CN111372083B - SHVC video encryption method based on interlayer processing - Google Patents

SHVC video encryption method based on interlayer processing Download PDF

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CN111372083B
CN111372083B CN202010197574.8A CN202010197574A CN111372083B CN 111372083 B CN111372083 B CN 111372083B CN 202010197574 A CN202010197574 A CN 202010197574A CN 111372083 B CN111372083 B CN 111372083B
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CN111372083A (en
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王晓东
张佳青
陈晓爱
章联军
吴奇元
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Ningbo University
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/30—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using hierarchical techniques, e.g. scalability
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/169—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding
    • H04N19/17—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being an image region, e.g. an object
    • H04N19/176—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being an image region, e.g. an object the region being a block, e.g. a macroblock
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/169—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding
    • H04N19/186—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being a colour or a chrominance component
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/46—Embedding additional information in the video signal during the compression process
    • H04N19/467—Embedding additional information in the video signal during the compression process characterised by the embedded information being invisible, e.g. watermarking
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/70—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals characterised by syntax aspects related to video coding, e.g. related to compression standards

Abstract

An SHVC video encryption method based on interlayer processing comprises processing an input video sequence to generate a base layer bit stream; encrypting the color mapping coefficient when generating the interlayer reference image according to the base layer; enhancement layer coding is then performed: transforming and quantizing the input video sequence, and entropy coding syntax elements of two encrypted syntax elements in each group of coefficient groups and other remaining syntax elements in each group of coefficient groups; finally, the input video sequence is subjected to intra-frame prediction, transformation, quantization and entropy coding and inter-frame prediction realized by an inter-layer reference image to obtain an enhancement layer bit stream; the base layer bitstream and the enhancement layer bitstream together constitute a bitstream after encoding of the input video sequence. The video quality is greatly reduced by an interlayer color mapping coefficient encryption means; and the two syntax elements in the enhancement layer are jointly encrypted, which has less influence on the compression ratio of the SHVC.

Description

SHVC video encryption method based on interlayer processing
Technical Field
The invention relates to the field of video encryption, in particular to an SHVC video encryption method based on interlayer processing.
Background
With the development of emerging technologies, the number of digital videos is increasing and expanding, and many copyright theft problems are also raised, and the privacy and security problems of videos become more and more demanding in many fields such as pay television, video conference, military secrets and the like. As an effective protection method, video encryption can effectively prevent the video content from being stolen, and confidentiality and integrity are provided for users. The scalable extensions of HEVC (SHVC) is a new generation of Video compression Coding standard proposed on the basis of High performance Video Coding (h.265/HEVC). The scalable characteristics, compatibility and compression rate supported by SHVC are all superior to Scalable Video Coding (SVC), and have significant research and application values. Compared with the previous standard, the scalable performance can solve the problem that a single-layer video structure only supports a single video size, a single video bit rate and a single video frame rate, is suitable for heterogeneous networks and various terminals, and can perform dynamic structure adjustment according to different network characteristics, terminal equipment and user requirements. The new generation coding standard HEVC and its extended SHVC sacrifice coding time and cost in achieving high compression efficiency, which results in increased coding complexity, which puts higher performance requirements on the hardware devices in practical use. How to encrypt the SHVC encoding process under the condition of negligible increase of time and cost becomes one of the research directions of new encoding methods.
Disclosure of Invention
The invention aims to solve the technical problem of providing an SHVC video encryption method based on interlayer processing, which conforms to the SHVC code stream format and greatly reduces the video quality, aiming at the current situation of the prior art.
