_header(){	描述符Descriptor	i_picture_start_codeI_picture_start_code	f(32)f(32)

bbv_delayBbv_delay	u(16)u(16)
bbv_delayBbv_delay	u(16)u(16)	if(profile_id＝＝0x40\|\|profile_id＝＝0x24)If(profile_id==0x40\|\|profile_id==0x24)
marker_bitMarker_bit	f(1)f(1)
marker_bitMarker_bit	f(1)f(1)	bbv_delay_extensionBbv_delay_extension	u(7)u(7)
}}		bbv_delay_extensionBbv_delay_extension	u(7)u(7)
}}		if(profile_id＝＝0x24){If(profile_id==0x24){
if(background_picture_disable＝＝`0`)If(background_picture_disable==`0`)		if(profile_id＝＝0x24){If(profile_id==0x24){
		background_picture_flagBackground_picture_flag	u(1)u(1)
if(core_picture_disable＝＝`0`)If(core_picture_disable==`0`)		background_picture_flagBackground_picture_flag	u(1)u(1)
if(core_picture_disable＝＝`0`)If(core_picture_disable==`0`)		core_picrure_flagCore_picrure_flag	u(1)u(1)
}}		core_picrure_flagCore_picrure_flag	u(1)u(1)

P and B frames are preceded by pb_picture_header as shown in Table 3. The G frame header information g_picture_header can be increased accordingly, and i_picture_header can be changed to r_picture_header at the same time if necessary. It is confirmed whether it needs to be displayed according to the frame type of the header information record. If it is g_picture_header, it needs to be displayed, otherwise it does not need to be displayed.

The image frame is encoded with reference to the background frame.

table 3

In summary, by generating a background frame for the video sequence to be encoded, the video to be encoded is encoded into two video code streams of an image frame and a background frame, and an identifier is added to the video stream to confirm whether the corresponding image needs to be displayed during decoding. The code stream layer supports non-display frame coding to support background image reference and improve coding efficiency. And corresponding to the coding method that may be adopted, the corresponding identification method is designed.

The following is an embodiment of a device for video coding provided in an embodiment of the present invention. The embodiment of the device for video coding is implemented based on the embodiment of the method for video coding described above, and is not implemented in the embodiment of the device for video coding. For an explanation, please refer to the embodiment of the above video coding method.

Please refer to FIG. 6 , which is a structural block diagram of a first embodiment of a video encoding apparatus according to an embodiment of the present invention. As shown, the apparatus includes:

a background frame generating unit 310, configured to generate a background frame for the video sequence to be encoded;

a code stream generating unit 320, configured to respectively encode an image frame and a background frame of the video sequence to be encoded to generate a video code stream;

The identifier insertion unit 330 is configured to insert, in the video code stream, an identifier of whether each frame image is displayed at the time of decoding.

Preferably, the identifier insertion unit 330 is specifically configured to:

Another preferred embodiment, the code stream generating unit 320 is specifically configured to:

The identifier insertion unit 330 is specifically configured to:

Further, the added syntax element includes is_output, the type is u(1), is not displayed when u(1) is assigned a value of 0, and is displayed when the value of u(1) is 1.

In another preferred embodiment, the identifier insertion unit 330 is specifically:

The image frame is encoded with reference to the background frame.

In summary, the cooperation of the above units works by generating a background frame for the video sequence to be encoded, encoding the video to be encoded into two video code streams of the image frame and the background frame, and adding an identifier to the video stream to confirm the corresponding image. Whether to display when decoding, non-display frame encoding is supported at the code stream layer to support background image reference and improve coding efficiency.

The following is an embodiment of a video decoding method provided in the specific implementation manner of the present invention. The embodiment of the video decoding method is mainly used to decode the video code stream obtained in the foregoing video coding method embodiment. As shown in Figure 7, the method includes:

Step S401: Acquire a video code stream, where the video code stream is encoded by an image frame and a background frame, and an identifier of whether each frame image is displayed at the time of decoding is inserted into the video code stream.

Step S402: Decoding an image frame of the video code stream based on the background frame;

Step S403: Display an image of the corresponding frame based on the identifier.

In this solution, since the code stream corresponding to the background frame is added with an identifier, when decoding, it is no longer directly decoding and displaying all the frames according to the reference relationship, but the image to be displayed is selectively displayed according to the identifier, and the display is improved. effectiveness. The specific decoding process is described in the prior art and will not be further described herein.

