Stream programming for image and video compression

Abstract

Video playback devices rely on compression algorithms to minimize storage, transmission bandwidth, and overall cost. Compression techniques have high realtime and sustained throughput requirements, and the end of CPU clock scaling means that parallel implementations for novel system architectures are needed. Parallel implementations increase the complexity of application design. Current languages force the programmer to trade off productivity for performance; the performance demands dictate that the parallel programmer choose a low-level language in which he can explicitly control the degree of parallelism and tune his code for performance. This methodology is not cost effective because this architecture-specific code is neither malleable nor portable. Reimplementations must be written from scratch for each of the existing parallel and reconfigurable architectures. This thesis shows that multimedia compression algorithms, composed of many independent processing stages, are a good match for the streaming model of computation. Stream programming models afford certain advantages in terms of programmability, robustness, and achieving high performance.

(cont.) This thesis intends to influence language design towards the inclusion of features that lend to the efficient implementation and parallel execution of streaming applications like image and video compression algorithms. Towards this I contribute i) a clean, malleable, and portable implementation of an MPEG-2 encoder and decoder expressed in a streaming fashion, ii) an analysis of how a streaming language improves programmer productivity, iii) an analysis of how a streaming language enables scalable parallel execution, iv) an enumeration of the language features that are needed to cleanly express compression algorithms, v) an enumeration of the language features that support large scale application development and promote software engineering principles such as portability and reusability. This thesis presents a case study of MPEG-2 encoding and decoding to explicate points about language expressiveness. The work is in the context of the StreamIt programming language.