ETSI TS 103 634 V1.1.1 (2019-08)

Digital Enhanced Cordless Telecommunications (DECT); Low Complexity Communication Codec plus (LC3plus)

DTS/DECT-00338

General Information

• Status: Published
• Publication Date: 28-Aug-2019
• Technical Committee: DECT - Digital Enhanced Cordless Telecommunications (DECT)
• Current Stage: 12 - Completion
• Due Date: 23-Aug-2019
• Completion Date: 29-Aug-2019

Standards Content (Sample)

TECHNICAL SPECIFICATION
Digital Enhanced Cordless Telecommunications (DECT);
Low Complexity Communication Codec plus (LC3plus)

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2 ETSI TS 103 634 V1.1.1 (2019-08)

Reference
DTS/DECT-00338
Keywords
audio, codec, DECT, Full-Band, LC3plus,
superwideband, voice, VoIP
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ETSI
3 ETSI TS 103 634 V1.1.1 (2019-08)

Contents
Intellectual Property Rights . 9
Foreword . 9
Modal verbs terminology . 9
Executive summary . 9
Introduction . 10
1 Scope . 11
2 References . 11
2.1 Normative references . 11
2.2 Informative references . 12
3 Definition of terms, symbols and abbreviations . 13
3.1 Terms . 13
3.2 Symbols . 14
3.2.1 Mathematical symbols . 14
3.2.2 Operator symbols . 14
3.3 Abbreviations . 14
4 General description. 16
4.1 Overview . 16
4.2 Transcoding functions . 17
4.3 ANSI C-code . 19
4.4 Conformance testing. 19
4.5 RTP payload format . 20
4.6 Performance characterization . 20
5 Codec algorithm description . 20
5.1 General codec description . 20
5.2 General codec parameters. 21
5.2.1 Audio channels . 21
5.2.2 Sampling rates . 21
5.2.3 Bits per sample . 21
5.2.4 Frame size and delay. 21
5.2.5 Bit budget and bitrate . 22
5.3 Encoding process . 22
5.3.1 Encoder modules . 22
5.3.2 Input signal . 23
5.3.3 Input signal scaling . 23
5.3.4 Low delay MDCT analysis . 23
5.3.4.1 Overview . 23
5.3.4.2 Update time buffer . 24
5.3.4.3 Time-frequency transformation. 24
5.3.4.4 Energy estimation per band . 25
5.3.5 Bandwidth detector . 25
5.3.5.1 Algorithm . 25
5.3.5.2 Parameters . 26
5.3.6 Time Domain Attack Detector . 26
5.3.6.1 Overview . 26
5.3.6.2 Downsampling and Filtering of Input Signal . 27
5.3.6.3 Energy Calculation . 27
5.3.6.4 Attack Detection . 27
5.3.7 Spectral Noise Shaping . 27
5.3.7.1 Overview . 27
5.3.7.2 SNS analysis . 28
5.3.7.2.1 Overview . 28
5.3.7.2.2 Padding . 28
5.3.7.2.3 Smoothing . 28
ETSI
4 ETSI TS 103 634 V1.1.1 (2019-08)

5.3.7.2.4 Pre-emphasis . 29
5.3.7.2.5 Noise floor . 29
5.3.7.2.6 Logarithm . 29
5.3.7.2.7 Band Energy Grouping . 29
5.3.7.2.8 Mean removal and scaling, attack handling. 29
5.3.7.3 SNS quantization . 30
5.3.7.3.1 General . 30
5.3.7.3.2 Stage 1 . 31
5.3.7.3.3 Stage 2 . 31
5.3.7.3.3.1 General . 31
5.3.7.3.3.2 Transform . 31
5.3.7.3.3.3 Stage 2 Target Preparation . 32
5.3.7.3.3.4 Shape Candidates . 32
5.3.7.3.3.5 Stage 2 Shape Search . 32
5.3.7.3.3.6 Adjustment Gain Candidates . 34
5.3.7.3.3.7 Shape and Gain combination determination . 35
5.3.7.3.3.8 Enumeration of the selected PVQ pulse configurations . 35
5.3.7.3.4 Multiplexing of SNS VQ Codewords . 36
5.3.7.3.5 Synthesis of the Quantized SNS scale factor vector . 38
5.3.7.4 SNS scale factors interpolation . 38
5.3.7.5 Spectral shaping . 39
5.3.8 Bandwidth control . 39
5.3.9 Temporal noise shaping (TNS) . 39
5.3.9.1 Overview . 39
5.3.9.2 TNS analys
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