CN108810545B - Method, apparatus, computer readable medium and electronic device for video encoding - Google Patents

Abstract

The embodiment of the invention provides a method, a device, a computer readable medium and an electronic device for video coding. The video sequence adopts n-way coding, and the method comprises the following steps: performing (n-1) th path coding on the video sequence to generate an (n-1) th path analysis file, and obtaining (n-1) th path coding information of video frames in the video sequence; obtaining quantization parameters of the nth path coding rate control stage of the video frame; performing nth coding on the video sequence based on the (n-1) th path analysis file, and correcting a quantization parameter of an nth path coding rate control stage of the video frame according to the (n-1) th path coding information of the video frame; wherein n is a positive integer greater than or equal to 2. The technical scheme of the embodiment of the invention can correct the quantization parameter of the current path coding code rate control stage of the video frame in the video sequence by the coding information of the previous path coding, thereby reducing the quality fluctuation of the video sequence.

Description

Method, device, computer-readable medium and electronic device for video encoding

technical field

The present application relates to the field of computer technology, in particular, to a video encoding method, device, computer-readable medium and electronic equipment.

Background technique

Video coding technology is continuously used in live video and on-demand video, and it is becoming more and more mature. In the case of a huge amount of source data, there are often some darker or near-black scenes in common TV dramas or movies. For example, in a movie scene, there are often scenes in which consecutive 3s or more frames are low-brightness or dark. Although the existence of these low-brightness frames will not affect people's visual experience during the movie viewing process, when the current frame in the video sequence is used as a reference frame for subsequent video frames, it will affect subsequent video frames.

The above problems exist in traditional non-distributed video coding, and this situation is more serious in distributed coding by analyzing distributed coding data.

In distributed coding, since the complete video sequence is cut into multiple small video sequences, the integrity and continuity of the video are cut off. The impact of the frame type change that may occur at the cut-off distributed slice point and/or the lack of coding information generated during the coding process on the subsequent video quality is a gradual cumulative process, especially for the similar scenarios mentioned above The quality impact of low-brightness or dark frames is more prominent, which will cause large quality fluctuations in the video sequence in these specific scenes.

Therefore, there is a need for a new method, device, computer-readable medium and electronic device for video encoding.

It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present invention, and therefore may include information that does not constitute prior art known to those of ordinary skill in the art.

Contents of the invention

Embodiments of the present invention provide a method, device, computer-readable medium, and electronic device for video encoding, which can reduce quality fluctuations of video sequences.

Other features and advantages of the invention will become apparent from the following detailed description, or in part, be learned by practice of the invention.

According to an aspect of the embodiments of the present invention, a method for video coding is provided, and the video sequence adopts n-pass encoding; wherein, the method includes: performing (n-1)-th pass encoding on the video sequence to generate the first (n-1) path analysis file, and obtain the (n-1) path encoding information of the video frame in the video sequence; obtain the quantization parameter of the n-th path encoding bit rate control stage of the video frame; based on the described The (n-1)th path analysis file performs the nth path encoding on the video sequence, and corrects the nth path encoding rate control stage of the video frame according to the (n-1)th path encoding information of the video frame The quantization parameter of ; wherein, n is a positive integer greater than or equal to 2.

In some embodiments of the present invention, based on the aforementioned solution, the (n-1)th channel of encoding information includes the peak signal-to-noise ratio of the (n-1)th channel of luminance component and chrominance component of the video frame; wherein, The modifying the quantization parameters of the nth encoding rate control stage of the video frame according to the (n-1)th encoding information of the video frame includes: if the (nth) of the current frame in the video frame -1) The peak signal-to-noise ratio of the luminance component and the chrominance component of the path is greater than the first threshold and the current frame is not a scene switching frame, then according to the peak signal-to-noise ratio of the (n-1)th path of the luminance component and the chrominance component of the current frame The noise ratio modifies the quantization parameter of the current frame.

In some embodiments of the present invention, based on the foregoing solution, the modifying the quantization parameter of the current frame according to the peak signal-to-noise ratio of the (n-1)th path of the luminance component and the chrominance component of the current frame includes: if If the peak signal-to-noise ratio of the (n-1)th luminance component and chrominance component of the current frame is in any one of the first interval to the m1th interval, the quantization parameter of the current frame is corrected by using a corresponding regulation factor; Wherein, m1 is a positive integer greater than or equal to 1.

In some embodiments of the present invention, based on the foregoing solution, m1 is equal to 5; wherein, if the peak signal-to-noise ratio of the (n-1)th path of the current frame is between the luminance component and the chrominance component in the first interval to the first interval In any one of the m intervals, the quantization parameter of the current frame is corrected by using the corresponding control factor, including: if the peak signal-to-noise ratio of the (n-1)th road luminance component and chrominance component of the current frame is at the first interval, the quantization parameter of the current frame is corrected by using the first control factor; or if the peak signal-to-noise ratio of the (n-1)th road luminance component and chrominance component of the current frame is in the second interval, the second modifying the quantization parameter of the current frame by the regulatory factor; or if the peak signal-to-noise ratio of the (n-1)th road brightness component and chrominance component of the current frame is in the third interval, the third regulatory factor is used to modify the current The quantization parameter of the frame; or if the peak signal-to-noise ratio of the (n-1)th road luminance component and chrominance component of the current frame is in the fourth interval, then the quantization parameter of the current frame is corrected by using the fourth regulation factor; or If the peak signal-to-noise ratio of the (n-1)th channel of the current frame is in the fifth interval, the quantization parameter of the current frame is corrected by using a fifth regulation factor.

In some embodiments of the present invention, based on the foregoing solutions, if the video sequence is a segmented video sequence, the first to fifth regulatory factors are respectively: 1.2, 1.8, 2.2, 3, and 4.5.

In some embodiments of the present invention, based on the aforementioned solution, the (n-1)th channel of encoding information includes the peak signal-to-noise ratio of the (n-1)th channel of luminance component and chrominance component of the video frame; wherein, The modifying the quantization parameters of the nth encoding rate control stage of the video frame according to the (n-1)th encoding information of the video frame includes: if the (nth) of the current frame in the video frame -1) The peak signal-to-noise ratio of the luminance component and the chrominance component of the road is greater than the second threshold and is in the m2th interval, and the current frame is the first inter-frame prediction frame, then obtain the quantization of the forward reference frame of the current frame Parameter; modify the quantization parameter of the current frame according to the quantization parameter of the forward reference frame; wherein, m2 is a positive integer greater than or equal to 1.

In some embodiments of the present invention, based on the foregoing solution, the following formula is used to modify the quantization parameter of the first inter-frame prediction frame: q'=q-(ref0Qp+a)*b, where ref0Qp is the forward A quantization parameter of the reference frame; a and b are constants; q is a quantization parameter of the first inter-prediction frame; q' is a corrected quantization parameter of the first inter-prediction frame.

In some embodiments of the present invention, based on the aforementioned solution, the (n-1)th channel of encoding information includes the peak signal-to-noise ratio of the (n-1)th channel of luminance component and chrominance component of the video frame; wherein, The modifying the quantization parameters of the nth encoding rate control stage of the video frame according to the (n-1)th encoding information of the video frame includes: if the (nth) of the current frame in the video frame -1) The peak signal-to-noise ratio of the luminance component and the chrominance component of the road is greater than the second threshold and is in the m2th interval, and the current frame is the second inter-frame prediction frame, then obtain the quantization of the forward reference frame of the current frame parameter and/or the quantization parameter of the backward parameter frame of the current frame; modify the current frame according to the quantization parameter of the forward reference frame of the current frame and/or the quantization parameter of the backward parameter frame of the current frame The quantization parameter of ; wherein, m2 is a positive integer greater than or equal to 1.

In some embodiments of the present invention, based on the foregoing solution, the following formula is used to modify the quantization parameter of the second inter-frame prediction frame: q'=q-((ref0Qp+c1)+(ref1Qp+c2))*d, Wherein, ref0Qp is the quantization parameter of the forward reference frame; ref1Qp is the quantization parameter of the backward reference frame; c1, c2 and d are constants; q is the quantization parameter of the second inter-frame prediction frame; q' A modified quantization parameter for the second inter-frame prediction frame.

According to an aspect of the embodiments of the present invention, there is provided a device for video encoding, where the video sequence adopts n-pass encoding; wherein, the device includes: a first encoding module configured to perform (nth) encoding on the video sequence -1) Encoding generates the (n-1)th path analysis file, and obtains the (n-1)th path encoding information of the video frame in the video sequence; the quantization parameter acquisition module is configured to obtain the first (n-1) path of the video frame. The quantization parameters of the n-way encoding rate control stage; the second encoding module is configured to carry out the n-th way encoding to the video sequence based on the (n-1)th way analysis file, and according to the (n-1)th way of the video frame. n-1) channel encoding information modifying the quantization parameters of the nth encoding rate control stage of the video frame; wherein, n is a positive integer greater than or equal to 2.

