JP2010193399A - Image coding apparatus and image coding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a code amount from becoming excessive, while suppressing a redundant memory region or redundant code amount consumption. <P>SOLUTION: An image coding apparatus codes an inputted moving image by performing intra-screen prediction or inter-screen prediction thereon. When it is determined that an estimate code amount calculated before entropy coding exceeds a preset predetermined code amount, the inputted moving image is switched to intra-screen prediction. When the code amount exceeds the predetermined code amount after entropy coding, macro block pixels are restored from an inputted predictive pixel value and a transform coefficient. The restored image data are switched as data prior to entropy coding. Thus, it is not necessary to secure a redundant memory region and the code amount can be prevented from exceeding a maximum code amount. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image encoding device and an image encoding method. The present invention relates to a technique suitable for use in a moving image encoding apparatus such as H.264 / MPEG-4 AVC.

  MPEG-4 AVC (ISO / IEC 14496-10) is one of the moving image encoding systems, and is widely used in digital television broadcasting and video recording media. In MPEG-4 AVC, context-adaptive variable length coding (CAVLC). Alternatively, a context adaptive entropy coding method such as context-adaptive binary arithmetic coding (CABAC) is employed to increase coding efficiency.

  In MPEG-4 AVC, the maximum code amount per macroblock is defined, and when encoding is performed with 4: 2: 0 components and 8 bits, 3200 bits is the upper limit. For this reason, it is stipulated that encoding must be performed so as not to exceed the maximum code amount.

  Therefore, if the maximum code amount exceeds the maximum value as a result of encoding, it is a violation of the standard, and it is necessary to re-encode by changing the encoding conditions such as the prediction method and the quantization parameter. In this case, the processing of the next macroblock cannot be performed until the re-encoding process is completed, and the code amount after the re-processing may exceed the maximum code amount. Is done.

  In addition to the re-encoding method, there is also a method of encoding using a prediction mode called I_PCM mode in which pixel values are multiplexed as they are without performing orthogonal transform and quantization encoding. However, in this encoding method, it is necessary to store the I_PCM data in advance because it is not possible to determine whether the final code amount exceeds the entropy encoding after entropy encoding.

  In order to protect the excess of the maximum code amount per macroblock using such a mechanism, a method is disclosed in which the code amount is determined based on a certain threshold value from information before entropy coding and replaced with I_PCM data. (For example, refer to Patent Document 1).

JP 2007-166039 A

  As described above, the method of predicting the code amount in advance and switching to I_PCM before entropy coding is effective in terms of preventing the maximum code amount from being exceeded. However, when data is passed to the entropy encoding unit via the memory, assuming the worst case, it is necessary to secure image data for one screen. Therefore, this method also has a disadvantage that a redundant memory area must be secured.

  In addition, since the final code amount is predicted and determined from information before entropy coding until it gets tired, even when the maximum code amount is not exceeded, there is a case where switching to I_PCM is considered, and the code amount is consumed redundantly. There is a possibility that.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to prevent excessive code amounts while suppressing redundant memory areas and redundant code amount consumption.

An image encoding device according to the present invention is an image encoding device that encodes an input moving image by intra prediction or inter prediction, and is calculated before entropy encoding. When it is determined from the estimated code amount that it exceeds a predetermined code amount set in advance, it is switched to intra prediction, and when the code amount exceeds a predetermined code amount after entropy coding, it is input A macroblock pixel is restored from a predicted pixel value and a transform coefficient, and the restored image data is replaced as data before the entropy encoding.
Another feature of the image encoding device of the present invention is an image encoding device that encodes an input moving image by intra-screen prediction or inter-screen prediction, and a pixel having a predetermined size. A prediction image determining unit that calculates an estimated code amount for each block, determines a prediction method based on the calculated estimated code amount, and performs predictive coding according to a prediction method determined by the prediction method determining unit. Prediction encoding means for performing orthogonal transform processing and quantization processing on difference data between the prediction image and the encoding target image in the moving image, and the prediction generated by the prediction encoding means An entropy encoding unit that performs entropy encoding on the encoded data, and the prediction method determination unit compares a first code amount ratio that compares the calculated estimated code amount with a first predetermined value. When the estimated code amount exceeds the first predetermined value by the first code amount comparison process, intra prediction is applied as a prediction method, and the entropy encoding means When the code amount exceeds the second predetermined value, a macro is calculated from the input predicted pixel value and the conversion coefficient. A block pixel is restored, and a replacement process is performed in which the restored image data is replaced with I_PCM data.

