JP2004242056A - Encoding apparatus and method, recording medium, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an encoding apparatus and method, a recording medium, and a program capable of performing a more effective encoding processing. <P>SOLUTION: A rounding arithmetic section 32 controlled by a control section 31 first decides whether or not a value of 4 bits below a decimal point of effective digits or below of a DCT arithmetic coefficient subjected to quantization arithmetic operation is 10 or over in step S21, and when the arithmetic section 32 decides the value to be 10 or over, the processing continues to step S22, the value of the effective digits or below is rounded up, and the quantization rounding processing is finished. Further, when the arithmetic section 32 decides that the value of the effective digits or below of the DCT coefficient subjected to the quantization arithmetic processing is not 10 or over in step S21, the rounding arithmetic section 32 proceeds its processing to step S23, rounds off the value of the effective digits and below and finishes the quantization rounding processing. The encoding apparatus and method or the like is applicable to encoders. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an encoding device and method, a recording medium, and a program, and more particularly to an encoding device and method, a recording medium, and a program capable of performing more effective encoding processing.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, when an image signal such as moving image data is transmitted or recorded, the image signal is compressed by a predetermined compression encoding method to reduce the data amount.
[0003]
As a method of compressing video data and audio data to reduce the amount of information, various compression encoding methods have been proposed. Representative methods include MPEG2 (Moving Picture Experts Group Phase 2) and MPEG4 (Moving Picture Experts). Group Phase 4) and the like.
[0004]
In the MPEG system, each frame of an image signal is assigned to an I picture, a P picture, or a B picture, and intra-frame coding or inter-frame coding using motion compensation is performed.
[0005]
At this time, the encoder on the data transmission side needs to control the generated code amount of the encoded data (rate control) in order to prevent overflow and underflow from occurring in the decoder. However, since the generated code amount of the I picture necessary for updating the screen is large, a long transmission time of the image data of the I picture is required, and this time is delayed.
[0006]
When performing real-time transmission that requires real-time properties, such as image data for videophone calls and video conferences, if a delay due to the transmission time or a reordering delay occurs, the There is a time difference between receiving the encoded data received on the receiving side and displaying the reproduced image. On the other hand, in order to reduce such a delay, there is a method called low delay coding (Low Delay Coding) for reducing the delay time to 150 [ms] or less (for example, see Patent Document 1).
[0007]
In low-delay coding, B slices that cause reordering delay and I-pictures with a large amount of generated code are not used, and several slices composed of only blocks to be subjected to intra-frame coding, and intra-frame coding are used. By using a P picture composed of all remaining slices in which blocks to be encoded and blocks to be subjected to inter-frame encoding coexist, encoding can be performed without reordering.
[0008]
In this method, several slices composed only of blocks to be subjected to intra-frame encoding are arranged such that the position in the corresponding image area is shifted by the number of slices in the preceding and succeeding frames. These frames are arranged so that, when the corresponding regions of several frames are combined, the entire image region is obtained.
[0009]
The encoder encodes the block for performing intra-frame encoding as it is as transmission data without referring to another frame, and for the block for performing inter-frame encoding, a frame image existing before the frame. Inter-frame coding is performed by using a block in the same area for performing intra-frame coding as a reference image. Hereinafter, this encoding method is referred to as an intra slice method.
[0010]
By performing encoding using the intra-slice method in this way, the amount of code generated in each frame can be made uniform, decoding control can be facilitated, and problems due to delay and reordering delay can be eliminated. Images can be displayed without delay.
[0011]
By the way, the encoder that encodes image data in the MPEG system as described above, when encoding image data, obtains a DCT coefficient obtained by performing DCT (Discrete Cosine Transform) processing on the image data. , And performs efficient encoding by deleting image data of high-frequency components that are hardly visible to human eyes.
[0012]
At the time of the quantization, the encoder performs a rounding process (hereinafter, referred to as quantization rounding) on the quantized DCT coefficient so as to round down or round up a value below the significant digit, and to perform conversion within the significant digit. Extract the value of Normally, DCT coefficients quantized in inter-frame coding are truncated to values less than significant digits by quantization rounding, and DCT coefficients quantized in intra-frame coding are converted to valid digits by quantization rounding. Any value below the decimal place is rounded.
[0013]
For example, when an integer value is used as an effective digit for quantized DCT coefficients in intra-frame encoding and quantization rounding is performed on 4 bits after the decimal point, the quantization rounding is illustrated in FIG. It is executed as shown in the flowchart.
[0014]
First, in step S1, the encoder determines whether or not the value of the quantized DCT coefficient that is less than the significant digit, that is, the value of 4 bits after the decimal point, is 8 or more (0x8 or more in hexadecimal). If it is determined that the value is 8 or more, the process proceeds to step S2, rounds up the value below the significant digit (four bits after the decimal point), and ends the quantization rounding process.
[0015]
If it is determined in step S1 that the value of the quantized DCT coefficient below the significant digit (four bits after the decimal point) is not 8 or more (0x8 or more in hexadecimal), the encoder performs the processing in step S1. Proceeding to S3, the value below the significant digit (four bits after the decimal point) is discarded, and the quantization and rounding process ends.
[0016]
[Patent Document 1]
JP-A-11-205803 (pages 3-6, FIGS. 10 and 11)
[0017]
[Problems to be solved by the invention]
However, when using the quantization and rounding method as described above, the encoder is more effective in comparing the image data of the block for performing the intra-frame encoding with the image data of the block for performing the inter-frame encoding. Although high-frequency components can be encoded in detail, at the same time, a lot of mosquito noise and the like due to quantization errors are generated.