In some embodiments of the present invention, based on the aforementioned solution, the (n-1)th channel of encoding information includes the peak signal-to-noise ratio of the (n-1)th channel of luminance component and chrominance component of the video frame; wherein, The second encoding module includes: a first quantization parameter correction unit, configured to if the peak signal-to-noise ratio of the (n-1)th luma component and chrominance component of the current frame in the video frame is greater than a first threshold and the If the current frame is not a scene-switching frame, the quantization parameter of the current frame is corrected according to the peak signal-to-noise ratio of the (n-1)th luminance component and chrominance component of the current frame.

In some embodiments of the present invention, based on the foregoing solution, the first quantization parameter modification unit includes: a first quantization parameter modification subunit configured to, if the (n-1)th way of the current frame in the video frame The peak signal-to-noise ratio of the luminance component and the chrominance component is greater than the first threshold and the current frame is not a scene switching frame, and the peak signal-to-noise ratio of the (n-1)th path of the luminance component and the chrominance component of the current frame is at the first In any one of intervals to the m1th interval, the quantization parameter of the current frame is corrected using a corresponding regulation factor; wherein, m1 is a positive integer greater than or equal to 1.

In some embodiments of the present invention, based on the aforementioned solution, the (n-1)th channel of encoding information includes the peak signal-to-noise ratio of the (n-1)th channel of luminance component and chrominance component of the video frame; wherein, The second encoding module includes: a second quantization parameter modification unit, configured to if the peak signal-to-noise ratio of the (n-1)th road brightness component and chrominance component of the current frame in the video frame is greater than a second threshold and is in In the m2th interval, and the current frame is the first inter-frame prediction frame, then obtain the quantization parameter of the forward reference frame of the current frame; modify the quantization parameter of the current frame according to the quantization parameter of the forward reference frame ; and/or a third quantization parameter correction unit, configured to if the peak signal-to-noise ratio of the (n-1)th luma component and chrominance component of the current frame in the video frame is greater than the second threshold and is in the m2th interval, and the current frame is a second inter-frame prediction frame, then obtain the quantization parameter of the forward reference frame of the current frame and/or the quantization parameter of the backward parameter frame of the current frame; according to the current frame The quantization parameter of the forward reference frame and/or the quantization parameter of the backward parameter frame of the current frame modifies the quantization parameter of the current frame; wherein, m2 is a positive integer greater than or equal to 1.

According to an aspect of the embodiments of the present invention, a computer-readable medium is provided, on which a computer program is stored, and when the program is executed by a processor, the method for video encoding as described in the above-mentioned embodiments is implemented.

According to an aspect of the embodiments of the present invention, there is provided an electronic device, including: one or more processors; a storage device configured to store one or more programs, when the one or more programs are executed by the one or more When executed by multiple processors, the one or more processors implement the method for video encoding as described in the foregoing embodiments.

In the technical solution provided by some embodiments of the present invention, the (n-1)th encoding information of the video frame in the video sequence is obtained by performing the (n-1)th encoding on the video sequence, and based on the The (n-1)th coding information modifies the quantization parameters of the nth coding rate control stage of the video frame, so as to reduce the quality fluctuation of the video sequence and bring better visual experience to the user.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention.

Description of drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description serve to explain the principles of the invention. Apparently, the drawings in the following description are only some embodiments of the present invention, and those skilled in the art can obtain other drawings according to these drawings without creative efforts. In the attached picture:

FIG. 1 shows a schematic diagram of an exemplary system architecture of a method for video encoding or an apparatus for video encoding to which an embodiment of the present invention can be applied;

FIG. 2 shows a schematic structural diagram of a computer system suitable for implementing an electronic device according to an embodiment of the present invention;

Fig. 3 schematically shows a flowchart of a method for video encoding according to an embodiment of the present invention;

FIG. 4 shows a schematic diagram of the processing process of step S310 shown in FIG. 3 in an embodiment;

FIG. 5 shows a schematic diagram of the processing process of step S330 shown in FIG. 3 in an embodiment;

FIG. 6 schematically shows a flowchart of a method for video encoding according to yet another embodiment of the present invention;

Fig. 7 schematically shows a flowchart of a method for video encoding according to yet another embodiment of the present invention;

Fig. 8 schematically shows a block diagram of a device for video encoding according to an embodiment of the present invention;

Fig. 9 schematically shows a block diagram of an apparatus for video encoding according to yet another embodiment of the present invention.

Detailed ways

Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments may, however, be embodied in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete and fully convey the concept of example embodiments to those skilled in the art.

Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided in order to give a thorough understanding of embodiments of the invention. However, those skilled in the art will appreciate that the technical solutions of the present invention may be practiced without one or more of the specific details, or other methods, components, means, steps, etc. may be employed. In other instances, well-known methods, apparatus, implementations, or operations have not been shown or described in detail to avoid obscuring aspects of the invention.

The block diagrams shown in the drawings are merely functional entities and do not necessarily correspond to physically separate entities. That is, these functional entities may be implemented in software, or in one or more hardware modules or integrated circuits, or in different networks and/or processor devices and/or microcontroller devices entity.

The flow charts shown in the drawings are only exemplary illustrations, and do not necessarily include all contents and operations/steps, nor must they be performed in the order described. For example, some operations/steps can be decomposed, and some operations/steps can be combined or partly combined, so the actual order of execution may be changed according to the actual situation.

Fig. 1 shows a schematic diagram of an exemplary system architecture 100 to which a method for video coding or an apparatus for video coding according to an embodiment of the present invention can be applied.

As shown in FIG. 1 , the system architecture 100 may include one or more of terminal devices 101 , 102 , and 103 , a network 104 and a server 105 . The network 104 is used as a medium for providing communication links between the terminal devices 101 , 102 , 103 and the server 105 . Network 104 may include various connection types, such as wires, wireless communication links, or fiber optic cables, among others.

It should be understood that the numbers of terminal devices, networks and servers in Fig. 1 are only illustrative. According to the implementation needs, there can be any number of terminal devices, networks and servers. For example, the server 105 may be a server cluster composed of multiple servers.

Users can use terminal devices 101 , 102 , 103 to interact with server 105 via network 104 to receive or send messages and the like. The terminal devices 101, 102, 103 may be various electronic devices with display screens, including but not limited to smartphones, tablet computers, portable and desktop computers, digital cinema projectors, and so on.

The server 105 may be a server that provides various services. For example, the user uses the terminal device 103 (or the terminal device 101 or 102 ) to send a live video or video on demand request to the server 105 . The server 105 can retrieve the matching search results in the database based on the relevant information carried in the live video broadcast or video on demand, and feed back the search results, such as corresponding video information, to the terminal device 103, and then the user can display the corresponding video information based on the terminal device 103. content to watch the corresponding video.

Another example is that the terminal device 103 (or the terminal device 101 or 102 ) may be a digital cinema projector in a movie theater, and the user may send a video playback instruction to the server 105 through the digital cinema projector. Based on the video playing instruction, the server 105 may retrieve the matching movie video from the database and return it to the digital movie projector, and then play the returned movie video through the digital movie projector.

Fig. 2 shows a schematic structural diagram of a computer system suitable for implementing the electronic device of the embodiment of the present invention.

It should be noted that the computer system 200 of the electronic device shown in FIG. 2 is only an example, and should not limit the functions and scope of use of the embodiments of the present invention.

As shown in FIG. 2 , a computer system 200 includes a central processing unit (CPU) 201 that can be programmed according to a program stored in a read-only memory (ROM) 202 or a program loaded from a storage section 208 into a random-access memory (RAM) 203 Instead, various appropriate actions and processes are performed. In RAM 203, various programs and data necessary for system operation are also stored. The CPU 201, ROM 202, and RAM 203 are connected to each other via a bus 204. An input/output (I/O) interface 205 is also connected to the bus 204 .

The following components are connected to the I/O interface 205: an input section 206 including a keyboard, a mouse, etc.; an output section 207 including a cathode ray tube (CRT), a liquid crystal display (LCD), etc., and a speaker; a storage section 208 including a hard disk, etc. and a communication section 209 including a network interface card such as a LAN card, a modem, or the like. The communication section 209 performs communication processing via a network such as the Internet. A drive 210 is also connected to the I/O interface 205 as needed. A removable medium 211, such as a magnetic disk, an optical disk, a magneto-optical disk, a semiconductor memory, etc., is mounted on the drive 210 as necessary so that a computer program read therefrom is installed into the storage section 208 as necessary.