An image encoding method of the present invention is an image encoding method for encoding an input moving image by intra-screen prediction or inter-screen prediction, and the input moving image is calculated before entropy encoding. When it is determined from the estimated code amount that it exceeds a predetermined code amount set in advance, it is switched to intra prediction, and when the code amount exceeds a predetermined code amount after entropy coding, it is input A macroblock pixel is restored from a predicted pixel value and a transform coefficient, and the restored image data is replaced as data before the entropy encoding.
Another feature of the image encoding method of the present invention is an image encoding method for encoding an input moving image by intra-screen prediction or inter-screen prediction, and encoding a pixel having a predetermined size. A prediction image is calculated in accordance with the prediction method determined in the prediction method determination step in which the estimated code amount is calculated for each block and the prediction method is determined based on the calculated estimated code amount, and the prediction method determined in the prediction method determination step. A prediction encoding step of performing orthogonal transformation processing and quantization processing on difference data between the prediction image and the encoding target image in the moving image, and the prediction generated in the prediction encoding step An entropy encoding step of performing entropy encoding on the encoded data, and the prediction method determination step compares the calculated estimated code amount with a first predetermined value. When the estimated code amount exceeds the first predetermined value by the first code amount comparison process, intra prediction is applied as a prediction method, and in the entropy encoding step, Then, a second code amount comparison process for comparing the code amount after entropy coding and a second predetermined value is performed, and when the code amount exceeds the second predetermined value, the input predicted pixel value And a macroblock pixel is restored from the transform coefficient, and a replacement process is performed in which the restored image data is replaced with I_PCM data.

  The computer program of the present invention is a program for causing a computer to execute an image encoding method for encoding an input moving image by intra prediction or inter prediction and encoding the input moving image by entropy encoding. When it is determined from the estimated code amount calculated before that it exceeds a predetermined code amount set in advance, it is switched to intra prediction, and when the code amount exceeds a predetermined code amount after entropy coding The image coding method for restoring a macroblock pixel from the input predicted pixel value and transform coefficient and replacing the restored image data as data before the entropy coding is executed by the computer.

  According to the present invention, when the estimated code amount calculated at the stage of the prediction method determination process exceeds a predetermined value, the intra-screen prediction that hardly generates the code amount is applied. Thereby, the code amount after performing the entropy encoding process in the entropy encoding unit can be made difficult to exceed the maximum code amount. In addition, when the code amount after entropy coding exceeds the maximum code amount, it is replaced with I_PCM data by a simple decoding process limited to intra prediction. As a result, it is possible to prevent the inconvenience of exceeding the maximum code amount without requiring a redundant memory area and without performing reprocessing before the entropy encoding unit.

1 is a block diagram illustrating a configuration example of an image encoding device according to a first embodiment of this invention. FIG. It is a flowchart which shows the 1st Embodiment of this invention and demonstrates the prediction method determination procedure. 5 is a flowchart illustrating an I_PCM data replacement procedure according to the first embodiment of this invention. It is a flowchart which shows the 2nd Embodiment of this invention and demonstrates the prediction method determination procedure performed in an image coding apparatus.

(First embodiment)
In the following, the configuration and processing flow of an image encoding apparatus that encodes a video signal using the MPEG-4 AVC system, which is the first embodiment to which the present invention can be applied, will be described with reference to the block diagram of FIG. . Note that the video signal is a 1920 × 1088 pixel 4: 2: 0 component signal and is encoded with 8 bits, but the screen resolution, chroma format, and quantization bit number are not limited to this specification. It does not affect the invention.

  The image encoding apparatus 100 according to the present embodiment performs an encoding process in units of macroblocks obtained by dividing an encoding target screen into 16 × 16 pixel blocks. The prediction method determination unit 101 performs processing for determining a prediction method for each macroblock in the encoding target screen.

  The prediction method determination unit 101 performs simple intra-screen prediction or inter-screen prediction processing including motion detection from the encoding target image in the input moving image and the pixel value of the encoded image read from the memory 103. By doing so, the prediction method with the optimum encoding efficiency is determined.