[0018]
As a result, in the image of the image data decoded by the decoder, the visual image quality changes between the region corresponding to the block performing the intra-frame encoding and the region corresponding to the block performing the inter-frame encoding, The user has a problem that an image in an area corresponding to a block for performing intra-frame encoding appears as an unnatural image floating in an area corresponding to a block for performing inter-frame encoding.
[0019]
The present invention has been made in view of such a situation, and is intended to perform more effective encoding processing.
[0020]
[Means for Solving the Problems]
The encoding apparatus according to the present invention is configured to add a predetermined value to the quantized first data corresponding to the frame image so that a quantization error in a high-frequency component of the first data is reduced. When the value less than the significant digit of the first data is greater than or equal to the first threshold, the value less than the significant digit of the first data is rounded up, and the value less than the significant digit of the first data is the first value. An arithmetic unit for performing a rounding process for rounding down a value of the first data below the significant digit when the value is smaller than the threshold value is provided.
[0021]
The calculating means may add, to the quantized second data different from the first data corresponding to the frame image, the second data irrespective of the magnitude of the value of the second data which is smaller than the effective digit. Further, a truncation process of truncating a value less than or equal to the effective digit of the first data is performed, and the first threshold value is set between the first decoded image corresponding to the first data and the second decoded image corresponding to the second data. The quantization error in the high-frequency component of the first data can be set to be predetermined so that the visual change by the user does not occur.
[0022]
The control device further includes control means for controlling the calculation of the calculation means, wherein the calculation means sets a value determined so as to reduce a quantization error in a high-frequency component of the first data as a first threshold value, Either a first rounding process that performs rounding on the first data, or a second rounding process that performs rounding on the first data using a median of a range of values that the first data can take as a first threshold value And the control means controls the calculation of the calculation means, selects either the first rounding processing or the second rounding processing, and causes the calculation means to execute the processing.
[0023]
The control means is set based on a coding scheme of coding set based on a user's instruction, or a user's command, or a state of a network through which the coded first data is transmitted. Either the first rounding process or the second rounding process can be selected based on at least one of the encoding bit rates.
[0024]
The control means performs the first rounding process when the encoding method is an intra-slice method in which encoding is performed so that one frame includes data to be intra-coded and data to be inter-coded. Selection, otherwise a second rounding operation may be selected.
[0025]
The control means may select the first rounding process when the bit rate is smaller than a second predetermined threshold value, and may select the second rounding process otherwise.
[0026]
The encoding method according to the present invention provides a quantized data corresponding to a frame image, in which a predetermined value is set as a threshold so that a quantization error in a high frequency component of the data is reduced. If the value of the data is greater than or equal to the threshold value, a rounding process is performed to round up the value less than the significant digit of the data and to round down the value less than the significant digit of the data if the value less than the significant digit of the data is smaller than the threshold And
[0027]
The program of the recording medium according to the present invention uses a predetermined value such that a quantization error in a high-frequency component of the data is reduced as a threshold value in the quantized data corresponding to the frame image. If the following value is greater than or equal to the threshold value, round up the value less than the significant digit of the data, and if the value less than the significant digit of the data is smaller than the threshold value, round off the value less than the significant digit of the data. Features.
[0028]
The program according to the present invention provides a quantized data corresponding to a frame image, wherein a predetermined value such that a quantization error in a high-frequency component of the data is reduced is set as a threshold, and a value less than or equal to an effective digit of the data is set. If the value is greater than or equal to the threshold value, round up the value less than the significant digit of the data, and if the value less than the significant digit of the data is smaller than the threshold value, round down the value less than the significant digit of the data. Features.
[0029]
In the encoding device and method, the recording medium, and the program according to the present invention, a predetermined value such that a quantization error in a high-frequency component of data is reduced in quantized data corresponding to a frame image. Is set as the threshold, and if the value of the data below the significant digit is greater than or equal to the threshold, the value of the data below the significant digit is rounded up. Rounding is performed.
[0030]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 2 is a block diagram illustrating a configuration example of an encoder to which the present invention has been applied.
[0031]
The encoder 1 encodes image data by an intra-slice method using all P pictures. The pre-processing unit 11 of the encoder 1 receives input of image data supplied from outside.
[0032]
The pre-processing unit 11 divides each frame image of the sequentially input image data (all P pictures in this case) into a macroblock composed of a luminance signal of 16 pixels × 16 lines and a color difference signal corresponding to the luminance signal. Then, this is supplied to the calculation unit 12 and the motion detection unit 21 as macroblock data.
[0033]
The motion detection unit 21 receives the input of the macroblock data, calculates a motion vector of each macroblock, and sends the motion vector data to the motion compensation unit 25 as motion vector data.
[0034]
The arithmetic unit 12 performs, for the macroblock data supplied from the preprocessing unit 11, a block for performing inter-frame encoding for a block for performing intra-frame encoding in an intra mode based on an image type of each macroblock. , Motion compensation is performed in the forward prediction mode.
[0035]
Here, the intra mode is a method in which a frame image to be encoded is directly used as transmission data, and the forward prediction mode is a method in which a prediction residual between the frame image to be encoded and a past reference image is transmitted data. Is a method. The encoder 1 uses only P pictures to perform coding by dividing into blocks for performing intra-frame coding and blocks for performing inter-frame coding.