In particular, according to an embodiment of the present invention, the processes described below with reference to the flowcharts may be implemented as computer software programs. For example, the embodiments of the present invention include a computer program product, which includes a computer program carried on a computer-readable medium, where the computer program includes program codes for executing the methods shown in the flowcharts. In such an embodiment, the computer program may be downloaded and installed from a network via communication portion 209 and/or installed from removable media 211 . When the computer program is executed by the central processing unit (CPU) 201, various functions defined in the method and/or apparatus of the present application are performed.

It should be noted that the computer-readable medium shown in the present invention may be a computer-readable signal medium or a computer-readable storage medium or any combination of the above two. A computer readable storage medium may be, for example, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of computer-readable storage media may include, but are not limited to, electrical connections with one or more wires, portable computer diskettes, hard disks, random access memory (RAM), read-only memory (ROM), erasable Programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination of the above. In the present invention, a computer-readable storage medium may be any tangible medium that contains or stores a program that can be used by or in conjunction with an instruction execution system, apparatus, or device. In the present invention, however, a computer-readable signal medium may include a data signal propagated in baseband or as part of a carrier wave, in which computer-readable program codes are carried. Such propagated data signals may take many forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination of the foregoing. A computer-readable signal medium may also be any computer-readable medium other than a computer-readable storage medium, which can send, propagate, or transmit a program for use by or in conjunction with an instruction execution system, apparatus, or device. . Program code embodied on a computer readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing.

The flowchart and block diagrams in the figures illustrate the architecture, functions and operations of possible implementations of methods, apparatuses and computer program products according to various embodiments of the present invention. In this regard, each block in a flowchart or block diagram may represent a module, program segment, or portion of code that includes one or more logical functions for implementing specified executable instructions. It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or they may sometimes be executed in the reverse order, depending upon the functionality involved. It should also be noted that each block in the block diagrams or flowchart illustrations, and combinations of blocks in the block diagrams or flowchart illustrations, can be implemented by a dedicated hardware-based system that performs the specified function or operation, or can be implemented by a A combination of dedicated hardware and computer instructions.

The modules and/or units and/or subunits involved in the embodiments described in the present invention can be realized by software or by hardware. The described modules and/or units and/or subunits It can also be set in the processor. Wherein, the names of these modules and/or units and/or subunits do not constitute limitations on the modules and/or units and/or subunits themselves under certain circumstances.

As another aspect, the present application also provides a computer-readable medium. The computer-readable medium may be included in the electronic device described in the above-mentioned embodiments; or it may exist independently without being assembled into the electronic device. middle. The above-mentioned computer-readable medium carries one or more programs, and when the above-mentioned one or more programs are executed by an electronic device, the electronic device is made to implement the methods described in the following embodiments. For example, the electronic device may implement various steps as shown in FIG. 3 or FIG. 4 or FIG. 5 or FIG. 6 or FIG. 7 .

Fig. 3 schematically shows a flowchart of a method for video encoding according to an embodiment of the present invention.

In the video encoding method provided by the embodiment of the present invention, the video sequence may adopt n-pass encoding, where n is a positive integer greater than or equal to 2.

For example, if n can be 2, then the current video sequence adopts 2-pass encoding, that is, the current video sequence is first encoded (1pass); and then based on the analysis file encoded by 1pass, the current video sequence is encoded in the second pass (2pass). When the current video sequence adopts 2-way encoding, 1pass encoding generally only retains the required effective information and stores it as a file, so that the effective information in the file can be read for 2pass encoding to perform the second-pass encoding.

Among them, the 2pass encoding method can accurately obtain the desired average bit rate. 2pass means that the video sequence is encoded twice. The first encoding video encoder such as x264 first analyzes the entire video sequence, and a stats file and an mbtree file can be obtained. (By default mbtree is used). The second encoding can use these two files as a reference to assign a reasonable bit rate. If you need a specific bit rate or file size, you need to use 2pass or multi-pass encoding.

For another example, n can be 3, then the current video sequence adopts 3-pass encoding, that is, the current video sequence is first encoded (1pass); and then based on the analysis file after 1pass encoding, the current video sequence is encoded in the second pass Encoding (2pass); then, based on the analysis file encoded by 2pass, a third pass of encoding (3pass) is performed on the current video sequence. By analogy, the current video sequence can be encoded in multiple channels, and the specific number of encoding channels can be determined according to the application scenario, which is not limited in the present invention. That is to say, in addition to 2pass, there are also multi-pass encoding methods. Continuing the analysis on the basis of the previous analysis will theoretically make the code rate allocation more reasonable, but in fact 2pass is enough.

It should be noted that, in the following examples, the video sequence adopts 2-way encoding as an example for illustration, but the present invention is not limited thereto.

As shown in FIG. 3 , the method for video coding provided by the embodiment of the present invention may include the following steps. The method in the embodiment of the present invention may be executed by a terminal device, or may be executed by a server, or may be executed interactively by a terminal device and a server, for example, may be executed by the server 105 in FIG. 1 above, but the present invention is not limited thereto .

In step S310, the (n-1)th pass encoding is performed on the video sequence to generate the (n-1)th pass analysis file, and the (n-1)th pass encoding information of the video frame in the video sequence is obtained.

In an exemplary embodiment, the (n-1)th way of encoding information may include the peak signal-to-noise ratio of the (n-1)th way of the video frame luminance component and chrominance component (that is, the (n-th)th way of the video frame -1) pass YUV PSNR, hereinafter denoted as (n-1)passPSNR).

Among them, PSNR (Peak Signal to Noise Ratio, peak signal-to-noise ratio) is an objective standard for evaluating images. Usually after image compression, the output image will be different from the original image to some extent. In order to measure the image quality after processing, the PSNR value is usually used to measure whether a certain processing is satisfactory. The unit of PSNR is dB, and the larger the value, the smaller the distortion. PSNR is a common and widely used image objective evaluation index, which is based on the error between corresponding pixels, that is, image quality evaluation based on error sensitivity.

In step S320, the quantization parameter (Quantization Parameter, QP, hereinafter denoted as q) of the nth coding rate control stage of the video frame is obtained.

In the embodiment of the present invention, before encoding the nth channel in the video sequence, the video encoder will automatically assign an initial quantization parameter q to each video frame in the video sequence in advance.

In step S330, the video sequence is encoded based on the (n-1)th way analysis file, and the video frame is corrected according to the (n-1)th way encoding information of the video frame Quantization parameter in the rate control stage of the n-th encoding.

In the embodiment of the present invention, the (n-1)th coding information of each video frame is used to modify the quantization parameter value used in coding, and then the coding is performed using the modified quantization parameter value.

In an exemplary embodiment, the modifying the quantization parameters of the nth encoding rate control stage of the video frame according to the (n-1)th encoding information of the video frame may include: if the video frame The peak signal-to-noise ratio of the (n-1)th path luminance component and chrominance component of the current frame in the current frame is greater than the first threshold and the current frame is not a scene switching frame, then according to the (n-1)th path of the current frame The peak signal-to-noise ratio of the luma component and the chrominance component modifies the quantization parameter of the current frame.

For example, the first threshold may be 61. However, the present invention is not limited thereto, and the value of the first threshold may be determined according to whether the video sequence is a segmented video sequence and a specific application scenario.

In the embodiment of the present invention, a video frame whose (n-1) passPSNR is greater than the first threshold may be referred to as a low-brightness frame. For example, the low-brightness frame may refer to a video frame whose YUV PSNR value of the (n-1)th way of the video frame is greater than 61.

Here is a brief description of the basic principle of video coding: video image data has a strong correlation, that is to say, there is a large amount of redundant information. The redundant information can be divided into air domain redundant information and time domain redundant information. Compression technology is to remove redundant information in the data and remove the correlation between data. Compression technology includes intra-frame image data compression technology, inter-frame image data compression technology and entropy coding compression technology. Video files generally involve three parameters: frame rate, resolution and bit rate. Among them, the frame rate refers to the number of pictures displayed per second, and the frame rate affects the smoothness of the picture, and is directly proportional to the fluency of the picture. The bit rate refers to the amount of data after compressing the pictures displayed per second. The bit rate affects the volume and is proportional to the volume. Resolution refers to the length and width of a (rectangular) picture, ie the dimensions of the picture. Wherein, the frame rate multiplied by the resolution is equal to the amount of data per second before compression, and the unit is byte. The compression ratio is equal to the amount of data/bit rate per second before compression. For the same video source and the same video coding algorithm, the higher the compression ratio, the worse the picture quality.

