JP2015186120A - Encoding method conversion apparatus and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a frequency at which a code amount more than necessity is consumed for making an image close to that including quantization distortion by a first encoding method and to improve encoding efficiency.SOLUTION: An encoding method conversion apparatus for converting an input stream of an image encoded by a first encoding method into a stream of an image encoded by a second encoding method includes: decoding means for decoding the image of the input stream by the first encoding method; encoding means for encoding a decoded image decoded by the decoding means by the second encoding method; and quantization parameter control means for referring to a first quantization parameter obtained by decoding with the decoding means and adjusting a second quantization parameter on encoding by the second encoding method.

Description

  The present invention relates to an encoding method conversion apparatus and program, and is particularly applicable to an encoding method conversion apparatus and program for transcoding video streams having different encoding methods.

  For example, MPEG-2 and H.264 standardized by the Moving Picture Experts Group (MPEG). The compression coding processing of video information by a video coding method represented by H.264 / MPEG-4 AVC (Advanced Video Coding: hereinafter also referred to as AVC) is performed for each processing unit obtained by dividing the input target image. The prediction residual signal, which is the difference between the predicted image subjected to motion compensation prediction and the input target image, is quantized with a transform coefficient obtained by performing spatial transformation such as discrete cosine transformation, and this is entropy-coded. This realizes highly efficient video compression.

  In recent years, in order to achieve higher image quality and higher compression efficiency, H.C. H.265 / MPEG-H HEVC (High Efficiency Video Coding: hereinafter also referred to as HEVC) is defined.

  These various video encoding methods are used in a mixed manner, and a transcoding technique for video streams with different encoding methods is required.

  In the case of conversion to a video stream with a different encoding method, a method is generally used in which a stream according to the first encoding method as an input is decoded, and the encoded image is used as an input to perform encoding according to the second encoding method (see FIG. 3).

  As a method for efficiently performing such transcoding, for example, Patent Document 1 discloses a method of performing encoding by a second encoding method using motion vector information obtained from a stream by the first encoding method. Has been.

JP 2003-309851 A

  However, when performing the encoding process according to the second encoding method using the decoded image according to the first encoding method as an input image, the decoded image according to the first encoding method includes quantization distortion due to quantization, The video deteriorated from the original video before encoding by the first encoding method is encoded.

  In such a case, when encoding by the second encoding method, even if a large amount of code is used so as to reduce the quantization distortion as in normal encoding processing, the first encoding method is used. Just approaching an image containing quantization distortion does not necessarily improve the image quality of the original image.

  Therefore, there is a need for an encoding method conversion apparatus and program that can reduce the amount of code more than is necessary to approximate an image including quantization distortion by the first encoding method and improve the encoding efficiency. It has been.

  The present invention has been made to solve the above-described problems, and has the following configuration.

  According to a first aspect of the present invention, there is provided an encoding method conversion apparatus for converting an input stream of an image encoded by the first encoding method into an image stream encoded by the second encoding method. Decoding means for decoding the image of the input stream by the first encoding method; (2) encoding means for encoding the decoded image decoded by the decoding means by the second encoding method; and (3) decoding means. And a quantization parameter control means for adjusting a second quantization parameter related to encoding by the second encoding method with reference to the first quantization parameter obtained by decoding by This is a conversion method conversion device.

  According to a second aspect of the present invention, there is provided an encoding method conversion apparatus for converting an input stream of an image encoded by the first encoding method into an image stream encoded by the second encoding method. Decoding means for decoding the image of the input stream by the first encoding method; (2) encoding means for encoding the decoded image decoded by the decoding means by the second encoding method; and (3) encoding. The first quantization obtained by decoding the Lagrangian multiplier related to the rate distortion optimization processing determined based on the second quantization parameter relating to the encoding by the second encoding method used in the means A coding method conversion apparatus comprising: a Lagrange multiplier control unit that adjusts with reference to a parameter.

