speech compression using voiced excited loosy predictive coding (lpc)

Base paper: - http://www.ijetae.com/files/Volume2Issue6/IJETAE_0612_54.pdf

Speech Compression using Voiced Excited Loosy Predictive Coding

International Journal of Emerging Technology and Advanced

Engineering

Abstract:

The aim of the project to develop a system for encoding good quality speech at a low bit rate .To

implement this we have used very efficient speech analysis technique Linear Predictive Coding (LPC). It

provides accurate estimation of speech parameters. An alternate explanation is that the linear

prediction filters attempt to predict future values of the input signal based on past signals. The speech

signals of males and females were coded. The encoding process of LPC involves determining a set of

accurate parameters for modeling the vocal tract during the production of a given speech signal.

Decoding involves using the parameters acquired in the encoding and analysis to build a synthesized

version of the original speech signal. The conclusion indicates that project was successful in coding the

speech signal at relatively low bit rates with good quality.


(a) Path of Human Speech Production


(b) Human vs. Voice Coder Speech Production

(c) Block Diagram of Voice Excited LPC Vocoder


(d) Block Diagram of LPC Vocoder


A: - Waveforms

B: - Spectrograms


Conclusion:

We can see that the voice excited waveform looks closer to the original sound than the plain LPC

reconstructed one. Voice –discrimination tests indicate that voice identity is well preserved. Crucial

factors influencing the remade speech quality are accuracy of spectral flattening and the impulse

response of the analyzer low pass filters. Though there is an improvement in quality when we use voice

excited method, the bits per sample increase causing an increase in Bandwidth of signal. But at same

time when SNR for both cases were compared it was observed that the sound due to Plain LPC was

found to be noisier having a negative SNR. The voice excited LPC having a positive SNR.

References:

[1] L R Rabiner and R W Schafer, ―Digital Processing Of Speech Signal‖ Prentice-Hall, Eaglewood Cliffs, NJ,1978 *2+ Speech coding overview‖ Jason Woodard, http://www-mobile.ecs.soton.ac.uk/speech_codecs/ *3+ Richard V.Cox ―Speech Coding(1999)‖,chapter9,1-9 [4] Mark Nelson and Jean-loup Gailly,‖Speech compression‖. *5+ Landy Goldbarg and Lance Reik , ―A practical handbook of Speech coding‖ chapter 4,1-4 *6+ Jerry. D. Gibson. ―Media Signal Processing‖. *7+ Study of Linear Prediction Model for Audio Synthesis‖, Anjini Shukla , [8] Voice–Excited Vocoders for practical Speech‖, by. E.E. David, Jr. M.R. Schroeder, B.F. Logan [9] en.wikipedia.org/wiki/linear_predictive_coding *10+ Roger M. Golden, ―Digital Computer Simulation of a Sampled-Data Voice-Excited Vocoder *11+ Voice Exciting LPC‖ ,Taguchi ,Deptartment of Electronics. Eng., Saskatchewan Univ., Saskatoon, Sask., conference Publications [12] www.data-compression.com [13]www.acostic,hut.fi/publications/file/theses/lemetty_mst/chap3.html [14] V. Hardman and O. Hodson. Internet / Mbone Audio(2000)5-7

http://www.data-compression.com/

http://www.acostic,hut.fi/publications/file/theses/lemetty_mst/chap3.html

speech compression using voiced excited loosy predictive coding (lpc)

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