JP2009055315A - Transcoder, transcoding method, and transcoding program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transcoder that optimizes both a reduction amount of a CPU load and encryption strength. <P>SOLUTION: The transcoder is provided with a decoder which decodes an encoded input image so as to obtain a restored image, and an encoder for re-encoding the restored image. The decoder is provided with an encryption means for encrypting the restored image. The encoder is provided with a decryption means for decrypting the encrypted restored image. The encryption means is provided with an encryption processing amount regulation means for changing a processing amount required for encryption corresponding to a CPU load. The heavier the CPU load is, the further the encryption processing amount regulation means reduces a processing amount required for encryption. The lighter the CPU load is, the further the encryption processing amount regulation means increases a processing amount required for encryption. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a transcoder that includes a decoder that decodes an encoded input image to obtain a restored image, and an encoder that re-encodes the restored image.

  Digital broadcast recording files are encrypted for copyright protection. Since this file is of an HD (High Definition) image and has a large size, it may be converted into an SD (Standard) image to reduce the size.

  When a plurality of DirectShow filters, which are standard module formats of Microsoft (registered trademark), are used for this conversion, the interface between the filters is open, so that the image can be easily extracted.

  In order to prevent this, the image data must be encrypted. However, in general, encryption is a heavy process, and since the size of image data is large, if all pixels are encrypted, the load on the CPU becomes very heavy.

  Therefore, in order to reduce the load on the CPU without reducing the encryption effect, it is necessary to encrypt the optimal portion of the image.

For example, there is a method of encrypting only high frequency components (see, for example, Patent Document 1). There is also a method of encrypting only low frequency components (see, for example, Patent Document 2).
JP-A-6-54325 JP-A-11-88857

  However, when only the high frequency component is encrypted or only the low frequency component is encrypted, if the frequency component to be encrypted is determined in advance, the CPU load may not be sufficiently reduced. On the other hand, in this case, the encryption strength may be insufficient.

  Accordingly, an object of the present invention is to provide a transcoder, a transcoding method, and a transcoding program that can effectively control the amount of encryption processing according to the load on the CPU.

  According to the present invention, there is provided a transcoder including a decoder that decodes an encoded input image to obtain a restored image, and an encoder that re-encodes the restored image, wherein the decoder An encryption unit for encrypting, and the encoder includes a descrambling unit for descrambling the encrypted restored image, and the encryption unit determines a processing amount required for the encryption according to a load of the CPU. An encryption processing amount adjusting unit for changing, and the encryption processing amount adjusting unit reduces the processing amount required for encryption as the load on the CPU is heavier, and the processing required for encryption as the load on the CPU is lighter. A transcoder is provided that is characterized by increasing volume.

  In addition, according to the present invention, there is provided a transcoding method comprising: a decoding step for decoding a coded input image to obtain a restored image; and an encoding step for re-encoding the restored image. The coding step includes an encryption step for encrypting the restored image, and the encoding step includes a descrambling step for descrambling the restored restored image, and the encryption step is performed on a load of the CPU. And an encryption processing amount adjustment step for changing the processing amount required for encryption in accordance with the CPU, and the encryption processing amount adjustment step reduces the processing amount required for encryption as the load on the CPU increases. There is provided a transcoding method characterized by increasing the amount of processing required for encryption as the load is lighter.

  Furthermore, according to the present invention, there is provided a program for causing a computer to function as a transcoder including a decoder that decodes an encoded input image to obtain a restored image, and an encoder that re-encodes the restored image, The decoder includes an encryption unit that encrypts the restored image, and the encoder includes a descrambling unit that decrypts the encrypted restored image, and the encryption unit corresponds to a load on the CPU. Encryption processing amount adjustment means for changing the processing amount required for encryption, and the encryption processing amount adjustment means reduces the processing amount required for encryption as the load on the CPU increases. A program for causing a computer to function as a transcoder characterized by increasing the amount of processing required for encryption as the lighter is provided.