  According to a third aspect of the present invention, there is provided an encoding method conversion program for converting an input stream of an image encoded by the first encoding method into an image stream encoded by the second encoding method. (1) Decoding means for decoding an image of the input stream by the first encoding method, (2) Encoding means for encoding the decoded image decoded by the decoding means by the second encoding method, (3) Decoding The first quantization parameter obtained by the decoding by the means is referred to function as a quantization parameter control means for adjusting the second quantization parameter related to the encoding by the second encoding method. It is an encoding system conversion program.

  According to the present invention, it is possible to reduce the amount of code that is more than necessary in order to approach an image including quantization distortion by the first encoding method, and to improve encoding efficiency.

It is a block diagram which shows the structure of the encoding system converter which concerns on 1st Embodiment. It is a block diagram which shows the structure of 1 A of encoding system converters which concern on 2nd Embodiment. It is a block diagram which shows the structure of the conventional encoding system converter.

(A) 1st Embodiment Below, the 1st Embodiment of the encoding system converter and program which concern on this invention are described in detail, referring drawings.

(A-1) Configuration of First Embodiment FIG. 1 is a block diagram showing a configuration of a coding method conversion apparatus 1 according to the first embodiment. The encoding method conversion apparatus 1 according to the first embodiment may be configured as hardware such as a dedicated IC chip mounted with each unit, or configured as software centered on a program executed by the CPU. Functionally, it can be represented functionally in FIG.

  In FIG. 1, the coding method conversion apparatus 1 according to the first embodiment includes a decoding unit 11, an encoding unit 12, and a quantization parameter control unit 111.

  The encoding method conversion apparatus 1 decodes an input stream encoded by the first encoding method using the first encoding method, and encodes a decoded image obtained by the decoding using the second encoding method. In this way, an image obtained by converting the encoding method is output as an output stream.

  Here, the first encoding method and the second encoding method can be various video encoding methods, for example, MPEG-2, H.264, and the like. H.264 / MPEG-4 AVC, H.264. Any one of H.265 / MPEG-H HEVC and the like can be applied. Note that the first encoding method and the second encoding method may be different types of encoding methods or the same type of encoding method.

  The decoding unit 11 entropy-decodes the input stream encoded by the first encoding method using the first encoding method, generates a decoded image, and gives the decoded image to the encoding unit 12. The decoding unit 11 gives the quantization parameter of the coding unit obtained by entropy decoding to the quantization parameter control unit 111.

  As illustrated in FIG. 1, the decoding unit 11 includes an entropy decoding unit 101, an inverse quantization unit 102, an inverse transformation unit 103, a predicted image generation unit 104, and an addition unit 112.

  The entropy decoding unit 101 performs entropy decoding on the input stream that is input, and obtains transform coefficients, encoding mode information, motion vector information, and the like for each encoding processing unit. Also, the entropy decoding unit 101 gives the quantization parameter obtained by decoding to the inverse quantization unit 102.

  Here, when the encoding method (first encoding method) of the input stream is MPEG-2, the entropy decoding unit 101 can apply a Huffman encoding method or the like. In this case, the entropy decoding unit 101 obtains transform coefficients of 8 × 8 discrete cosine transform, 16 × 16 block or 8 × 8 block inter prediction information, and the like.

  When the encoding method of the input stream is AVC, the entropy decoding unit 101 can apply a context adaptive variable length coding method (CAVLC), a context adaptive arithmetic coding method (CABAC), or the like. Integer coefficient of either block size of x4 or 8x8, predicted in 9 modes with 4x4 blocks, 9 types with 8x8 blocks, and 4 types with 16x16 blocks Intra prediction information, inter prediction information in which motion is predicted in any of seven types of 16 × 16 modes, and the like are acquired.

  Furthermore, when the encoding method of the input stream is HEVC, the entropy decoding unit 101 can apply a context-applied arithmetic coding method (CABAC) or the like, and the entropy decoding unit 101 can select any block of 4 × 4 to 32 × 32 Integer coefficient of size, intra prediction information predicted in any one of 35 modes of 4 × 4 to 64 × 64 blocks, and inter prediction information predicted motion in any of 8 × 4/4 × 8 to 64 × 64 Etc.