[0036]
First, when the macroblock data is composed of blocks for performing intra-frame coding, the macroblock data is processed in the intra mode. That is, the arithmetic unit 12 sends the macroblock of the input macroblock data to the orthogonal transform unit 13 as arithmetic data as it is. The orthogonal transform unit 13 performs a DCT transform process on the input operation data to convert it into a DCT coefficient, and supplies this to the quantization unit 14 as DCT coefficient data.
[0037]
The quantization unit 14 performs a quantization process on the input DCT coefficient data using the quantization index supplied from the rate control unit 17. At that time, the quantization unit 14 supplies the data after the calculation to the rounding processing unit 30 to perform the quantization rounding process.
[0038]
The rounding section 30 has a control section 31 for controlling the rounding section 30 and a rounding section 32 for performing a rounding operation. In the case of the intra mode, the control unit 31 controls the rounding operation unit 32 so as to cause the data input from the quantization unit 14 to perform a rounding operation with a value that is less than the effective digit of the data, as described later.
[0039]
The rounding operation unit 32 is controlled by the control unit 31 and, when the value of the significant digit of the input data is equal to or greater than a predetermined threshold, the value of the significant digit of the data is equal to or less than the significant digit. When the value is rounded up and the value of the data below the significant digit is smaller than a predetermined threshold value, a rounding operation for rounding down the value of the data below the significant digit is performed. At this time, the rounding operation unit 32 performs a rounding operation by a normal rounding operation (that is, an operation in which a median of a range of values to be taken by a target data is set as a threshold, rounded down when the threshold is smaller than the threshold, and rounded up when the threshold is equal to or larger than the threshold). In addition, the above-described calculation rounding process is performed using a predetermined value adjusted as a threshold so that the quantization error of the high-frequency component becomes equal to that in the case of the inter mode. The operation result in the rounding operation unit 32 is supplied to the quantization unit 14.
[0040]
Then, the quantization unit 14 supplies the data subjected to quantization and rounding to the VLC (Variable Length Code) unit 15 and the inverse quantization unit 22 as quantized DCT coefficient data.
[0041]
The quantized DCT coefficient data supplied to the inverse quantization unit 22 undergoes an inverse quantization process using the same quantization step size as the quantization unit 14, and is supplied to the inverse orthogonal transform unit 23 as DCT coefficient data. The inverse orthogonal transform unit 23 performs an inverse DCT process on the supplied DCT coefficient data, and the generated operation data is supplied to the motion compensation unit 25 via the operation unit 24 as reference image data.
[0042]
When the macroblock data is composed of blocks for performing inter-frame coding, the operation unit 12 performs a motion compensation process in the forward prediction mode on the macroblock data.
[0043]
The motion compensator 25 performs motion compensation on the supplied reference image data according to the motion vector data, and calculates forward prediction image data. The calculation unit 12 performs a subtraction process on the macroblock data using the forward prediction image data supplied from the motion compensation unit 25.
[0044]
That is, in the forward prediction mode, the motion compensation unit 25 selects the reference image data according to the motion vector data, and supplies this to the calculation unit 12 and the calculation unit 24 as the forward prediction image data. The operation unit 12 subtracts the forward prediction image data from the supplied macroblock data to obtain difference data as a prediction residual. Then, the arithmetic unit 12 supplies the difference data to the orthogonal transform unit 13.
[0045]
Further, the forward prediction image data from the motion compensation unit 25 is supplied to the calculation unit 24, and the calculation unit 24 adds the forward prediction image data to the calculation data supplied from the inverse orthogonal transform unit 23. Thereby, the reference image data is locally reproduced and supplied to the motion compensation unit 25.
[0046]
The difference data output from the arithmetic unit 12 is subjected to DCT transform processing in the orthogonal transform unit 13 as in the case of the intra mode, and DCT coefficients are supplied to the quantization unit 14. When quantizing the supplied DCT coefficients, the quantization processing unit 14 supplies the data after the calculation to the rounding processing unit 30 to perform the quantization rounding processing, as in the case of the intra mode.
[0047]
In the case of the forward prediction mode, the control unit 31 of the rounding unit 30 performs an operation of truncating the value of the data input from the quantization unit 14 that is less than the significant digit regardless of the value of the value, as described later. Is controlled to perform the rounding operation. The rounding operation unit 32 is controlled by the control unit 31 and performs an operation of truncating a value of the input data that is lower than the effective digit, regardless of the size of the value. The operation result in the rounding operation unit 32 is supplied to the quantization unit 14.
[0048]
Thus, the image data input to the encoder 1 undergoes motion compensation prediction processing, DCT processing, and quantization processing, and is supplied to the VLC unit 15 as quantized DCT coefficient data. The VLC unit 15 performs a variable length coding process on the quantized DCT coefficient data based on a predetermined conversion table, and supplies the resulting variable length coded data to the storage buffer 16.
[0049]
The rate control unit 17 generates a quantization index based on, for example, the encoding difficulty, the accumulation state of the accumulation buffer 16, or other parameters, and outputs the quantization index to the quantization unit 14. Any method may be used for the calculation of the quantization index, and various parameters are used for the calculation of the quantization index according to the method.
[0050]
The accumulation buffer 16 temporarily accumulates the supplied variable-length encoded data, and then outputs it as a bit stream output to the outside of the encoder 1.
