5 Requirements

26.1913GPPAdaptive Multi-Rate - Wideband (AMR-WB) speech codecError concealment of erroneous or lost framesRelease 17Speech codec speech processing functionsTS

5.1 Error detection

If the most sensitive bits of the AMR-WB speech data (class A in [4]) are received in error, the network shall indicate RX_TYPE = SPEECH_BAD in which case the BFI flag is set. When the frame is not received, the network shall indicate RX_TYPE = RX_SPEECH_LOST in which case the BFI flag is set as well. If a SID frame is received in error, the network shall indicate RX_TYPE = SID_BAD..

5.2 Erroneous or lost speech frames

Normal decoding of erroneous/lost speech frames would result in very unpleasant noise effects. In order to improve the subjective quality, erroneous/lost speech frames shall be substituted with either a repetition or an extrapolation of the previous good speech frame(s). This substitution is done so that it gradually will decrease the output level, resulting in silence at the output. Subclause 6 provides example solution.

5.3 First lost SID frame

A lost SID frame shall be substituted by using the SID information from earlier received valid SID frames and the procedure for valid SID frames be applied as described in [3].

5.4 Subsequent lost SID frames

For many subsequent lost SID frames, a muting technique shall be applied to the comfort noise that will gradually decrease the output level. For subsequent lost SID frames, the muting of the output shall be maintained. Subclause 6 provides example solutions.