  The entropy decoding unit 101 supplies the quantization parameter for each encoding processing unit to the quantization parameter control unit 111 as the first quantization parameter.

  Here, the quantization parameter will be briefly described. For example, when the first encoding method is MPEG-2, an encoder that encodes an image performs an encoding process on an image constituting an image in a predetermined encoding process unit. At this time, the encoder calculates a difference between the input image and a predicted image obtained by processing such as motion compensation prediction, and performs spatial transformation such as discrete cosine on the generated prediction residual signal, A set of transform coefficients is obtained by the spatial transform. The encoder quantizes the transform coefficient in order to reduce the amount of information to be encoded. Quantization means to scale a transform coefficient at a predetermined quantization step and then discretize the scaled transform coefficient to a predetermined level value (integer value). An index for determining this quantization step is quantized. This is called a parameter.

  The quantization parameter represents the quantization step size in the case of MPEG-2 or the like, and indicates a value proportional to the logarithm of the quantization step size in the case of AVC or HEVC.

  The entropy decoding unit 101 extracts a quantization parameter for each coding processing unit obtained by entropy decoding, and supplies the quantization parameter for the coding processing unit to the quantization parameter control unit 111 as a first quantization parameter. To do.

  The inverse quantization unit 102 inversely quantizes the transform coefficient decoded by the entropy decoding unit 101 according to a quantization parameter.

  The inverse transform unit 103 performs inverse transform (such as inverse discrete cosine transform) on the inversely quantized transform coefficient to generate a residual image.

  The prediction image generation unit 104 generates a prediction image by performing motion compensation, intra prediction, and the like on the residual image inversely converted by the inverse conversion unit 103.

  The addition unit 112 adds the predicted image and the residual image from the inverse transform unit 103 in the predicted image generation unit 104 to generate a decoded image. The adding unit 112 outputs the generated decoded image to the encoding unit 12.

  The encoding unit 12 outputs an encoded image obtained by encoding the decoded image decoded by the decoding unit 11 using the second encoding method as an output stream.

  In FIG. 1, the encoding unit 12 includes a conversion unit 105, a quantization unit 106, an entropy encoding unit 107, an inverse quantization unit 108, an inverse conversion unit 109, a predicted image generation unit 110, a subtraction unit 113, and an addition unit 114. .

  The subtraction unit 113 obtains a prediction residual signal that is a difference between a prediction image generated by performing motion compensation prediction or intra prediction in the prediction image generation unit 110 and an input decoded image for each encoding processing unit. It is.

  The conversion unit 105 performs spatial conversion such as discrete cosine on the video information from the subtraction unit 113.

  The quantization unit 106 quantizes the transform coefficient obtained by the spatial transform by the transform unit 105 according to the second quantization parameter controlled by the quantization parameter control unit 111. The quantization unit 106 provides the quantized variable coefficient to the entropy encoding unit 107 and the inverse quantization unit 108.

  The inverse quantization unit 108 performs inverse quantization on the quantized variable coefficient from the quantization unit 106 in accordance with the second quantization parameter.

  The inverse transform unit 109 performs inverse transform (such as inverse discrete cosine transform) on the transform coefficient inversely quantized by the inverse quantization unit 108 to generate a residual image.

  The predicted image generation unit 110 generates a predicted image by performing motion compensation prediction, intra prediction, or the like. The predicted image generation unit 110 gives the generated predicted image to the subtraction unit 113 and the addition unit 114.

  The addition unit 114 adds the prediction image generated by the prediction image generation unit 110 and the residual image from the inverse conversion unit 103, and decodes the output stream by the decoder of the second encoding method. The obtained decoded image is generated. The generated decoded image is given to the predicted image generation unit 110 as a reference image for the encoding process.

  The entropy encoding unit 107 encodes the quantized transform coefficient from the quantization unit 106 using a predetermined entropy encoding method, and outputs it together with the motion vector information and prediction mode information used by the prediction image generation unit 110. Output as a stream.