  According to the present invention, since the area to be encrypted is adjusted according to the load on the CPU, an optimal balance between the load on the CPU and the encryption strength can be obtained.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

  FIG. 1 shows the configuration of a system including a transcoder according to an embodiment of the present invention.

  This system includes a file reader 101, a demultiplexer 103, a decoder 105, an encoder 107, and a file writer 109. Each of these is a DirectShow filter.

  The file reader 101 reads the encrypted HD image TS file 111 and outputs an encrypted TS code. Here, TS is an abbreviation for transport stream.

  The demultiplexer 103 receives the encrypted TS code, separates it into an encrypted video code and an encrypted audio code, and outputs them.

  The decoder 105 receives the encrypted video code, generates decrypted image data encrypted in a unique format based on the encrypted video code, and outputs this. Also, the decoder 105 receives the encrypted audio data, generates encrypted audio data based on this, and outputs this.

  The encoder 107 inputs the restored image data and the encrypted audio data encrypted in a unique format, generates an encrypted PS code based on these, and outputs this. Here, PS is an abbreviation for Program Stream.

  The file writer 109 writes the encrypted PS code as an encrypted SD image PS file 113 on the recording medium.

  Here, the conversion from the HD format to the SD format is performed inside the decoder 105.

  Also, referring to FIG. 2, conceptually, the decoder 105 expands the encryption area or makes the encryption scheme heavy when the load on the CPU is light. On the other hand, the decoder narrows the encryption area or reduces the encryption method when the load on the CPU is heavy.

  Enlarging or narrowing the encryption area includes expanding or narrowing the frequency area for encryption as shown in FIG.

  FIG. 4 is a block diagram showing an internal configuration of the decoder 105.

  Referring to FIG. 4, the decoder 105 includes a descrambling unit 105-1, a decryption core unit 105-3, an HD / SD conversion unit 105-5, and an encryption unit 105-7.

  The descrambling unit 105-1 decrypts the encrypted video code.

  Based on the video code, the decoding core unit 105-3 generates an HD restored image in accordance with an MPEG (Moving Picture Experts Group) system, and outputs this.

  The HD / SD conversion unit 105-5 generates an SD restored image based on the HD restored image.

  The encryption unit 105-7 encrypts the SD restored image in a unique format, generates restored image data and encrypted supplementary information encrypted in the unique format, and outputs these. The encryption supplementary information is information that is referred to when descrambling.

  The encryption unit 105-7 refers to the macroblock information output from the decryption core unit 105-3 when performing encryption. The macro block information is, for example, information on the maximum significant coefficient of each DCT block or a motion vector of each macro block.

  Referring to FIG. 5, the encoder 107 includes a descrambling unit 107-1, an encoding core unit 107-3, and an encryption unit 107-5.

  The descrambling unit 107-1 receives the restored image encrypted in the original format and the encrypted supplementary information, and decrypts the restored image encrypted in the unique format while referring to the encrypted supplementary information. Then, the descrambling unit 107-1 outputs the decompressed restored image.

  The encoding core unit 107-3 generates a PS code according to the MPEG method based on the decrypted restored image.

  The encryption unit 107-5 encrypts the PS code, generates an encrypted PS code, and outputs this.

  Next, various examples of unique format encryption performed by the encryption unit 105-7 (see FIG. 4) will be described.

  FIG. 6 is a flowchart for explaining a threshold value updating method. The threshold value is referred to when the frame is encrypted. The threshold is updated at the beginning of each frame.

  Referring to FIG. 6, first, the encryption processing time T of the previous frame is checked (step S201).

  Next, it is checked whether or not the encryption processing time T of the previous frame is longer than the upper threshold value α (step S203). If it is longer (YES in step S203), the threshold is lowered by a predetermined amount from the current threshold (step S205).

  Next, it is checked whether or not the encryption processing time T of the previous frame is shorter than the lower threshold value β (step S207). If it is shorter (YES in step S207), the threshold is increased by a predetermined amount from the current threshold (step S209).