The technical scheme adopted by the invention for solving the technical problems is as follows: an SHVC video encryption method based on interlayer processing is characterized in that: the method comprises the following steps:
step 1, down-sampling an input video sequence to obtain a sequence with low spatial resolution, inputting the sequence obtained after down-sampling into a base layer, and encoding the sequence input by the base layer by using an HEVC (high efficiency video coding) encoder to generate a base layer encoding bit stream;
step 2, decoding the coded bit stream of the base layer to obtain a reconstructed image of the base layer, and respectively performing texture resampling, motion domain resampling and color mapping on the reconstructed image of the base layer to generate an interlayer reference image; the method comprises the following specific steps of carrying out color mapping on a reconstructed image of a base layer:
step 2-1, performing color mapping on the reconstructed image of the base layer to obtain color mapping coefficients of three channels, and recording the color mapping coefficients as LutY, lutU and LutV, wherein LutY is a brightness mapping coefficient, and LutU and LutV are two mapping coefficients with different chromaticities;
step 2-2, encrypting the absolute values of the color mapping coefficients of the three channels obtained in the step 2-1 respectively to obtain the encrypted color mapping coefficients of the three channels, namely LutY ', lutU ' and LutV ';
step 2-3, cutting the YUV color space of the reconstructed image of the basic layer into n1 x n2 x n3 cuboid partitions; n1, n2 and n3 are integers;
step 2-4, for each cuboid partition, calculating a mapping sample value of an enhancement layer color space according to the color mapping coefficients encrypted by the three channels in the step 2-2;
step 3, constructing a reference image list of the enhancement layer, and putting the interlayer reference image obtained in the step 2 into the reference image list of the enhancement layer for the coding prediction of the enhancement layer;
step 4, inputting the input video sequence into the enhancement layer, transforming and quantizing the input video sequence to obtain quantized transform coefficients, recording 16 quantized transform coefficients contained in a 4 × 4 sub-block in a quantized transform unit, marking as a group of coefficient groups, and describing the characteristics of each group of coefficient groups by using syntax elements, wherein two syntax elements in each group of coefficient groups are extracted: encrypting the binarization result of the absolute value remainder M of the non-zero coefficient and hiding symbol data of the symbol information coeff _ sign _ flag of the non-zero coefficient, and then entropy coding the two encrypted syntax elements and other remaining syntax elements in each group of coefficient groups;
the specific steps of encrypting the binarization result of the absolute value remainder M of the nonzero coefficient are as follows:
step 4-1, carrying out binarization on an absolute value remainder M of a non-zero coefficient by adopting a truncation Rice coding and k-order exponential Golomb coding binarization combined method to obtain a result after binarization; the method comprises the following specific steps:
step 4-1a, calculating a prefix value and a suffix value of the syntax element; the prefix value prefix _ value and suffix value suffix _ value of the syntax element are calculated as:
prefix_value＝min(cMax,M)
suffix_value＝M-cMax
wherein, cMax is a truncation value in truncation Rice coding, cMax =4< < p, wherein < < is left shift operation, and p is Rice parameter;
step 4-1b, using truncated rice coding to code a prefix value prefix _ value of the syntax element to obtain a first sub-prefix code M1 and a first sub-suffix code N1, and using k-order exponential golomb coding to code a suffix value suffix _ value of the syntax element to obtain a second sub-prefix code M2 and a second sub-suffix code N2, wherein k = p +1;
step 4-1c, judging whether M is smaller than cMax, if so, turning to step 4-1d; if not, the binarization result of the absolute value remainder M of the nonzero coefficient consists of a first sub-prefix code M1, a second sub-prefix code M2 and a second sub-suffix code N2 which are sequentially arranged;
step 4-1d, judging whether p is equal to 0, if so, forming a result after binarization of an absolute value remainder M of the nonzero coefficient by a first sub prefix code M1; if not, the result of binarization of the absolute value remainder M of the nonzero coefficient consists of a first sub-prefix code M1 and a first sub-suffix code N1 which are sequentially arranged according to the sequence;
step 4-2, judging whether a first sub suffix code N1 and/or a second sub suffix code N2 exist in the binarization result obtained in the step 4-1, if so, encrypting the existing first sub suffix code N1 and/or the second sub suffix code N2, replacing the original first sub suffix code N1 and/or the original second sub suffix code N2 with the encrypted result, and recombining the binarization result; if not, directly outputting a result after binarization;
the specific steps of hiding the symbol data of the symbol information coeff _ sign _ flag of the nonzero coefficient are as follows:
step a, solving the sum of the absolute values of the amplitudes of all non-zero coefficients in a group of coefficient groups, then carrying out parity check, if the sum is an even number, judging the sign of the last non-zero coefficient in the group of coefficient groups to be '+', namely SDH =1; if the sum is odd, the sign of the last non-zero coefficient in a group of coefficient groups is judged to be '-', i.e. SDH =0;
b, respectively carrying out different encryption on the symbol information coeff _ sign _ flag of the non-zero coefficient according to two different symbols of the last non-zero coefficient in the step a to obtain the encrypted symbol information coeff _ sign _ flag' of the non-zero coefficient;
and 5: the enhancement layer input video sequence is subjected to intra-frame prediction, transformation, quantization and entropy coding in step 4 and inter-frame prediction realized by a reference image list of the enhancement layer in step 3 to obtain an enhancement layer coding bit stream;
and 6, constructing the base layer coded bit stream obtained in the step 1 and the enhancement layer coded bit stream obtained in the step 5 into a bit stream coded by the input video sequence.
