DOCSLIB.ORG

Speech Processing (Vocoders)

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Speech Processing (Vocoders) Vocoders 1 The Channel Vocoder (analyzer): The channel vocoder employs a bank of bandpass filters, Each having a bandwidth between 100 Hz and 300 Hz. Typically, 16-20 linear phase FIR filter are used. The output of each filter is rectified and lowpass filtered. The bandwidth of the lowpass filter is selected to match the time variations in the characteristics of the vocal tract. For measurement of the spectral magnitudes, a voicing detector and a pitch estimator are included in the speech analysis. 2 The Channel Vocoder (analyzer block diagram): Bandpass Lowpass A/D Rectifier Filter Filter Converter Bandpass Lowpass A/D Rectifier Encoder Filter Filter Converter To S(n) Channel Voicing detector Pitch detector 3 The Channel Vocoder (synthesizer): 16-20 linear-phase FIR filters Covering 0-4 kHz Each having a bandwidth between 100- 300 Hz 20-ms frames, or 50 Hz changing of spectral magnitude LPF bandwidth: 20-25 Hz Sampling rate of the output of the filters: 50 Hz 4 The Channel Vocoder (synthesizer): Bit rate: 1 bit for voicing detector 6 bits for pitch period For 16 channels, each coded with 3-4 bits, updated 50 times per second Then the total bit rate is 2400-3200 bps Further reductions to 1200 bps can be achieved by exploiting frequency correlations of the spectrum magnitude 5 The Channel Vocoder (synthesizer): At the receiver the signal samples are passed through D/A converters. The outputs of the D/As are multiplied by the voiced or unvoiced signal sources. The resulting signal are passed through bandpass filters. The outputs of the bandpass filters are summed to form the synthesized speech signal. 6 The Channel Vocoder (synthesizer block diagram): D/A Bandpass Converter Filter Output ∑ speech D/A Bandpass Decoder Converter Filter From Channel Voicing Information Switch Random Pitch Pulse Noise period generator generator 7 The Phase Vocoder : The phase vocoder is similar to the channel vocoder. However, instead of estimating the pitch, the phase vocoder estimates the phase derivative at the output of each filter. By coding and transmitting the phase derivative, this vocoder destroys the phase information . 8 The Phase Vocoder (analyzer block diagram, kth channel) Short-term magnitude ak n Lowpasscosk n sink n Decimator Filter Differentiator Compute Short-term Encoder S(n) To Magnitude And Channel Phase Differentiator Derivative Lowpass Decimator Filter bk n Short-term phase sink n derivative 9 The Phase Vocoder (synthesizer block diagram, kth channel) Decimated Short-term amplitude cosk n Decoder From Channel Cos Interpolator Integrator ∑ Decimated Sin Interpolator Short-term Phase sink n derivative 10 The Phase Vocoder : LPF bandwidth: 50 Hz Demodulation separation: 100 Hz Number of filters: 25-30 Sampling rate of spectrum magnitude and phase derivative: 50-60 samples per second Spectral magnitude is coded using PCM or DPCM Phase derivative is coded linearly using 2-3 bits The resulting bit rate is 7200 bps 11 The Formant Vocoder : The formant vocoder can be viewed as a type of channel vocoder that estimates the first three or four formants in a segment of speech. It is this information plus the pitch period that is encoded and transmitted to the receiver. 12 The Formant Vocoder : Example of formant: (a) : The spectrogram of the utterance “day one” showing the pitch and the harmonic structure of speech. (b) : A zoomed spectrogram of the fundamental and the second harmonic. (a) (b) 13 The Formant Vocoder (analyzer block diagram): F3 F3 B3 F2 F2 B2 Input Speech F1 F1 B1 Pitch V/U And V/U F0 Decoder Fk :The frequency of the kth formant Bk :The bandwidth of the kth formant 14 The Formant Vocoder (synthesizer block diagram): F3 F3 B3 F2 F2 ∑ B2 F1 F1 B1 V/U Excitation F0 Signal 15 Linear Predictive Coding : The objective of LP analysis is to estimate parameters of an all-pole model for the vocal tract. Several methods have been devised for generating the excitation sequence for speech synthesizes. Various LPC-type speech analysis and synthesis methods differ primarily in the type of excitation signal generated for speech synthesis. 