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Traditional chaos-based encryption techniques use pseudorandom codes to implement encryption (e.g., XOR; exclusive or operation) directly, resulting in the violation of requirements for media compression formats for image transmission. In this study, a programmable spatial light modulator (SLM)-based optical wavelength filter was investigated for implementing a scrambling-based cryptographic scheme in WDM networks. A new chaotic tent/hologram mapping algorithm (THmA) and advanced THmA are proposed for triggering the programmable SLM-based filter array. Similarly, an approximately symmetric scheme was used to configure a scrambling SLM-based decryption scheme for performing decryption operations when the initial value and control parameters of the chaotic sequence as individual secret keys are communicated in advance over a private channel. The proposed scheme was evaluated using video application-layer experiments. The results revealed that compared with conventional reconfigurable schemes involving triggered registers and switches behind an AWG router, the number of code space sizes involved in the proposed cryptographic scheme increased by more than 1.31E + 89 times, thereby avoiding eavesdropping attacks in the physical layer. Furthermore, on the basis of the reduced peak signal-to-noise ratio of the encrypted videos and the unidentifiability of the videos to unauthorized users, the scrambling efficiency of the proposed scheme was sufficiently high.

In this paper, a prediction technique for the best coding unit (CU) partition tree is proposed to avoid the repeated computation on the variable-sized prediction units (PU) and transform units (TU) in high efficiency video coding (HEVC). In HEVC, many advanced coding tools are introduced to decrease the bit-rate of coded videos with higher visual quality. Of these tools, many seek to partition each CU in the incoming frame into a quad-tree structure of variable sized blocks while performing prediction and transform computations to obtain the optimal rate-distortion performance. During partition tree generation, the CU block and its four partitioned child-blocks need to become PU and TU for calculating the coding rate-distortion cost. This process requires more execution time from the processor because of highly repeated computations on PUs and TUs before finding the best quad-tree partition tree. The proposed prediction technique is based on edge information from the content of the considered CU and the depth information of partition tree from the co-located CU in the neighboring video frames for being able to adapt the reduction of computation time with the varying content in the incoming frames. When the CU is in a smooth frame, the information from the neighboring frames would dominate the prediction results of the partition tree; however, the edge information of the current CU mainly determines the partition tree. With the prediction technique, experiments on several benchmark videos show that the encoding time of HEVC can be reduced by 44.1 % at an acceptable degradation of coding efficiency.

To enhance the security of H.264/AVC streaming, such as that for Internet protocol television, over a passive optical network (PON), a dynamic reconfigurable coding---decoding scheme, based on a chaotic sequence, was demonstrated and characterised by pseudo randomness and a maximal period. Compared with conventional optical code-division multiple-access (OCDMA) PONs, without providing a dynamic reconfigurable mechanism and trigger timing, a secure mechanism was generated using a proposed chaos/maximal length sequence (M-sequence) mapping algorithm and embedded in a codebook to control an electrical controller (register). Because the state of the electrical controller (register) is used by the chaos/M-sequence mapping time sequence pattern to trigger a switch matrix and then vary the M-sequence signature address code for each authorised user, the scrambling and interleaving function of the encryption scheme was implemented in the OCDMA-PON physical layer for various M-sequence signature address codes to carry individual H.264/AVC transmissions of the same channel. The proposed chaos/M-sequence mapping algorithm provided similar pseudo randomness and higher variance effectiveness compared with a general uniform distribution of the pseudo-random, autocorrelation, and cross-correlation properties of the proposed time sequence. In addition, the scrambling and interleaving efficiency was determined to be sufficiently high by the reduced peak signal-to-noise ratio of encrypted videos and the produced unidentifiable videos for unauthorised users.