Bidirectional cascaded long term prediction for frame loss concealment in polyphonic audio signals
This paper proposes a frame loss concealment technique for audio signals, which is designed to overcome the main challenge due to the polyphonic nature of most music signals and is inspired by our recent research on compression of such signals. The underlying idea is to employ a cascade of long term prediction filters (tailored to the periodic components) to circumvent the pitfalls of naive waveform repetition, and to enable effective time-domain prediction of every periodic component from the immediate history. In the first phase, a cascaded filter is designed from available past samples and is used to predict across the lost frame(s). Available future reconstructed samples allow refinement of the filter parameters to minimize the squared prediction error across such samples. In the second phase a prediction is similarly performed in reverse from future samples. Finally the lost frame is interpolated as a weighted average of forward and backward predicted samples. Objective and subjective evaluation results for the proposed approach, in comparison with existing techniques, all incorporated within an MPEG AAC low delay decoder, provide strong evidence for considerable gains across a variety of polyphonic signals.