  FIG. 7 is a flowchart for explaining a method of encrypting each frame.

  Steps S213 to S223 are repeated for each macroblock scanning line region in the frame.

  Here, referring to FIG. 8, the macroblock scanning line region is a region of a set of macroblocks arranged horizontally from the left end to the right end of the screen. The macroblock scanning line area is an area of horizontal 720 pixels × vertical 16 pixels in the case of an SD image.

  At the beginning of each iteration, the counter N is reset to zero (step S213).

  Next, step S217 and the like are repeated for each macroblock in the macroblock scanning line area.

  In step S217, it is checked whether or not the highest significant frequency component of the current macroblock is higher than a threshold value. Here, when the HD / SD conversion is a conversion that reduces to half the size both vertically and horizontally, the highest-order significant frequency component of the current macroblock is a position corresponding to the current macroblock of the current SD restored image. Are obtained from the highest-order significant frequency components of about 16 luminance DCT blocks in total included in about 4 macroblocks of the HD restored image. For example, the maximum value of 16 highest-order significant frequency components may be the highest-order significant frequency component of the current macroblock. The average value of the 16 highest-order significant frequency components may be the highest-order significant frequency component of the current macroblock.

  If the highest significant frequency component of the current macroblock is higher than the threshold, 1 is added to the counter N (step S219).

  When the repetition of step S215 is completed, it is checked whether or not the value of the counter N is larger than a predetermined threshold value M (step S221). If so (YES in step S221), the current macroblock scanning line area is not encrypted. On the other hand, if not (NO in step S221), the current macroblock scanning line area is encrypted (step S223).

  According to the first embodiment, if the number N of macroblocks whose highest significant frequency component is higher than the threshold is greater than the predetermined threshold, the macroblock scanning line area is not encrypted. In other words, if the number N of macroblocks in which the highest-order significant frequency component is higher than the threshold is equal to or smaller than the predetermined threshold, the macroblock scanning line region is encrypted. Therefore, the macroblock scanning line area having many macroblocks whose significant frequency components remain in the low band is preferentially encrypted. Therefore, this embodiment is suitable for an image having a large number of macroblocks in which important portions remain in the low frequency range.

  FIG. 9 is a flowchart for explaining a threshold value updating method. The threshold value is referred to when the frame is encrypted. The threshold is updated at the beginning of each frame.

  Referring to FIG. 9, first, the encryption processing time T of the previous frame is examined (step S201).

  Next, it is checked whether or not the encryption processing time T of the previous frame is longer than the upper threshold value α (step S203). If longer (YES in step S203), the threshold is increased by a predetermined amount than the current threshold (step S205B).

  Next, it is checked whether or not the encryption processing time T of the previous frame is shorter than the lower threshold value β (step S207). If it is shorter (YES in step S207), the threshold is lowered by a predetermined amount from the current threshold (step S209B).

  FIG. 10 is a flowchart for explaining a method of encrypting each frame.

  Steps S213 to S223 are repeated for each macroblock scanning line region in the frame.

  At the beginning of each iteration, the counter N is reset to zero (step S213).

  Next, step S217 and the like are repeated for each macroblock in the macroblock scanning line area.

  In step S217, it is checked whether or not the highest significant frequency component of the current macroblock is higher than a threshold value. Here, when the HD / SD conversion is a conversion that reduces to half the size in both vertical and horizontal directions, the highest-order significant frequency component of the current macroblock is a position corresponding to the current macroblock of the current SD restored image. Are obtained from the highest-order significant frequency components of about 16 luminance DCT blocks in total included in the four macroblocks of the HD restored image. For example, the maximum value of 16 highest-order significant frequency components may be the highest-order significant frequency component of the current macroblock. Further, an average value of about 16 highest-order significant frequency components may be used as the highest-order significant frequency component of the current macroblock.

  If the highest significant frequency component of the current macroblock is lower than the threshold value, 1 is added to the counter N (step S219).

