JP2007158804A - Code amount controller, code amount control method and code amount control program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve processing time shortening required for code amount control in image encoding processing. <P>SOLUTION: A counter 105 measures a generated code amount for each block generated by an encoding part 104 and stores the generated code amount for each block. A generated code amount predicting part 106 extracts a typical block on the basis of the measured generated code amount for each block and determines quantization coefficients that are predicted to converge on a target code amount for the typical block. The generated code amount predicting part 106 predicts the total generated code amounts for the entire pixel area when generated code amounts for each block converge on the target code amount or less. Thus, quantization coefficient changing/requantization/reencoding are attempted only to the typical block to predict the total code amounts for the entire pixel area. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a code amount control device, a code amount control method, and a code amount control program for compressing and encoding a still image, and in particular, high-speed code amount control aimed at keeping a generated code amount below a target value. The present invention relates to an improvement in a possible code amount control apparatus and code amount control method.

  Conventionally, still picture encoding methods such as JPEG (Joint Photographics Experts Group) recommended by the International Organization for Standardization (ISO), the International Electrotechnical Commission (IEC), and the International Telecommunication Standardization Sector (ITU-T) are used. Many of these devices are distributed in the market, and many digital still cameras, digital video cameras, camera-equipped mobile phones, and the like have a still image shooting function using these encodings.

  In the apparatus as described above, a function for adjusting the code amount size of image data at the time of shooting / editing is indispensable due to the limitation due to the memory capacity of the recording device and the limitation due to the file size of the transmission system.

Patent Document 1 is known as a conventional technique capable of controlling the code amount at the time of shooting. According to this method, the generated code amount at the time of encoding is counted, and when the generated code amount does not fit in the target code amount, the quantization coefficient is changed and the data after DCT (Discrete Cosine Transform) is applied. Re-quantization / re-encoding is executed. For example, DCT / quantization / encoding is performed on the encoding target image, the quantization coefficient is changed using the count result of the code amount, and the requantization / recoding is performed on the DCT result. Code amount control is realized.
Japanese Patent Publication No. 8-32037

  However, such a conventional code amount control device has the following problems.

  In general, an increase in the number of pixels of still image data leads to an increase in the processing time of the entire encoding. Among them, there is a code amount control process that converges to the target code amount in the encoding process, but in the case of a code amount control process that repeats the encoding process several times until it converges to the target code amount, the percentage of the processing time of the entire encoding Is very big. In this case, the influence of the increase in the number of pixels of still image data on the code amount control processing time is also large, and reduction of the processing time in the code amount control processing is an essential matter.

  If the code amount does not fall within the target code amount, the quantization coefficient is changed and the re-quantization / re-encoding is repeated for all pixel regions. Will have adverse effects. Therefore, since re-quantization / re-encoding is repeatedly performed on all pixel regions, an increase in processing time due to an increase in the number of pixels is remarkable. There was a problem of being subject to claims.

  The present invention has been made in view of the above points, and a code amount control device, an image encoding device, a code amount control method, and a code amount control program capable of reducing the time required for code amount control in image encoding processing. The purpose is to provide.

  The code amount control apparatus of the present invention includes an orthogonal transform unit that performs orthogonal transform on an encoding target image, a quantization unit that quantizes an output result of the orthogonal transform unit using a quantization coefficient, An encoding unit that assigns a predetermined code to a value quantized by the quantizing unit to obtain encoded data; a measuring unit that measures a generated code amount for each block generated by the encoding unit; Representative block extracting means for extracting a representative block based on the generated code quantity, a generated code quantity predicting means for determining a quantized coefficient predicted to converge to a target code quantity for the representative block, and A quantization coefficient control unit that sets the quantization coefficient determined by the generated code amount prediction unit in the quantization unit, and the measurement unit sets the generated code amount for each block to be equal to or less than the target code amount. If you bundle, and outputs the coded data as the final encoding result, the generated code quantity predicting means has a configuration to predict the total amount of generated code for the entire pixel area.

