Development of Scalable Coding of Encrypted Images Using Modified Absolute Moment Block Truncation Code

Many researchers worked on scalable coding for unencrypted images, and there is more space for research in scalable coding for encrypted images. This paper proposes a novel method of scalable coding for encrypted images, especially for lossy compression images using the Modified Absolute Moment Block Truncation Code (MAMBTC) technique. The given input image is compressed using MAMBTC and then encrypted using a Pseudo-Random Number (PRNG) at the encryption phase. The PRNG is shared between the encoder and the decoder. At the decryption phase, the compressed pixel value is obtained by decryption using the PRNG and then reconstructed using MAMBTC, scaled by scaling factor 2 and Bilinear Interpolation Technique to obtain the original image. MAMBTC gives better image quality than Block Truncation Code (BTC), a higher PSNR of 36.32 dB, and a Compression ratio of 1.09, which makes the proposed system ready for the signal processing community/applications.

Video bit-rate requirements for 8K 120-Hz HEVC/H.265 temporal scalable coding: experimental study based on 8K subjective evaluations

8K video parameters were designed to provide an immersive experience; meanwhile, special considerations are necessary to assess the entire screen subjectively. This paper studies the video bit-rate required for 8K 119.88-Hz (120-Hz) and 59.94-Hz (60-Hz) the high efficiency video coding (HEVC)/H.265 temporal scalable coding based on subjective evaluation experiments. To investigate the appropriate bit-rate for both 8K 120- and 60-Hz videos for broadcasting purposes, we compress 8K 120-Hz test sequences using software that emulates our real-time HEVC encoder and conduct two types of experiments. The experimental results demonstrate that the required video bit-rate for 8K 120-Hz temporal scalable coding is estimated to be 85–110 Mbps, which is equivalent to the practical bit-rate for 8K 60-Hz videos, and the appropriate bit-rate for 8K 60-Hz video in 8K 120-Hz video at 85 Mbps is assumed to be ~80 Mbps. From the analyses of the encoded videos, it is confirmed that the experimental results are primarily influenced by the image quality on the slice boundary positioned at the middle of the screen height. When conducting the experiments, we determined settings referring to an initial 8K subjective assessment; we further mention requirements for future 8K subjective evaluations from the experimental results.

Development of a Scalable Coding for the Encryption of Images using Diagonal Min-Max Block Truncation Code

This paper proposes a scalability coding on encrypted images, especially resolution scalability on lossy compression images. In the compression stage, the input gray level image is compressed using Diagonal Min-Max Block Truncation Coding technique. The compressed input image is encrypted using pseudorandom numbers masked by modulo-256, and then the encoded bit streams are transmitted. The pseudorandom numbers generated will be the encrypted key and the same is shared to the receiver. In the receiver side, the encoded bit stream is decrypted by using the shared encrypted key, which gives the compressed pixel value. Then the original image is reconstructed by using Diagonal Min-Max Block Truncation Coding Technique.