16 LPC 10 : This methods is called LPC-10 because of 10 coefficient are typically employed. LPC-10 partitions the speech into the 180 sample frame. Pitch and voicing decision are determined by using the AMDF and zero crossing measures. 17 A General Discrete-Time Model For Speech Production Pitch Gain s(n) DT G(z) Speech Impulse Glottal Signal Voiced U(n) generator Filter Voiced Volume V H(z) R(z) velocity Vocal tract LP U Filter Filter Uncorrelated Unvoiced Noise generator Gain 18 پيشگويي خطي تعيين مرتبه پيشگويي صفحه 19 از 54 پيشگويي خطي تعيين مرتبه پيشگويي صفحه 20 از 54 پيشگويي خطي تعيين مرتبه پيشگويي m s 2[n] nmM 1 PG 10log m e2[n] nmM 1 صفحه 21 از 54 پيشگويي خطي مثال M=4 M=10 صفحه 22 از 54 پيشگويي خطي مثال M=2 M=10 M=54 صفحه 23 از 54 پيشگويي خطي ايده پيشگويي خطي بلند مدت M=10 M=50 صفحه 24 از 54 پيشگويي خطي پيشگويي خطي بلند مدت صفحه 25 از 54 وكدر LPC10 مشخصات عمومي LPC10 صفحه 26 از 54 وكدر LPC10 كد كننده PCM LPC LPC LPC Bit Encoder صفحه 27 از 54 تشخيص پريود پيچ m R[l,m] s[n]s[nl] n m N 1 m MDF[l,m] s[n] s[n l] n m N 1 YMC s[n] b. s[n N] e[n], m N 1 m صفحه 28 از 54 وكدر LPC10 MDF T=20,21,…,39,40,42,…,80,84 ,…,154 صفحه 29 از 54 وكدر LPC10 كد كننده LPC RC صفحه 30 از 54 وكدر LPC10 سنتز گفتار سيگنال اصلي بخش كد كننده • تعيين صدادار/بي صدا بودن فريم • تعيين دوره گام فثط براي حالت صدادار • محاسبه بهره سيگنال V/U قطار ضربه با پريود G يراير دوره گام گفتار سنتز شده نويز تصادفي صفحه 31 از 54 وكدر LPC10 محدوديتها AR صفحه 32 از 54 Residual Excited LP Vocoder : Speech quality can be improved at the expense of a higher bit rate by computing and transmitting a residual error, as done in the case of DPCM. One method is that the LPC model and excitation parameters are estimated from a frame of speech. 33 Residual Excited LP Vocoder : The speech is synthesized at the transmitter and subtracted from the original speech signal to form the residual error. The residual error is quantized, coded, and transmitted to the receiver At the receiver the signal is synthesized by adding the residual error to the signal generated from the model. 34 Residual Excited LP Vocoder : The residual signal is low-pass filtered at 1000 Hz in the analyzer to reduce bit rate In the synthesizer, it is rectified and spectrum flattened (using a HPF), the lowpass and highpass signals are summed and the resulting residual error signal is used to excite the LPC model. RELP vocoder provides communication-quality speech at about 9600 bps. 35 RELP Analyzer (type 1): S(n) Buffer f (n; m) e (n; m) And ∑ Residual window error LP Parameters {aˆ(i;m)} stLP Encoder analysis To Θˆ , gain estimate Excitation 0 Channel V/U, decision parameters Pˆ, pitch estimate LP Synthesis model 36 RELP Analyzer (type 2): Prediction Residual S(n) Buffer f (n; m) Inverse (n;m) Lowpass To And Filter Decimator DFT Encoder Filter Channel window Aˆ (z;m) {aˆ(i;m)} LP stLP Parameters analysis 37 Synthesizer for a RELP vocoder Buffer From Residual Highpass Decoder And Interpolator Rectifier Filter Channel Controller ∑ LP model Parameter updates LP Excitation synthesizer 38 Multipulse LPC Vocoder RELP needs to regenerate the high- frequency components at the decoder. A crude approximation of the high frequencies The multipulse LPC is a time domain analysis-by-synthesis method that results in a better excitation signal for the LPC vocal system filter. 