Media authentication and tampering localization are important in content delivery via untrusted intermediaries, such as peer-to-peer (P2P) file sharing. Many differently encoded versions of a media file might exist. Our previous work applied distributed source coding to authenticate the legitimate diversity of encoded images and also localize the tampered regions in an inauthentic image. The authentication/localization decoder was supplied with a Slepian-Wolf encoded image projection as authentication data. We extend our scheme to localize tampering in contrast and brightness adjusted images using an expectation maximization algorithm at the decoder. Experimental results demonstrate that tampered image blocks can be identified with high probability using data of only a few hundred bytes for a 512 times 512 image.

Media authentication is important in content delivery via untrusted intermediaries, such as peer-to-peer (P2P) file sharing. Many differently encoded versions of a media file might exist. Our previous work applied distributed source coding not only to distinguish the legitimate diversity of encoded images from tampering but also localize the tampered regions in an image already deemed to be inauthentic. An authentication decoder was supplied with a Slepian-Wolf encoded image projection as authentication data. We extend our scheme to authenticate contrast and brightness adjusted images using an Expectation Maximization algorithm. Experimental results demonstrate that the proposed algorithm can distinguish legitimate encodings of authentic contrast and brightness adjusted images from illegitimately modified versions using authentication data of about 100 bytes.

A fast mode decision algorithm for an H.264 encoder is proposed which reduces computation by using a statistical dependency of macroblock rate-distortion (RD) costs. The algorithm skips the motion estimation and/or intra prediction mode decision with an adaptive threshold. The simulation results show that the proposed algorithm achieves an almost 2X speedup with negligible degradation in coding efficiency.

Media processing system-on-chips (SoCs) mainly consist of audio encoding/decoding (e.g. AC-3, MP3), video encoding/decoding (e.g. H263, MPEG-2) and video pixel processing functions (e.g. de-interlacing, noise reduction). Video pixel processing functions have very high computational demands, as they require a large amount of computations on large amount of data (note that the data are pixels of completely decoded pictures). In this paper, we focus on video pixel processing functions. Usually, these functions are implemented in dedicated hardware. However, flexibility (by means of programmability or reconfigurability) is needed to introduce the latest innovative algorithms, to allow differentiation of products, and to allow bug fixing after fabricating chips. It is impossible to fulfill the computational requirements of these functions by current programmable media processors. To achieve efficient implementations for flexible solutions, we will study, in this paper, the application characteristics of some representative video pixel processing functions. The characteristics considered are granularity of operations, amount and kind of data accesses and degree of parallelism present in these functions. We observe that from computational granularity point of view many functions can be expressed in terms of kernels e.g. Median3 (i.e. median of three values), finite impulse response (FIR) filters, table lookups (LUT) etc. that are coarser grain than ALU, Mult, MAC, etc. Regarding the kind of data accesses, we categorize these functions as regular, regular with some data rearrangement and irregular data access patterns. Furthermore, the degree of parallelism present in these functions is expressed in terms of data level parallelism (DLP) and instruction/operation level parallelism (ILP). We show with an example that these properties can be exploited to make specialized programmable processors.

The techniques for video format conversion have reached a maturity, where they no longer prohibit application in the consumer domain because of high price or clear picture degradation. Given the resulting new freedom, the question arises how to optimally choose a display format, i.e. free from the television history. We present an evaluation of various realistic display formats, all using the same pixel frequency, obtained from a subjective assessment of critical image material originated either for television, or obtained from Internet pages.

The question "to interlace or not to interlace" divides the television and the personal computer communities. A proper answer requires a common understanding of what is possible nowadays in deinterlacing video signals. This paper outlines the most relevant proposals, ranging front simple linear methods to advanced motion-compensated algorithms, and provides a relative performance comparison for 12 of these methods. Next to objective performance indicators, screen photographs have been used to illustrate typical artifacts of individual deinterlacers. The overview provides no final answer in the interlace debate, as such requires unavailable capabilities in balancing technical and nontechnical issues.