  When the repetition of step S215 is completed, it is checked whether or not the value of the counter N is larger than a predetermined threshold value M (step S221). If so (YES in step S221), the current macroblock scanning line area is not encrypted. On the other hand, if not (NO in step S221), the current macroblock scanning line area is encrypted (step S223).

  According to the second embodiment, if the number N of macroblocks whose highest significant frequency component is lower than the threshold is greater than the predetermined threshold, the macroblock scanning line region is not encrypted. In other words, if the number N of macroblocks whose highest significant frequency component is lower than the threshold is equal to or less than the predetermined threshold, the macroblock scanning line region is encrypted. Therefore, a macroblock scanning line area with few macroblocks having significant frequency components remaining in the low band is preferentially encrypted. Therefore, this embodiment is suitable for an image having a large number of macroblocks in which important portions remain in the mid-high range.

  As a modification of the first and second embodiments, the larger the counter N, the fewer scanning lines to be encrypted in the macroblock scanning line area.

  FIG. 11 is a flowchart for explaining a level update method. The level is referred to when the frame is encrypted. Level updates occur at the beginning of each frame.

  Referring to FIG. 11, first, the encryption processing time T of the previous frame is examined (step S231).

  Next, it is checked whether or not the encryption processing time T of the previous frame is longer than the upper threshold value α (step S233). If it is long (YES in step S233), the level is lowered by 1 (step S235).

  Next, it is checked whether or not the encryption processing time T of the previous frame is shorter than the lower threshold value β (step S237). If it is shorter (YES in step S237), the level is increased by 1 (step S239).

  In the fourth embodiment, the macroblock to be encrypted is determined according to the level.

  For example, as shown in FIG. 12, at level 1, no encryption is performed at all, and as the level increases, the area to be encrypted is expanded from the top, bottom, left, and right center to the top, bottom, left, and right. You may make it encrypt.

  Also, as shown in FIG. 13, at level 1, no encryption is performed at all, and as the level increases, the area to be encrypted is expanded vertically from the center in the vertical direction, and the entire screen is encrypted at level 5. You may make it do.

  FIG. 14 is a flowchart for explaining a method of encrypting each frame.

  Step S243 and the like are repeated for each macroblock in the frame (step S241).

  In step S243, it is checked whether the current block is a block to be encrypted at the current level.

  If so (YES in step S243), the current macroblock is encrypted (step S245).

  In the fifth embodiment, the frequency component to be encrypted is determined according to the level.

  For example, as shown in FIG. 15, at level 1, no encryption is performed, and as the level increases, the frequency component region to be encrypted is expanded in the high frequency direction. At level 5, all frequency components are expanded. You may make it encrypt.

  Further, as shown in FIG. 16, encryption may be performed by giving priority to the frequency component in the middle range.

  Since the level updating method in the fifth embodiment is the same as that in the fourth embodiment, a description thereof will be omitted.

  FIG. 17 is a flowchart for explaining a method of encrypting each frame.

  Step S253 and the like are repeated for each macroblock in the frame (step S251).

  Within each macroblock, step S255 and the like are repeated for each DCT block included in the macroblock (step S253).

  Within each DCT block, step S257 and the like are repeated up to the highest significant frequency component (step S255).

  In step S257, it is checked whether the current frequency component is a frequency component to be encrypted at the current level.

  If so (YES in step S257), the current frequency component is encrypted (step S259).

  In the sixth embodiment, whether to encrypt a macro block is determined according to the magnitude of the absolute value of the motion vector.

  Since the threshold value updating method in the sixth embodiment is the same as that in the first embodiment, the description thereof is omitted.

  FIG. 18 is a flowchart for explaining a method of encrypting each frame.

  Step S263 and the like are repeated for each macroblock in the frame (step S261).

  In step S263, it is checked whether or not the absolute value of the motion vector of the current macroblock is larger than the threshold value.

  If so (YES in step S263), the current macroblock is not encrypted.

  Otherwise (NO in step S263), the current macroblock is encrypted (step S265).

