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Master-Vortrag: Extension of speech and audio codecs for low-delay multi-channel transmission
Ganlong Wang
25. Januar 2013
11:00 Uhr
Hörsaal 4G IKS
Multi-channel audio signals contain spatial information of the audio source. They are already very common in many everyday applications such as home theater or cinema. The current multi-channel coding techniques (which usually use subband coding) have got algorithmic delays in the range of a few hundreds of milliseconds. Thus, these techniques are not suitable for real time communication scenarios where a low algorithmic delay is essential. Due to this, linear prediction-based coders are a very attractive alternative as they can achieve lower delay.
In this thesis, an existing low-delay audio coding scheme, which uses inter-channel prediction, was reviewed and its characteristics with respect to audio quality, transmission robustness, and delay were investigated. Previous results have shown that long filter lengths can increase the transmission robustness. However, further research on the codec in this thesis shows that long filter lengths can decrease the average audio quality as determined by instrumental quality measures. Therefore, the focus is first on the investigation of possible reasons for this phenomenon. Subsequently, a modified codec is proposed which incorporates noise shaping and phase alignment. Finally, its structure is analyzed and its performance is evaluated which is shown to be superior to the previous system.