  As the predetermined entropy encoding method, when the second encoding method is MPEG-2, a Huffman encoding method or the like can be applied. In addition, when the second encoding scheme is AVC, a context adaptive variable length encoding scheme (CAVLC), a context adaptive arithmetic encoding scheme (CABAC), or the like can be applied. Furthermore, when the second encoding scheme is HEVC, a context-applied arithmetic encoding scheme (CABAC) or the like can be applied.

  The quantization parameter control unit 111 acquires the first quantization parameter from the entropy decoding unit 101 and the second quantization parameter related to the second encoding method applied by the encoding unit 12, and performs the first quantization. With reference to the parameter, control is performed so that the value of the second quantization parameter does not become smaller than necessary.

  Here, the second quantization parameter is used in the second encoding method that is the conversion destination of the encoding method, and can be supplied from, for example, a rate control unit that controls the bit rate of the output stream. May be.

(A-2) Operation of the First Embodiment Next, the operation of the coding method conversion apparatus 1 according to the first embodiment will be described in detail with reference to FIG.

  First, in FIG. 1, a stream encoded by the first encoding method is input to the decoding unit 11. In the decoding unit 11, the entropy decoding unit 101 performs entropy decoding on the input stream, and for example, transform coefficients such as discrete cosine transform, encoding mode information, motion vector information, and the like are acquired.

  The transform coefficient obtained by the entropy decoding unit 101 is generated by performing inverse quantization / inverse transform by the inverse quantization unit 102 / inverse transform unit 103 and performing motion compensation or intra prediction by the predicted image generation unit 104. The decoded image is obtained by adding the predicted image.

  The decoded image obtained by the adding unit 112 is supplied to the encoding unit 12 as an image to be encoded by the second encoding method, and is also supplied to the predicted image generation unit 104 as a reference image for subsequent input stream decoding processing. Supplied.

  In the decoding unit 11, the entropy decoding unit 101 decodes the quantization parameter used in the inverse quantization unit 102, and the quantization parameter for each encoding processing unit is supplied to the quantization parameter control unit 111 as the first quantization parameter. Is done.

  In the quantization parameter control unit 111, for example, a second quantization parameter is set from a rate control unit (not shown) or the like for encoding by the second encoding method.

  Here, the first quantization parameter obtained from the entropy decoding unit 101 serves as an index of how much quantization error the decoded image contains. Even if the second quantization parameter is made smaller than necessary, quantization is performed. It only works in a direction to reproduce a decoded image including an error more faithfully, and does not necessarily approach an original video before encoding by the first encoding method.

  That is, quantization is performed in order to reduce the amount of code when encoding with the second encoding method. When the quantization parameter value is decreased, the distortion of the decoded image is decreased, but the code amount is increased. Conversely, when the quantization parameter value is increased, the distortion of the decoded image increases, but the code amount can be reduced. Therefore, in order to improve the image quality of the decoded image, the value of the quantization parameter is reduced. However, if the value of the second quantization parameter is too small as necessary, it does not approach the original video, and on the other hand, the amount of code increases, resulting in a decrease in coding efficiency and a change in coding method conversion. Processing load increases.

  Therefore, the quantization parameter control unit 111 refers to the first quantization parameter and performs control to limit the second quantization parameter so that the value does not increase.

  For example, the quantization parameter control unit 111 may simply limit the value of the second quantization parameter so that the first quantization parameter becomes the lower limit value or near the lower limit value. . As a result, it is possible to reduce the amount of code in the second encoding scheme while maintaining the same image quality as the decoded image decoded in the first encoding scheme.

  Further, for example, the quantization parameter control unit 111 uses a predetermined function equation according to the magnitude of the value of the first quantization parameter, and the value of the second quantization parameter is the first quantization parameter. You may correct | amend so that it may approach a value.