39 Multipulse LPC Vocoder The information concerning the excitation sequence includes: the location of the pulses an overall scale factor corresponding to the largest pulse amplitude The pulse amplitudes relative to the overall scale factor The scale factor is logarithmically quantized into 6 bits. The amplitudes are linearly quantized into 4 bits. The pulse locations are encoded using a differential coding scheme. The excitation parameters are updated every 5 msec. The LPC vocal-tract parameters and the pitch period are updated every 20 msec. The bit rate is 9600 bps. 40 Analysis-by-synthesis coder A stored sequence from a Gaussian excitation codebook is scaled and used to excite the cascade of a pitch synthesis filter and the LPC synthesis filter The synthetic speech is compared with the original speech Residual error signal is weighted perceptually by a filter ˆ(z / c) Aˆ(z) W (z) ˆ(z) Aˆ(z / c) 41 Obtaining the multipulse excitation: (Analysis by synthesis method) Input speech s(n) Buffer And Pˆ LP analysis f(n;m) + (n;m) Pitch LP - Synthesis Synthesis ∑ filter fˆ(n;m) filterΘp (z) Perceptual Weighting filter W(z) Multipulse Error Excitation minimization generator W (n;m) 42 Code Excited LP : CELP is an analysis-by-synthesis method in which the excitation sequence is selected from a codebook of zero-mean Gaussian sequence. The bit rate of the CELP is 4800 bps. 43 CELP (analysis-by-synthesis coder) : Speech samples Buffer and Side LP LP analysis information Gain parameters Gaussian Pitch Spectral Envelope ∑ Excitation Synthesis (LP) codebook filter Synthesis filter Perceptual Weighting Filter W(z) Computer Index of Energy Excitation (square and sum) sequence 44 Analysis-by-synthesis coder This weighted error is squared and summed over a subframe block to give the error energy By performing an exhaustive search through the codebook we find the excitation sequence that minimize the error energy 45 Analysis-by-synthesis coder The gain factor for scaling the excitation sequence is determined for each codeword in the codebook by minimizing
Load more

Recommended publications
  • The Phase Vocoder: a Tutorial Author(S): Mark Dolson Source: Computer Music Journal, Vol
    The Phase Vocoder: A Tutorial Author(s): Mark Dolson Source: Computer Music Journal, Vol. 10, No. 4 (Winter, 1986), pp. 14-27 Published by: The MIT Press Stable URL: http://www.jstor.org/stable/3680093 Accessed: 19/11/2008 14:26 Your use of the JSTOR archive indicates your acceptance of JSTOR's Terms and Conditions of Use, available at http://www.jstor.org/page/info/about/policies/terms.jsp. JSTOR's Terms and Conditions of Use provides, in part, that unless you have obtained prior permission, you may not download an entire issue of a journal or multiple copies of articles, and you may use content in the JSTOR archive only for your personal, non-commercial use. Please contact the publisher regarding any further use of this work. Publisher contact information may be obtained at http://www.jstor.org/action/showPublisher?publisherCode=mitpress. Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printed page of such transmission. JSTOR is a not-for-profit organization founded in 1995 to build trusted digital archives for scholarship. We work with the scholarly community to preserve their work and the materials they rely upon, and to build a common research platform that promotes the discovery and use of these resources. For more information about JSTOR, please contact [email protected]. The MIT Press is collaborating with JSTOR to digitize, preserve and extend access to Computer Music Journal. http://www.jstor.org MarkDolson The Phase Vocoder: Computer Audio Research Laboratory Center for Music Experiment, Q-037 A Tutorial University of California, San Diego La Jolla, California 92093 USA Introduction technique has become popular and well understood.