[0051]
As described above, in the case of the intra mode, that is, in the case of a block on which intra-frame encoding is performed, the rounding operation unit 32 of the rounding processing unit 30 supplies the supplied data (the DCT coefficient quantized by the quantization unit 14). ) Is subjected to quantization and rounding processing for the value less than or equal to the significant digit. In the following, a case will be described in which the integer value of the quantized DCT coefficient is used as an effective digit and the value of 4 bits after the decimal point is used as a value below the effective digit.
[0052]
With reference to the flowchart of FIG. 3, the quantization and rounding processing by the rounding operation unit 32 will be described.
[0053]
First, in step S21, the rounding operation unit 32 controlled by the control unit 31 performs a rounding operation using a value of a significant digit or less as a predetermined value as a threshold value. It is determined whether or not the value of the value of the significant digit of the value of the DCT coefficient), that is, the value of 4 bits after the decimal point, is 10 or more (0xa or more in hexadecimal), and when it is determined that it is 10 or more, The process proceeds to step S22 to round up the value below the significant digit (four bits after the decimal point) and terminate the quantization rounding process.
[0054]
In step S21, if it is determined that the value of the quantized DCT coefficient below the significant digit (four bits after the decimal point) is not 10 or more (0xa or more in hexadecimal), the rounding operation unit 32 The process proceeds to step S23, in which the value below the effective digit (the value of 4 bits after the decimal point) is discarded, and the quantization rounding process ends.
[0055]
FIG. 4 is a diagram illustrating a state of the quantization rounding process performed by the rounding operation unit 32.
[0056]
In FIG. 4, input data 40 is a quantized DCT coefficient supplied from the quantization unit 14 of FIG. 2 to the rounding unit 30, and the left-most bits in the figure are higher-order bits. That is, bits 41 and 42 are the lower two bits within the significant digit, and bits 43 to 46 are the four bits (four bits after the decimal point) below the significant digit. As shown in FIG. 4, the value of bit 42, which is the least significant bit in the significant digits of input data 40, is “0”, and the value of 4 bits after the decimal point (bits 43 to 46) of input data 40 is “ 10 "(" 1010 "in binary," 0xa "in hexadecimal).
[0057]
For such input data 40, the rounding operation unit 32 rounds up when the value below the significant digit is “10” to “15” and rounds down when the value below the significant digit is “0” to “9”. The process 50 is executed, and the output data 60 is output. In this case, the value less than the significant digit of the input data 40 is “10”, so the arithmetic processing 50 rounds up the 4-bit value less than the significant digit of the input data 40, and The value of the least significant bit 62 of “60” is “1”.
[0058]
Further, similarly to the input data 40, the input data 70 is a quantized DCT coefficient supplied from the quantizing unit 14 of FIG. . That is, bits 71 and 72 are the lower two bits in the significant digit, and bits 73 to 76 are the four bits (four decimal places) below the significant digit. As shown in FIG. 4, the value of bit 72 which is the least significant bit in the significant digits of input data 70 is “0”, and the value of 4 bits after the decimal point (bits 73 to 76) of input data 70 is “0”. 9 "(" 1001 "in binary," 0x9 "in hexadecimal).
[0059]
For such input data 70, the rounding operation unit 32 executes the operation processing 50 and outputs output data 80. In this case, the value less than the significant digit of the input data 70 is “9”, so the arithmetic processing 50 truncates the 4-bit value less than the significant digit of the input data 70, and The value of the least significant bit 82 of 80 remains "0".
[0060]
As described above, in the quantization rounding of a block on which intra-frame encoding is performed, the encoder 1 sets the threshold value of the rounding operation to a value larger than a normal median value, so that the encoder 1 The amount of the quantization error in the high-frequency component can be adjusted to be substantially equal to the amount of the quantization error in the high-frequency component of the block for performing the interframe coding.
[0061]
Thereby, the encoder 1 reduces a visual change occurring between an image corresponding to a block for performing intra-frame encoding and an image corresponding to a block for performing inter-frame encoding in an image decoded by the decoder. , It is possible to execute more effective encoding processing such that a more natural decoded image is obtained.
[0062]
In the above description, the threshold value of the rounding operation by the rounding operation unit 32 is set to “10”. However, the present invention is not limited to this. Any value may be used as long as it is a predetermined value adjusted so as to be equivalent to the case of the block that performs inter-coding.
[0063]
Further, in the above description, it has been described that the integer of the quantized DCT coefficient is set as an effective digit and the value of 4 bits after the decimal point is set as the value of the effective digit or less, and the rounding process is performed. Any digit may be used as a significant digit, and the value below the significant digit may be any number of bits.
[0064]
Furthermore, the rounding operation unit 32 may be configured to execute a plurality of rounding operation processes having different threshold values, and the control unit 31 may select a rounding operation to be executed.
[0065]
FIG. 5 is a diagram showing another configuration example of the encoder to which the present invention is applied.
[0066]
In FIG. 5, an encoder 100 supports a plurality of encoding schemes such as a normal encoding scheme using I pictures, P pictures, and B pictures, and an intra slice encoding scheme used in low delay coding and the like. In this case, the input image data is encoded according to the encoding method determined by the encoding control unit 142.