  As described above, the quantization parameter is the quantization step size when the encoding method is MPEG-2 or the like, and is a value proportional to the quantization step size when the encoding method is AVC or HEVC. The types of quantization parameters are different. Therefore, the quantization parameter control unit 111 performs conversion processing so that the first quantization parameter and the second quantization parameter are the same type of parameters.

  For example, when the first encoding method is MPEG-2 and the second encoding method is HEVC, the quantization parameter control unit 111 sets the quantization step size, which is the first quantization parameter, to the quantization step size. It may be converted to a value proportional to the logarithm of the conversion step size. Conversely, when the first encoding method is AVC and the second encoding method is MPEG-2, the quantization parameter control unit 111 calculates the logarithm of the quantization step size that is the first quantization parameter. May be converted into a quantization step size. As a result, the first quantization parameter and the second quantization parameter can be the same type of parameter.

  Further, when the block size is different between the first encoding method and the second encoding method, the quantization parameter control unit 111 may perform block size conversion processing. Thereby, the value of the quantization parameter at the corresponding position in the converted block size can be obtained.

  In the encoding unit 12, the decoded image from the decoding unit 11 is input as an encoding target image.

  In the encoding unit 12, the subtraction unit 113 performs the difference between the prediction image generated by performing the motion compensation prediction or the intra prediction on the prediction image generation unit 110 and the input decoded image for each processing unit. A prediction residual signal is obtained.

  The prediction residual signal from the subtraction unit 113 is subjected to spatial transformation such as discrete cosine transformation by the transformation unit 105, and a set of transformation coefficients is obtained by the spatial transformation.

  In the quantization unit 106, the transform coefficient is quantized according to the second quantization parameter for each encoding processing unit controlled by the quantization parameter control unit 111.

  The quantized transform coefficient is subjected to predetermined entropy coding using, for example, a variable length code or an arithmetic code by the entropy coding unit 107. The entropy-encoded information is output as an output stream together with the motion vector information and the prediction mode information used in the predicted image generation unit 110.

  The transform coefficient quantized by the quantization unit 106 is inversely quantized and inversely transformed by the inverse quantization unit 108 and the inverse transform unit 109. The inversely transformed transform coefficient is added to the predicted image from the predicted image generation unit 110 by the adding unit 114. Thereby, a decoded image obtained when the output stream is decoded by the decoder of the second encoding method is generated. Further, the image output from the adding unit 114 is supplied to the predicted image generation unit 110 as a reference image for the subsequent image encoding process.

  Through the above processing, a stream according to the first encoding method can be converted into a stream according to the second encoding method.

(A-3) Effects of First Embodiment As described above, according to the first embodiment, the following effects can be obtained.

  It is possible to improve the coding efficiency because less code amount is wasted than necessary in order to approach an image including quantization distortion by the first coding method.

(B) Second Embodiment Next, a second embodiment of the encoding method conversion apparatus and program according to the present invention will be described in detail with reference to the drawings.

(B-1) Configuration of the Second Embodiment In the first embodiment, the quantization parameter control unit that controls the second quantization parameter used for the encoding process by the second encoding method is provided. On the other hand, the second embodiment is different in that control is performed on a Lagrangian multiplier for rate distortion optimization processing, which is used in encoding processing by the second encoding scheme.

  FIG. 2 is a block diagram illustrating a configuration of an encoding scheme conversion apparatus 1A according to the second embodiment. The encoding method conversion apparatus 1A according to the second embodiment may be configured as hardware such as a dedicated IC chip mounted with each unit, or configured as software centered on a program executed by the CPU. However, functionally, it can be represented in FIG.

  In FIG. 2, the coding method conversion apparatus 1A according to the second embodiment includes a decoding unit 11, an encoding unit 22, and a Lagrange multiplier control unit 211.

  Similar to the first embodiment, the decoding unit 11 includes an entropy decoding unit 101, an inverse quantization unit 102, an inverse transform unit 103, a predicted image generation unit 104, and an addition unit 112. Since the decoding unit 11 is the same as or corresponds to the first embodiment, a detailed description thereof is omitted here.

