IEEE Transactions on Circuits and Systems for Video Technology

We investigate the image authentication system SARI, proposed by Lin and Chang (see ibid., vol.11, p.153-68, Feb. 2001), that distinguishes JPEG compression from malicious manipulations. In particular, we took at the image digest component of this system. We show that if multiple images have been authenticated with the same secret key and the digests of these images are known to an attacker, Oscar... View full abstract»

We formulate a congestion control problem for multipoint videoconferencing by introducing the concept of generalized fairness. A numerical method is provided to solve such a congestion control problem. The proposed method is much simpler than an earlier proposed method. This is desirable because congestion control is executed in real time. View full abstract»

Both high-definition television (HDTV) and, standard-definition television (SDTV) use the MPEG-2 video coding standard, but they have different spatial resolutions. In order to support the interlaced video coding, MPEG-2 incorporates various macroblock prediction modes. Thus, the HDTV-to-SDTV transcoding needs to handle spatial resolution downscaling and various MEPG-2 macroblock prediction modes.... View full abstract»

Transform approximations are explored for speeding up the software compression of images and video. Approximations are used to replace the regular discrete cosine transform (DCT) whenever only a few DCT coefficients are actually encoded. We employ a novel hierarchical vector quantization (HVQ)-based image analyzer to drive a bank of coders, thus switching to the fastest coder depending on the imag... View full abstract»

This paper investigates linearly combined motion-compensated signals for video compression. In particular, we discuss multiple motion-compensated signals that are jointly estimated for efficient prediction and video coding. First, we extend the wide-sense stationary theory of motion-compensated prediction (MCP) for the case of jointly estimated prediction signals. Our theory suggests that the gain... View full abstract»

Despite the availability of video-on-demand (VoD) services in a number of cities around the world, large-scale deployment of VoD services in a metropolitan area is still economically impractical. This study presents a novel super-scalar architecture for building very large-scale and efficient VoD systems. The proposed architecture combines the use of static multicast, dynamic multicast, and intell... View full abstract»

MPEG-4 is the first object-based audiovisual coding standard. To control the minimum decoding complexity resources required at the decoder, the MPEG-4 Visual standard defines the so-called video buffering verifier mechanism, which includes three virtual buffer models, among them the video complexity verifier (VCV). This paper proposes an alternative VCV model, based on a set of macroblock (MB) rel... View full abstract»

This paper discusses the problem of reduced-resolution transcoding of compressed video bitstreams. An analysis of drift errors is provided to identify the sources of quality degradation when transcoding to a lower spatial resolution. Two types of drift error are considered: a reference picture error, which has been identified in previous works, and error due to the noncommutative property of motio... View full abstract»

We show that, in any typical transform coding system, there is always a linear relationship between the coding bit rate R and the percentage of zeros among the quantized transform coefficients, denoted by ρ. Based on Shannon's source coding theorem, a theoretical justification is provided for this linear source model. The physical meaning of the model parameter is also discussed. We show that ... View full abstract»