  For example, when the encoding target macroblock is an I slice, the intra prediction pixel block size and the prediction mode are determined. In the case of P slices or B slices, the one with higher coding efficiency is selected from among intra prediction or inter prediction. In the present embodiment, in the case of inter-screen prediction, intra-screen prediction encoding parameters such as an intra-screen prediction pixel block size and an intra-screen prediction mode are determined. In the case of inter-screen prediction, parameters for inter-screen prediction encoding such as a reference image frame, a macroblock division pattern, and a motion vector are determined.

  Here, in the prediction method determination unit 101, the encoding efficiency is optimized by selecting a prediction method so that the calculated estimated code amount is minimized. The estimated code amount is calculated as a sum of absolute values (SATD) of transform coefficients obtained by performing orthogonal transform on difference data, which is a difference value obtained by subtracting an encoding target image from a prediction image generated by performing a simple prediction process. Is done.

  Furthermore, when the estimated code amount for the selected prediction method (hereinafter referred to as CUR_SATD) exceeds a preset maximum estimated code amount (hereinafter referred to as MAX_SATD), intra-screen prediction using an average value of 16 × 16 pixels To apply.

Hereinafter, an example of a procedure for determining a prediction method will be described with reference to the flowchart shown in FIG.
First, in step S201, an estimated code amount in intra-screen and inter-screen prediction is calculated depending on whether the encoding target slice in the moving image is an I slice or another slice (P slice or B slice). In order to do this, the slice type is determined.

  As a result of the determination in step S201, in the case of an I slice, the process proceeds to step S202, where the estimated code amount for each mode in intra prediction is calculated, and the prediction mode with the smallest estimated code amount is selected. Thereafter, the process proceeds to step S204.

  On the other hand, if the result of determination in step S201 is P slice or B slice, the process proceeds to step S203, where the estimated code amount for each mode in inter-screen prediction is calculated, and the prediction mode with the smallest estimated code amount is selected. select. Thereafter, the process proceeds to step S204.

  In step S204, the estimated code amount CUR_SATD in the prediction mode selected by the processing in step S202 or step S203 described above is compared with a preset maximum estimated code amount MAX_SATD. As a result of this comparison, if CUR_SATD is smaller than MAX_SATD, the process proceeds to step S205, and the prediction method selected at the time of calculating CUR_SATD is applied as it is.

  If CUR_SATD is greater than or equal to MAX_SATD as a result of the comparison in step S204, the process proceeds to step S206, and the in-screen prediction mode (luminance: average value of 16 × 16 pixels, average value of color difference 8 × 8 pixels) is applied. Is done.

  When the process of step S205 or step S206 ends, the process proceeds to step S207 to determine whether or not the process for determining the prediction method is ended. As a result of this determination, if the process is not completed, the process returns to step S201 and the above-described processing is performed. Further, if the process is ended as a result of the determination in step S207, an end process is performed.

  As described above, the prediction method determination unit 101 performs the first code amount comparison process for comparing the calculated estimated code amount with the first predetermined value, and the calculated estimated code amount exceeds the first predetermined value. In this case, intra prediction is applied as a prediction method. Specifically, when CUR_SATD exceeds MAX_SATD (first processing value), the prediction method determination unit 101 applies the intra-screen prediction mode having a luminance of 16 × 16 pixels and a color difference of 8 × 8 pixels. As a result, it is possible to suppress the amount of code after entropy encoding from occurring to some extent while suppressing constituent elements necessary for MB encoding. The predictive encoding parameters determined in this way are output to the predictive processing unit 102 and used for performing predictive encoding processing.

  The prediction processing unit 102 generates a prediction image from the encoded image read from the memory 103 according to the prediction encoding parameter determined by the prediction method determination unit 101, and outputs the prediction image to the local decoding unit 105. In addition, a prediction residual signal (difference data) that is a difference between an encoding target image (pixel block) input as a video and a predicted image is generated and output to the orthogonal transform / quantization unit 104.

  Here, when the above-mentioned CUR_SATD exceeds MAX_SATD and the prediction method determination unit 101 applies the intra prediction mode, the prediction processing unit 102 outputs the generated predicted image to the entropy encoding unit 106. At this time, since the 16 × 16 pixel average value prediction is applied in the above-described example, the prediction pixel for one pixel may be output.