  The Lagrange multiplier control unit 211 acquires the first quantization parameter from the entropy decoding unit 101 of the decoding unit 11 and the second quantization parameter related to the second encoding method applied by the encoding unit 12, and first The Lagrangian multiplier for the rate distortion optimization process determined based on the second quantization parameter is controlled so as not to become a value smaller than necessary.

  The encoding unit 22 includes a conversion unit 105, a quantization unit 206, an entropy encoding unit 107, an inverse quantization unit 108, an inverse conversion unit 109, a predicted image generation unit 210, a subtraction unit 113, and an addition unit 114. Note that the components other than the quantization unit 206 and the predicted image generation unit 210 in the encoding unit 22 are the same as or correspond to those in the first embodiment, and therefore the same reference numerals as those in FIG. doing.

  The predicted image generation unit 210 generates a predicted image by performing motion compensation prediction, intra prediction, or the like, as in the first embodiment. Also, the predicted image generation unit 210 searches for a motion vector used for motion compensation and selects a prediction mode using the Lagrange multiplier λ calculated by the Lagrange multiplier control unit 211.

  The quantization unit 206 quantizes the transform coefficient transformed by the transform unit 105 by rate distortion optimization processing using the Lagrange multiplier λ calculated by the Lagrange multiplier control unit 211.

(B-2) Operation of Second Embodiment Next, the operation of the coding method conversion apparatus 1A according to the second embodiment will be described in detail with reference to FIG.

  A stream encoded by the first encoding method is input to the decoding unit 11. In the decoding unit 11, as in the first embodiment, the entropy decoding unit 101 performs entropy decoding on the input stream, and for example, transform coefficients such as discrete cosine transform, coding mode information, motion vector information, and the like are acquired. The

  The transform coefficient obtained by the entropy decoding unit 101 is generated by performing inverse quantization / inverse transform by the inverse quantization unit 102 / inverse transform unit 103 and performing motion compensation or intra prediction by the predicted image generation unit 104. The decoded image is obtained by adding the predicted image. In addition, the operation | movement which acquires the decoding image in the decoding part 11 can be calculated | required similarly to 1st Embodiment.

  The entropy decoding unit 101 decodes the quantization parameter used by the inverse quantization unit 102 and supplies the quantization parameter for each encoding processing unit to the Lagrange multiplier control unit 211 as the first quantization parameter.

  The Lagrange multiplier control unit 211 refers to the first quantization parameter from the entropy decoding unit 101, and is rate distortion optimized that is determined based on the second quantization parameter according to the second encoding method that is input. The Lagrange multiplier for processing is controlled so as not to be a value smaller than necessary.

  Here, in an encoding method such as HEVC, it is possible to select from a plurality of encoding candidates such as a prediction mode and a motion vector for motion compensation. Optimizing the encoding candidate selection improves encoding efficiency. It has a big impact. There is a rate distortion optimization technique as a technique used for selection of such encoding candidates.

  In the rate distortion optimization technique, for a plurality of options such as encoding modes, a distortion D with respect to an input image when the option is selected, a code amount R generated when the option is encoded, and a Lagrange multiplier are included. In this method, encoding is performed so that the trade-off between rate and distortion is optimal by making a selection so as to minimize the expressed RD cost J (J = D + λR).

  The Lagrangian multiplier λ is usually calculated as a function depending on the quantization parameter. When the square norm is used as the distortion D, a value that is proportional to the square of the quantization step, and when the absolute value norm is used as the distortion D, It is calculated as a value proportional to the quantization step.

  In HEVC and the like, since the quantization parameter is a value representing the logarithm of the quantization step, the Lagrange multiplier λ is calculated by an exponential function. Therefore, for example, as the quantization parameter becomes smaller, the Lagrangian multiplier λ becomes a smaller value, and works to prioritize candidates that make the distortion D smaller than making the code amount R smaller.