Video quality can be expressed in subjective and objective ways. The subjective way is usually referred to as video clarity, while the objective parameters are quantization parameters or compression ratio or bit rate. Comparing on the premise that the video source is the same and the compression algorithm is the same, there is a direct proportional relationship between quantization parameters, compression ratio and bit rate.

Among them, the bit rate of the video directly affects the encoding quality of the video. In order to effectively transmit video data to meet the service requirements of network video services under the condition of limited channel bandwidth and transmission delay, it is usually necessary to perform rate control on video coding. The so-called bit rate control is to make the bit rate generated by video encoding as close to the set target bit rate as possible under the premise of ensuring the restored video quality by setting appropriate encoding parameters.

In an exemplary embodiment, the modifying the quantization parameter of the current frame according to the peak signal-to-noise ratio of the (n-1)th luminance component and chrominance component of the current frame may include: if the current frame The peak signal-to-noise ratio of the (n-1)th road luminance component and chrominance component is in any one of the first interval to the m1th interval, and the corresponding control factor is used to modify the quantization parameter of the current frame; wherein, m1 is greater than A positive integer equal to 1.

In the embodiment of the present invention, m1 is equal to 5. However, the present invention is not limited thereto, and specific interval divisions may be selected according to actual application scenarios, which are only used for illustration here.

In an exemplary embodiment, if the peak signal-to-noise ratio of the (n-1)th luminance component and chrominance component of the current frame is in any one of the first interval to the mth interval, the corresponding regulation is adopted Modifying the quantization parameter of the current frame by a factor may include:

If the peak signal-to-noise ratio of the (n-1)th luma component and chrominance component of the current frame is in the first interval, then use the first regulation factor qFactor1 to modify the quantization parameter of the current frame; or

If the peak signal-to-noise ratio of the (n-1)th luminance component and chrominance component of the current frame is in the second interval, the quantization parameter of the current frame is corrected by using the second regulation factor qFactor2; or

If the peak signal-to-noise ratio of the (n-1) luminance component and chrominance component of the current frame is in the third interval, the quantization parameter of the current frame is corrected by using the third regulation factor qFactor3; or

If the peak signal-to-noise ratio of the (n-1) luminance component and chrominance component of the current frame is in the fourth interval, the quantization parameter of the current frame is corrected by using the fourth regulation factor qFactor4; or

If the peak signal-to-noise ratio of the (n-1)th channel of the current frame is in the fifth interval, the quantization parameter of the current frame is corrected by using the fifth adjustment factor qFactor5.

The embodiment of the present invention divides the video frames of the low-brightness scene into 5 intervals by evaluating the low-brightness video frames (which can be abbreviated as low-brightness frames) and counting the YUV PSNR values of the low-brightness video frames. In the method, the corresponding regulatory factors derived from the empirical value of a large amount of data are used to adjust the quantization parameters, which can effectively improve the video quality of video frames in low-brightness scenes and reduce quality fluctuations. Especially for distributed coding, the effect is remarkable, and it can be applied to video-on-demand and live platform.

In an exemplary embodiment, if the video sequence is a segmented video sequence, the first to fifth regulation factors are respectively: 1.2, 1.8, 2.2, 3, and 4.5.

It should be noted that the above-mentioned first to fifth regulatory factors are empirical values obtained by statistical analysis of a large amount of data for segmented video sequences in distributed coding. , then the corresponding above-mentioned first to fifth regulatory factors can undergo corresponding changes. In addition, although the description above takes distributed video coding as an example, the method provided in the embodiment of the present invention may also be applied in a non-distributed coding manner.

Among them, video conversion coding is referred to as video transcoding, which refers to the conversion of video from one format to another, where the format is characterized by bit rate, frame rate, spatial distribution rate and coding algorithm. With the development of high-definition movies, the capacity of movie sources has increased from a few gigabytes to tens of gigabytes, and the time required to transcode such movie sources has also increased dramatically. In addition, as the types of user terminals that need to be adapted for transcoding increase, transcoding tasks become increasingly numerous. At present, the mainstream transcoding mode is distributed, that is, multiple transcoding servers are used to transcode video files at the same time. Divide the video into segments at the source, transmit each segment to the corresponding transcoding server, merge each segment into a video file after transcoding, and return the video. The advantage of this method is parallel transcoding, low time cost, and can handle concurrent transcoding tasks. For example, the distributed video transcoding solution based on the Hadoop platform uses HDFS (Hadoop Distributed System, distributed file system) to store video files and uses the MapReduce programming framework for distributed transcoding. The transcoding tool uses FFMPEG to store and transcode video Integrated to achieve the purpose of reducing the network bandwidth and time-consuming required for transcoding.

Wherein, the whole system may include a WebServer and a Hadoop cluster. WebServer is responsible for processing user requests, including video access and transcoding. The NameNode in the Hadoop cluster is responsible for receiving user requests forwarded by the WebServer, and dispatching the DataNodes in the cluster for video storage or transcoding. Files in HDFS are stored in the form of data blocks. A file is composed of one or more data blocks, and the size of the data blocks can be adjusted. Therefore, segmentation is required when storing video files (segmentation of video is block).

In distributed coding, a slice point of a segmented video sequence is also a video frame. On the one hand, the frame type (such as I frame, or P frame, or B frame) may change in the video frame at the slice point; on the other hand, even if the frame type does not change in the video frame at the slice point, due to distributed Video continuity is affected during encoding, which also affects video quality. For example, if the current frame is an inter-frame prediction frame, it needs to refer to the forward video frame, and slicing will result in the loss of coding information. Therefore, in the distributed encoding, the change of the frame type of the slice point and/or the lack of encoding information will lead to more serious fluctuations in the quality of the video.

In an exemplary embodiment, wherein, the modifying the quantization parameters of the nth encoding rate control stage of the video frame according to the (n-1)th encoding information of the video frame may include: if the The peak signal-to-noise ratio of the (n-1) luminance component and chrominance component of the current frame in the video frame is greater than the second threshold and is in the m2th interval, and the current frame is the first inter-frame prediction frame, then the obtained The quantization parameter of the forward reference frame of the current frame; the quantization parameter of the current frame is corrected according to the quantization parameter of the forward reference frame; wherein, m2 is a positive integer greater than or equal to 1.

In an exemplary embodiment, m1 may be equal to m2, eg m1=m2=5. However, the present invention is not limited thereto.

In an exemplary embodiment, the quantization parameter of the first inter-frame prediction frame may be corrected by using the following formula:

q'＝q-(ref0Qp+a)*b (1)

Wherein, in the above formula (1), ref0Qp is the quantization parameter of the forward reference frame of the first inter-frame prediction frame; a and b are constants, for example, a can take a value of 4, and b can take a value of 2, but The present invention is not limited thereto; q is a quantization parameter of the first inter-frame prediction frame; q' is a corrected quantization parameter of the first inter-frame prediction frame.

In an exemplary embodiment, the modifying the quantization parameters of the nth encoding rate control stage of the video frame according to the (n-1)th encoding information of the video frame may include: if the video frame The peak signal-to-noise ratio of the (n-1)th luminance component and chrominance component of the current frame in the current frame is greater than the second threshold and is in the m2th interval, and the current frame is the second inter-frame prediction frame, then the current The quantization parameter of the forward reference frame of the frame and/or the quantization parameter of the backward parameter frame of the current frame; according to the quantization parameter of the forward reference frame of the current frame and/or the backward parameter frame of the current frame The quantization parameter of the current frame is modified by the quantization parameter; wherein, m2 is a positive integer greater than or equal to 1.

In an exemplary embodiment, the second threshold is greater than or equal to the first threshold, for example, the second threshold may be 97. In the embodiment of the present invention, on the one hand, corresponding control factors can be used to optimize the quantization parameters of low-brightness frames; on the other hand, the quantization parameters of the forward reference frame and/or backward reference frame of the current frame can be used to The quantization parameter of the current frame is further optimized for the lower brightness frame or even the video frame of an approximately dark scene.

In an exemplary embodiment, the quantization parameter of the second inter-frame prediction frame may be modified by using the following formula:

q’＝q–((ref0Qp+c1)+(ref1Qp+c2))*d (2)

Wherein, in the above formula (2), ref0Qp is the quantization parameter of the forward reference frame of the second inter-frame prediction frame; ref1Qp is the quantization parameter of the backward reference frame of the second inter-frame prediction frame; c1, c2 and d are constants, for example, c1 and c2 can be equal, both of which can take a value of 4, and d can take a value of 2, but the present invention is not limited thereto; q is the quantization parameter of the second inter-frame prediction frame; q' is a modified quantization parameter of the second inter-frame prediction frame.

In the embodiment of the present invention, since coding standards such as H.261, H.263, H.264, MPEG2, and MPEG4 all use the frame layer rate control algorithm to compress video, the scope of application of the present invention covers the above coding standards.