[0067]
Pre-processing unit 111, arithmetic unit 112, orthogonal transformation unit 113, quantization unit 114, VLC unit 115, accumulation buffer 116, rate control unit 117, motion detection unit 121, inverse quantization unit 122, inverse orthogonal transformation unit of encoder 100 In the case of the intra slice system, the 123, the arithmetic unit 124, and the motion compensating unit 125 respectively include the pre-processing unit 11, the arithmetic unit 12, the orthogonal transform unit 13, the quantization unit 14, and the VLC unit of the encoder 1 shown in FIG. 15, the accumulation buffer 16, the rate control unit 17, the motion detection unit 21, the inverse quantization unit 22, the inverse orthogonal transform unit 23, the operation unit 24, and the motion compensation unit 25. Omitted.
[0068]
Note that, even in the case of a normal encoding method, each unit of the encoder 100 performs intra-frame encoding on an I picture, performs inter-frame forward prediction encoding on a P picture, and performs Since the same processing as in the case of the above-described intra slice method is performed except for performing the inter-frame bidirectional prediction encoding, the description thereof is omitted.
[0069]
The rounding unit 130 of the encoder 100 controls a unit in the rounding unit 130, a storage unit 132 that stores setting information supplied from the encoding control unit 142, and performs rounding calculation using different thresholds. It has a first rounding operation unit 133 and a second rounding operation unit 134.
[0070]
The control unit 131 performs a setting process as described later, updates the setting information stored in the storage unit 132 based on the information supplied from the encoding control unit 142, and executes a quantization rounding control process. Then, it is determined which of the first rounding operation unit 133 and the second rounding operation unit 134 is to be used to execute the quantization rounding process.
[0071]
The storage unit 132 is configured by a storage element such as a DRAM (Dynamic Random Access Memory) or an EEPROM (Electrically Erasable and Programmable Read Only Memory). The storage unit 132 includes coding information supplied from the coding control unit 142. The setting information set based on the information on the bit rate at the time of transmission is stored.
[0072]
The first rounding operation unit 133 performs a process similar to the rounding operation unit 32 in FIG. 2 when the quantized DCT coefficient is data of a block to be subjected to intra-frame encoding, such as an I-picture block. For the four bits after the decimal point below the significant digits, a rounding operation is performed using a value of “10” as a threshold value, for example, for a block to be subjected to inter-frame encoding, such as a block of a P picture or a B picture. If the data is data, a process of truncating 4 bits after the decimal point below the effective digit is performed.
[0073]
When the quantized DCT coefficient is data of a block to be subjected to intra-frame encoding, the second rounding operation unit 134 applies a value as shown in FIG. A conventional rounding calculation process using "8" (median value) as a threshold value is performed, and in the case of data of a block to be subjected to inter-frame coding, a process of truncating 4 bits after the decimal point below the effective digit is performed.
[0074]
The operation result in the first rounding operation unit 133 or the second rounding operation unit 134 is supplied to the quantization unit 14.
[0075]
The encoding control unit 142 determines an encoding system based on a user instruction input via the input unit 141, and controls each unit of the encoder 100 so that encoding is performed using the encoding system. .
[0076]
In addition, the encoding control unit 142 outputs a bit stream output supplied from the communication unit 143 that outputs a user instruction input via the input unit 141 or a bit stream output that is encoded data to another device. The bit rate is determined based on information on the status of the network as the transmission path, and the components of the encoder 100 are controlled so that encoding is performed at the bit rate.
[0077]
Then, the encoding control unit 142 supplies information on the encoding method and information on the bit rate to the rounding processing unit 130.
[0078]
The control unit 131 of the rounding unit 130 supplied with the above information performs the setting process, and updates the setting information regarding the quantization rounding process stored in the storage unit 132.
[0079]
The setting process by the control unit 131 will be described with reference to the flowchart of FIG.
[0080]
First, in step S41, the control unit 131 determines whether or not information on the encoding scheme has been acquired from the encoding control unit 142. If it is determined that the information has been acquired, in step S42, the information on the acquired encoding scheme has been acquired. Is supplied to the storage unit 132, and the encoding system information included in the setting information regarding the quantization and rounding processing stored in the storage unit 132 is updated. After finishing the process in step S42, the control unit 131 advances the process to step S43.
[0081]
If it is determined in step S41 that the information on the encoding method has not been obtained from the encoding control unit 142, the control unit 131 skips the processing in step S42 and proceeds to step S43.
[0082]
In step S43, the control unit 131 determines whether or not information on the bit rate has been obtained from the encoding control unit 142. If it is determined that the information has been obtained, in step S44, the control unit 131 stores the obtained information on the bit rate in the storage unit 132. And updates the bit rate information included in the setting information regarding the quantization and rounding processing stored in the storage unit 132. The control unit 131 that has completed the process in step S44 advances the process to step S45.
[0083]
If it is determined in step S43 that the information on the bit rate has not been obtained from the encoding control unit 142, the control unit 131 skips the processing in step S44 and proceeds to step S45.
[0084]
In step S45, the control unit 131 determines whether to end the setting process, and if not, returns the process to step S41 and repeats the subsequent processes. If it is determined in step S45 that the setting process is to be ended based on a user instruction or the like, the control unit 131 proceeds to step S46, executes the end process, and ends the setting process.
[0085]
When the quantized DCT coefficient of the block to be subjected to intra-frame encoding is supplied from the quantization unit 14, the control unit 131 performs the setting as described above, and sets the setting stored in the storage unit 132. Based on the information, a quantization rounding control process is executed, and the first rounding operation unit 133 or the second rounding operation unit 134 is controlled to execute the quantization rounding process.