  However, in the encoding conversion process in which the decoded image of the stream encoded by the first encoding method is the encoding target image, even if the encoding efficiency for the decoded image including the quantization error is optimized, the first is not necessarily performed. The encoding efficiency for the original video before encoding by the encoding scheme 1 is not always optimal. This is because, in the rate distortion optimization process, the RD cost J is evaluated by the distortion D with respect to the decoded image including the quantization error.

  Therefore, in the second embodiment, the entropy decoding unit 101 extracts the first quantization parameter obtained in the decoding process by the decoding unit 11, and the entropy decoding unit 101 converts the first quantization parameter into the Lagrange multiplier. The Lagrange multiplier control unit 211 controls the Lagrange multiplier λ so as to perform rate distortion optimization considering the quantization error included in the decoded image in the encoding unit 22.

  Here, in the Lagrange multiplier control unit 211, for example, when the second quantization parameter used for calculating the Lagrange multiplier λ is smaller than the first quantization parameter, the Lagrange multiplier λ is set using the first quantization parameter. calculate. Alternatively, when the second quantization parameter is smaller than a value that is smaller than the first quantization parameter value by a predetermined offset, the Lagrange multiplier control unit 211 is smaller than the first quantization parameter by the predetermined offset. The value is used to calculate the Lagrange multiplier λ. In addition to the above, the Lagrange multiplier control unit 211 may calculate the Lagrange multiplier λ according to various functions using the value of the first quantization parameter and the value of the second quantization parameter.

  In the encoding unit 22, the predicted image generation unit 210 searches for a motion vector used for motion compensation and selects a prediction mode using the Lagrange multiplier λ calculated by the Lagrange multiplier control unit 211.

  In addition, when the quantization unit 206 performs a quantization process using the rate distortion optimization technique, the Lagrange multiplier λ calculated by the Lagrange multiplier control unit 211 is used as the Lagrange multiplier λ used in the quantization process. Also good.

  Note that, for example, the predicted image generation unit 210 may use a Lagrange multiplier λ for a plurality of uses, such as using an absolute value norm for distortion D in motion vector search and using a square norm for mode selection. The Lagrange multiplier control unit 211 may be configured to calculate a plurality of Lagrange multipliers λ for each application.

  Through the above processing, the stream according to the first encoding method is converted into the stream according to the second encoding method.

(B-3) Effects of Second Embodiment As described above, according to the second embodiment, the following effects can be obtained.

  By performing rate distortion optimization processing in consideration of quantization distortion by the first encoding method, it is possible to suppress unnecessary distortion minimization, and to improve coding efficiency by avoiding waste of code amount. Can do.

(C) Other Embodiments The present invention is not limited to the first and second embodiments described above, and can be used for various other encoding method conversion processes.

  For example, the present invention is not limited to transcoding processing between different encoding methods, and can also be applied to transcoding processing such as bit rate conversion and resolution conversion between the same encoding methods.

  In the first and second embodiments, the use of the quantization parameter as information obtained from the stream of the first encoding method has been described. However, in addition to this, motion vector information and encoding mode information are extracted to You may comprise so that the encoding process by 2 encoding systems may be performed efficiently.

  The present invention may be configured as an apparatus having the configuration described in the first and second embodiments described above. For example, the configuration of the present invention may be mounted on a personal computer, a tablet terminal, a mobile phone, a smartphone, a game machine, a mobile terminal, a television receiver, a set top box, a digital camera, or the like. Further, the CPU mounted on the apparatus may be executed by executing the program according to the present invention.

  In addition, the present invention may be realized in cooperation with a plurality of devices instead of a single device. Furthermore, the present invention can be connected to a network represented by the Internet, and may receive an input stream from the network and convert the encoding method.

  In addition, an apparatus equipped with the encoding method conversion apparatus according to the present invention includes an input stream from a recording medium (disk) such as a DVD disk, a Blu-Ray (registered trademark) disk, a flash storage device, or a video device such as a digital video camera. May be input to output an output video on a display or to record on another recording medium (disc).