  The code amount control apparatus of the present invention includes a decoding unit that decodes input encoded data, and dequantizes the data decoded by the decoding unit using a quantization coefficient. Inverse quantization means, quantization means for quantizing using a quantization coefficient, encoding means for assigning a predetermined code to a value quantized by the quantization means to obtain encoded data, and the encoding means Measuring the generated code amount for each block generated by the above, or measuring means for measuring the generated code amount for each block with respect to the input encoded data, and the representative based on the measured generated code amount for each block A representative block extracting means for extracting a block, a generated code quantity predicting means for determining a quantized coefficient predicted to converge to a target code quantity for the representative block, and the generated code quantity predicting means Quantizing coefficient control means for setting the determined quantizing coefficient in the quantizing means, and when the generated code amount for each block converges below the target code amount, the measuring means finalizes the encoded data. The generated code amount predicting means outputs a result of encoding, and adopts a configuration for predicting the total generated code amount for all pixel regions.

  The code amount control method of the present invention includes a step of performing orthogonal transformation on an encoding target image, a step of quantizing an output result of the orthogonal transformation using a quantization coefficient, and a predetermined value for the quantized value. A step of outputting encoded data by assigning a code of the step, a step of measuring a generated code amount for each generated block, a step of extracting a representative block based on the generated generated code amount for each block, and For the representative block, a step of determining a quantized coefficient predicted to converge to the target code amount and a step of setting the determined quantized coefficient in the quantizing means are executed, and the generated code amount for each block Is converged below the target code amount, the encoded data is output as the final encoding result, and the total generated code amount for all pixel regions is predicted.

  The code amount control method of the present invention includes a step of decoding input encoded data, a step of inversely quantizing the decoded data using a quantization coefficient, and a quantization coefficient Using the quantization step, assigning a predetermined code to the quantized value to obtain encoded data, measuring the generated code amount for each generated block, or for the input encoded data The step of measuring the generated code amount for each block, the step of extracting a representative block based on the generated generated code amount for each block, and the representative block are predicted to converge to the target code amount. The step of determining the quantization coefficient and the step of setting the determined quantization coefficient in the quantization means are executed, and the generated code amount for each block converges to the target code amount or less. If, and outputs the coded data as the final encoding result, to predict the total amount of generated code for the entire pixel area.

  From another viewpoint, the present invention is a program for causing a computer to execute the steps of the code amount control method.

  According to the present invention, a representative block is extracted from the generated code amount for each block, and quantization coefficient change / requantization / recoding is attempted only for the representative block, By predicting the total code amount, the total processing time until the code amount control converges can be shortened, and the processing time required for the code amount control can be shortened. Thereby, even when the size of the encoding target image increases, it is possible to minimize an increase in the processing time of the code amount control.

  In addition, at the time of re-encoding, by measuring the generated code amount for each block with respect to the input encoded data, the encoding process for the first all pixel regions becomes unnecessary and the code amount control converges. The total processing time up to 1 can be shortened, and the processing time required for re-encoding the decoded image can be shortened.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of a code amount control apparatus according to Embodiment 1 of the present invention. The code amount control apparatus according to the present embodiment is an example applied to an image data encoding apparatus that compresses and encodes still image data.

  1, the code amount control apparatus 100 includes an orthogonal transform unit 101, an orthogonal transform coefficient memory 102, a quantization unit 103, an encoding unit 104, a counter 105, a generated code amount prediction unit 106, and a quantization coefficient change unit 107. It is prepared for.

  The orthogonal transform unit 101 performs orthogonal transform on the input image to be encoded and stores the orthogonal transform result in the orthogonal transform coefficient memory 102. Orthogonal transformation includes, for example, DCT.

  The quantization unit 103 performs quantization on the orthogonal transformation result stored in the orthogonal transformation coefficient memory 102 based on the quantization coefficient set by the quantization coefficient changing unit 107.