[0086]
With reference to the flowchart of FIG. 7, a description will be given of quantization / rounding control processing performed by the control unit 131 in the case where an arithmetic unit to be used for quantization / rounding processing is determined based on the encoding method information of the setting information.
[0087]
First, in step S61, the control unit 131 controls the storage unit 132 and reads out the encoding method information of the setting information stored in the storage unit 132.
[0088]
Then, in step S62, the control unit 131 determines whether or not the encoding scheme is the intra slice scheme based on the read encoding scheme information. And controls the first rounding operation unit 133 to execute the first quantization rounding process using the value “10” as a threshold.
[0089]
The first quantization rounding process controlled by the control unit 131 and executed by the first rounding calculation unit 133 is basically the same as the quantization rounding process described with reference to the flowchart of FIG. , The description of which will be omitted.
[0090]
The control unit 131 that has completed the processing in step S63 ends the quantization and rounding control processing.
[0091]
If it is determined in step S62 that the encoding method is not the intra slice method, the control unit 131 advances the processing to step S64, controls the second rounding operation unit 134, and sets the second rounding operation unit 134 to the value “8” as a threshold. 2 is performed.
[0092]
The second quantization rounding process controlled by the control unit 131 and executed by the second rounding calculation unit 134 is basically the same as the quantization rounding process described with reference to the flowchart of FIG. , The description of which will be omitted.
[0093]
The control unit 131 that has completed the processing in step S64 ends the quantization and rounding control processing.
[0094]
As described above, the control unit 131 of the rounding processing unit 130 performs the quantization and rounding control processing, so that the encoder 100 includes only the block for performing the intra-frame coding in the case of the normal coding method. Therefore, in order to be able to encode the high-frequency component of the block to be subjected to intra-frame encoding in more detail, a rounding operation with a value “8” as a threshold is performed. Since the block for performing intra-frame coding and the block for performing inter-frame coding are mixed, the quantization error of the high-frequency component of the block for performing the intra-frame coding is reduced by the quantization error of the high-frequency component of the block for performing the inter-frame coding. In order to perform encoding so as to conform to, a rounding operation using a value “10” as a threshold is performed.
[0095]
Thereby, the encoder 100 can adjust the quantization error of the high-frequency component of the block for performing the intra-frame encoding to an optimal value in a plurality of encoding schemes, and perform more effective encoding processing. it can.
[0096]
In the above description, the control unit 131 has been described to control the quantization and rounding processing based on the encoding scheme information. However, the present invention is not limited to this, and the encoding bit rate determined by the encoding control unit 142 is not limited to this. May be used to control the quantization and rounding processing.
[0097]
With reference to the flowchart of FIG. 8, a description will be given of quantization / rounding control processing performed by the control unit 131 when an arithmetic unit to be used for quantization / rounding processing is determined based on bit rate information of setting information.
[0098]
First, in step S81, the control unit 131 controls the storage unit 132 and reads out the bit rate information of the setting information stored in the storage unit 132.
[0099]
Then, in step S82, the control unit 131 determines whether or not the bit rate set by the encoding control unit 142 is smaller than a predetermined threshold A based on the read bit rate information. If it is determined that the threshold value is smaller than the threshold value A, the process proceeds to step S83, and the first rounding operation unit 133 is controlled and the first quantum having the value “10” as the threshold value, as in the case of step S63 in FIG. Execute the rounding process. The control unit 131 that has completed the processing in step S83 ends the quantization and rounding control processing.
[0100]
If it is determined in step S82 that the bit rate set by the encoding control unit 142 is not smaller than the predetermined threshold A, the control unit 131 advances the process to step S84, and proceeds to step S84. As in the case of step S64, the second rounding calculation unit 134 is controlled to execute a second quantization rounding process using the value “8” as a threshold. The control unit 131 that has completed the processing in step S84 ends the quantization and rounding control processing.
[0101]
As described above, the control unit 131 of the rounding processing unit 130 performs the quantization and rounding control process, so that the encoder 100 can perform the encoding in the frame when the bit rate is larger than the threshold value A and the amount of data that can be transferred is sufficient. In order to be able to encode the high-frequency component of the block to be encoded in more detail, a rounding operation using a value “8” as a threshold is performed, the bit rate is smaller than the threshold A, and there is a margin in the amount of transferable data. If not, to quantize the high-frequency component quantization error of the block performing intra-frame encoding to the quantization error of the high-frequency component of the block performing inter-frame encoding, to encode so as to reduce the amount of encoded data, A rounding operation using the value “10” as a threshold is performed.
[0102]
That is, in this case, even if the encoding method is a normal encoding method using an I picture, a P picture, and a B picture, the encoder 100 At 130, as described above, a rounding operation using the value “8” as a threshold is performed.
[0103]
Thereby, the encoder 100 can adjust the quantization error of the high-frequency component of the block on which intra-frame encoding is performed to an optimal value in accordance with the bit rate, and can perform more effective encoding processing. .
[0104]
In the above, the control unit 131 determines the threshold value of the rounding calculation in the quantization rounding process of the block for performing the intra-frame coding based on the coding method information of the setting information or the bit rate information. As described above, the threshold value of the rounding operation in the quantization rounding process of the block to be subjected to intra-frame coding may be determined based on both the coding method information and the bit rate information of the setting information.