  According to the sixth embodiment, if the absolute value of the motion vector is larger than the threshold value, the macroblock is not encrypted. In other words, if the absolute value of the motion vector is less than or equal to the threshold value, the macroblock is encrypted. Therefore, a macroblock having a small absolute value of the motion vector is preferentially encrypted. Therefore, this embodiment is suitable for an image in which an important part remains in a part with little movement.

  In the seventh embodiment, whether to encrypt a macro block is determined according to the magnitude of the absolute value of the motion vector.

  Since the threshold value updating method in the seventh embodiment is the same as that in the second embodiment, the description thereof is omitted.

  FIG. 19 is a flowchart for explaining a method of encrypting each frame.

  Step S263B and the like are repeated for each macroblock in the frame (step S261).

  In step S263B, it is checked whether the absolute value of the motion vector of the current macroblock is smaller than a threshold value.

  If so (YES in step S263B), the current macroblock is not encrypted.

  Otherwise (NO in step S263B), the current macroblock is encrypted (step S265).

  According to the seventh embodiment, if the absolute value of the motion vector is smaller than the threshold value, the macroblock is not encrypted. In other words, if the absolute value of the motion vector is greater than or equal to the threshold, the macroblock is encrypted. Therefore, a macroblock having a large absolute value of the motion vector is preferentially encrypted. Therefore, this embodiment is suitable for an image in which an important part remains in a part with a lot of movement.

  Example 8 is a combination of Example 5 and Example 6.

  Since the level update method in the eighth embodiment is the same as that in the fourth embodiment, a description thereof will be omitted. Further, the threshold value updating method in the eighth embodiment is the same as that in the first embodiment, and thus the description thereof is omitted.

  FIG. 20 is a flowchart for explaining a method of encrypting each frame.

  Step S273 and the like are repeated for each macroblock in the frame (step S271).

  In step S273, it is checked whether or not the absolute value of the motion vector of the current macroblock is larger than a threshold value.

  If so (YES in step S273), the current macroblock is not encrypted.

  Otherwise, step S277 and the like are repeated for each DCT block in the current macroblock (step S275).

  In step S277, step S279 and the like are repeated for each frequency component of the current DCT block.

  In step S279, it is checked whether or not the current weekly lotus component is a frequency component to be encrypted at the current level.

  If so (YES in step S279), the current frequency component is encrypted (step S281).

  In the ninth embodiment, only frequency components equal to or less than the threshold value are encrypted.

  Since the threshold updating method in the ninth embodiment is the same as that in the first embodiment, the description thereof is omitted.

  FIG. 21 is a flowchart for explaining a method of encrypting each frame.

  Step S293 and the like are repeated for each macroblock in the frame (step S291).

  In step S293, step S295 and the like are repeated for each DCT block in the current macroblock.

  In step S295, step S297 and the like are repeated for each frequency component up to the highest significant frequency component of the current DCT block.

  In step S297, it is checked whether the current frequency component order is equal to or less than a threshold value.

  If so (YES in step S297), the current frequency component is encrypted (step S299).

  According to the ninth embodiment, frequency components having an order equal to or higher than the threshold are not encrypted. In other words, only the frequency components of order smaller than the threshold are encrypted. Therefore, this embodiment is suitable for an image having a large number of macroblocks in which important portions remain in the low band.

  In the tenth embodiment, only frequency components equal to or higher than the threshold are encrypted.

  Since the threshold value updating method in the tenth embodiment is the same as that in the second embodiment, a description thereof will be omitted.

  FIG. 22 is a flowchart for explaining a method of encrypting each frame.

  Step S293 and the like are repeated for each macroblock in the frame (step S291).

  In step S293, step S295 and the like are repeated for each DCT block in the current macroblock.

  In step S295, step S297B and the like are repeated for each frequency component up to the highest significant frequency component of the current DCT block.

  In step S297B, it is checked whether or not the current frequency component order is greater than or equal to a threshold value.

  If so (YES in step S297B), the current frequency component is encrypted (step S299).