  The orthogonal transform / quantization unit 104 performs orthogonal transform processing by integer precision discrete cosine transform and discrete Hadamard transform on a specified pixel block unit of a predetermined size (8 × 8 pixel or 4 × 4 pixel block unit). . The discrete Hadamard transform is only for a DC (direct current) component obtained as a result of integer-precision discrete cosine transform of each pixel block with respect to a luminance signal or a color difference signal subjected to intra-screen prediction processing in units of 16 × 16 pixel blocks. Done.

  Further, the orthogonal transform / quantization unit 104 performs a quantization process on the orthogonally transformed transform coefficient by a quantization step according to a designated quantization parameter. The data after the quantization process (predictive encoded data) is input to the entropy encoding unit 106. The data quantized by the orthogonal transform / quantization unit 104 (predictive encoded data) is also input to the local decoding unit 105 at the same time.

  The local decoding unit 105 performs prediction processing on the data obtained by performing inverse quantization processing and inverse orthogonal transform processing (inverse discrete Hadamard transform and inverse integer precision discrete cosine transform) on the input predictive encoded data. The prediction image input from 102 is added to perform decoding processing. The decrypted data is output to the memory 103 and held in the memory 103.

  The decoded data held in the memory 103 is used for intra-screen prediction processing performed thereafter. Further, the decoded data subjected to the deblocking filter process is held in the memory 103. The decoded data after the deblocking filter process held in the memory 103 is used for the inter-screen prediction process performed thereafter.

  The entropy encoding unit 106 performs entropy encoding processing by CAVLC or CABAC on the input prediction encoded data, and outputs the encoded video data to the multiplexing processing unit 107. CAVLC is an abbreviation for Context-based Adaptive Variable Length Coding (context adaptive variable length coding). In this method, when a DCT coefficient is encoded, a run and a level, which are continuous zero lengths, are encoded from a direction opposite to the scan direction using a variable-length encoding table.

  CABAC is an abbreviation for Context-based Adaptive Binary Arithmetic Coding (context-adaptive binary arithmetic coding method), and is a method of changing the appearance frequency of an encoding object that changes with time. This is generally called arithmetic coding. In CABAC, in addition to normal arithmetic coding, a context is assigned to each code to be compressed, and the appearance frequency is changed for each context.

  Here, the entropy encoding unit 106 compares the code amount after entropy encoding (hereinafter, CUR_BRATE) with the maximum code amount (hereinafter, MAX_BRATE) preset as the second predetermined value. A quantity comparison process is performed. As a result of the comparison, when the code amount after entropy coding exceeds MAX_BRATE, the following processing is performed.

  That is, the entropy encoding unit 106 of the present embodiment restores macroblock pixels from the input predicted pixel value and transform coefficient by the built-in simple decoding processing unit 106a, and replaces the restored image data as I_PCM data. A replacement function is provided. Here, the simple decoding processing unit 106 a is built in the entropy coding unit 106, but the simple decoding processing unit 106 a may be separated from the entropy coding unit 106.

The I_PCM data replacement procedure will be described below with reference to the flowchart shown in FIG.
First, in step S301, entropy encoding is performed. When the code amount CUR_BRATE is calculated, the process proceeds to step S302. In step S302, CUR_BRATE is compared with a preset maximum code amount MAX_BRATE. Here, MAX_BRATE per MB is set to 3200 bits, which is the upper limit in the standard.

  As a result of the comparison in step S302, when CUR_BRATE is smaller than MAX_BRATE, the process proceeds to step S303, and the encoded data after entropy encoding is encoded as it is. Thereafter, the process proceeds to step S307.

  On the other hand, if CUR_BRATE is larger than MAX_BRATE as a result of the comparison in step S302, it is out of the standard and cannot be encoded as it is. Therefore, the process proceeds to steps S304 to S306 and normal encoding processing is performed.

  In step S304, the entropy encoding unit 106 is returned to the state before the entropy encoding of the target MB. Subsequently, the process proceeds to step S305, in which the simple decoding processing unit 106a built in the entropy encoding unit 106 performs decoding processing from the pre-entropy encoding data and the input predicted pixel value, and the image data, that is, I_PCM data is generated.