The method for video encoding provided by the embodiment of the present invention is based on a multi-channel (including two-channel) encoding method, and the code rate control stage of the current channel encoding can be controlled by performing the previous encoding information on the video sequence and retaining the previous encoding information. The quantization parameters are optimized, so that the quality fluctuation of the video frame can be compensated to achieve the effect of reducing quality loss and reducing fluctuation. Especially for local special scenes such as low-brightness video frames in distributed coding, quality fluctuations can be effectively adjusted.

The method for video encoding provided by the above embodiment will be illustrated below with reference to FIGS. 4-7 and taking two-way encoding as an example for a video sequence.

In the embodiment of the present invention, before entering the quantization parameter adjustment of the second coding rate control stage, the first coding information (such as the onepassPSNR of the first coding) of the first coding (1pass coding) will be first performed on the video sequence ) is acquired and stored in the analysis file file, and the encoding information of one pass is acquired during the second pass encoding (2pass) stage of the video file. The specific operations are shown in flowchart 4 and flowchart 5.

FIG. 4 shows a schematic diagram of a processing procedure of step S310 shown in FIG. 3 in an embodiment. The method steps in the embodiments of the present invention may be executed by a terminal device, or may be executed by a server, or may be executed interactively by a terminal device and a server, for example, may be executed by the server 105 in FIG. 1 above, but the present invention is not limited to this.

As shown in FIG. 4 , in the implementation manner of the present invention, the above step S310 may further include the following steps.

In step S311, determine whether the video sequence exists; if the video sequence exists, proceed to step S312; otherwise, jump to step S315 to end the operation.

In step S312, it is judged whether the video sequence is currently the first-pass encoding (1pass encoding); if it is the first-pass encoding, proceed to step S313; otherwise, proceed to step S314.

In step S313, a first-pass encoding (1-pass encoding) is performed on the video frames in the video sequence and first-pass encoding information of the video frames is collected.

In step S314, an error message is output.

In step S315, end.

FIG. 5 shows a schematic diagram of the processing process of step S330 shown in FIG. 3 in an embodiment. The method steps in the embodiments of the present invention may be executed by a terminal device, or may be executed by a server, or may be executed interactively by a terminal device and a server, for example, may be executed by the server 105 in FIG. 1 above, but the present invention is not limited to this.

As shown in FIG. 5 , in the implementation manner of the present invention, the above step S330 may further include the following steps.

In step S331, determine whether the video sequence exists; if the video sequence exists, proceed to step S332; otherwise, jump to step S336 to end this operation.

In step S332, it is judged whether the video sequence is currently the second-pass encoding (2pass encoding); if it is the second-pass encoding (2pass encoding), proceed to step S333; otherwise, proceed to step S335.

In the embodiment of the present invention, 2pass means 2 times of encoding, and fil analyzes the file and records the information in 1pass. Two encodings are equivalent to two conversions. Although the conversion time will be extended, the compressed video will have better image quality, better picture details, and smaller size. 2pass is mainly for non-real-time video encoding such as files. The first encoding is to scan the entire video file and record some statistical information. The second encoding is based on the previously recorded statistical information before encoding. The advantage is that the quality of the encoding can be improved.

In step S333, it is judged whether there is a first path analysis file (file); if there is the first path analysis file, then go to step S334; otherwise, jump to step S336 to end this operation.

In step S334, the first path analysis file is read, and a second path of encoding is performed on the video frames in the video sequence based on the first path analysis file.

In step S335, an error message is output.

In step S336, end.

The schemes of modifying the quantization parameters in the rate control stage of the second encoding pass are illustrated below with reference to FIG. 6 and FIG. 7 respectively.

It should be noted that the following schemes in Figure 6 and Figure 7 can be combined to optimize the quantization parameter q, or only one of the schemes in Figure 6 or Figure 7 can be used to optimize the quantization parameter q, in the following implementation In the example, the optimization of the quantization parameter q by combining the schemes in FIG. 6 and FIG. 7 is taken as an example for illustration.

Fig. 6 schematically shows a flowchart of a method for video encoding according to yet another embodiment of the present invention.

In the embodiment of the present invention, by analyzing multiple video sequence data and scenes, it is obtained that video frames are artificially classified based on the first encoding information (YUV PSNR value), for example, it is assumed here that the YUV PSNR value is between 0-60dB 61-89dB is a darker video scene, and 90-100dB is divided into a near-night video scene. The specific flow chart is shown in Figure 6.

It should be noted that the above numerical values are only used for illustration, and corresponding adjustments can be made in practical applications.

In the embodiment of the present invention, when performing the second code rate control coding, the first code information is obtained first, and then the quantization parameter is adjusted when the code rate control stage is formally started.

As shown in FIG. 6 , the method for video coding provided by the embodiment of the present invention may include the following steps. The method steps in the embodiments of the present invention may be executed by a terminal device, or may be executed by a server, or may be executed interactively by a terminal device and a server, for example, may be executed by the server 105 in FIG. 1 above, but the present invention is not limited to this.

In step S601, determine whether the current frame in the video sequence is an IDR (Instantaneous Decoding Refresh, instant decoding refresh) frame; if the current frame is an IDR frame, then jump to step S612; if the current frame is not an IDR frame, then Go to step S602.

In the embodiment of the present invention, the frame types of the video frame may include I frame, P frame and B frame, wherein the IDR frame belongs to one of the I frames.

An I-frame is an intra-coded frame, which is an independent frame with all its information, and can be decoded independently without referring to other images. The first frame in a video sequence is always an I-frame. Both I and IDR frames use intra prediction. For convenience in encoding and decoding, in order to distinguish the first I frame from other I frames, the first I frame is called an IDR frame, which is convenient for controlling the encoding and decoding process.

Among them, the function of the IDR frame is to refresh immediately, so that the error will not be propagated. Starting from the IDR frame, a new sequence is recalculated to start encoding. The I frame does not have the ability of random access, this function is undertaken by the IDR. IDR will cause DPB (Decoded Picture Buffer, reference frame list) to be cleared, but I will not. An IDR frame must be an I frame, but an I frame is not necessarily an IDR frame. There may be many I frames in a video sequence, and the video frames after the I frame may refer to the video frames between the I frames as motion references.

For IDR frames, all frames after the IDR frame cannot refer to the content of any frame before the IRD frame. On the contrary, for ordinary I frames, the B and P frames located after it can refer to the content of the ordinary I The I frame before the frame. From a random access video stream, the player can always play from an IDR frame, because no frame after it refers to the previous frame. However, it is not possible to start playback from an arbitrary point in a video without an IDR frame, because subsequent frames will always refer to previous frames.

The processing of the IDR frame is the same as that of the I frame: perform intra-frame prediction, determine the intra-frame prediction mode used; subtract the predicted value from the pixel value to obtain the residual; transform and quantize the residual; variable length coding and arithmetic Coding; reconstructing the image and filtering, and the obtained image is used as a reference frame for other frames.

It should be noted that, in the embodiments of the present invention, the IDR is used as an identifier for judging whether the current frame is a scene switching frame, but the present invention is not limited thereto.

In the embodiment of the present invention, first judge whether the frame type of the current frame is an IDR frame, if it is an IDR frame, enter the default operation of the encoder, and do not adjust the quantization parameter q of the current frame at this time; otherwise, judge the current frame next Corresponding to the YUV PSNR value in one encoding.

In step S602, it is judged whether the YUV PSNR value onepassPSNR in the first coded information of the current frame is greater than 97 and less than or equal to 100; if 97<onepassPSNR≤100 of the current frame, then jump to step S611; if If the current frame does not satisfy 97<onepassPSNR≤100, go to step S603.

In step S603, it is judged whether the YUV PSNR value onepassPSNR in the first coded information of the current frame is greater than 90 and less than or equal to 97; if 90<onepassPSNR≤97 of the current frame, then jump to step S610; if If the current frame does not satisfy 90<onepassPSNR≤97, go to step S604.

In step S604, it is judged whether the YUV PSNR value onepassPSNR in the first coded information of the current frame is greater than 85 and less than or equal to 90; if 85<onepassPSNR≤90 of the current frame, then jump to step S609; if If the current frame does not satisfy 85<onepassPSNR≤90, go to step S605.

In step S605, it is judged whether the YUV PSNR value onepassPSNR in the first coded information of the current frame is greater than 70 and less than or equal to 85; if 70<onepassPSNR≤85 of the current frame, then jump to step S608; if If the current frame does not satisfy 70<onepassPSNR≤85, go to step S606.

In step S606, it is judged whether the YUV PSNR value onepassPSNR in the first coded information of the current frame is greater than 60 and less than or equal to 70; if 60<onepassPSNR≤70 of the current frame, then jump to step S607; if If the current frame does not satisfy 60<onepassPSNR≤70, go to step S612.

