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Content for TS 26.445 Word version: 18.0.0

1… 2… 5… 5.2… 5.4… 6… 7…

5.2 LP-based Coding 5.3 MDCT Coding Mode
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5.2 LP-based Coding p. 135

5.2.1 Perceptual weighting p. 135

5.2.2 LP filter coding and interpolation p. 136

5.2.2.1 LSF quantization p. 136

5.2.2.1.1 LSF weighting function p. 136

5.2.2.1.2 Bit allocation p. 139

5.2.2.1.3 Predictor allocation p. 140

5.2.2.1.4 LSF quantizer structure p. 140

5.2.2.1.5 LSFQ for voiced coding mode at 16 kHz internal sampling frequency : BC-TCVQ p. 145

5.2.2.1.6 Mid-frame LSF quantizer p. 152

5.2.3 Excitation coding p. 153

5.2.3.1 Excitation coding in the GC, VC and high rate IC/UC modes p. 153

5.2.3.1.1 Computation of the LP residual signal p. 154

5.2.3.1.2 Target signal computation p. 155

5.2.3.1.3 Impulse response computation p. 155

5.2.3.1.4 Adaptive codebook p. 155

5.2.3.1.5 Algebraic codebook p. 158

5.2.3.1.6 Combined algebraic codebook p. 168

5.2.3.1.7 Gain quantization p. 182

5.2.3.2 Excitation coding in TC mode p. 187

5.2.3.2.1 Glottal pulse codebook search p. 187

5.2.3.2.2 TC frame configurations p. 191

5.2.3.3 Excitation coding in UC mode at low rates p. 196

5.2.3.3.1 Structure of the Gaussian codebook p. 196

5.2.3.3.2 Correction of the Gaussian codebook spectral tilt p. 197

5.2.3.3.3 Search of the Gaussian codebook p. 198

5.2.3.3.4 Quantization of the Gaussian codevector gain p. 199

5.2.3.3.5 Other parameters in UC mode p. 200

5.2.3.3.6 Update of filter memories p. 200

5.2.3.4 Excitation coding in IC and UC modes at 9.6 kbps p. 200

5.2.3.4.1 Algebraic codebook p. 201

5.2.3.4.2 Gaussian noise generation p. 202

5.2.3.4.3 Gain coding p. 202

5.2.3.4.4 Memory update p. 204

5.2.3.5 Excitation coding in GSC mode p. 204

5.2.3.5.1 Determining the subframe length p. 205

5.2.3.5.2 Computing time-domain excitation contribution p. 205

5.2.3.5.3 Frequency transform of residual and time-domain excitation contribution p. 206

5.2.3.5.4 Computing energy dynamics of transformed residual and quantization of noise level p. 207

5.2.3.5.6 Find and encode the cut-off frequency p. 207

5.2.3.5.7 Band energy computation and quantization p. 209

5.2.3.5.8 PVQ Bit allocation p. 209

5.2.3.5.9 Quantization of difference signal p. 210

5.2.3.5.10 Spectral dynamic and noise filling p. 210

5.2.3.5.11 Quantized gain addition, temporal and frequency contributions combination p. 210

5.2.3.5.12 Specifics for wideband 8kbps p. 211

5.2.3.5.13 Inverse DCT p. 212

5.2.3.5.14 Remove pre-echo in case of onset detection p. 212

5.2.4 Bass post-filter gain quantization p. 213

5.2.5 Source Controlled VBR Coding p. 213

5.2.5.1 Principles of VBR Coding p. 213

5.2.5.2 EVS VBR Encoder Coding Modes and Bit-Rates p. 214

5.2.5.3 Prototype-Pitch-Period (PPP) Encoding p. 214

5.2.5.3.1 PPP Algorithm p. 214

5.2.5.3.2 Amplitude Quantization p. 216

5.2.5.3.3 Phase Quantization p. 216

5.2.5.4 Noise-Excited-Linear-Prediction (NELP) Encoding p. 216

5.2.5.5 Average Data Rate (ADR) Control for the EVS VBR mode p. 216

5.2.6 Coding of upper band for LP-based Coding Modes p. 220

5.2.6.1 Bandwidth extension in time domain p. 220

5.2.6.1.1 High band target signal generation p. 221