Preferably, the specific encryption method in step 2-2 is an AES block encryption method in a CFB mode that can generate a stream cipher, and the calculation formulas of the color mapping coefficients LutY ', lutU ', and LutV ' after encryption of three channels are:
Figure BDA0002418169570000031
Figure BDA0002418169570000032
Figure BDA0002418169570000033
wherein, | | is an absolute value,
Figure BDA0002418169570000034
for an XOR operation, k i Is a subkey generated by an encryptor in the AES block encryption method in CFB mode.
Specifically, the calculation formulas of the first sub-prefix code M1, the second sub-prefix code M2, the first sub-postfix code N1, and the second sub-postfix code N2 in step 4-1b are as follows:
Figure BDA0002418169570000041
Figure BDA0002418169570000042
wherein bin () represents a binary conversion; if yes, right shift operation is carried out;
Figure BDA0002418169570000043
a number of "1" + "0";
wherein the content of the first and second substances,
Figure BDA0002418169570000044
Figure BDA0002418169570000045
is an integer taking function;
Figure BDA0002418169570000046
in this embodiment, the method for encrypting the first sub-suffix code N1 in step 4-2 includes:
judging whether the value of M is in the following value range,
Figure BDA0002418169570000047
wherein, the baseleval is a related value of the syntax element, and the value is [1,2,3];
if yes, encrypting the first sub suffix code N1; if not, the first sub suffix code N1 is not encrypted; the calculation formula of the encryption of the first sub postfix code N1 is as follows:
Figure BDA0002418169570000048
wherein, N1' is the result obtained after the first sub suffix code N1 is encrypted;
the calculation formula for encrypting the second sub-postfix code N2 is:
Figure BDA0002418169570000049
/>
wherein, N2' is the result obtained after the second sub suffix code N2 is encrypted.
Further, the calculation formula for encrypting the symbol information coeff _ sign _ flag of the syntax element in step b is as follows:
Figure BDA00024181695700000410
compared with the prior art, the invention has the advantages that: by introducing an interlayer color mapping coefficient encryption means, the quality of the EL video in perceptual encryption is greatly reduced; in addition, the scheme conforms to the SHVC format and has little influence on the compression ratio of the SHVC by encrypting the color mapping coefficients of the interlayer reference image and jointly encrypting the two syntax elements in the enhancement layer; after the encoding stage of the input video is encrypted by the method, the original decoding mode cannot carry out normal analysis on the enhancement layer of the input video, the content of the decoded video cannot be completely identified, and obvious distortion exists, so that the video encrypted by the method can realize high security level and can be effectively applied to the protection of high-definition video.
Detailed Description
The present invention is described in further detail below with reference to examples.
SHVC coding is an existing coding scheme, and includes base layer coding, enhancement layer coding, and an inter-layer reference picture disposed between the base layer and the enhancement layer, where the inter-layer reference picture is obtained by processing a reconstructed picture of the base layer and is used for coding prediction of the enhancement layer.