In step S607, 60<onepassPSNR≤70, q'=q-qFactor1, then enter step S612 to enter other encoding stages.

In the embodiment of the present invention, when the onepassPSNR is in the (60,70] interval, q'=q-qFactor1.

Among them, q is the quantization parameter of the two-way coding rate control stage; q' is the quantization parameter of the modified two-way coding rate control stage. It should be noted that if the current video sequence adopts n-pass encoding, then q is the quantization parameter of the n-pass encoding rate control stage, and the corresponding onepassPSNR is modified to (n-1)passPNSR, which is the YUV of the (n-1)th encoding PSNR value.

In step S608, 70<onepassPSNR≤85, q'=q-qFactor2, then enter step S612 to enter other encoding stages.

In the embodiment of the present invention, when the onepassPSNR is in the (70,85] interval, q'=q-qFactor2.

In step S609, 85<onepassPSNR≤90, q'=q-qFactor3, then enter step S612 to enter other encoding stages.

In the embodiment of the present invention, when the onepassPSNR is in the (85,90] interval, q'=q-qFactor3.

In step S610, 90<onepassPSNR≤97, q'=q-qFactor4, then enter step S612 to enter other encoding stages.

In the embodiment of the present invention, when the onepassPSNR is in the (90,97] interval, q'=q-qFactor4.

In step S611, 97<onepassPSNR≤100, q'=q-qFactor5, then enter step S612 to enter other encoding stages.

In the embodiment of the present invention, when the onepassPSNR is in the (97,100] interval, q'=q-qFactor5.

It should be noted that, in actual situations, the value of onepassPSNR is not an integer. In general encoding, the value of onepassPSNR is of double type, and there are two digits after the decimal point. Therefore, although the interval division of the value of onepassPSNR in the embodiment of the present invention is divided into integers such as 100 , 97, 90, 85, 70, and 60 are taken as the endpoint values, but this division is only an approximate value.

In the embodiment of the present invention, qFactor1-qFactor5qFactor are optimized empirical values obtained according to statistical analysis, for example, the values of qFactor1 to qFactor5 may be 1.2, 1.8, 2.2, 3, 4.5 respectively. However, the present invention is not limited thereto.

In step S612, another encoding stage.

In step S613, end.

Fig. 7 schematically shows a flowchart of a method for video encoding according to yet another embodiment of the present invention.

As shown in FIG. 7 , the method for video encoding provided by the embodiment of the present invention may further include the following steps. The method steps in the embodiments of the present invention may be executed by a terminal device, or may be executed by a server, or may be executed interactively by a terminal device and a server, for example, may be executed by the server 105 in FIG. 1 above, but the present invention is not limited to this.

In step S701, it is judged whether the YUV PSNR value onepassPSNR in the first coding information of the current frame in the video sequence is greater than 97 and less than or equal to 100 and is the second coding; if 97<onepassPSNR≤100 of the current frame is For the second pass of encoding, proceed to step S702; if the current frame does not satisfy 97<onepassPSNR≤100 or is not for the second pass of encoding, proceed to step S709 to end this operation.

In the embodiment of the present invention, by analyzing a plurality of video sequence data, when the onePassPSNR is in the interval (97,100) and the current encoding is non-one-way encoding (here, two-way encoding is used as an example), the method described in the above-mentioned Figure 6 is used for this type of After video frame optimization, quality fluctuations can still be further improved. Therefore, when such video frames are non-scene switching frames (here, IDR frames are taken as an example, but the present invention is not limited thereto), reference frames (such as forward reference frames and/or backward reference frames) of such video frames are used Reference frame) information, the quantization parameters of such video frames can be further optimized.

In the embodiment of the present invention, the reference frame of the current frame can not only refer to several frames before and after. In this type of encoder, the longest reference frame can be, for example, 16 frames before and after reference. The video frame time of the scene can play a certain effect.

In the embodiment of the present invention, when the rate control encoding of the second encoding is performed, the encoding information of the first encoding is obtained first, and then the quantization parameter is adjusted when the rate control stage of the second encoding is formally started.

In the embodiment of the present invention, it is first judged whether the range of the onePassPSNR interval of the current frame is within the interval of (97,100].

In step S702, determine whether the current frame is an inter-frame prediction frame; if the current frame is an inter-frame prediction frame, proceed to step S703; if the current frame is not an inter-frame prediction frame, then jump to step S708 .

In the embodiment of the present invention, if the onePassPSNR interval of the current frame is within the interval (97,100], then it is judged whether the current frame performs inter-frame prediction; if the current frame does not perform inter-frame prediction, the current The frame is for intra-frame prediction, and the q value of the current frame remains unchanged at this time.

It should be noted that the current frame described here is for intra-frame prediction, and keeping the q value of the current frame unchanged at this time does not mean that the q value must be the quantization parameter of the initial preset value of the video encoder. If Simultaneously adopt the method described in Figure 6 and Figure 7 to process the video sequence, then the quantization parameter q of the current frame has been processed by the method described in Figure 6 above, that is, 97<onepassPSNR≤100, q'=q- qFactor5.

In step S703, determine whether the current frame is a P frame; if the current frame is a P frame, proceed to step S704; if the current frame is not a P frame, proceed to step S706.

In the embodiment of the present invention, if the current frame is an inter-frame prediction frame, it is further judged whether the current frame is an inter-frame P frame or a B frame.

Wherein, the P frame is a forward predictive coding frame. When encoding continuous dynamic images, several consecutive images are divided into three types: P, B, and I. The P frame is predicted from the P frame or I frame in front of it, and it is compared with the P frame or I frame in front of it. The same information or data between frames, that is, considering the characteristics of motion for inter-frame compression. The P frame method is to compress the data of this frame according to the difference between this frame and the adjacent previous frame I frame or P frame. The joint compression method of P frame and I frame can achieve higher compression without obvious compression trace.

Among them, the P frame uses the I frame as the reference frame, finds out the predictive value and motion vector of the "certain point" of the P frame in the I frame, and transmits the predicted difference value and the motion vector together. At the receiving end, find out the predicted value of a certain point of the P frame from the I frame according to the motion vector and add it to the difference to obtain the sample value of a certain point of the P frame, so as to obtain a complete P frame.

In step S704, it is judged whether there is a forward reference frame in the current frame; if there is a forward reference frame in the current frame, then enter step S705; if there is no forward reference frame in the current frame, then jump to step S709 ends this operation.

In the embodiment of the present invention, the reference frame is a frame that needs to be referred to during IPB encoding. Referring to the relationship between frames and IPB, it is necessary to know the encoding method of each frame type. Wherein, the I frame refers to the coding of the block in the image, and does not need a reference frame. The P frame is coded with reference to the previous I frame or P frame, and the reference frames are all forward. The B frame is coded with reference to the previous and subsequent I frame or P frame, for example, one frame before and after each, or only a forward reference frame or a backward reference frame (three options).

In step S705, if the current frame is a P frame, the quantization parameter q of the current frame can be adjusted by using the following formula:

ref0Qp'=ref0Qp+4,

q'=q-ref0Qp'*2,

In the embodiment of the present invention, if the current frame is an inter-frame P frame, obtain the ref0Qp value of refSlice0; if the current frame is an inter-frame B frame, obtain the ref0Qp and ref1Qp values of refSlice0 and refSlice1.

Wherein, refSlice0 represents the forward reference frame of the current frame; ref0Qp represents the quantization parameter of refSlice0, that is, the QP value.

In step S706, if the current frame is a B frame, it is judged whether the current reference has a forward reference frame and/or a backward reference frame; if the current reference has a forward reference frame and/or a backward reference frame frame, go to step S707; if the current reference does not have a forward reference frame and/or a backward reference frame, go to step S709 to end this operation.

In the embodiment of the present invention, if the current frame is an inter-frame predicted B frame and the current frame has both a forward reference frame and a backward reference frame, the ref0Qp and ref1Qp values of refSlice0 and refSlice1 are obtained.

Wherein, refSlice0 and refSlice1 are the forward reference frame and the backward reference frame of the current frame respectively; ref0Qp and ref1Qp respectively represent the quantization parameters of refSlice0 and refSlice1 ie QP values.

In the embodiment of the present invention, some video sequences may not have B frames because they are relatively simple.

Wherein, the B frame is a bidirectional predictive interpolation coded frame. The B-frame method is a two-way predictive inter-frame compression algorithm. When compressing a frame into a B frame, it compresses this frame according to the difference between the data of the adjacent previous frame, this frame, and the next frame, that is, only records the difference between this frame and the preceding and following frames. High compression can be achieved by using B-frame compression. The B frame uses the previous I frame or P frame and the following P frame as reference frames to find out the predicted value and two motion vectors of "a certain point" in the B frame, and take the prediction difference and the motion vector for transmission. The receiver is in two reference frames according to the motion vector.

