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Content for TS 26.447 Word version: 18.0.0

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5.1 Concealment operation related to signal classification 5.2 Concealment operation related to spectral envelope (LPC) representation 5.3 Concealment operation related to ACELP modes 5.4 Concealment operation related to MDCT modes 5.5 SID frame concealment operation

5 Detailed description p. 8

5.1 Concealment operation related to signal classification p. 8

5.1.1 Overview p. 8

5.1.2 Signal class estimation p. 8

5.2 Concealment operation related to spectral envelope (LPC) representation p. 11

5.2.1 Specifics to rates 9.6, 16.4 and 24.4kbps p. 12

5.2.2 Specifics to AMR-WB IO mode p. 12

5.2.3 Check for Mid LSF stability p. 12

5.2.4 Adaptive interpolation of LSFs p. 13

5.2.5 LPC gain compensation p. 14

5.3 Concealment operation related to ACELP modes p. 15

5.3.1 General p. 15

5.3.1.1 Extrapolation of future pitch p. 15

5.3.1.2 Construction of the periodic part of the excitation p. 17

5.3.1.2.1 Particularity of rate 5.9, 7.2, 8.0 and 13.2 kbps p. 18

5.3.1.3 Glottal pulse resynchronization p. 18

5.3.1.3.1 Condition to perform resynchronisation p. 18

5.3.1.3.2 Performing glottal pulse resynchronization p. 19

5.3.1.4 Construction of the random part of the excitation p. 20

5.3.1.5 Spectral envelope concealment, synthesis and updates p. 21

5.3.1.5.1 Specifics for rates 9.6, 16.4 and 24.4 kbps p. 21

5.3.1.6 GSC mode concealment p. 21

5.3.1.7 Specifics for AMR-WB IO modes p. 22

5.3.1.8 Reconstructed excitation p. 23

5.3.1.8.1 Particularity of rate 5.9, 7.2, 8.0 and 13.2 kbps p. 23

5.3.2 Concealment for bandwidth extension for ACELP modes p. 24

5.3.2.1 Time domain bandwidth extension p. 24

5.3.2.1.1 SWB time domain bandwidth extension p. 24

5.3.2.1.1.1 The reconstruction of the global frame gain p. 24

5.3.2.1.1.2 The reconstruction of the gain attenuation factor p. 25

5.3.2.1.1.3 Specifics for rates 13.2 and 32 kbps p. 27

5.3.3 Guided concealment and recovery p. 28

5.3.3.1 Specifics for rate 24.4 kbps p. 28

5.3.3.2 Specifics for rates 9.6, 16.4 and 24.4 kbps p. 29

5.3.3.3 Energy control during recovery p. 29

5.3.3.4 Specifics for rates 32 and 64 kbps p. 32

5.3.3.4.1 Adaptive codebook resynchronization and fast recovery (WB) p. 32

5.3.3.4.1.1 Decoding glottal pulse position p. 32

5.3.3.4.1.2 Performing glottal pulse resynchronization p. 32

5.3.3.4.2 Artificial onset reconstruction p. 33

5.3.4 Handling of multiple frame losses and muting p. 34

5.3.4.1 Specifics for rates 5.9, 6.8, 8.0, 13.2, 32 and 64 kbps p. 34

5.3.4.2 Specifics for rates 9.6, 16.4 and 24.4 kbps p. 35

5.3.4.2.1 Fading to background level p. 35

5.3.4.2.2 Fading to background spectral shape p. 36

5.3.4.2.3 Fading speed p. 36

5.4 Concealment operation related to MDCT modes p. 37

5.4.1 PLC method selection p. 37

5.4.2 TCX MDCT p. 37

5.4.2.1 PLC method selection p. 37

5.4.2.2 TCX time domain concealment p. 39

5.4.2.2.1 Construction of the periodic part of the excitation p. 39

5.4.2.2.2 Construction of the random part of the excitation p. 40

5.4.2.2.3 Construction of the total excitation, synthesis and updates p. 41

5.4.2.3 MDCT frame repetition with sign scrambling p. 41

5.4.2.4 Tonal MDCT concealment using phase prediction p. 41

5.4.2.4.1 Overview p. 41

5.4.2.4.2 Peak detection of tonal components p. 42

5.4.2.4.3 Phase prediction p. 44

5.4.2.5 Non-tonal concealment with waveform adjustment p. 45

5.4.2.5.1 Preliminary concealment in frequency domain p. 45

5.4.2.5.2 Waveform adjustment in time domain p. 46

5.4.2.6 Intelligent gap filling p. 49

5.4.3 HQ MDCT p. 50

5.4.3.1 Preliminary signal analysis of past synthesis p. 50

5.4.3.1.1 Resampling to 8 kHz p. 50

5.4.3.1.2 Pitch search by cross-correlation p. 50

5.4.3.2 PLC method selection p. 51

5.4.3.3 MDCT frame repetition with random sign and gain scaling p. 54

5.4.3.4 MDCT frame repetition with sign prediction p. 59

5.4.3.5 Phase ECU p. 60

5.4.3.5.1 Transient analysis p. 60

5.4.3.5.2 Spectrum analysis p. 62

5.4.3.5.3 Frame reconstruction p. 63

5.4.3.6 MDCT concealment based on sinusoidal synthesis and adaptive noise filling p. 64

5.4.3.6.1 FFT p. 64

5.4.3.6.2 Selection of sinusoidal components p. 65

5.4.3.6.3 Sinusoidal synthesis p. 65

5.4.3.6.4 Adaptive noise filling p. 65

5.4.3.6.5 Synthesis p. 66

5.4.3.7 Time-domain PLC and OLA p. 66

5.4.3.7.1 PLC mode selection p. 66

5.4.3.7.2 Phase matching p. 70

5.4.3.7.3 Repetition and smoothing p. 73

5.4.4 Void

5.4.5 Guided concealment and recovery p. 78

5.4.5.1 Transmission of the synthesis class p. 78

5.4.5.2 Transmission of the LTP pitch lag p. 78

5.4.5.3 Transmission of a voicing indicator p. 78

5.4.5.3a Transmission of a tonality flag p. 78

5.4.5.4 ACELP to MDCT mode recovery p. 78

5.4.5.5 Recovery after TCX MDCT concealment p. 79

5.4.6 Handling of multiple frame losses and muting p. 79

5.4.6.1 TCX MDCT p. 79

5.4.6.1.1 Background level tracing for rates 48, 96 and 128 kbps p. 79

5.4.6.1.2 TCX time domain concealment p. 79

5.4.6.1.3 MDCT frame repetition with sign scrambling p. 80

5.4.6.1.4 Fading speed p. 82

5.4.6.1.5 Waveform adjustment p. 82

5.4.6.2 HQ MDCT p. 82

5.4.6.2.1 Burst loss handling for 8 kHz audio output sampling rate p. 82

5.4.6.2.2 Burst loss handling audio output sampling rates larger or equal to 16 kHz p. 82

5.5 SID frame concealment operation p. 83

$ Change history p. 84