An SHVC video encryption method based on interlayer processing comprises the following steps:
step 1, down-sampling an input video sequence to obtain a sequence with low spatial resolution, inputting the sequence obtained after down-sampling into a base layer, and encoding the sequence input by the base layer by using an HEVC (high efficiency video coding) encoder to generate a base layer encoding bit stream;
step 2, decoding the coded bit stream of the base layer to obtain a reconstructed image of the base layer, and respectively performing texture resampling, motion domain resampling and color mapping on the reconstructed image of the base layer to generate an interlayer reference image; the method for carrying out color mapping on the reconstructed image of the base layer comprises the following specific steps:
step 2-1, performing color mapping on the reconstructed image of the basic layer to obtain color mapping coefficients of three channels, and recording the color mapping coefficients as LutY, lutU and LutV, wherein LutY is a brightness mapping coefficient, and LutU and LutV are mapping coefficients of two different chromaticities;
step 2-2, encrypting the absolute values of the color mapping coefficients of the three channels obtained in the step 2-1 respectively to obtain the color mapping coefficients of the three channels after encryption, which are LutY ', lutU ' and LutV ' respectively;
in this embodiment, the specific encryption method is an AES block encryption method in a CFB mode that can generate a stream cipher, and the calculation formulas of the color mapping coefficients LutY ', lutU ', and LutV ' after encryption in the three channels are:
Figure BDA0002418169570000051
Figure BDA0002418169570000052
Figure BDA0002418169570000053
wherein, | | is an absolute value,
Figure BDA0002418169570000054
for XOR operation, k i Is a sub-key generated by an encryptor in the AES block encryption method in the CFB mode;
step 2-3, cutting the YUV color space of the reconstructed image of the basic layer into n1 x n2 x n3 cuboid partitions; n1, n2 and n3 are integers; wherein, in Y dimension, the method is divided into at most 8 subareas by uniform division, namely n1 is less than or equal to 8; in the dimensions of U and V, non-uniform partition is used to form at most two partitions, namely n2 is less than or equal to 2, and n3 is less than or equal to 2. When U and V are non-uniformly divided, an offset compared with uniform division is generated and is used for defining the self-adaptive U and V division threshold;
step 2-4, for each cuboid partition, calculating mapping sample values of the color space of the enhancement layer according to the color mapping coefficients encrypted by the three channels in the step 2-2;
storing the calculated mapping sample value of the enhancement layer color space in an interlayer reference image for subsequent use in encoding of the enhancement layer; the method for calculating the mapping sample value of the color space of the enhancement layer is the prior art;
step 3, constructing a reference image list of the enhancement layer, and putting the interlayer reference image obtained in the step 2 into the reference image list of the enhancement layer for the coding prediction of the enhancement layer;
step 4, inputting the input video sequence into the enhancement layer, transforming and quantizing the input video sequence to obtain quantized transform coefficients, recording 16 quantized transform coefficients contained in a 4 × 4 sub-block in a quantized transform unit, marking as a group of coefficient groups, and describing the characteristics of each group of coefficient groups by using syntax elements, wherein two syntax elements in each group of coefficient groups are extracted: encrypting the binarization result of the absolute value remainder M of the nonzero coefficient and hiding symbol data of the symbol information coeff _ sign _ flag of the nonzero coefficient, and then entropy coding the two encrypted syntax elements and other remaining syntax elements in each group of coefficients;
the specific steps of encrypting the binarization result of the absolute value remainder M of the nonzero coefficient are as follows:
step 4-1, adopting truncated Rice code TR p And order k exponential Golomb encoding EG k A binarization combination method is used for carrying out binarization on the absolute value remainder M of the nonzero coefficient to obtain a binarized result; the method comprises the following specific steps:
step 4-1a, calculating a prefix value and a suffix value of the syntax element; the prefix value prefix _ value and suffix value suffix _ value of the syntax element are calculated as:
prefix_value＝min(cMax,M)
suffix_value＝M-cMax
wherein, cMax is a truncation value in truncation Rice coding, cMax =4< < p, wherein < < is left shift operation, and p is Rice parameter;
step 4-1b, using a truncated Rice code TR p Encoding prefix value prefix _ value of syntax element to obtain first sub-prefix code M1 and first sub-postfix code N1, and encoding EG using exponential Golomb of order k k Coding a suffix value suffix _ value of the syntax element to obtain a second sub-prefix code M2 and a second sub-suffix code N2, wherein k = p +1;
the calculation formulas of the first sub-prefix code M1, the second sub-prefix code M2, the first sub-postfix code N1 and the second sub-postfix code N2 are as follows:
Figure BDA0002418169570000061
Figure BDA0002418169570000062
wherein bin () represents a binary conversion; if yes, right shift operation is carried out;
Figure BDA0002418169570000071
a number of "1" + "0";
wherein, the first and the second end of the pipe are connected with each other,
Figure BDA0002418169570000072
Figure BDA0002418169570000073
is an integer taking function; />
Figure BDA0002418169570000074