In step S707, in the embodiment of the present invention, if the current frame is an inter-frame predicted B frame and the current frame has a forward reference frame and a backward reference frame at the same time, the following formula can be used for the current frame The quantization parameter q is corrected:

ref0Qp'=ref0Qp+4

ref1Qp'=ref1Qp+4

combine_ref=(ref0Qp'+ref1Qp')*2

q'=q-combine_ref,

Wherein, combine_ref represents an tuning constant of the quantization parameter of the current frame if the current frame is a B frame and both forward and backward reference frames exist.

It should be noted that, the above steps all take a forward reference frame and/or a backward reference frame of the current frame as an example for illustration, but in other embodiments, there may be multiple previous reference frames in the current frame A forward reference frame and/or a plurality of backward reference frames, at this time, the quantization parameters of the current frame may also be determined according to the quantization parameters of the multiple forward reference frames and/or the multiple backward reference frames of the current frame optimization, which is not limited by the present invention.

In step S708, if the current frame is an intra-frame predicted frame, q remains unchanged.

In step S709, end.

In the embodiment of the present invention, the quality fluctuation of the video sequence can be measured by SSIM, that is, the smaller the standard deviation of the SSIM and the larger the average value of the SSIM, the smaller the quality fluctuation of the corresponding video sequence.

Among them, SSIM (Structual Ssimilarity) is also a full-reference image quality evaluation index, which measures image similarity from three aspects: brightness, contrast, and structure. The value range of SSIM is [0,1]. The larger the value, the smaller the image distortion.

In the actual test, taking test sequence 1 and test sequence 2 as examples, the above method is used to optimize the video sequence, and the specific effects are shown in the following table:

According to the test results in the above table, it can be seen that after the video sequence is sliced and optimized by the method provided by the embodiment of the present invention, the SSIM standard deviation at the position corresponding to the low-brightness video frame is smaller than the SSIM standard deviation at the corresponding position of the original unsliced video sequence At the same time, corresponding to the SSIM average value of the video frame position in the darker region of the local scene, after the video sequence is sliced and optimized by the method provided by the embodiment of the present invention, its SSIM average value is greater than that of the corresponding position of the original unsliced video sequence SSIM average. It can be seen from this that the method for video encoding provided by the embodiment of the present invention is feasible, and can ensure video quality while speeding up video encoding and decoding; optimize the video-on-demand and live broadcast platforms, and bring better visual experience to users. experience.

Fig. 8 schematically shows a block diagram of a device for video encoding according to an embodiment of the present invention.

In the apparatus 800 for video coding provided in the embodiment of the present invention, a video sequence may use n-pass coding. Wherein, n is a positive integer greater than or equal to 2.

As shown in FIG. 8 , an apparatus 800 for video encoding provided by an embodiment of the present invention may include: a first encoding module 810 , a quantization parameter acquisition module 820 and a second encoding module 830 .

Wherein, the first coding module 810 can be configured to perform (n-1)th pass encoding on the video sequence to generate the (n-1)th pass analysis file, and obtain the (n-1)th pass of the video frame in the video sequence ) road encoding information.

In an exemplary embodiment, the (n-1)th channel of encoding information includes the peak signal-to-noise ratio of the (n-1)th channel of luminance component and chrominance component of the video frame.

The quantization parameter acquisition module 820 may be configured to acquire the quantization parameter of the n-th coding rate control stage of the video frame.

The second coding module 830 may be configured to perform n-th pass encoding on the video sequence based on the (n-1)-th pass analysis file, and modify the The quantization parameter of the nth coding rate control stage of the video frame.

For specific implementation of each module in the device for video coding provided in the embodiment of the present invention, reference may be made to the content in the method for video coding above, and details are not repeated here.

Fig. 9 schematically shows a block diagram of an apparatus for video encoding according to yet another embodiment of the present invention.

As shown in FIG. 9 , an apparatus 900 for video encoding provided by an embodiment of the present invention may include: a first encoding module 910 , a quantization parameter acquisition module 920 and a second encoding module 930 .

Wherein, the first encoding module 910 may be configured to perform (n-1)th pass encoding on the video sequence to generate the (n-1)th pass analysis file, and obtain the (n-1)th pass of the video frame in the video sequence ) road encoding information.

In an exemplary embodiment, the (n-1)th channel of encoding information includes the peak signal-to-noise ratio of the (n-1)th channel of luminance component and chrominance component of the video frame.

The quantization parameter acquisition module 920 may be configured to acquire the quantization parameter of the nth coding rate control stage of the video frame.

Wherein, the first encoding module 910 and the quantization parameter acquisition module 920 may refer to the first encoding module 810 and the quantization parameter acquisition module 820 in the above embodiment shown in FIG. 8 .

The second encoding module 930 may be configured to perform nth pass encoding on the video sequence based on the (n-1)th pass analysis file, and modify the The quantization parameter of the nth coding rate control stage of the video frame.

In an exemplary embodiment, the second encoding module 930 may further include: an n-th encoding unit (not shown in the figure). Wherein, the nth encoding unit may be configured to perform nth encoding on the video sequence based on the (n-1)th analysis file.

In the embodiment shown in FIG. 9 , the second coding module 930 may further include a first quantization parameter modification unit 931 . Wherein, the first quantization parameter modification unit 931 may be configured as if the peak signal-to-noise ratio of the (n-1)th luminance component and chrominance component of the current frame in the video frame is greater than the first threshold and the current frame is not a scene Switching frames, modifying the quantization parameter of the current frame according to the peak signal-to-noise ratio of the (n-1)th path of luma component and chrominance component of the current frame.

With continued reference to FIG. 9 , the first quantization parameter modification unit 931 may include: a first quantization parameter modification subunit 9311 . Wherein, the first quantization parameter modification subunit 9311 may be configured as if the peak signal-to-noise ratio of the (n-1)th luminance component and chrominance component of the current frame in the video frame is greater than the first threshold and the current frame is not Scene switching frame, and the peak signal-to-noise ratio of the (n-1)th channel luminance component and chrominance component of the current frame is in any one of the first interval to the m1th interval, then the corresponding control factor is used to correct the current The quantization parameter of the frame; among them, m1 is a positive integer greater than or equal to 1.

Continuing to refer to FIG. 9 , the second encoding module 930 may further include: a second quantization parameter modification unit 932 and/or a third quantization parameter modification unit 933 .

Wherein, the second quantization parameter modification unit 932 may be configured as if the peak signal-to-noise ratio of the (n-1)th luminance component and chrominance component of the current frame in the video frame is greater than the second threshold and is in the m2th interval, and If the current frame is the first inter-frame prediction frame, the quantization parameter of the forward reference frame of the current frame is obtained; the quantization parameter of the current frame is corrected according to the quantization parameter of the forward reference frame; and/or

The third quantization parameter modification unit 933 may be configured as if the peak signal-to-noise ratio of the (n-1)th luminance component and chrominance component of the current frame in the video frame is greater than the second threshold and is in the m2th interval, and The current frame is a second inter-frame prediction frame, then obtain the quantization parameter of the forward reference frame of the current frame and/or the quantization parameter of the backward parameter frame of the current frame; according to the forward Modifying the quantization parameter of the current frame with the quantization parameter of the reference frame and/or the quantization parameter of the backward parameter frame of the current frame; wherein, m2 is a positive integer greater than or equal to 1.

In an exemplary embodiment, the second threshold is greater than the first threshold.

For the specific implementation of each module and/or unit and/or subunit in the device for video coding provided by the embodiment of the present invention, reference may be made to the content in the method for video coding above, and details are not repeated here.

It should be noted that although several modules or units or subunits of the device for action execution are mentioned in the above detailed description, this division is not mandatory. Actually, according to the embodiment of the present invention, the features and functions of two or more modules or units or subunits described above may be embodied in one module or unit or subunit. Conversely, the features and functions of one module or unit or subunit described above can be further divided to be embodied by multiple modules or units or subunits.

Through the description of the above implementations, those skilled in the art can easily understand that the example implementations described here can be implemented by software, or by combining software with necessary hardware. Therefore, the technical solution according to the embodiment of the present invention can be embodied in the form of a software product, and the software product can be stored in a non-volatile storage medium (which can be a CD-ROM, U disk, mobile hard disk, etc.) or on a network , including several instructions to make a computing device (which may be a personal computer, a server, a touch terminal, or a network device, etc.) execute the method according to the embodiment of the present invention.