    [Show full text]
  • TAL-Vocoder-II
    TAL-Vocoder-II http://kunz.corrupt.ch/ TAL - Togu Audio Line © 2011, Patrick Kunz Tutorial Version 0.0.1 Cubase and VST are trademarks of Steinberg Soft- und Hardware GmbH TAL - Togu Audio Line – 2008 1/9 TAL-Vocoder-II ........................................................................................................... 1 Introduction ................................................................................................................. 3 Installation .................................................................................................................. 4 Windows .............................................................................................................. 4 OS X .................................................................................................................... 4 Interface ...................................................................................................................... 5 Examples .................................................................................................................... 6 Credits ........................................................................................................................ 9 TAL - Togu Audio Line – 2008 2/9 Introduction TAL-Vocoder is a vintage vocoder emulation with 11 bands that emulates the sound of vocoders from the early 80’s. It includes analog modeled components in combination with digital algorithms such as the SFFT (Short-Time Fast Fourier Transform). This vocoder does not make a direct convolution
    [Show full text]
  • The Futurism of Hip Hop: Space, Electro and Science Fiction in Rap
    Open Cultural Studies 2018; 2: 122–135 Research Article Adam de Paor-Evans* The Futurism of Hip Hop: Space, Electro and Science Fiction in Rap https://doi.org/10.1515/culture-2018-0012 Received January 27, 2018; accepted June 2, 2018 Abstract: In the early 1980s, an important facet of hip hop culture developed a style of music known as electro-rap, much of which carries narratives linked to science fiction, fantasy and references to arcade games and comic books. The aim of this article is to build a critical inquiry into the cultural and socio- political presence of these ideas as drivers for the productions of electro-rap, and subsequently through artists from Newcleus to Strange U seeks to interrogate the value of science fiction from the 1980s to the 2000s, evaluating the validity of science fiction’s place in the future of hip hop. Theoretically underpinned by the emerging theories associated with Afrofuturism and Paul Virilio’s dromosphere and picnolepsy concepts, the article reconsiders time and spatial context as a palimpsest whereby the saturation of digitalisation becomes both accelerator and obstacle and proposes a thirdspace-dromology. In conclusion, the article repositions contemporary hip hop and unearths the realities of science fiction and closes by offering specific directions for both the future within and the future of hip hop culture and its potential impact on future society. Keywords: dromosphere, dromology, Afrofuturism, electro-rap, thirdspace, fantasy, Newcleus, Strange U Introduction During the mid-1970s, the language of New York City’s pioneering hip hop practitioners brought them fame amongst their peers, yet the methods of its musical production brought heavy criticism from established musicians.
    [Show full text]
  • Overview of Voice Over IP
    Overview of Voice over IP February 2001 – University of Pennsylvania Technical Report MS-CIS-01-31* Princy C. Mehta Professor Sanjay Udani [email protected] [email protected] * This paper was written for an Independent Study course. Princy Mehta Overview of Voice over IP Professor Udani Table of Contents ACRONYMS AND DEFINITIONS...............................................................................................................3 INTRODUCTION...........................................................................................................................................5 IMPLEMENTATION OF VOICE OVER IP...............................................................................................6 OVERVIEW OF TCP/IP ...................................................................................................................................6 PACKETIZATION.............................................................................................................................................7 COMPONENTS OF VOIP..................................................................................................................................8 SIGNALING ....................................................................................................................................................8 H.323 .............................................................................................................................................................8 Logical Entities..........................................................................................................................................9
    [Show full text]
  • Software Sequencers and Cyborg Singers
