Seyfullah H. Oguz

Seamless Audio Splicing for ISO/IEC 13818 Transport Streams

This paper addresses the processing of packetized audio elementary streams (ES) during the splicing of ISO/IEC 13818 (MPEG-2) transport streams (TS). An algorithm is developed that produces a continuous audio ES across the splicing point, avoids all noticeable audio artifacts, and hence provides a seamless audio splice without the need to decode and reencode audio ESs. Perfect continuity with respect to the presentation time stamps (PTS) and careful management of the audio buffer level at all times lead to a glitch-free audio playout for an unlimited number of splices. The proposed algorithm parses the packetized audio ES up to the audio access unit (AAU) level and is very simple to implement.

A scalable representation for motion vectors for rate adaptation to network constraints

There is a growing need for mechanisms to shape the rate of precompressed video for adaptation to network constraints. The motion vector data component in an encoded bitstream might constitute some considerable portion of P and especially B type pictures, yet no technique currently exists to scale it. Motion vectors of neighboring macroblocks tend to be well-correlated in both horizontal and vertical directions. However, the current standards only exploit the horizontal correlations through predictive coding, introducing dependency and thus resulting in a nonscalable representation. In this paper, we propose a new representation and encoding algorithm for the motion vector information enabling the exploitation of two-dimensional (2-D) correlations, and realizing the signal-to-noise ratio (SNR) scaling of an already encoded video object to an alternate (lower) rate - (higher) distortion level. In the proposed approach, the values of the motion vectors are represented in a binary format. Consequently, the individual bit planes of this representation are coded through a novel 2-D hierarchical bit plane encoding scheme. Scaling, when necessary, is achieved by discarding the least significant bit plane(s). Simulations based on MPEG-2 standard demonstrate that up to 20% scaling is achievable without visually noticeable distortion.

Efficient rate adaptation of precompressed video to network constraints via controlled noise injection

In our prior work, we presented an algorithm called largest magnitude coefficient selection (LMCS) for realizing the signal-to-noise-ratio (SNR) scaling an already encoded video object to an alternate (lower) rate (higher) distortion level. We showed that LMCS retains semantically important image features and successfully avoids the common artifacts of blur and ringing noise. However, it suffers from a significant coding inefficiency problem. In this paper, we first identify the mechanisms, which lead to the problem, and consequently present a novel technique called pivoting in order to alleviate it. The comparison of the resulting algorithm, LMCS-pivot, against the conventional SNR scaling techniques demonstrates its effectiveness according to both objective and subjective performance measures.

Objective image quality metrics for dct-based video compression

In this paper, three objective image quality metrics are introduced. These metrics are designed to quantify the severity of the three major types of artifacts associated with block-DCT-based image/video compression schemes, in a manner compatible with HVS. Experimental results from some commercially available encoding applications are reported in a vendor transparent manner, to illustrate the practical usefulness of the proposed metrics to assess compressed image quality aside from their theoretical significance.