Other embodiments of the invention will be readily apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any modification, use or adaptation of the present invention, these modifications, uses or adaptations follow the general principles of the present invention and include common knowledge or conventional technical means in the technical field not disclosed in the present invention . The specification and examples are to be considered exemplary only, with a true scope and spirit of the invention being indicated by the following claims.

It should be understood that the present invention is not limited to the precise constructions which have been described above and shown in the accompanying drawings, and various modifications and changes may be made without departing from the scope thereof. The scope of the invention is limited only by the appended claims.

Claims (13)

1. A method for video coding, characterized in that a video sequence is coded using n-way coding; wherein the method comprises the following steps:

performing (n-1) th path coding on the video sequence to generate an (n-1) th path analysis file, and obtaining (n-1) th path coding information of a video frame in the video sequence, wherein the (n-1) th path coding information comprises (n-1) th path brightness component and chrominance component peak signal-to-noise ratio of the video frame;

obtaining quantization parameters of the nth path coding rate control stage of the video frame;

performing nth coding on the video sequence based on the (n-1) th path analysis file, and correcting a quantization parameter of an nth path coding rate control stage of the video frame according to the (n-1) th path coding information of the video frame;

wherein n is a positive integer greater than or equal to 2;

wherein, the correcting the quantization parameter of the nth path coding rate control stage of the video frame according to the (n-1) th path coding information of the video frame comprises:

and if the peak signal-to-noise ratios of the (n-1) th luminance component and the chrominance component of the current frame in the video frame are greater than a first threshold and the current frame is not a scene switching frame, correcting the quantization parameter of the current frame according to the peak signal-to-noise ratios of the (n-1) th luminance component and the chrominance component of the current frame.

2. The method according to claim 1, wherein said modifying the quantization parameter of the current frame according to the (n-1) th peak snr of the luma component and the chroma components of the current frame comprises:

if the peak signal-to-noise ratio of the (n-1) th luminance component and the chrominance component of the current frame is in any one of the 1 st interval to the m1 st interval, correcting the quantization parameter of the current frame by adopting a corresponding regulation factor;

wherein m1 is a positive integer of 1 or more.

3. The method of claim 2, wherein m1 is equal to 5; wherein, if the (n-1) th peak signal-to-noise ratio of the luminance component and the chrominance component of the current frame is in any one of the 1 st interval to the m1 st interval, the modifying the quantization parameter of the current frame by using the corresponding regulation factor includes:

if the (n-1) th peak signal-to-noise ratio of the luminance component and the chrominance component of the current frame is in a 1 st interval, correcting the quantization parameter of the current frame by adopting a first regulation factor; or

If the peak signal-to-noise ratio of the (n-1) th luminance component and the chrominance component of the current frame is in the 2 nd interval, correcting the quantization parameter of the current frame by adopting a second regulation factor; or

If the (n-1) th peak signal-to-noise ratio of the luminance component and the chrominance component of the current frame is in a 3 rd interval, correcting the quantization parameter of the current frame by adopting a third regulating and controlling factor; or

If the (n-1) th peak signal-to-noise ratio of the luminance component and the chrominance component of the current frame is in a 4 th interval, correcting the quantization parameter of the current frame by adopting a fourth regulation factor; or

And if the peak signal-to-noise ratio of the (n-1) th luminance component and the chrominance component of the current frame is in the 5 th interval, correcting the quantization parameter of the current frame by adopting a fifth regulation factor.

4. The method of claim 3, wherein if the video sequence is a segmented video sequence, the first through fifth adjustment factors are: 1.2,1.8,2.2,3,4.5.

5. The method according to any of claims 1 to 4, wherein the modifying the quantization parameter of the n-th encoding rate control stage of the video frame according to the (n-1) -th encoding information of the video frame further comprises:

if the peak signal-to-noise ratio of the (n-1) th path of luminance component and chrominance component of the current frame in the video frame is larger than a second threshold value and is in the m2 th interval, and the current frame is a first inter-frame prediction frame, acquiring the quantization parameter of the forward reference frame of the current frame;

correcting the quantization parameter of the current frame according to the quantization parameter of the forward reference frame;

wherein m2 is a positive integer of 1 or more.

6. The method of claim 5, wherein the quantization parameter of the first inter-predicted frame is modified using the following equation:

q’＝q-(ref0Qp+a)*b，

wherein ref0Qp is a quantization parameter of the forward reference frame; a and b are constants; q is a quantization parameter of the first inter-frame prediction frame; q' is the quantization parameter after the first inter prediction frame is modified.

7. The method according to any of claims 1 to 4, wherein the modifying the quantization parameter of the n-th encoding rate control stage of the video frame according to the (n-1) -th encoding information of the video frame further comprises:

if the peak signal-to-noise ratio of the (n-1) th path of luminance component and chrominance component of the current frame in the video frame is larger than a second threshold value and is in an m2 th interval, and the current frame is a second inter-frame prediction frame, acquiring the quantization parameter of a forward reference frame of the current frame and/or the quantization parameter of a backward parameter frame of the current frame;

correcting the quantization parameter of the current frame according to the quantization parameter of the forward reference frame of the current frame and/or the quantization parameter of the backward parameter frame of the current frame;

wherein m2 is a positive integer of 1 or more.

8. The method of claim 7, wherein the quantization parameter of the second inter-predicted frame is modified using the following equation:

q’＝q–((ref0Qp+c1)+(ref1Qp+c2))*d，

wherein ref0Qp is a quantization parameter of the forward reference frame; ref1Qp is a quantization parameter of the backward reference frame; c1, c2 and d are constants; q is a quantization parameter of the second inter-frame prediction frame; q' is the quantization parameter of the second inter-frame prediction frame after modification.

9. An apparatus for video coding, characterized in that a video sequence employs n-way coding; wherein the apparatus comprises:

the first coding module is configured to perform (n-1) th path coding on the video sequence to generate an (n-1) th path analysis file, and obtain (n-1) th path coding information of a video frame in the video sequence, wherein the (n-1) th path coding information comprises an (n-1) th path luminance component and a chrominance component peak signal-to-noise ratio of the video frame;

a quantization parameter obtaining module configured to obtain a quantization parameter of the nth path coding rate control stage of the video frame;

the second coding module is configured to perform nth coding on the video sequence based on the (n-1) th path analysis file, and modify the quantization parameter of the nth path coding rate control stage of the video frame according to the (n-1) th path coding information of the video frame;

wherein n is a positive integer greater than or equal to 2;

wherein the second encoding module comprises:

and the first quantization parameter correction unit is configured to correct the quantization parameter of the current frame according to the (n-1) th peak signal-to-noise ratio of the luminance component and the chrominance component of the current frame if the (n-1) th peak signal-to-noise ratio of the luminance component and the chrominance component of the current frame in the video frame is greater than a first threshold and the current frame is not a scene switching frame.

10. The apparatus of claim 9, wherein the first quantization parameter modification unit comprises:

a first quantization parameter modification subunit, configured to modify a quantization parameter of a current frame by using a corresponding adjustment factor if a peak signal-to-noise ratio of an (n-1) th luminance component and a chrominance component of the current frame in the video frame is greater than a first threshold, the current frame is not a scene switching frame, and the peak signal-to-noise ratio of the (n-1) th luminance component and the chrominance component of the current frame is in any one of a 1 st interval to an m1 st interval;

wherein m1 is a positive integer of 1 or more.

11. The apparatus of claim 9 or 10, wherein the second encoding module further comprises:

a second quantization parameter modification unit, configured to obtain a quantization parameter of a forward reference frame of a current frame if a (n-1) th peak snr of a luminance component and a chrominance component of the current frame in the video frame is greater than a second threshold and is in an m2 th interval, and the current frame is a first inter-frame prediction frame; correcting the quantization parameter of the current frame according to the quantization parameter of the forward reference frame; and/or

A third quantization parameter modification unit, configured to obtain a quantization parameter of a forward reference frame of a current frame and/or a quantization parameter of a backward parameter frame of the current frame if an (n-1) th peak snr of a luminance component and a chrominance component of the current frame in the video frame is greater than the second threshold and is in an m2 th interval, and the current frame is a second inter-frame prediction frame; correcting the quantization parameter of the current frame according to the quantization parameter of the forward reference frame of the current frame and/or the quantization parameter of the backward parameter frame of the current frame;

wherein m2 is a positive integer of 1 or more.

12. A computer-readable medium, on which a computer program is stored which, when being executed by a processor, carries out the method for video encoding according to any one of claims 1 to 8.

13. An electronic device, comprising:

one or more processors;

a storage device configured to store one or more programs that, when executed by the one or more processors, cause the one or more processors to implement the method for video encoding as claimed in any of claims 1 to 8.

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