Step 4-1c, judging whether M is smaller than cMax, if so, switching to step 4-1d; if not, the binarization result of the absolute value remainder M of the nonzero coefficient consists of a first sub-prefix code M1, a second sub-prefix code M2 and a second sub-suffix code N2 which are sequentially arranged;
step 4-1d, judging whether p is equal to 0, if so, forming a result after binarization of an absolute value remainder M of the non-zero coefficient by using a first sub-prefix code M1; if not, the result of binarization of the absolute value remainder M of the non-zero coefficient consists of a first sub prefix code M1 and a first sub suffix code N1 which are sequentially arranged;
step 4-2, judging whether a first sub suffix code N1 and/or a second sub suffix code N2 exist in the binarization result obtained in the step 4-1, if so, encrypting the existing first sub suffix code N1 and/or the second sub suffix code N2, replacing the original first sub suffix code N1 and/or the original second sub suffix code N2 with the encrypted result, and recombining the binarization result; if not, directly outputting a result after binarization;
if the first sub postfix code N1 exists in the result after binarization, only the first sub postfix code N1 is encrypted; if the second sub postfix code N2 exists in the result after the binarization, only the second sub postfix code N2 is encrypted; if the first sub postfix code N1 and the second sub postfix code N2 exist in the result after the binarization, the first sub postfix code N1 and the second sub postfix code N2 are encrypted simultaneously;
in the embodiment, the first sub suffix code N1 and the second sub suffix code N2 also adopt an AES block encryption method in a CFB mode that can generate a stream cipher;
the method for encrypting the first sub postfix code N1 comprises the following steps:
judging whether the value of M is in the following value range,
Figure BDA0002418169570000075
wherein, the baseleval is a related value of the syntax element, and the value is [1,2,3];
if yes, encrypting the first sub suffix code N1; if not, the first sub suffix code N1 is not encrypted; the calculation formula of the encryption of the first sub postfix code N1 is as follows:
Figure BDA0002418169570000076
wherein, N1' is the result obtained after the first sub suffix code N1 is encrypted;
the calculation formula for encrypting the second sub suffix code N2 is:
Figure BDA0002418169570000081
wherein, N2' is the result obtained after the second sub suffix code N2 is encrypted;
the specific steps of hiding the symbol data of the symbol information coeff _ sign _ flag of the nonzero coefficient are as follows:
step a, solving the sum of the absolute values of the amplitudes of all non-zero coefficients in a group of coefficient groups, then carrying out parity check, if the sum is an even number, judging the sign of the last non-zero coefficient in the group of coefficient groups to be '+', namely SDH =1; if the sum is odd, the sign of the last non-zero coefficient in a group of coefficient groups is judged to be '-', i.e. SDH =0;
b, respectively carrying out different encryption on the symbol information coeff _ sign _ flag of the non-zero coefficient according to two different symbols of the last non-zero coefficient in the step a to obtain the encrypted symbol information coeff _ sign _ flag' of the non-zero coefficient;
the formula for encrypting the symbol information coeff _ sign _ flag of the syntax element is as follows:
Figure BDA0002418169570000082
wherein, the symbol information coeff _ sign _ flag of the syntax element is a numerical value of a binary system;
and 5: the enhancement layer input video sequence is subjected to intra-frame prediction, transformation, quantization and entropy coding in step 4 and inter-frame prediction realized by a reference image list of the enhancement layer in step 3 to obtain an enhancement layer coding bit stream;
the invention adds the encryption of the color mapping coefficient in the interlayer reference image and the encryption of two syntax elements in the coding process of the enhancement layer, thereby encrypting the bit stream after the enhancement layer is coded, ensuring that the content of the video obtained after the enhancement layer is decoded can not be completely identified, and ensuring the safety of the video;
and 6, constructing the base layer coded bit stream obtained in the step 1 and the enhancement layer coded bit stream obtained in the step 5 into a bit stream coded by the input video sequence.
In the invention, on one hand, the time complexity and the operation amount are reduced as much as possible, so that the sampling value of a base layer reconstructed image with larger data volume is not adopted for encryption, but the color mapping coefficient in the color mapping process is selected for encryption, the video quality in the perceptual encryption is greatly reduced, and in order to meet the code stream compatibility, the exclusive or operation is carried out on the absolute value of the sub-secret key and the color mapping coefficient which are generated by a secret key sequence generator in the AES block encryption method under the CFB mode capable of generating the stream cipher, and the sign bit of the coefficient is kept unchanged; on the other hand, considering that the compatibility of the code stream format is not changed, the absolute value remainder of the nonzero coefficient of the syntax element in the enhancement layer and the sign information of the nonzero coefficient are selected to be encrypted, the format compatibility of the code stream is not changed and the compression efficiency of the code is not influenced when the absolute value remainder and the sign information of the nonzero coefficient are encrypted, and meanwhile, a larger coding space exists to enhance the safety of the encryption algorithm.
