Error Concealment for Speech or Audio

The repairing or loss recovery techniques, as stated in [60], for speech are summarized as follows.

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(i)

Silence Substitution - substitution of the lost packet with silence. That technique causes voice clipping. This deteriorates voice quality when packet size is large, and loss rate is high.

(ii)

Noise Substitution - substitution of lost packet by white (background) noise is better than silence substitution. This has been attributed to the ability of the human brain to repair the received message if there is some background noise (known as phonemic restoration).

(iii)

Packet Repetition - replaying the last correctly received packet in place of the lost one. The Global System for Mobile (GSM) recommends that the repeated signal be damped or faded to ensure better quality.

(iv)

Packet Interpolation - Interpolation-based repairs use the characteristics of the packets in the neighborhood of the lost one to produce a replacement. This technique is also known as waveform repetition. This ensure that the replacement will follow the changing characteristics of the whole voice stream, and hence yield better quality.

(v)

Frame Interleaving - The effect of packet loss can be reduced by interleaving voice frames across different packets. The loss of a single packet will produce multiple short gaps in different streams, which is more tolerable than long gaps. But this technique produces longer delays.