  Encoding section 104 encodes the output result of quantization section 103 and outputs encoded data. Examples of encoding include Huffman encoding and run-length encoding.

  The counter 105 measures the generated code amount for each block generated by the encoding unit 104 and holds the generated code amount for each block. In other words, the counter 105 counts the code amount of the encoded data, and monitors the generated code amount based on the designated target code amount.

  The generated code amount prediction unit 106 determines a quantization coefficient to be used at the time of re-encoding for the purpose of code amount control, based on the generated code amount for each block counted by the counter 105. In particular, the generated code amount prediction unit 106 extracts a representative block based on the measured generated code amount for each block, and determines a quantization coefficient predicted to converge to the target code amount for the representative block. . Also, the generated code amount prediction unit 106 predicts the total generated code amount for all pixel regions when the generated code amount for each block converges to the target code amount or less.

  The quantization coefficient changing unit 107 sets the quantization coefficient designated by the generated code amount prediction unit 106 for the quantization unit 103.

  Hereinafter, the code amount control operation of the code amount control apparatus configured as described above will be described.

  The encoding amount control apparatus 100 receives an encoding target image that is an encoding target. The orthogonal transform unit 101 performs orthogonal transform on the input encoding target image, and stores an orthogonal transform result for one frame of image data in the orthogonal transform coefficient memory 102. The quantization unit 103 quantizes the orthogonal transformation result stored in the orthogonal transformation coefficient memory 102, and the quantized result is encoded by the encoding unit 104 and outputs encoded data. At the same time, the counter 105 counts the code amount of the encoded data, and monitors the generated code amount based on the designated target code amount. The counter 105 holds a generated code amount for each block. In the present embodiment, the counter 105 monitors the generated code amount so as to be less than or equal to the target code amount by the code amount count, but monitors so that it exceeds the specified target code amount and is close to the target code amount. An aspect may be sufficient.

  When the generated code amount converges below the target code amount, the encoded data is output as the final encoding result.

  When the generated code amount does not converge below the target code amount, the generated code amount prediction unit 106 uses the generated code amount for each block counted by the counter 105 to perform quantization used for re-encoding for the purpose of code amount control. Determine the coefficient.

  FIG. 2 is a diagram showing a histogram of the generated code amount for each block. The generated code amount for each block used by the generated code amount prediction unit 106 to predict the generated code amount is made into a histogram for each size.

The generated code amount prediction unit 106 determines representative blocks B0 to Bn (n is an arbitrary natural number) for each code amount size based on the histogram of the generated code amount for each block. Here, when the code amount sizes in the representative blocks B0 to Bn are X0 to Xn and the number of blocks is Z0 to Zn, the following equation (1) holds.
Generated code amount ≒ X0 x Z0 + X1 x Z1 + ... + Xn x Zn (1)

Next, when the code amount size is Y0 to Yn when quantization / encoding is performed on the representative blocks B0 to Bn using arbitrary quantization coefficients, the following calculation formula (2) is used. The generated code amount is predicted.
Predicted code amount = Y0 × Z0 + Y1 × Z1 +... + Yn × Zn (2)

  The generated code amount prediction unit 106 compares the predicted code amount with the target code amount, and determines a quantization coefficient that is predicted to converge to the target code amount.

  Finally, the quantization coefficient changing unit 107 sets the quantization coefficient designated by the generated code amount prediction unit 106 for the quantization unit 103 and prepares for re-encoding processing for the purpose of code amount control. Thereafter, the encoding process / code amount control process is repeated. With the above processing, the processing time required for code amount control can be reduced.

  FIG. 3 is a flowchart showing a code amount control method of the code amount control apparatus 100, where S indicates each step of the flow.

  First, an encoding target image is input in step S1, and orthogonal transformation processing is performed on the encoding target image input in step S2. Next, the result of the orthogonal transformation process is stored in the orthogonal transformation coefficient memory 102 in step S3.