5.2.6.1.2 TBE LP analysis p. 222

5.2.6.1.3 Quantization of linear prediction parameters p. 224

5.2.6.1.4 Interpolation of LSF coefficients p. 227

5.2.6.1.5 Target and residual energy calculation and quantization p. 229

5.2.6.1.6 Generation of the upsampled version of the lowband excitation p. 229

5.2.6.1.7 Non-Linear Excitation Generation p. 230

5.2.6.1.8 Spectral flip of non-linear excitation in time domain p. 231

5.2.6.1.9 Down-sample using all-pass filters p. 231

5.2.6.1.10 Adaptive spectral whitening p. 232

5.2.6.1.11 Envelope modulated noise mixing p. 232

5.2.6.1.12 Spectral shaping of the noise added excitation p. 234

5.2.6.1.13 Post processing of the shaped excitation p. 235

5.2.6.1.14 Estimation of temporal gain shape parameters p. 236

5.2.6.1.15 Estimation of frame gain parameters p. 239

5.2.6.1.16 Estimation of TEC/TFA envelope parameters p. 241

5.2.6.1.17 Estimation of full-band frame energy parameters p. 244

5.2.6.2 Multi-mode FD Bandwidth Extension Coding p. 246

5.2.6.2.1 SWB/FB Multi-mode FD Bandwidth Extension p. 246

5.2.6.2.2 WB Multi-mode FD Bandwidth Extension p. 257

5.2.6.3 Coding of upper band at 64 kb/s p. 261

5.2.6.3.1 Coding in normal mode p. 261

5.2.6.3.2 Coding in transient mode p. 265

5.3 MDCT Coding Mode p. 268

5.3.1 General description p. 268

5.3.2 Time-to-frequency transformations p. 268

5.3.2.1 Transform sizes and MDCT configurations p. 268

5.3.2.2 Long block transformation (ALDO window) p. 268

5.3.2.2.1 Folding and on-the-fly window decimation p. 270

5.3.2.2.2 eDCT p. 272

5.3.2.3 Transient location dependent overlap and transform length p. 274

5.3.2.4 Short block transformation p. 275

5.3.2.4.1 Short window transform in TDA domain p. 275

5.3.2.4.2 Short window transform for MDCT based TCX p. 279

5.3.2.5 Special window transitions p. 280

5.3.2.5.1 ALDO to short transition p. 280

5.3.2.5.2 Short to ALDO transition p. 280

5.3.2.6 Modified Discrete Sine Transform p. 280

5.3.3 MDCT based TCX p. 281

5.3.3.1 General description p. 281

5.3.3.1.1 High level overview p. 281

5.3.3.1.2 Rate dependent configuration p. 281

5.3.3.2 General encoding procedure p. 282

5.3.3.2.1 LPC parameter calculation p. 282

5.3.3.2.2 Temporal Noise Shaping p. 286

5.3.3.2.3 LPC shaping in MDCT domain p. 288

5.3.3.2.4 Adaptive low frequency emphasis p. 291

5.3.3.2.5 Spectrum noise measure in power spectrum p. 292

5.3.3.2.6 Low pass factor detector p. 293

5.3.3.2.7 Uniform quantizer with adaptive dead-zone p. 293

5.3.3.2.8 Arithmetic coder p. 293

5.3.3.2.9 Global gain coding p. 305

5.3.3.2.10 Noise Filling p. 306

5.3.3.2.11 Intelligent Gap Filling p. 309

5.3.3.2.12 Memory updates p. 324

5.3.3.2.13 Global Gain Adjuster p. 324

5.3.4 High Quality MDCT coder (HQ) p. 325

5.3.4.1 Low-rate HQ coder p. 325

5.3.4.1.1 Tonality Estimation p. 326

5.3.4.1.2 Grouping of spectral coefficients p. 326

5.3.4.1.3 Energy Envelope coding p. 331

5.3.4.1.4 MDCT coefficients quantization p. 338

5.3.4.2 High-rate HQ coder p. 374

5.3.4.2.1 Normal Mode p. 376

5.3.4.2.2 Transient Mode p. 386

5.3.4.2.3 Generic, Harmonic and HVQ mode detector p. 387

5.3.4.2.4 Harmonic Mode p. 388

5.3.4.2.5 HVQ p. 389

5.3.4.2.6 Generic Mode p. 392

5.3.4.2.7 Pyramid Vector Quantization (PVQ) and indexing p. 400