Because the encryption of the absolute value remainder of the nonzero coefficient of the syntactic element in the enhancement layer and the sign information of the nonzero coefficient is the texture information encryption, the bit stream of the compressed video can be directly decoded and output under the condition of not decrypting the input video image which is subjected to the coding and the combined encryption, and the bit stream has code stream format compatibility. Therefore, the video encrypted by the method can realize high-security-level protection, so that the interlayer reference image can perform network adaptation on the bit stream and further reduce end-to-end delay, lower compression load and time overhead are introduced, the compatibility of the video format is reserved, the method has practical application value and provides a new solution for the encryption algorithm of scalable coding.

Claims (5)

1. An SHVC video encryption method based on interlayer processing is characterized in that: the method comprises the following steps:
step 1, down-sampling an input video sequence to obtain a sequence with low spatial resolution, inputting the sequence obtained after down-sampling into a base layer, and encoding the sequence input by the base layer by using an HEVC (high efficiency video coding) encoder to generate a base layer encoding bit stream;
step 2, decoding the coded bit stream of the base layer to obtain a reconstructed image of the base layer, and respectively performing texture resampling, motion domain resampling and color mapping on the reconstructed image of the base layer to generate an interlayer reference image; the method comprises the following specific steps of carrying out color mapping on a reconstructed image of a base layer:
step 2-1, performing color mapping on the reconstructed image of the basic layer to obtain color mapping coefficients of three channels, and recording the color mapping coefficients as LutY, lutU and LutV, wherein LutY is a brightness mapping coefficient, and LutU and LutV are mapping coefficients of two different chromaticities;
step 2-2, encrypting the absolute values of the color mapping coefficients of the three channels obtained in the step 2-1 respectively to obtain the color mapping coefficients of the three channels after encryption, which are LutY ', lutU ' and LutV ' respectively;
2-3, cutting a YUV color space of the reconstructed image of the basic layer into n1 x n2 x n3 cuboid partitions; n1, n2 and n3 are integers;
step 2-4, for each cuboid partition, calculating a mapping sample value of an enhancement layer color space according to the color mapping coefficients encrypted by the three channels in the step 2-2;
step 3, constructing a reference image list of the enhancement layer, and putting the interlayer reference image obtained in the step 2 into the reference image list of the enhancement layer for the coding prediction of the enhancement layer;
step 4, inputting the input video sequence into the enhancement layer, transforming and quantizing the input video sequence to obtain quantized transform coefficients, recording 16 quantized transform coefficients contained in 4 × 4 sub-blocks in a quantized transform unit, recording the 16 quantized transform coefficients as a group of coefficient groups, describing the features in each group of coefficient groups by using syntax elements, wherein two syntax elements in each group of coefficient groups are extracted: encrypting the binarization result of the absolute value remainder M of the nonzero coefficient and hiding symbol data of the symbol information coeff _ sign _ flag of the nonzero coefficient, and then entropy coding the two encrypted syntax elements and other remaining syntax elements in each group of coefficients;
the specific steps of encrypting the binarization result of the absolute value remainder M of the nonzero coefficient are as follows:
step 4-1, adopting truncation Rice coding (TR) p ) And order k exponential Golomb Encoding (EG) k ) A binarization combination method is used for carrying out binarization on the absolute value remainder M of the nonzero coefficient to obtain a binarized result; the method comprises the following specific steps:
step 4-1a, calculating a prefix value and a suffix value of the syntax element; the prefix value prefix _ value and suffix value suffix _ value of the syntax element are calculated as:
prefix_value＝min(cMax,M)
suffix_value＝M-cMax
wherein, cMax is a truncation value in truncation Rice coding, cMax =4< < p, wherein < < is left shift operation, and p is Rice parameter;
step 4-1b, using truncated Rice code (TR) p ) Encoding a prefix value prefix-value of a syntax element to obtain a first sub-prefix code M1 and a first sub-postfix code N1, using order k exponential Golomb coding (EG) k ) Coding a suffix value suffix _ value of the syntax element to obtain a second sub-prefix code M2 and a second sub-suffix code N2, wherein k = p +1;
