Analysis of "Dropout Concealment" Algorithmen

Diploma thesis 1200KB

Wireless transmission of audio data is afflicted with transmission errors. To account for these dropouts different concealment techniques have been developed. We discern two different methods: substitution (pattern matching) and extrapolation algorithms.

The aim of this diploma thesis is to investigate different concealment methods, and to estimate their applicability and efficiency. By means of a subjective and an objective test the analysis can be executed. Both tests rest upon the ITU-R five-grade impairment scale given in Recommendation ITU-R BS.1284. With these results it is possible to compare the algorithms amongst each other and to find the most efficient methods. Further on optimizations of the algorithms can be determined.

Two enhancements of the substitution algorithm are implemented. The „average magnitude difference function“ and the „zero crossing rate“ are the basis for these enhancements. After the implementation a further subjective test can be executed. With these results it is possible to compare the quality of the enhanced algorithms and the quality of the original algorithms amongst each other. In addition to that it is possible to find out if the enhancements have really improved the quality of the concealment.