    Edinburgh Research Explorer Software Sequencers and Cyborg Singers Citation for published version: Prior, N 2009, 'Software Sequencers and Cyborg Singers: Popular Music in the Digital Hypermodern', New Formations: A Journal of Culture, Theory, Politics, vol. 66, no. Spring, pp. 81-99. https://doi.org/10.3898/newf.66.06.2009 Digital Object Identifier (DOI): 10.3898/newf.66.06.2009 Link: Link to publication record in Edinburgh Research Explorer Document Version: Publisher's PDF, also known as Version of record Published In: New Formations: A Journal of Culture, Theory, Politics Publisher Rights Statement: © Prior, N. (2009). Software Sequencers and Cyborg Singers: Popular Music in the Digital Hypermodern. New Formations, 66(Spring), 81-99 doi: 10.3898/newf.66.06.2009. General rights Copyright for the publications made accessible via the Edinburgh Research Explorer is retained by the author(s) and / or other copyright owners and it is a condition of accessing these publications that users recognise and abide by the legal requirements associated with these rights. Take down policy The University of Edinburgh has made every reasonable effort to ensure that Edinburgh Research Explorer content complies with UK legislation. If you believe that the public display of this file breaches copyright please contact [email protected] providing details, and we will remove access to the work immediately and investigate your claim. Download date: 26. Sep. 2021 SOFTWARE SEQUENCERS AND CYBORG SINGERS: POPULAR MUSIC IN THE DIGITAL HYPERMODERN Nick Prior It has been almost twenty years since Andrew Goodwin’s classic essay, ‘Sample and Hold’, claimed that pop music had entered a new phase of digital reproduction.1 If the digital sampler was postmodernism’s musical engine, then hip hop was its recombinant form, and the erosion of divisions between original and copy the celebrated consequence.
    [Show full text]
  • A Vocoder (Short for Voice Encoder) Is a Synthesis System, Which Was
    The Vocoder Thomas Carney 311107435 Digital Audio Systems, DESC9115, Semester 1 2012 Graduate Program in Audio and Acoustics Faculty of Architecture, Design and Planning, The University of Sydney A vocoder (short for voice encoder) is Dudley's breakthrough device a synthesis system, which was initially analysed wideband speech, developed to reproduce human converted it into slowly varying control speech. Vocoding is the cross signals, sent those over a low-band synthesis of a musical instrument with phone line, and finally transformed voice. It was called the vocoder those signals back into the original because it involved encoding the speech, or at least a close voice (speech analysis) and then approximation of it. The vocoder was reconstructing the voice in also useful in the study of human accordance with a code written to speech, as a laboratory tool. replicate the speech (speech synthesis). A key to this process was the development of a parallel band pass A Brief History filter, which allowed sounds to be The vocoder was initially conceived filtered down to a fairly specific and developed as a communication portion of the audio spectrum by tool in the 1930s as a means of attenuating the sounds that fall above coding speech for delivery over or below a certain band. By telephone wires. Homer Dudley 1 is separating the signal into many recognised as one of the father’s of bands, it could be transmitted easier the vocoder for his work over forty and allowed for a more accurate years for Bell Laboratories’ in speech resynthesis. and telecommunications coding. The vocoder was built in an attempt to It wasn’t until the late 1960s 2 and save early telephone circuit early 1970s that the vocoder was bandwidth.
    [Show full text]
  • Mediated Music Makers. Constructing Author Images in Popular Music
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Helsingin yliopiston digitaalinen arkisto Laura Ahonen Mediated music makers Constructing author images in popular music Academic dissertation to be publicly discussed, by due permission of the Faculty of Arts at the University of Helsinki in auditorium XII, on the 10th of November, 2007 at 10 o’clock. Laura Ahonen Mediated music makers Constructing author images in popular music Finnish Society for Ethnomusicology Publ. 16. © Laura Ahonen Layout: Tiina Kaarela, Federation of Finnish Learned Societies ISBN 978-952-99945-0-2 (paperback) ISBN 978-952-10-4117-4 (PDF) Finnish Society for Ethnomusicology Publ. 16. ISSN 0785-2746. Contents Acknowledgements. 9 INTRODUCTION – UNRAVELLING MUSICAL AUTHORSHIP. 11 Background – On authorship in popular music. 13 Underlying themes and leading ideas – The author and the work. 15 Theoretical framework – Constructing the image. 17 Specifying the image types – Presented, mediated, compiled. 18 Research material – Media texts and online sources . 22 Methodology – Social constructions and discursive readings. 24 Context and focus – Defining the object of study. 26 Research questions, aims and execution – On the work at hand. 28 I STARRING THE AUTHOR – IN THE SPOTLIGHT AND UNDERGROUND . 31 1. The author effect – Tracking down the source. .32 The author as the point of origin. 32 Authoring identities and celebrity signs. 33 Tracing back the Romantic impact . 35 Leading the way – The case of Björk . 37 Media texts and present-day myths. .39 Pieces of stardom. .40 Single authors with distinct features . 42 Between nature and technology . 45 The taskmaster and her crew.