  Here, in the simple decoding processing unit 106a built in the entropy encoding unit 106, when the estimated code amount is larger than a predetermined value by the prediction method determination unit 101 in the previous stage, the intra-screen prediction mode based on the average value is set. Is selected.

  For this reason, it is possible to restore the image data by simply performing inverse quantization and inverse orthogonal transform on the data before entropy encoding and adding the input prediction pixels. That is, it is only necessary to be able to perform decoding processing only for intra prediction, and it can be implemented as a relatively easy decoding processing circuit that does not require a complicated motion compensation circuit. Subsequently, the process proceeds to step S306, and processing for replacing the encoding target data with the generated I_PCM data is performed. Thereafter, the process proceeds to step S307.

  In step S307, it is determined whether or not to end the process. As a result of this determination, if the process is not completed, the process returns to step S301 and the above-described processing is performed. Further, if the process is ended as a result of the determination in step S307, an end process is performed.

  Since the image encoding apparatus 100 according to the present embodiment performs processing as described above, even if the code amount after entropy encoding exceeds a predetermined value, it can be replaced with I_PCM data by the simple decoding processing unit 106a. It has become.

  The multiplexing processing unit 107 multiplexes the encoded video data input in this way and system data (not shown) (slice header or the like) and outputs the multiplexed data.

  As described above, in the image coding apparatus 100 according to the present embodiment, first, when the estimated code amount calculated in the prediction method determination process performed by the prediction method determination unit 101 is larger than a predetermined value. In-screen average value prediction mode in which the amount of code hardly occurs is applied. Thereby, it is possible to prevent the code amount after the entropy encoding process in the entropy encoding unit 106 from exceeding the maximum code amount.

  Furthermore, even if the code amount after entropy encoding exceeds the maximum code amount, it is replaced with I_PCM data by a simple decoding process limited to intra prediction. As a result, an encoding process capable of preventing the inconvenience of exceeding the maximum code amount without requiring a redundant memory area and without performing reprocessing before the entropy encoding unit 106 is possible. It becomes.

(Second Embodiment)
Next, a second embodiment of an image encoding apparatus that encodes a video signal using the MPEG-4 AVC method to which the present invention is applicable will be described. The image coding apparatus according to the present embodiment has the same configuration as that of the image coding apparatus 100 shown in the first embodiment. Therefore, with respect to the block diagram, FIG. 1 is used, and the redundant description of the operation is omitted. In the following description, a prediction method determination procedure in the prediction method determination unit 101 that becomes a difference will be described.

  The prediction method determination unit 101 in the image encoding device 100 of the present embodiment selects a prediction method so that the calculated estimated code amount is minimized, and determines the encoding efficiency to be optimal. The determined estimated code amount is calculated as the sum of absolute values (SAD) of difference data obtained by subtracting the encoding target image from the prediction image generated by performing a simple prediction process.

  Furthermore, when the estimated code amount (hereinafter referred to as CUR_SAD) for the selected prediction method exceeds a preset maximum estimated code amount (hereinafter referred to as MAX_SAD), intra-screen prediction using an average value of 16 × 16 pixels is applied. Like to do.

The prediction method determination procedure will be described below with reference to the flowchart shown in FIG.
First, in step S401, it is determined whether the encoding target slice is an I slice or another slice (P slice or B slice). If the result of this determination is that the current slice is an I slice, the process proceeds to step S402, where the estimated code amount for each mode in intra prediction is calculated, and the prediction mode with the smallest estimated code amount is selected. . Thereafter, the process proceeds to step S404.

  On the other hand, if the result of determination in step S401 is P slice or B slice, the process proceeds to step S403, where the estimated code amount for each mode in inter prediction is calculated, and the prediction mode with the smallest estimated code amount is selected. To do. Thereafter, the process proceeds to step S404.

  In step S404, the estimated code amount CUR_SAD in the prediction mode selected in step S402 or step S403 is compared with a preset maximum estimated code amount MAX_STD. As a result of this comparison, if CUR_SAD is smaller than MAX_SAD, the process proceeds to step S405, and the prediction method selected at the time of calculating CUR_SAD is applied as it is. Thereafter, the process proceeds to step S407.

