ilbc.rar_iL_ili_ilibc_libilbc source code_语音库

Internet Draft S. V. Andersen Document: draft-ietf-avt-ilbc-codec-05.txt Aalborg University Category: Experimental A. Duric May 29th, 2004 Telio Expires: November 29th, 2004 H. Astrom R. Hagen W. B. Kleijn J. Linden Global IP Sound Internet Low Bit Rate Codec Status of this Memo This document specifies an Internet experimental standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited. By submitting this Internet-Draft, we certify that any applicable patent or other IPR claims of which we am aware have been disclosed, and any of which we become aware will be disclosed, in accordance with RFC 3668. Copyright Notice Copyright (C) The Internet Society (2004). All Rights Reserved. Abstract This document specifies a speech codec suitable for robust voice communication over IP. The codec is developed by Global IP Sound (GIPS). It is designed for narrow band speech and results in a payload bit rate of 13.33 kbit/s for 30 ms frames and 15.20 kbit/s for 20 ms frames. The codec enables graceful speech quality degradation in the case of lost frames, which occurs in connection with lost or delayed IP packets. Andersen et. al. 1 Internet Low Bit Rate Codec May 04 Table of Contents Status of this Memo................................................1 Copyright Notice...................................................1 Abstract...........................................................1 Table of Contents..................................................2 1. INTRODUCTION....................................................5 2. OUTLINE OF THE CODEC............................................5 2.1 Encoder........................................................6 2.2 Decoder........................................................7 3. ENCODER PRINCIPLES..............................................8 3.1 Pre-processing.................................................9 3.2 LPC Analysis and Quantization..................................9 3.2.1 Computation of Autocorrelation Coefficients..................9 3.2.2 Computation of LPC Coefficients.............................11 3.2.3 Computation of LSF Coefficients from LPC Coefficients.......11 3.2.4 Quantization of LSF Coefficients............................11 3.2.5 Stability Check of LSF Coefficients.........................12 3.2.6 Interpolation of LSF Coefficients...........................12 3.2.7 LPC Analysis and Quantization for 20 ms frames..............13 3.3 Calculation of the Residual...................................14 3.4 Perceptual Weighting Filter...................................14 3.5 Start State Encoder...........................................15 3.5.1 Start State Estimation......................................15 3.5.2 All-Pass Filtering and Scale Quantization...................16 3.5.3 Scalar Quantization.........................................17 3.6 Encoding the remaining samples................................17 3.6.1 Codebook Memory.............................................19 3.6.2 Perceptual Weighting of Codebook Memory and Target..........20 3.6.3 Codebook Creation...........................................21 3.6.3.1 Creation of a Base Codebook...............................21 3.6.3.2 Codebook Expansion........................................22 3.6.3.3 Codebook Augmentation.....................................22 3.6.4 Codebook Search.............................................23 3.6.4.1 Codebook Search at Each Stage.............................24 3.6.4.2 Gain Quantization at Each Stage...........................24 3.6.4.3 Preparation of Target for Next Stage......................26 3.7 Gain Correction Encoding......................................26 3.8 Bitstream Definition..........................................27 4. DECODER PRINCIPLES.............................................30 4.1 LPC Filter Reconstruction.....................................30 4.2 Start State Reconstruction....................................31 4.3 Excitation Decoding Loop......................................31 4.4 Multistage Adaptive Codebook Decoding.........................32 4.4.1 Construction of the Decoded Excitation Signal...............32 4.5 Packet Loss Concealment.......................................33 4.5.1 Block Received Correctly and Previous Block also Received...33 Andersen et. al. Experimental - Expires November 29th, 2004 2 Internet Low Bit Rate Codec May 04 4.5.2 Block Not Received..........................................33 4.5.3 Block Received Correctly When Previous Block Not Received...34 4.6 Enhancement...................................................34 4.6.1 Estimating the pitch........................................36 4.6.2 Determination of the Pitch-Synchronous Sequences............36 4.6.3 Calculation of the smoothed excitation......................37 4.6.4 Enhancer criterion..........................................38 4.6.5 Enhancing the excitation....................................38 4.7 Synthesis Filtering...........................................39 4.8 Post Filtering................................................39 5. IANA CONSIDERATIONS............................................39 6. SECURITY CONSIDERATIONS........................................39 7. EVALUATION OF THE ILBC IMPLEMENTATIONS.........................39 8. REFERENCES.....................................................40 8.1 Normative.....................................................40 8.2 Informative...................................................40 9. ACKNOWLEDGEMENTS...............................................40 10. AUTHOR'S ADDRESSES............................................41 Full Copyright Statement..........................................42 Intellectual Property.............................................42 APPENDIX A REFERENCE IMPLEMENTATION...............................43 A.1 iLBC_test.c...................................................44 A.2 iLBC_encode.h.................................................49 A.3 iLBC_encode.c.................................................50 A.4 iLBC_decode.h.................................................59 A.5 iLBC_decode.c.................................................60 A.6 iLBC_define.h.................................................71 A.7 constants.h...................................................74 A.8 constants.c...................................................76 A.9 anaFilter.h...................................................89 A.10 anaFilter.c..................................................89 A.11 createCB.h...................................................90