[0105]
In this case, the control unit 131 performs intra-frame encoding by combining the quantization and rounding control processing described with reference to the flowchart in FIG. 7 and the quantization and rounding control processing described with reference to the flowchart in FIG. A threshold value of a rounding operation in a quantization rounding process of a block is determined.
[0106]
For example, the control unit executes the processing of step S61 of FIG. 7 and step S81 of FIG. 8, acquires the encoding method information and the bit rate information of the setting information stored in the storage unit 132, and When the processing of S62 is executed and it is determined that the encoding method is the intra slice method, the processing of step S82 of FIG. 8 is executed, and when it is determined that the bit rate is smaller than the threshold A, the processing of step S63 of FIG. The process of (Step S83 in FIG. 8) is executed to control the first rounding operation unit 133 to execute the first quantization rounding process using the value “10” as a threshold.
[0107]
Also, the processing of step S62 in FIG. 7 is performed, and it is determined that the encoding scheme is not the intra slice scheme, or the processing of step S82 in FIG. 8 is performed, and it is determined that the bit rate is not smaller than the threshold A. In this case, the control unit 131 executes the process of step S64 in FIG. 7 (step S84 in FIG. 8), controls the second rounding operation unit 134, and performs the second quantization rounding process using the value “8” as a threshold. Is executed.
[0108]
Note that the control unit 131 may execute the processing of step S62 of FIG. 7 and, if it determines that the encoding scheme is not the intra slice scheme, execute the processing of step S82 of FIG.
[0109]
In that case, the control unit 131 determines that the encoding scheme is the intra slice scheme in the processing of step S62 in FIG. 7 or determines that the bit rate is smaller than the threshold A in the processing of step S82 in FIG. If it is determined, the process of step S63 in FIG. 7 (step S83 in FIG. 8) is executed to control the first rounding operation unit 133 and execute the first quantization rounding process using the value “10” as a threshold value Let it.
[0110]
When it is determined in step S62 in FIG. 7 that the encoding method is not the intra slice method, and when it is determined in step S82 in FIG. Then, the process of step S64 (step S84 in FIG. 8) is executed, and the second rounding operation unit 134 is controlled to execute the second quantization rounding process using the value “8” as a threshold.
[0111]
In addition to the above, the determination process in step S82 of FIG. 8, that is, the determination process based on the bit rate information is prioritized over the determination process based on the encoding system information in step S62 in FIG. Of course it is good.
[0112]
In this case, the control unit 131 executes the processing of step S61 of FIG. 7 and step S81 of FIG. 8, acquires the encoding method information and the bit rate information of the setting information stored in the storage unit 132, and If the bit rate is determined to be smaller than the threshold A, the process of step S62 in FIG. 7 may be performed, or if the bit rate is determined to be not smaller than the threshold A, Alternatively, the processing of step S62 in FIG. 7 may be executed.
[0113]
That is, the control unit 131 determines that the bit rate is smaller than the threshold value A in the processing of step S82 in FIG. 8, and further determines that the encoding scheme is the intra slice scheme in the processing of step S62 in FIG. Only in this case, the processing of step S63 of FIG. 7 (step S83 of FIG. 8) may be executed, and in other cases, the processing of step S64 of FIG. 7 (step S84 of FIG. 8) may be executed. When it is determined in the process of step S82 in FIG. 8 that the bit rate is smaller than the threshold value A, or when it is determined in the process of step S62 in FIG. 7 that the encoding system is the intra slice system, The processing in step S63 (step S83 in FIG. 8) is executed; otherwise, the processing in step S64 in FIG. 7 (step S84 in FIG. 8) is performed. The may be executed.
[0114]
Further, the control unit 131 may determine the threshold value of the rounding operation in the quantization rounding process of the block for performing the intra-frame coding based on the information other than the coding method and the bit rate described above. Needless to say, the threshold values to be determined are not limited to the two types described above, but may be other values, or may be selected from among three or more threshold values.
[0115]
The above-described series of processing can be executed by hardware, or can be executed by software as described above. When a series of processing is executed by software, various functions can be executed by installing a computer in which the programs constituting the software are embedded in dedicated hardware, or by installing various programs For example, it is installed in a general-purpose personal computer from a recording medium or the like.
[0116]
FIG. 9 is a diagram illustrating an example of the internal configuration of a personal computer that executes such processing.
[0117]
A CPU (Central Processing Unit) 201 of the personal computer 200 executes various processes according to a program stored in a ROM (Read Only Memory) 202. A RAM (Random Access Memory) 203 appropriately stores data, programs, and the like necessary for the CPU 201 to execute various processes.
[0118]
The CPU 201, the ROM 202, and the RAM 203 are mutually connected via a bus 204. The bus 204 is also connected to an input / output interface 210.
[0119]
The input / output interface 210 is connected to an input unit 211 including a keyboard and a mouse, and outputs a signal input to the input unit 211 to the CPU 201. The input / output interface 210 is also connected to an output unit 212 including a display and a speaker.
[0120]
Further, a storage unit 213 composed of a hard disk and the like, and a communication unit 214 for communicating data with other devices via a network such as the Internet are also connected to the input / output interface 210. The drive 215 is used to read data from or write data to a removable medium 221 formed of a recording medium such as a magnetic disk, an optical disk, a magneto-optical disk, or a semiconductor memory.
