Linear Predictive Coding in Mixed-Excitation Linear Predictive Coder - MELP

1. Linear Predictive Coding in Mixed-Excitation Linear Predictive Coder - MELP MELP LPC LSFs demonstration Subject: Adaptive Digital Signal Processing Scientific Postgraduate Study of Electronics, FESB, University of Split Professor: dr. sc. Dinko Begušić Student: Zoran Sambol LPC impact on MELP

2. Adaptive DSP - Study • Subject program • Literature - Simon Haykin: Adaptive filter theory, Prentice Hall, 1991. • Practical work based on MELP codec • Study subject – Speech coding - Presentation • Three phases • Adaptive Filter theory – Seminar documents • MELP codec adjustment - coding • LPC LSF impact on MELP – today presentation LPC impact on MELP

3. LPC – show impact on MELP • Task was given during MELP codec presentation – September 2002. • MELP codec is based on Linear Predictive Coding. • Its LPC coder has 10th order • My task was to show impact of LPC coder on overall MELP algorithm LPC impact on MELP

4. LPC web & resources • MELP documents - MELP Presentation page 3. • DDVPC Homepage, Standard draft, ASPI digital – Polycom, Texas Instruments and Noam Amir educational site. • Most of the resources has samples coded in Matlab • Google groups search – Line Spectrum Pairs (LSP) • Cite – William M. Wiese Jr. [ In the real world, if two adjoining LSF values are equal we separate them by some small value like 35 – 50 Hz.] What will happen if I change LSF that minimum distance is greater or less than 50 Hz? LPC impact on MELP

5. Encoder MELP – LPC LPC impact on MELP

6. Parameters Voiced Unvoiced LSF’s 25 25 Fourier Magnitudes 8 - Gain (2 per frame) 8 8 Pitch (overall voicing) 7 7 Bandpass voicing 4 - Aperiodic Flag 1 - Error protection - 13 Sync Bit 1 1 Total bits/ 22.5 ms Frame 54 54 Decoder MELP - LPC 44/54 = 81.48% LPC impact on MELP

7. MELP codec • Windows console application • What were changed? • Command prompt – additional argument • ConsoleMelp –a –i dam9.bin –o dam9.ccl –f 150 • Parse function - void parse(int argc,char **argv) • Clamping function (sort LSFs and minimum separation) • int lpc_clmp(float *w, float delta, int p); • Minimum LSF separation • #define BWMIN (50.0*2/FSAMP) /* minimum LSF separation */ • Changed with float fLSFFrequency variable LPC impact on MELP

8. Recorder - Player • Windows MELPCodec application • Known interface • Equalizer dialog • 50 Hz default value • Check button • Log slider • Easy canceling Equalizer LPC impact on MELP

9. Batch – Console applications • Four different console application integrated using DOS Batch files • Waveopt, ConsoleMelp, CCRemover and CCInserter • Console applications with input and output parameters – files • ConsoleMelp –a –i dam9.bin –o dam9.ccl –f 150 • Waveopt syntax: • Waveopt.exe [*.bin | *.wav] • Easy deleting, renaming, directory creating – • Read Me file. LPC impact on MELP

10. Testing • Well known record • Using MelpCodec application as a recorder and my own voice. LPC impact on MELP

11. Results • Subjective measurements • Overvoicing • Quality degradation – Male and Female • 180 samples segments impact on parameters • Real measurement – MOS (ITU) LPC impact on MELP

12. Opening WAV and MELP (Channel coded) files Playing files Recording and storing waves in MELP useful format Recording Channel coded and MELP files Size comparison - Explorer utility Useful Equalizer Windows – MELP Codec LPC impact on MELP

13. MelpCodec with Equalizer Education • Useful adjustable tool: • Statistics (MOS, DAM, DRT measurement) • Vocoder example for FEC • Internet and database connection • Visualization, Skins and additional GUI components • Laboratory exercise – Voice Coding subject • Digital Signal Adaptive Processing - Subject • Gathering measurement results • Symposium article (IEEE, SoftCOM, ELMAR, MiPRO) • Experience for some other voice and no-voice LP algorithms LPC impact on MELP

14. Thanks for your time! Contact: Zoran Sambol, Siemens d.d. Put Brodarice 6, 21000 Split Tel. +385 21 390 936 zoran.sambol@st.tel.hr, zoran.sambol@siemens.hr LPC impact on MELP