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Content for TS 26.445 Word version: 18.0.0

1… 2… 5… 5.2… 5.4… 6… 7…

5.4 Switching of Coding Modes 5.5 Frame erasure concealment side information 5.6 DTX/CNG operation 5.7 AMR-WB-interoperable modes 5.8 Channel Aware Coding
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5.4 Switching of Coding Modes p. 410

5.4.1 General description p. 410

5.4.2 MDCT coding mode to CELP coding mode p. 410

5.4.2.1 MDCT to CELP transition 1 (MC1) p. 411

5.4.2.2 MDCT to CELP transition 2 (MC2) p. 411

5.4.2.3 MDCT to CELP transition 3 (MC3) p. 411

5.4.3 CELP coding mode to MDCT coding mode p. 411

5.4.3.1 CELP coding mode to MDCT based TCX coding mode p. 411

5.4.3.2 CELP coding mode to HQ MDCT coding mode p. 412

5.4.3.2.1 Constrained CELP coding and simplified BWE coding p. 412

5.4.3.2.2 HQ MDCT coding with a modified analysis window p. 413

5.4.4 Internal sampling rate switching p. 414

5.4.4.1 Reset of LPC memory p. 414

5.4.4.2 Conversion of LP filter between 12.8 and 16 kHz internal sampling rates p. 414

5.5.4.1.1 Modification of the Power Spectrum p. 414

5.5.4.1.2 Computation of the Power Spectrum p. 415

5.5.4.1.3 Computation of the Autocorrelation p. 416

5.4.4.3 Extrapolation of LP filter p. 417

5.4.4.4 Buffer resampling with linear interpolation p. 417

5.4.4.5 Update of CELP input signal memories p. 417

5.4.4.6 Update of MDCT-based TCX input signal memories p. 418

5.4.4.7 Update of CELP synthesis memories p. 418

5.4.5 EVS primary and AMR-WB IO p. 418

5.4.5.1 Switching from primary modes to AMR-WB IO p. 418

5.4.5.2 Switching from AMR-WB IO mode to primary modes p. 419

5.4.6 Rate switching p. 419

5.4.6.1 Rate switching along with internal sampling rate switching p. 419

5.4.6.2 Rate switching along with coding mode switching p. 419

5.5 Frame erasure concealment side information p. 420

5.5.1 Signal classification parameter p. 420

5.5.2 Energy information p. 420

5.5.3 Phase control information p. 421

5.5.4 Pitch lag information p. 422

5.5.5 Spectral envelope diffuser p. 422

5.5.6 Tonality flag information p. 423

5.6 DTX/CNG operation p. 424

5.6.1 Overview p. 424

5.6.1.1 SID update p. 425

5.6.1.2 Spectral tilt based SID transmission p. 426

5.6.1.3 CNG selector p. 427

5.6.2 Encoding for LP-CNG p. 427

5.6.2.1 LP-CNG CN parameters estimation p. 428

5.6.2.1.1 LP-CNG Hangover analysis period determination p. 428

5.6.2.1.2 LP-CNG filter parameters evaluation for low-band signal p. 428

5.6.2.1.3 LP-CNG CNG-LSF quantization for low-band signal p. 429

5.6.2.1.4 LP-CNG synthesis filter computation for local CNG synthesis p. 430

5.6.2.1.5 LP-CNG energy calculation and quantization p. 431

5.6.2.1.6 LP-CNG energy smoothing for local CNG synthesis p. 432

5.6.2.1.7 LP-CNG LF-BOOST determination and quantization p. 432

5.6.2.1.8 LP-CNG high band analysis and quantization p. 433

5.6.2.2 LP-CNG local CNG synthesis p. 435

5.6.2.3 LP-CNG CNG Memory update p. 435

5.6.3 Encoding for FD-CNG p. 435

5.6.3.1 Spectral partition energies p. 436

5.6.3.1.1 Computation of the FFT partition energies p. 436

5.6.3.1.2 Computation of the CLDFB partition energies p. 436

5.6.3.1.3 FD-CNG configurations p. 436

5.6.3.2 FD-CNG noise estimation p. 437

5.6.3.2.1 Dynamic range compression for the input energies p. 437

5.6.3.2.2 Noise tracking p. 438

5.6.3.2.3 Dynamic range expansion for the estimated noise energies p. 442

5.6.3.3 Adjusting the first SID frame in FD-CNG p. 442

5.6.3.4 FD-CNG resetting mechanism p. 442

5.6.3.5 Encoding SID frames in FD-CNG p. 442

5.6.3.6 FD-CNG local CNG synthesis p. 444

5.6.3.6.1 SID parameters interpolation p. 445

5.6.3.6.2 LPC estimation from the interpolated SID parameters p. 445

5.6.3.6.3 FD-CNG encoder comfort noise generation p. 445

5.6.3.6.4 FD-CNG encoder memory update p. 445

5.7 AMR-WB-interoperable modes p. 446

5.7.1 Pre-processing p. 446

5.7.2 Linear prediction analysis and quantization p. 446

5.7.2.1 Windowing and auto-correlation computation p. 446

5.7.2.2 Levinson-Durbin algorithm p. 446

5.7.2.3 LP to ISP conversion p. 446

5.7.2.4 ISP to LP conversion p. 447

5.7.2.5 Quantization of the ISP coefficients p. 447

5.7.2.6 Interpolation of the ISPs p. 447

5.7.3 Perceptual weighting p. 447

5.7.4 Open-loop pitch analysis p. 447

5.7.5 Impulse response computation p. 447

5.7.6 Target signal computation p. 447

5.7.7 Adaptive codebook search p. 448

5.7.8 Algebraic codebook search p. 448

5.7.9 Quantization of the adaptive and fixed codebook gains p. 448

5.7.10 Memory update p. 448

5.7.11 High-band gain generation p. 448

5.7.12 CNG coding p. 448

5.8 Channel Aware Coding p. 448

5.8.1 Introduction p. 448

5.8.2 Principles of Channel Aware Coding p. 449

5.8.3 Bit-Rate Allocation for Primary and Partial Redundant Frame Coding p. 450

5.8.3.1 Primary frame bit-rate reduction p. 450

5.8.3.2 Partial Redundant Frame Coding p. 450

5.8.3.2.1 Construction of partial redundant frame for Generic and Voiced Coding modes p. 450

5.8.3.2.2 Construction of partial redundant frame for Unvoiced Coding mode p. 450

5.8.3.2.3 Construction of partial redundant frame for TCX frame p. 451

5.8.3.2.4 RF_NO_DATA partial redundant frame type p. 451

5.8.3.3 Decoding p. 451

5.8.4 Channel aware mode encoder configurable parameters p. 451