  Next, in step S4, a quantization process is performed on the result of the orthogonal transform process, and in step S5, an encoding process is performed on the quantization process result. At the same time, the generated code amount is counted in step S6, and the generated code amount is compared with the target code amount in step S7. When the generated code amount exceeds the target code amount (generated code amount> target code amount), the generated code amount is predicted in step S8 in order to perform code amount control for keeping the generated code amount below the target value, and in step S9 In step S4, the quantization coefficient used for re-encoding for the purpose of code amount control is determined, and the process returns to step S4. In the case of this re-encoding process, the quantization coefficient is changed by predicting the total generated code quantity when the quantization coefficient is changed from the generated code quantity for each block.

  If the target code amount is equal to or greater than the generated code amount (generated code amount ≦ target code amount), it is determined in step S10 that the output of the encoding result and the encoding have been completed, and the encoded data is output in step S10, and this flow ends. . Thereafter, the encoding process / code amount control process is repeated until the end of the encoding process.

  As described above, according to the first embodiment, a representative block is extracted from the generated code amount for each block held in the counter 105, and the quantization coefficient is changed / requantized / requantized only for the representative block. Since re-encoding is attempted and the total code amount for all pixel regions is predicted, the total processing time until the code amount control converges compared to the conventional example in which re-quantization / re-encoding is repeated for all pixel regions. Can be significantly shortened, and even when the size of the encoding target image is increased, an increase in the processing time of the code amount control can be minimized.

  In this embodiment, the orthogonal transform coefficient memory 102 that stores the orthogonal transform coefficients for one frame of image data reduces the orthogonal transform processing time during re-encoding. A device that starts the re-encoding process from the encoding target image without using it may be used.

  The code amount control device 100 can be incorporated as an image encoding device of a mobile terminal, for example, and can also be realized as a mobile communication system equipped with such a mobile terminal.

(Embodiment 2)
FIG. 4 is a block diagram showing the configuration of the code amount control apparatus according to Embodiment 2 of the present invention. In the description of the present embodiment, the same components as those in FIG.

  In FIG. 4, the code amount control apparatus 200 replaces the orthogonal transform unit 101 that orthogonally transforms the encoding target image in FIG. 1, a decoding unit 201 that decodes / dequantizes encoded data, and an inverse quantization unit 202. It is the composition provided with.

  The counter 203 has the same function as the counter 105 of FIG. 1 that measures the generated code amount for each block generated by the encoding unit 104, and further generates the generated code amount for each block with respect to the input encoded data. Measure.

  The decoding unit 201 decodes encoded data. The inverse quantization unit 202 performs an inverse quantization process on the decoded data output from the decoding unit 201.

  The encoded data is decoded by the decoding unit 201, and an inverse quantization process is performed on the decoded data by the inverse quantization unit 202. The inversely quantized data is stored in the orthogonal transform coefficient memory 102 and used as input data for re-encoding processing for the purpose of code amount control.

  Simultaneously with the decoding, the counter 203 counts the code amount of the encoded data and holds the generated code amount for each block. The generated code amount prediction unit 106 determines a quantization coefficient to be used at the time of re-encoding for the purpose of code amount control, based on the generated code amount for each block counted by the counter 203. Since the quantization coefficient determination method overlaps with the description in Embodiment 1, it is omitted here.

  Next, the quantization coefficient changing unit 107 sets the quantization coefficient designated by the generated code amount prediction unit 106 to the quantization unit 103 and prepares for re-encoding processing for the purpose of code amount control. Thereafter, the encoding process / code amount control process is repeated. With the above processing, the processing time required for code amount control can be reduced.

  Hereinafter, the code amount control operation of the code amount control apparatus configured as described above will be described.

  FIG. 5 is a flowchart showing a code amount control method of the code amount control apparatus 200. Steps that perform the same processing as in FIG. 3 are assigned the same step numbers, and description of overlapping portions is omitted.