  According to the tenth embodiment, the frequency components of the order below the threshold are not encrypted. In other words, only frequency components of order greater than the threshold are encrypted. Therefore, this embodiment is suitable for an image having a large number of macroblocks in which important portions remain in the mid-high range.

  Similarly to the combination of the fifth embodiment and the sixth embodiment, the fifth embodiment and the ninth embodiment may be combined. This combination is Example 11. That is, a macroblock whose absolute value of a motion vector is larger than a threshold is not encrypted, and only the macroblock whose absolute value of a motion vector is equal to or smaller than the threshold is used as shown in FIG.

It is a block diagram which shows the structure of the system containing the transcoder etc. by embodiment of this invention. It is a 1st figure for demonstrating the concept of this invention. It is a 2nd figure for demonstrating the concept of this invention. FIG. 2 is a block diagram showing an internal configuration of a decoder shown in FIG. 1. It is a block diagram which shows the structure inside the encoder shown in FIG. It is a flowchart for demonstrating the method of the threshold value update by Example 1 of this invention. 3 is a flowchart for explaining a frame encryption method according to the first embodiment of the present invention; It is a figure for demonstrating a macroblock scanning line area | region. It is a flowchart for demonstrating the method of the threshold value update by Example 2 of this invention. It is a flowchart for demonstrating the method of the encryption of the flame | frame by Example 2 of this invention. It is a flowchart for demonstrating the method of the level update by Example 4 of this invention. It is a figure which shows the 1st example which changes the encryption area | region in a flame | frame according to the level by Example 4 of this invention. It is a figure which shows the 2nd example which changes the encryption area | region in a flame | frame according to the level by Example 4 of this invention. It is a flowchart for demonstrating the method of the encryption of the flame | frame by Example 4 of this invention. It is a figure which shows the 1st example which changes the encryption area | region in a DCT block according to the level by Example 5 of this invention. It is a figure which shows the 2nd example which changes the encryption area | region in a DCT block according to the level by Example 5 of this invention. It is a flowchart for demonstrating the method of the encryption of the flame | frame by Example 5 of this invention. It is a flowchart for demonstrating the method of the encryption of the flame | frame by Example 6 of this invention. It is a flowchart for demonstrating the method of the encryption of the flame | frame by Example 7 of this invention. It is a flowchart for demonstrating the method of the encryption of the flame | frame by Example 8 of this invention. It is a flowchart for demonstrating the method of the encryption of the flame | frame by Example 9 of this invention. It is a flowchart for demonstrating the method of the encryption of the flame | frame by Example 10 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 File reader 103 Demultiplexer 105 Decoder 105-1 Decryption part 105-3 Decoding core part 105-5 HD / SD conversion part 105-7 Encryption part 107 Encoder 107-1 Decryption part 107-3 Encoding core part 107 -5 Encryption section 109 File writer 111 Encrypted HD image TS file 113 Encrypted SD image PS file

Claims (16)