step 4-1c, judging whether M is smaller than cMax, if so, turning to step 4-1d; if not, the binarization result of the absolute value remainder M of the non-zero coefficient consists of a first sub-prefix code M1, a second sub-prefix code M2 and a second sub-postfix code N2 which are sequentially arranged;
step 4-1d, judging whether p is equal to 0, if so, forming a result after binarization of an absolute value remainder M of the non-zero coefficient by using a first sub-prefix code M1; if not, the result of binarization of the absolute value remainder M of the non-zero coefficient consists of a first sub prefix code M1 and a first sub suffix code N1 which are sequentially arranged;
step 4-2, judging whether a first sub suffix code N1 and/or a second sub suffix code N2 exist in the binarization result obtained in the step 4-1, if so, encrypting the existing first sub suffix code N1 and/or second sub suffix code N2, replacing the original first sub suffix code N1 and/or second sub suffix code N2 with the encrypted result, and recombining the binarization result; if not, directly outputting a result after binarization;
the specific steps of hiding the symbol data of the symbol information coeff _ sign _ flag of the nonzero coefficient are as follows:
step a, solving the sum of absolute values of amplitudes of all non-zero coefficients in a group of coefficient groups, then carrying out parity check, if the sum is an even number, judging the sign of the last non-zero coefficient in the group of coefficient groups to be '+', namely SDH =1; if the sum is odd, the sign of the last non-zero coefficient in a group of coefficients is determined to be '-', i.e. SDH =0;
b, respectively carrying out different encryption on the symbol information coeff _ sign _ flag of the non-zero coefficient according to two different symbols of the last non-zero coefficient in the step a to obtain the encrypted symbol information coeff _ sign _ flag' of the non-zero coefficient;
and 5: the enhancement layer input video sequence is subjected to intra-frame prediction, transformation, quantization and entropy coding in step 4 and inter-frame prediction realized by a reference image list of the enhancement layer in step 3 to obtain an enhancement layer coding bit stream;
and 6, constructing the base layer coded bit stream obtained in the step 1 and the enhancement layer coded bit stream obtained in the step 5 into a bit stream coded by the input video sequence.
2. The SHVC video encryption method based on inter-layer processing according to claim 1, wherein: the specific encryption method in step 2-2 is an AES block encryption method in a CFB mode that can generate stream ciphers, and the calculation formulas of the color mapping coefficients LutY ', lutU ', and LutV ' after encryption of the three channels are:
Figure FDA0002418169560000031
Figure FDA0002418169560000032
Figure FDA0002418169560000033
wherein, | | is an absolute value,
Figure FDA0002418169560000034
for XOR operation, k i Is a subkey generated by an encryptor in the AES block encryption method in CFB mode.
3. The SHVC video encryption method based on inter-layer processing according to claim 2, wherein: the calculation formulas of the first sub-prefix code M1, the second sub-prefix code M2, the first sub-postfix code N1 and the second sub-postfix code N2 in the step 4-1b are as follows:
Figure FDA0002418169560000035
Figure FDA0002418169560000036
wherein bin () represents a binary conversion; > > is the right shift operation;
Figure FDA0002418169560000037
a number of "1" + "0";
wherein the content of the first and second substances,
Figure FDA0002418169560000038
Figure FDA0002418169560000039
is an integer taking function;
Figure FDA00024181695600000310
4. the SHVC video encryption method based on inter-layer processing according to claim 3, wherein: the method for encrypting the first sub suffix code N1 in the step 4-2 comprises the following steps:
judging whether the value of M is in the following value range,
Figure FDA00024181695600000311
wherein, the baseleval is a related value of the syntax element, and the value is [1,2,3];
if yes, encrypting the first sub suffix code N1; if not, the first sub suffix code N1 is not encrypted; the calculation formula of the encryption of the first sub suffix code N1 is as follows:
Figure FDA00024181695600000312
wherein, N1' is the result obtained after the first sub suffix code N1 is encrypted;
the calculation formula for encrypting the second sub-postfix code N2 is:
Figure FDA0002418169560000041
wherein, N2' is the result obtained after the second sub suffix code N2 is encrypted.
5. The SHVC video encryption method based on inter-layer processing according to claim 4, wherein: the calculation formula for encrypting the symbol information coeff _ sign _ flag of the syntax element in the step b is as follows:
Figure FDA0002418169560000042
/>
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