  First, encoded data is input in step S11, and the generated code amount is counted for the encoded data input in step S12. At the same time, a decoding process is performed on the encoded data input in step S13, and an inverse quantization process is performed in step S14. Next, the result of the inverse quantization process is stored in the orthogonal transform coefficient memory 102 in step S15. In step S16, the generated code amount is predicted by the method described in the first embodiment. In step S17, a quantization coefficient used for re-encoding for the purpose of code amount control is determined, and the process proceeds to step S4. Thereafter, the encoding process / code amount control process is repeated until the end of the encoding process.

  As described above, according to the second embodiment, at the time of re-encoding, first, the encoding process for the first all pixel regions is performed by measuring the generated code amount for each block of the input encoded data. Therefore, in addition to the effects described in the first embodiment, the processing time required for the re-encoding process of the decoded image can be shortened.

  Further, the code amount control apparatus 200 can be incorporated as an image encoding apparatus of a mobile terminal, for example, and can also be realized as a mobile communication system equipped with such a mobile terminal.

  The above description is an illustration of a preferred embodiment of the present invention, and the scope of the present invention is not limited to this.

  In each of the above-described embodiments, description has been made assuming a use such as a digital video camera. However, for example, it can be implemented as a coding method for a TV phone terminal.

  Further, the present invention can be applied to any apparatus as long as it is an electronic apparatus having a code amount control apparatus and method. For example, it can also be applied to devices equipped with a camera (built-in / external) such as digital cameras, mobile phone devices with cameras, portable information terminals such as PDAs (Personal Digital Assistants), and information processing devices such as personal computers. is there. Further, the image to be encoded may be any image data.

  In the above embodiments, the names of the code amount control device and the code amount control method are used. However, this is for convenience of explanation, and an image data compression device, an image encoding method, a mobile communication system, and the like may be used. Of course.

  Moreover, it goes without saying that the histogram of the generated code amount for each block shown in FIG. 2 is an example and may be another example.

  The type, number, connection method, and the like of each circuit unit constituting the code amount control apparatus for the image are not limited to the above-described embodiments.

  The code amount control apparatus and method described above are also realized by a program for causing the code amount control apparatus and the code amount control method to function. This program is stored in a computer-readable recording medium.

  The code amount control apparatus and method according to the present invention is suitable for use in an apparatus and method for compressing and recording still images, such as a digital video camera capable of taking a still image and a camera-equipped mobile phone. In particular, the present invention is useful as a device that can execute code amount control aimed at keeping the generated code amount below a target value at high speed. Further, it can be incorporated into an electronic apparatus such as an image processing apparatus as a code amount control program.

1 is a block diagram showing a configuration of a code amount control apparatus according to Embodiment 1 of the present invention. Explanatory drawing which shows the histogram of the generated code amount according to block which concerns on Embodiment 1. FIG. FIG. 7 is a flowchart showing processing of the code amount control method according to the first embodiment. The block diagram which shows the structure of the code amount control apparatus which concerns on Embodiment 2 of this invention. FIG. 9 is a flowchart showing processing of a code amount control method according to the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100,200 Code amount control apparatus 101 Orthogonal transformation part 102 Orthogonal transformation coefficient memory 103 Quantization part 104 Encoding part 105,203 Counter 106 Generated code quantity prediction part 107 Quantization coefficient change part 201 Decoding part 202 Dequantization part

Claims (7)