The following is an embodiment of a device for video decoding provided in an embodiment of the present invention. The embodiment of the device for video decoding is implemented based on the embodiment of the method for video decoding described above, and is not implemented in the embodiment of the device for decoding video. For an explanation, please refer to the above embodiment of the video decoding method.

Please refer to FIG. 8 , which is a structural block diagram of an embodiment of a video decoding apparatus according to an embodiment of the present invention. As shown in the figure, the apparatus includes:

The video code stream obtaining unit 510 is configured to obtain a video code stream, where the video code stream is encoded by an image frame and a background frame, and the video code stream is inserted with an identifier of whether each frame image is displayed during decoding;

Decoding unit 520, configured to decode an image frame of the video code stream based on the background frame;

The display unit 530 is configured to display an image of the corresponding frame based on the identifier.

In this solution, since the code stream corresponding to the background frame is added with an identifier, when decoding, it is no longer directly decoding and displaying all the frames according to the reference relationship, but the image to be displayed is selectively displayed according to the identifier, and the display is improved. effectiveness.

Finally, an embodiment of a video processing system is provided in the detailed description of the present invention. As shown in FIG. 9, the video processing system includes a video encoding device 30 and a video decoding device 50, wherein the video encoding device 30 includes:

The video decoding device 50 includes:

The video processing system generates a background frame for the video sequence to be encoded, encodes the video to be encoded into two video code streams of an image frame and a background frame, and adds an identifier to the video stream to confirm whether the corresponding image needs to be displayed during decoding. The code stream layer supports non-display frame coding to support background image reference and improve coding efficiency. At the time of decoding, it is no longer directly decoding and displaying all the frames according to the reference relationship, but selectively displaying the image to be displayed according to the identification, thereby improving the display efficiency.

The above-described embodiments of the present invention are intended to be illustrative only and not to limit the invention. Therefore, any modifications, equivalent substitutions, improvements, etc., which are made without departing from the spirit and scope of the invention, are intended to be included within the scope of the invention. Rather, the scope of the appended claims is intended to cover all such modifications and modifications

Although the embodiments of the present invention have been described in detail, it is understood that various modifications, changes and changes may be made to the embodiments of the present invention without departing from the spirit and scope of the invention.

Claims

A video encoding method comprising:

Generating a background frame for the video sequence to be encoded;

Encoding the image frame and the background frame of the encoded video sequence to generate a video code stream;

An identifier for displaying whether each frame image is displayed at the time of decoding is inserted in the video code stream.
The video encoding method according to claim 1, wherein the inserting, in the video code stream, whether the image of each frame is displayed during decoding comprises:

In the header information of the NAL unit of the video code stream, the type of the frame corresponding to the NAL unit is identified by 2 bits, wherein the identifier is not displayed when the frame is displayed as a background frame.
The video encoding method according to claim 1, wherein the encoding of the image frame and the background frame of the video sequence to be encoded respectively generates a video code stream, comprising:

The image frame and the background frame of the video sequence to be encoded are divided into corresponding strips to encode respective generated video streams;

The identifier for inserting each frame image in the video code stream to be displayed during decoding includes:

Adding a syntax element to the strip header information or modifying the semantics of the original syntax element to identify whether the stripe is displayed when decoded.
The video encoding method according to claim 1, wherein the inserting, in the video code stream, whether the image of each frame is displayed during decoding comprises:

A Picture Header carrying background frame header information is inserted at the front end of the video stream corresponding to the background frame.
A video encoding method according to claim 1, wherein said image frame is encoded with reference to said background frame.
A video encoding method according to claim 3, wherein the added syntax element comprises is_output, the type is u(1), and when u(1) is assigned a value of 0, it is not displayed, when u(1) When the assignment value is 1, it is displayed.
A video encoding device comprising:

a background frame generating unit, configured to generate a background frame for the video sequence to be encoded;

a code stream generating unit, configured to respectively encode an image frame and a background frame of the encoded video sequence to generate a video code stream;

An identifier insertion unit is configured to insert, in the video code stream, an identifier of whether each frame image is displayed at the time of decoding.
A video encoding apparatus according to claim 7, wherein said identification insertion unit is configured to:

In the header information of the NAL unit of the video code stream, the type of the frame corresponding to the NAL unit is identified by 2 bits, wherein the identifier is not displayed when the frame is displayed as a background frame.
A video encoding apparatus according to claim 7, wherein said code stream generating unit is configured to:

The image frame and the background frame of the video sequence to be encoded are divided into corresponding strips to encode respective generated video streams;

The identification insertion unit is used to:

Adding a syntax element to the strip header information or modifying the semantics of the original syntax element to identify whether the stripe is displayed when decoded.
A video encoding apparatus according to claim 7, wherein said identification insertion unit is configured to:

A Picture Header carrying background frame header information is inserted at the front end of the video stream corresponding to the background frame.
A video encoding apparatus according to claim 7, wherein said image frame is encoded with reference to said background frame.
A video encoding apparatus according to claim 9, wherein said added syntax element comprises is_output of type u(1), and when u(1) is assigned a value of 0, it is not displayed, when u(1) When the assignment value is 1, it is displayed.
A video decoding method includes:

Obtaining a video code stream, where the video code stream is encoded by an image frame and a background frame, and the video code stream is inserted with an identifier of whether each frame image is displayed at the time of decoding;

Decoding an image frame of the video code stream based on the background frame;

An image of the corresponding frame is displayed based on the identification.
The video decoding method according to claim 13, wherein the identifier is set to NAL unit header information of the video code stream, header information of a corresponding strip of each frame, or a Picture Header of a video stream stream front end.
The video decoding method according to claim 13, wherein the identifier corresponding to the background frame is not displayed, and the identifier corresponding to the image frame is displayed.
A video decoding device comprising:

a video code stream acquiring unit, configured to obtain a video code stream, where the video code stream is encoded by an image frame and a background frame, and the video code stream is inserted with an identifier of whether each frame image is displayed when decoding;

a decoding unit, configured to decode an image frame of the video code stream based on the background frame;

And a display unit, configured to display an image of the corresponding frame based on the identifier.
A video decoding apparatus according to claim 16, wherein said identifier is set to NAL unit header information of said video code stream, header information of a stripe corresponding to each frame, or a Picture Header of a video stream stream front end.
The video decoding device according to claim 16, wherein the identifier corresponding to the background frame is not displayed, and the identifier corresponding to the image frame is displayed.
A video processing system including a video encoding device and a video decoding device,

The video encoding device includes:

a background frame generating unit, configured to generate a background frame for the video sequence to be encoded;

a code stream generating unit, configured to respectively encode an image frame and a background frame of the encoded video sequence to generate a video code stream;

An identifier insertion unit, configured to insert, in the video code stream, an identifier of whether each frame image is displayed at the time of decoding;

The video decoding device includes:

a video code stream acquiring unit, configured to obtain a video code stream, where the video code stream is encoded by an image frame and a background frame, and the video code stream is inserted with an identifier of whether each frame image is displayed when decoding;

a decoding unit, configured to decode an image frame of the video code stream based on the background frame;

And a display unit, configured to display an image of the corresponding frame based on the identifier.
A video processing system according to claim 19, wherein said identification insertion unit is for:

In the header information of the NAL unit of the video code stream, the type of the frame corresponding to the NAL unit is identified by 2 bits, wherein the identifier is not displayed when the frame is displayed as a background frame.
A video processing system according to claim 19, wherein said code stream generating unit is configured to:

The image frame and the background frame of the video sequence to be encoded are divided into corresponding strips to encode respective generated video streams;

The identification insertion unit is used to:

Adding a syntax element to the strip header information or modifying the semantics of the original syntax element to identify whether the stripe is displayed when decoded.
A video processing system according to claim 19, wherein said identification insertion unit is for:

A Picture Header carrying background frame header information is inserted at the front end of the video stream corresponding to the background frame.
A video processing system according to claim 19, wherein said image frame is encoded with reference to said background frame.
A video processing system according to claim 21, wherein said added syntax element comprises is_output of type u(1), and when u(1) is assigned a value of 0, it is not displayed, when u(1) When the assignment value is 1, it is displayed.
A video processing system according to claim 19, wherein said identifier is set in NAL unit header information of said video code stream, header information of a stripe corresponding to each frame, or Picture Header of a video stream stream front end.
The video processing system according to claim 19, wherein the identifier corresponding to the background frame is not displayed, and the identifier corresponding to the image frame is displayed.