[0121]
As shown in FIG. 9, the recording medium is a magnetic disk (including a flexible disk) on which the program is recorded and an optical disk (CD-ROM) which are distributed to provide the program to the user separately from the personal computer. (Including Compact Disc-Read Only Memory), DVD (Digital Versatile Disc), magneto-optical disc (including MD (Mini-Disc) (registered trademark)), and removable media 221 including package media including semiconductor memory. And a hard disk including a ROM 202 and a storage unit 213 in which a program is stored, which is provided to a user in a state of being incorporated in a computer in advance.
[0122]
In this specification, the steps of describing a program provided by a medium include, in the order described, not only processing performed in chronological order but also processing in chronological order, or in parallel or individually. This includes the processing to be executed.
[0123]
【The invention's effect】
As described above, according to the present invention, image information can be encoded. In particular, more effective encoding processing can be performed.
[Brief description of the drawings]
FIG. 1 is a flowchart illustrating a conventional quantization rounding process.
FIG. 2 is a block diagram illustrating a configuration example of an encoder to which the present invention has been applied.
FIG. 3 is a flowchart illustrating an example of a quantization rounding process performed by a rounding operation unit 32 in FIG. 2;
FIG. 4 is a diagram illustrating a state of a quantization rounding process performed by a rounding operation unit 32 in FIG. 2;
FIG. 5 is a block diagram illustrating another configuration example of an encoder to which the present invention has been applied.
FIG. 6 is a flowchart illustrating an example of a setting process by a control unit in FIG. 5;
FIG. 7 is a flowchart illustrating an example of quantization and rounding control processing by a control unit in FIG. 5;
FIG. 8 is a flowchart illustrating another example of quantization / rounding control processing performed by the control unit in FIG. 5;
FIG. 9 is a block diagram illustrating a configuration example of a personal computer.
[Explanation of symbols]
1 encoder, 30 rounding section, 31 control section, 32 rounding section, 40 input data, 41 to 46 bits, 50 processing, 60 output data, 61 and 62 bits, 70 input data, 71 to 76 bits, 80 output data , 81 and 82 bits, 130 rounding section, 131 control section, 132 storage section, 133 first rounding section, 134 second rounding section, 141 input section, 142 encoding control section, 143 communication section

Claims (9)

In an encoding device that encodes a frame image,
The first data corresponding to the frame image, which has been subjected to the quantization operation, is set as a first threshold, using a predetermined value such that a quantization error in a high frequency component of the first data is reduced. If the value of the first data is less than or equal to the first threshold, the value of the first data that is less than the significant digit is rounded up, and the value of the first data that is less than the significant digit is the first threshold. An encoding apparatus, comprising: an arithmetic unit that performs a rounding process for rounding down the value of the first data that is less than the significant digit when the value is smaller than the first data. The arithmetic means, the second data subjected to the quantization operation, which is different from the first data and corresponds to the frame image, irrespective of the magnitude of the value less than the significant digit of the second data, Further perform a truncation process of truncating the value of the second data below the significant digit,
The first threshold value is set so that a visual change by a viewer does not occur between a first decoded image corresponding to the first data and a second decoded image corresponding to the second data. 2. The encoding apparatus according to claim 1, wherein a predetermined quantization error in a high-frequency component of the first data is reduced. Further comprising a control means for controlling the calculation of the calculation means,
A first rounding unit that performs the rounding process on the first data by using a value determined so that a quantization error in a high-frequency component of the first data is reduced as the first threshold value; Performing one of a process and a second rounding process of performing the rounding process on the first data, with the median of a range of values that the first data can take as the first threshold value,
The control unit controls an operation of the operation unit, selects one of the first rounding process and the second rounding process, and causes the operation unit to execute the operation. 2. The encoding device according to 1. The control means is configured based on an encoding method of the encoding set based on a user instruction, or an instruction of the user, or a state of a network through which the encoded first data is transmitted. 4. The method according to claim 3, wherein one of the first rounding process and the second rounding process is selected based on at least one of the set bit rates of the encoding. An encoding device according to claim 1. The control unit may be configured to perform the first rounding when the encoding method is an intra-slice method that performs encoding so that one frame includes data to be intra-coded and data to be inter-coded. 5. The encoding apparatus according to claim 4, wherein a processing is selected, and otherwise, the second rounding processing is selected. The control means selects the first rounding process when the bit rate is smaller than a predetermined second threshold value, and otherwise selects the second rounding process. The encoding device according to claim 4, wherein A coding method of a coding device for coding a frame image,
Corresponding to the frame image, the quantized data, as a threshold a predetermined value so that the quantization error in the high-frequency component of the data is reduced, the value of the data below the significant digit is the threshold In the case where the value is greater than or equal to, the value including the significant digit of the data is rounded up. Encoding method. A program that causes a computer to perform a process of encoding a frame image,
Corresponding to the frame image, the quantized data, as a threshold a predetermined value so that the quantization error in the high-frequency component of the data is reduced, the value of the data below the significant digit is the threshold In the case where the value is greater than or equal to, the value including the significant digit of the data is rounded up. A recording medium characterized by recording a computer-readable program. In a program that causes a computer to perform a process of encoding a frame image,
Corresponding to the frame image, the quantized data, as a threshold a predetermined value so that the quantization error in the high-frequency component of the data is reduced, the value of the data below the significant digit is the threshold If the value is greater than or equal to the value, the value of the data is rounded up to the significant digit, and if the value of the data is less than the threshold, the processing including a rounding process of rounding down the value of the data is reduced to a computer. A program characterized by being executed by a user.

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