1 and 1A: encoding conversion device,
DESCRIPTION OF SYMBOLS 11 ... Decoding part 101 ... Entropy decoding part 102 ... Inverse quantization part 103 ... Inverse transformation part 104 ... Predictive image generation part 105 ... Adder part
DESCRIPTION OF SYMBOLS 12 ... Encoding part, 105 ... Conversion part, 106 and 206 ... Quantization part, 108 ... Dequantization part, 109 ... Inverse conversion part, 110 and 210 ... Prediction image generation part, 113 ... Subtraction part, 114 ... Addition part,
111: Quantization parameter control unit, 211: Lagrange multiplier control unit

Claims (12)

In an encoding method conversion apparatus for converting an input stream of an image encoded by a first encoding method into an image stream encoded by a second encoding method,
Decoding means for decoding the image of the input stream by a first encoding method;
Encoding means for encoding the decoded image decoded by the decoding means by a second encoding method;
A quantization parameter control unit that adjusts a second quantization parameter related to encoding by the second encoding method with reference to the first quantization parameter obtained by decoding by the decoding unit. A coding method conversion apparatus.   The quantization parameter control means sets the second quantization parameter value so that it does not become smaller than the first quantization parameter value used in the encoding process by the first encoding method by decoding by the decoding means. The encoding method conversion apparatus according to claim 1, wherein the encoding method conversion apparatus is controlled.   The quantization parameter control means refers to the first quantization parameter obtained by decoding by the decoding means, and calculates a Lagrange multiplier related to the rate distortion optimization processing based on the second quantization parameter. The encoding method conversion apparatus according to claim 1, wherein: In an encoding method conversion apparatus for converting an input stream of an image encoded by a first encoding method into an image stream encoded by a second encoding method,
Decoding means for decoding the image of the input stream by a first encoding method;
Encoding means for encoding the decoded image decoded by the decoding means by a second encoding method;
A Lagrangian multiplier related to a rate distortion optimization process determined based on a second quantization parameter related to encoding by the second encoding method used in the encoding means is obtained by decoding by the decoding means. A coding method conversion apparatus comprising: a Lagrange multiplier control unit that adjusts with reference to one quantization parameter.   The quantization parameter control means or the Lagrange multiplier control means converts the scale information of the first quantization parameter into scale information of the second quantization parameter and uses it for control. The encoding method conversion apparatus according to any one of claims 1 to 4.   6. The encoding unit according to claim 3, wherein the encoding unit performs a motion vector search of the encoding process according to the second encoding method using the Lagrange multiplier from the Lagrange multiplier control unit. A coding method conversion apparatus according to claim 1.   7. The encoding unit selects an encoding mode of an encoding process according to the second encoding method using the Lagrange multiplier from the Lagrange multiplier control unit. The encoding system conversion apparatus in any one of.   The encoding means performs optimization processing of quantization of transform coefficients according to the second encoding method, using the Lagrange multiplier from the Lagrange multiplier control means. The encoding system conversion apparatus in any one of. In addition to the first quantization parameter, the decoding unit extracts motion vector information and encoding mode information related to a decoded image, and supplies the extracted information to the encoding unit.
The encoding means uses motion vector information and encoding mode information from the decoding means for encoding processing by the second encoding method. Encoding method converter.   The first encoding scheme or the second encoding scheme is H.264. The encoding system conversion apparatus according to claim 1, wherein the encoding system conversion apparatus is a H.264 / MPEG-4 AVC system.   The first encoding scheme or the second encoding scheme is H.264. 10. The encoding method conversion apparatus according to claim 1, wherein the encoding method conversion apparatus is a H.265 / MPEG-H HEVC method. In an encoding method conversion program for converting an input stream of an image encoded by a first encoding method into an image stream encoded by a second encoding method,
Computer
Decoding means for decoding an image of the input stream by a first encoding method;
Encoding means for encoding the decoded image decoded by the decoding means by a second encoding method;
The first quantization parameter obtained by the decoding by the decoding means is referred to function as a quantization parameter control means for adjusting the second quantization parameter related to the encoding by the second encoding method. Encoding method conversion program.

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