A transcoder comprising a decoder that decodes an encoded input image to obtain a restored image, and an encoder that re-encodes the restored image,
The decoder includes encryption means for encrypting the restored image,
The encoder includes a descrambling means for descrambling the restored restored image,
The encryption unit includes an encryption processing amount adjustment unit that changes a processing amount required for encryption according to a load on the CPU.
The transcoder is characterized in that the encryption processing amount adjustment means decreases the processing amount required for encryption as the load on the CPU is heavy, and increases the processing amount required for encryption as the load on the CPU is light. The transcoder of claim 1.
The encryption processing amount adjusting means reduces the number of scanning lines to be encrypted in the frame as the load on the CPU is heavier, and the number of scanning lines to be encrypted in the frame as the load on the CPU is lighter. Transcoder characterized by increasing The transcoder according to claim 2, wherein
The encryption processing amount adjustment means lowers the frequency threshold as the CPU load is heavier, increases the frequency threshold as the CPU load is lighter, and the macroblock having the highest frequency higher than the frequency threshold. A transcoder that does not encrypt a macroblock scanning line area having a number greater than a predetermined number. The transcoder according to claim 2, wherein
The encryption processing amount adjustment means increases the frequency threshold as the load on the CPU is heavier, lowers the frequency threshold as the load on the CPU is lighter, and a macroblock whose highest frequency is lower than the frequency threshold. A transcoder that does not encrypt a macroblock scanning line area having a number greater than a predetermined number. The transcoder of claim 1.
The encryption processing amount adjusting means decreases the number of macroblocks to be encrypted in a frame as the load on the CPU is heavier, and reduces the number of macroblocks to be encrypted in the frame as the load on the CPU is lighter. Transcoder characterized by a lot. The transcoder according to claim 5, wherein
The transcoder is characterized in that the encryption processing amount adjusting means predetermines macroblocks to be encrypted for each range of the load of the CPU. The transcoder according to claim 5, wherein
The encryption processing amount adjustment means lowers the threshold of the highest significant frequency as the load on the CPU is heavier, increases the threshold of the highest significant frequency as the load on the CPU is lighter, and the highest significant frequency becomes the highest significant frequency. A transcoder that does not encrypt macroblocks that are higher than a frequency threshold. The transcoder according to claim 5, wherein
The encryption region processing amount means increases the threshold value of the highest significant frequency as the load on the CPU is heavier, lowers the threshold value of the highest significant frequency as the load on the CPU is lighter, and the highest significant frequency is the highest significant frequency. A transcoder that does not encrypt macroblocks lower than a frequency threshold. The transcoder according to claim 5, wherein
The encryption processing amount adjusting unit decreases the absolute value of the motion vector as the CPU load is heavier, and increases the absolute value of the motion vector as the CPU load is lighter. A transcoder which does not encrypt a macroblock whose size is larger than the threshold motion vector. The transcoder according to claim 5, wherein
The encryption processing amount adjustment unit increases the absolute value of the motion vector as the CPU load is heavier, and decreases the absolute value of the motion vector as the CPU load is lighter. A transcoder that does not encrypt a macroblock having a size smaller than the threshold motion vector. The transcoder of claim 1.
The encryption processing amount adjusting means lowers the highest order frequency for encrypting each block as the load on the CPU is heavier, and the highest order for encrypting each block as the load on the CPU is lighter. A transcoder characterized by increasing the frequency. The transcoder according to claim 11, wherein
The encryption processing amount adjusting means lowers the frequency threshold as the load on the CPU is heavier, increases the frequency threshold as the load on the CPU is lighter, and encrypts blocks whose highest frequency is larger than the frequency threshold. Transcoder characterized by not converting to The transcoder of claim 1.
The transcoder is characterized in that the encryption processing amount adjusting means predetermines a frequency component to be encrypted for each range of the load of the CPU. The transcoder according to any one of claims 1 to 13,
The transcoder is characterized in that the load of the CPU is determined based on the time required to encrypt a past frame. A transcoding method comprising: a decoding step of decoding an encoded input image to obtain a restored image; and an encoding step of re-encoding the restored image,
The decoding step includes an encryption step for encrypting the restored image,
The encoding step includes a descrambling step for descrambling the restored restored image,
The encryption step includes an encryption processing amount adjustment step of changing a processing amount required for encryption according to a load on the CPU,
The encryption area processing amount adjusting step reduces the processing amount required for encryption as the load on the CPU is heavier, and increases the processing amount required for encryption as the load on the CPU is lighter. Method. A program that causes a computer to function as a transcoder including a decoder that decodes an encoded input image to obtain a restored image, and an encoder that re-encodes the restored image,
The decoder includes encryption means for encrypting the restored image,
The encoder includes a descrambling means for descrambling the restored restored image,
The encryption unit includes an encryption processing amount adjustment unit that changes a processing amount required for encryption according to a load on the CPU.
The encryption processing amount adjusting means reduces the processing amount required for encryption as the CPU load is heavier, and increases the processing amount required for encryption as the CPU load is lighter. A program that allows a computer to function.