    [Show full text]
  • Robotic Voice Effects
    Robotic voice effects From Wikipedia, the free encyclopedia Source : http://en.wikipedia.org/wiki/Robotic_voice_effects "Robot voices" became a recurring element in popular music starting in the late twentieth century, and several methods of producing variations on this effect have arisen. Though the vocoder is by far the best-known, the following other pieces of music technology are often confused with it: Sonovox This was an early version of the talk box used to create the voice of the piano in the Sparky's Magic Piano series from 1947. It was used as the voice of many musical instruments in Rusty in Orchestraville. It was used as the voice of Casey the Train in Dumbo and The Reluctant Dragon[citation needed]. Radio jingle companies PAMS and JAM Creative Productions also used the sonovox in many stations ID's they produced. Talk box The talk box guitar effect was invented by Doug Forbes and popularized by Peter Frampton. In the talk box effect, amplified sound is actually fed via a tube into the performer's mouth and is then shaped by the performer's lip, tongue, and mouth movements before being picked up by a microphone. In contrast, the vocoder effect is produced entirely electronically. The background riff from "Livin' on a Prayer" by Bon Jovi is a well-known example. "California Love" by 2Pac and Roger Troutman is a more recent recording featuring a talk box fed with a synthesizer instead of guitar. Steven Drozd of the The Flaming Lips used the talk box on parts of the groups eleventh album, At War with the Mystics, to imitate some of Wayne Coyne's repeated lyrics in the "Yeah Yeah Yeah Song".
    [Show full text]
  • Microkorg Owner's Manual
    E 2 ii Precautions Data handling Location THE FCC REGULATION WARNING (for U.S.A.) Unexpected malfunctions can result in the loss of memory Using the unit in the following locations can result in a This equipment has been tested and found to comply with the contents. Please be sure to save important data on an external malfunction. limits for a Class B digital device, pursuant to Part 15 of the data filer (storage device). Korg cannot accept any responsibility • In direct sunlight FCC Rules. These limits are designed to provide reasonable for any loss or damage which you may incur as a result of data • Locations of extreme temperature or humidity protection against harmful interference in a residential loss. • Excessively dusty or dirty locations installation. This equipment generates, uses, and can radiate • Locations of excessive vibration radio frequency energy and, if not installed and used in • Close to magnetic fields accordance with the instructions, may cause harmful interference to radio communications. However, there is no Printing conventions in this manual Power supply guarantee that interference will not occur in a particular Please connect the designated AC adapter to an AC outlet of installation. If this equipment does cause harmful interference Knobs and keys printed in BOLD TYPE. the correct voltage. Do not connect it to an AC outlet of to radio or television reception, which can be determined by Knobs and keys on the panel of the microKORG are printed in voltage other than that for which your unit is intended. turning the equipment off and on, the user is encouraged to BOLD TYPE.
