Flexcode

FlexCode

Communication systems form a defining aspect of modern society. Particularly important in this respect is the transmission of audio-visual information, since it is a fundamental means of human interaction. The rapid growth in network capacity and the increasing diversity of services is associated with a rapidly increasing heterogeneity of network attributes and quality of services (QoS). Current state-of-the-art coding systems for audio and video are designed for a particular scenario, and will fail if faced with a communication channel with different properties. In contrast, we propose to introduce flexibility into source and channel coding algorithms. To this purpose we will develop a new paradigm that replaces off-line coder design by real-time coder design, thus ensuring the optimality of the coder over a large range of environmental conditions (e.g., rate, quality, and robustness requirements imposed by the channel). The new algorithms are expected to retain or improve on the efficiency of current state-of-the-art algorithms. The new paradigm is based on the usage of universal statistical models of the sources and channels, and generic models of distortion. The flexibility is obtained through the use of models that allow analytically derived source and channel coding methods that do not require training.

The transmission of audio-visual information represents a fundamental means of human interaction. The rapid growth in network capacity and the increasing diversity of services is associated with a rapidly increasing heterogeneity of network attributes and quality of service (QoS). To retain high efficiency and thus low cost in the complex communication environment, it is imperative to transmit the audio-visual data in an efficient and yet flexible manner. In FlexCode, we propose to develop a new generation of generic coding algorithms that are significantly more flexible than existing algorithms, which are application-specific, while retaining or improving on the efficiency and quality of current state-of-the-art algorithms.

The first objective of FlexCode is to develop a practical flexible, parameterized, generic coding system with the following properties:

instantaneous adaptation to rate, quality, and robustness requirements;
usage of advanced perceptual error criteria;
adaptation to channel quality: packet loss rate and bit error rate;
the ability to decode if layer(s) of bits have been removed from the coded bit stream;
reasonable computational and memory complexity.

The new coding paradigm will be a break-through in terms of its ability to adapt in real-time to the environment (user and network requirements).

The second objective of FlexCode is to demonstrate practical implementations of our system for two relevant service applications, using speech and audio coding. We will create a software simulation with a coding performance that is similar to the performance obtained with corresponding state-of-the-art standardized coders in the considered service contexts. The advance over the state-of-the-art systems will be that the FlexCode system will maintain near-optimal performance under a large range of channel and QoS conditions and facilitates instantaneous adaptation to channel and QoS conditions. We will create a real-time version of this software simulation and test this on a commercial communication network. We will use both formal subjective testing and the objective quality measures PEAQ and PESQ to compare the performance of our system with that of state-of-the-art system, focusing on rates between 10 and 30 kb/s.