Orthogonal transform means for performing orthogonal transform on the encoding target image;
Quantization means for quantizing the output result of the orthogonal transform means using a quantization coefficient;
Encoding means for assigning a predetermined code to the value quantized by the quantization means to obtain encoded data;
Measuring means for measuring the amount of generated code for each block generated by the encoding means;
Representative block extraction means for extracting a representative block based on the measured code amount for each block;
For the representative block, generated code amount prediction means for determining a quantized coefficient predicted to converge to a target code amount;
A quantization coefficient control unit that sets the quantization coefficient determined by the generated code amount prediction unit in the quantization unit;
When the generated code amount for each block converges below the target code amount, the measuring unit outputs encoded data as a final encoding result, and the generated code amount predicting unit calculates the total generated code amount for all pixel regions. A code amount control device for prediction. Decoding means for decoding input encoded data;
Inverse quantization means for inversely quantizing the data decoded by the decoding means using a quantization coefficient;
A quantization means for performing quantization using a quantization coefficient;
Encoding means for assigning a predetermined code to the value quantized by the quantization means to obtain encoded data;
Measuring the generated code amount for each block generated by the encoding means, or measuring means for measuring the generated code amount for each block with respect to the input encoded data;
Representative block extraction means for extracting a representative block based on the measured code amount for each block;
For the representative block, generated code amount prediction means for determining a quantized coefficient predicted to converge to a target code amount;
A quantization coefficient control unit that sets the quantization coefficient determined by the generated code amount prediction unit in the quantization unit;
When the generated code amount for each block converges below the target code amount, the measuring unit outputs encoded data as a final encoding result, and the generated code amount predicting unit calculates the total generated code amount for all pixel regions. A code amount control device for prediction.   3. The code amount control apparatus according to claim 2, wherein the measurement unit initially measures a generated code amount for each block with respect to input encoded data. Performing orthogonal transform on the encoding target image;
Quantizing the output result of the orthogonal transform using a quantization coefficient;
Assigning a predetermined code to the quantized value and outputting encoded data;
Measuring a generated code amount for each generated block;
Extracting a representative block based on the generated code amount for each block;
Determining a quantization coefficient predicted to converge to a target code amount for the representative block;
Performing the step of setting the determined quantization coefficient in the quantization means;
A code amount control method for outputting encoded data as a final encoding result and predicting a total generated code amount for all pixel regions when a generated code amount for each block converges to the target code amount or less. Decoding input encoded data; and
Dequantizing the decoded data using quantization coefficients;
Quantizing using a quantization coefficient;
Assigning a predetermined code to the quantized value to obtain encoded data;
Measuring a generated code amount for each generated block, or measuring a generated code amount for each block with respect to input encoded data;
Extracting a representative block based on the generated code amount for each block;
Determining a quantization coefficient predicted to converge to a target code amount for the representative block;
Performing the step of setting the determined quantization coefficient in the quantization means;
A code amount control method for outputting encoded data as a final encoding result and predicting a total generated code amount for all pixel regions when a generated code amount for each block converges to the target code amount or less.   Performing orthogonal transformation on the encoding target image, quantizing the output result of the orthogonal transformation using a quantization coefficient, assigning a predetermined code to the quantized value, A step of outputting, a measuring step of measuring a generated code amount for each generated block, a step of extracting a representative block based on the measured generated code amount of each block, and a target code for the representative block A generated code amount prediction step for determining a quantized coefficient that is predicted to converge to a quantity, and a step for setting the determined quantized coefficient in the quantizing means; and in the measuring step, a generated code for each block When the amount converges below the target code amount, the encoded data is output as a final encoding result. In the generated code amount prediction step, the total amount for all pixel regions is output. Program for executing a step of predicting a raw code amount to the computer. Decoding the input encoded data, dequantizing the decoded data using a quantization coefficient, quantizing using the quantization coefficient, A step of assigning a predetermined code to the converted value to obtain encoded data, and measuring the generated code amount for each generated block, or measuring the generated code amount for each block with respect to the input encoded data A step of extracting a representative block based on the measured generated code amount for each block, and a generated code for determining a quantized coefficient predicted to converge to a target code amount for the representative block An amount prediction step and a step of setting the determined quantization coefficient in the quantization means, and in the measurement step, the generated code amount for each block is the target code amount. If it converged below, and outputs the encoded data as the final encoding result, and in the generated code quantity predicting step, a program for executing the steps of predicting the total generated code amount for the entire pixel area to the computer.

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