  On the other hand, if CUR_SAD is greater than or equal to MAX_SAD as a result of the comparison in step S404, the process proceeds to step S406, and the intra prediction mode (luminance: average value of 16 × 16 pixels, average value of color difference 8 × 8 pixels) is applied. To do. Thereafter, the process proceeds to step S407.

  In step S407, it is determined whether or not to end the prediction method determination process. As a result of this determination, if the process is not completed, the process returns to step S401 to perform the above-described processing. Further, as a result of the determination in step S407, an end process is performed when the prediction method determination process ends.

  As described above, in the present embodiment, when CUR_SAD exceeds MAX_SAD, by applying the intra prediction mode having a luminance of 16 × 16 pixels and a color difference of 8 × 8 pixels, components necessary for MB encoding are suppressed. I did it. As a result, it is possible to suppress the code amount after entropy encoding from occurring to some extent.

  As described above, even when SAD is adopted as the estimated code amount, similarly, when the estimated code amount calculated at the stage of the prediction method determination process is larger than a predetermined value, the screen is less likely to generate the code amount. Apply the inner average prediction mode.

  As a result, the code amount after entropy coding does not easily exceed the maximum code amount. Furthermore, even if the code amount after entropy encoding exceeds the maximum code amount, it is replaced with I_PCM data by a simple decoding process limited to intra prediction. Accordingly, it is possible to perform an encoding process that can prevent the maximum code amount from being exceeded without requiring a redundant memory area and without performing reprocessing before the entropy encoding unit.

(Other embodiments according to the present invention)
Each means constituting the image coding apparatus according to the above-described embodiment of the present invention can be realized by operating a program stored in a RAM or ROM of a computer. This program and a computer-readable recording medium recording the program are included in the present invention.

  In addition, the present invention can be implemented as, for example, a system, apparatus, method, program, storage medium, or the like. Specifically, the present invention may be applied to a system including a plurality of devices. The present invention may be applied to an apparatus composed of a single device.

  In the present invention, a software program (in the embodiment, a program corresponding to the flowcharts shown in FIGS. 2 to 4) for executing each step in the above-described image encoding method is directly or remotely supplied to a system or apparatus. To do. And the case where it is achieved also by reading and executing the supplied program code by the computer of the system or apparatus is included.

  Therefore, since the functions of the present invention are implemented by computer, the program code installed in the computer also implements the present invention. In other words, the present invention includes a computer program itself for realizing the functional processing of the present invention.

  In that case, as long as it has the function of a program, it may be in the form of object code, a program executed by an interpreter, script data supplied to the OS, and the like.

  Various recording media can be used as a recording medium for supplying the program. For example, floppy (registered trademark) disk, hard disk, optical disk, magneto-optical disk, MO, CD-ROM, CD-R, CD-RW, magnetic tape, nonvolatile memory card, ROM, DVD (DVD-ROM, DVD- R).

  As another program supply method, a browser on a client computer is used to connect to an Internet home page. It can also be supplied by downloading the computer program itself of the present invention or a compressed file including an automatic installation function from a homepage to a recording medium such as a hard disk.

  It can also be realized by dividing the program code constituting the program of the present invention into a plurality of files and downloading each file from a different homepage. That is, the present invention includes a WWW server that allows a plurality of users to download a program file for realizing the functional processing of the present invention on a computer.

  In addition, the program of the present invention is encrypted, stored in a storage medium such as a CD-ROM, distributed to users, and key information for decryption is downloaded from a homepage via the Internet to users who have cleared predetermined conditions. Let It is also possible to execute the encrypted program by using the key information and install the program on a computer.

  In addition to the functions of the above-described embodiments being realized by the computer executing the read program, the OS running on the computer may perform part or all of the actual processing. The functions of the above-described embodiments can be realized.

  Further, the program read from the recording medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer. Thereafter, the CPU of the function expansion board or function expansion unit performs part or all of the actual processing based on the instructions of the program, and the functions of the above-described embodiments are realized by the processing.