    [Show full text]
  • History of Electronic Sound Modification'
    PAPERS `)6 .)-t. corms 1-0 V History of Electronic Sound Modification' HARALD BODE Bode Sound Co., North Tonawanda, NY 14120, USA 0 INTRODUCTION 2 THE ELECTRONIC ERA The history of electronic sound modification is as After the Telharmonium, and especially after the old as the history of electronic musical instruments and invention of the vacuum tube, scores of electronic (and electronic sound transmission, recording, and repro- electronic mechanical) musical instruments were in- duction . vented with sound modification features . The Hammond Means for modifying electrically generated sound organ is ofspecial interest, since it evolved from Cahill's have been known. since the late 19th century, when work . Many notable inventions in electronic sound Thaddeus Cahill created his Telharmonium . modification are associated with this instrument, which With the advent of the electronic age, spurred first will be discussed later. by the invention of the electron tube, and the more Other instruments of the early 1930s included the recent development of solid-state devices, an astounding Trautonium by the German F. Trautwein, which was variety of sound modifiers have been created for fil- built in several versions . The Trautonium used reso- tering, distorting, equalizing, amplitude and frequency nance filters to emphasize selective overtone regions, modulating, Doppler effect and ring modulating, com- called formants [I 1]-[ 14] . In contrast, the German Jorg pressing, reverberating, repeating, flanging, phasing, Mager built an organlike instrument for which he used pitch changing, chorusing, frequency shifting, ana- loudspeakers with all types of driver systems and shapes lyzing, and resynthesizing natural and artificial sound. to obtain different sounds . In this paper some highlights of historical devel- In 1937 the author created the Warbo Formant organ, opment are reviewed, covering the time from 1896 to which had circuitry for envelope shaping as well as the present.
    [Show full text]
  • Advanced Speech Compression VIA Voice Excited Linear Predictive Coding Using Discrete Cosine Transform (DCT)
    International Journal of Innovative Technology and Exploring Engineering (IJITEE) ISSN: 2278-3075, Volume-2 Issue-3, February 2013 Advanced Speech Compression VIA Voice Excited Linear Predictive Coding using Discrete Cosine Transform (DCT) Nikhil Sharma, Niharika Mehta Abstract: One of the most powerful speech analysis techniques LPC makes coding at low bit rates possible. For LPC-10, the is the method of linear predictive analysis. This method has bit rate is about 2.4 kbps. Even though this method results in become the predominant technique for representing speech for an artificial sounding speech, it is intelligible. This method low bit rate transmission or storage. The importance of this has found extensive use in military applications, where a method lies both in its ability to provide extremely accurate high quality speech is not as important as a low bit rate to estimates of the speech parameters and in its relative speed of computation. The basic idea behind linear predictive analysis is allow for heavy encryptions of secret data. However, since a that the speech sample can be approximated as a linear high quality sounding speech is required in the commercial combination of past samples. The linear predictor model provides market, engineers are faced with using other techniques that a robust, reliable and accurate method for estimating parameters normally use higher bit rates and result in higher quality that characterize the linear, time varying system. In this project, output. In LPC-10 vocal tract is represented as a time- we implement a voice excited LPC vocoder for low bit rate speech varying filter and speech is windowed about every 30ms.
    [Show full text]
  • Revoicer Manual
    REVOICER SPECTRUM FILTER BANK VOCODER OSC [RACK EXTENSION] v. 1.0 MANUAL 2019 FX device by Turn2on Software Vocoders rely on two signals being present at the What makes the ReVoicer different from a typical same time in order to operate. These signals are the Vocoder? It is a Stereo Spectrum filter-bank Vocoder Carrier signal, which normally takes the form of a with an Internal Oscillator. synth, and the Modulator signal, which normally The External Carrier stereo inputs can be used, or takes the form of a human voice, although other use/mix the Internal oscillator (which includes basic instruments can work well (such as drums). waveforms such as Pulse, Saw, Tri, Sub and Noise), to The Modulator signal is analysed by the vocoder vocode the Modulator inputs. The Internal Oscillator and broken down into a number of frequency bands. can also be used as a simple Oscillator (it can be The more bands that are available, the better quality processed by the Vocoder) and as part of a vocoder of the analysis, which means that a clearer vocoded (internal carrier) for fast results without the need to sound will be available. create any external Carrier device in Reason’s rack. A typical Vocoder synthesizes a modulator (usually a ReVoicer comes with a variety of patches including voice) in the right channel of a stereo track with a 70+ Combi vocoder FX patches. carrier wave in the left channel (any active sound) to ReVoicer is a modern stereo Vocoder with internal produce a vocoded version of the modulator (right oscillator, limiter and frequency controls.
    [Show full text]