DESCRIPTION OF SYMBOLS 100 Image coding apparatus 101 Prediction method determination part 102 Prediction process part 103 Memory 104 Orthogonal transformation and quantization part 105 Local decoding part 106 Entropy encoding part 106a Simple decoding process part 107 Multiplexing process part

Claims (9)

An image encoding device that encodes an input moving image by intra-screen prediction or inter-screen prediction,
When it is determined that the input moving image exceeds the predetermined code amount set in advance from the estimated code amount calculated before entropy encoding, it is switched to intra prediction and the code amount after entropy encoding is changed. An image characterized in that when a predetermined code amount is exceeded, a macroblock pixel is restored from the inputted predicted pixel value and transform coefficient, and the restored image data is replaced as data before the entropy coding Encoding device. An image encoding device that encodes an input moving image by intra-screen prediction or inter-screen prediction,
A prediction method determining unit that calculates an estimated code amount for each pixel block of a predetermined size and determines a prediction method based on the calculated estimated code amount;
Predictive coding is performed according to the prediction method determined by the prediction method determining means to generate a predicted image, orthogonal transform processing is performed on difference data between the predicted image and the encoding target image in the moving image, and quantum Predictive encoding means for performing the encoding process;
Entropy encoding means for performing entropy encoding on the prediction encoded data generated by the prediction encoding means,
The prediction method determining unit performs a first code amount comparison process for comparing the calculated estimated code amount with a first predetermined value, and the estimated code amount is a first predetermined code amount by the first code amount comparison process. If the value is exceeded, apply in-screen prediction as the prediction method,
The entropy encoding means performs a second code amount comparison process for comparing a code amount after entropy encoding with a second predetermined value, and when the code amount exceeds a second predetermined value, An image coding apparatus characterized by performing a replacement process of restoring a macroblock pixel from an input predicted pixel value and a transform coefficient and replacing the restored image data with I_PCM data.   The pixel block of the predetermined size is a macroblock composed of 16 × 16 pixels, and the estimated code amount is generated by an absolute value sum (SAD) of difference values generated by the motion prediction process or a motion prediction process. The image coding apparatus according to claim 2, wherein the difference is a sum of absolute values (SATD) of coefficients obtained by orthogonal transformation of the difference value.   The in-screen prediction applied when the estimated code amount calculated by the prediction method determining means exceeds a predetermined value is a prediction mode using an average value of predetermined pixels. The image encoding device described in 1.   The image coding apparatus according to any one of claims 2 to 4, wherein the image coding method is an MPEG-4 AVC method. An image encoding method for encoding an input moving image by intra-screen prediction or inter-screen prediction,
When it is determined that the input moving image exceeds the predetermined code amount set in advance from the estimated code amount calculated before entropy encoding, it is switched to intra prediction and the code amount after entropy encoding is changed. An image characterized in that when a predetermined code amount is exceeded, a macroblock pixel is restored from the inputted predicted pixel value and transform coefficient, and the restored image data is replaced as data before the entropy coding Encoding method. An image encoding method for encoding an input moving image by intra-screen prediction or inter-screen prediction,
A prediction method determining step of calculating an estimated code amount for each pixel block of a predetermined size and determining a prediction method based on the calculated estimated code amount;
Predictive coding is performed in accordance with the prediction method determined in the prediction method determination step to generate a prediction image, orthogonal transform processing is performed on difference data between the prediction image and an encoding target image in the moving image, and quantum A predictive encoding step for performing the encoding process;
An entropy encoding step for performing entropy encoding on the prediction encoded data generated in the prediction encoding step,
In the prediction method determining step, a first code amount comparison process for comparing the calculated estimated code amount with a first predetermined value is performed, and the estimated code amount is determined by the first code amount comparison process. If it exceeds the specified value, apply in-screen prediction as the prediction method,
In the entropy encoding step, a second code amount comparison process for comparing a code amount after entropy encoding with a second predetermined value is performed, and when the code amount exceeds a second predetermined value, An image encoding method comprising: performing a replacement process of restoring a macroblock pixel from an input predicted pixel value and a transform coefficient and replacing the restored image data with I_PCM data. A program for causing a computer to execute an image encoding method for encoding an input moving image by performing intra prediction or inter prediction.
When it is determined that the input moving image exceeds the predetermined code amount set in advance from the estimated code amount calculated before entropy encoding, it is switched to intra prediction and the code amount after entropy encoding is changed. An image encoding method for restoring a macroblock pixel from an input predicted pixel value and a transform coefficient when a predetermined code amount is exceeded and replacing the restored image data as data before the entropy coding A computer program that is executed by a computer.   A computer-readable storage medium storing the computer program according to claim 8.

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