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Topic: Speech coding

Related Topics

Speech coder

Speech processing

HVXC

Linear predictive coding

Code

Speech synthesis

List of codecs

Speech recognition

Speaker recognition

Linear prediction

Vocoder

Speex

Endec

AC97

Audio signal processing

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	Speech Coding With Linear Predictive Coding (Site not responding. Last check: 2007-11-04)
		Speech coding has been and still is a major issue in the area of digital speech processing.
		Speech coding is the act of transforming the speech signal at hand, to a more compact form, which can then be transmitted with a considerably smaller memory.
		Speech coding is a lossy type of coding, which means that the output signal does not exactly sound like the input.
	www.dspexperts.com /dsp/projects/lpc (4881 words)

	Speech and Audio Coding (Site not responding. Last check: 2007-11-04)
		Audio coding tries to take advantage of these imperfections in our hearing system by arranging the distortions introduced by the compression process in such a way that they are inaudible or barely audible.
		Speech coding makes the same assumption, but in addition it makes assumptions about the original of the signals that it has to encode.
		Speech is produced by people as part of a physical process (a bunch of moving muscles), and the corresponding signal will have certain properties (such as correlations) which can be used to do more efficient processing.
	www.bell-labs.com /org/1133/Research/SpeechAudioCoding (685 words)

	Speech Coding
		Speech coding techniques can be broadly divided into two classes: waveform coding that aims at reproducing the speech waveform as faithfully as possible and vocoders that preserve only the spectral properties of speech in the encoded signal.
		Speech quality is usually evaluated on a five-point scale, known as the mean-opinion score (MOS) scale, in speech quality testing---an average over a large number of speech data, speakers, and listeners.
		The complexity of a coding algorithm is the processing effort required to implement the algorithm, and it is typically measured in terms of arithmetic capability and memory requirement, or equivalently in terms of cost.
	cslu.cse.ogi.edu /HLTsurvey/ch10node4.html (1978 words)

	Speech and Audio Coding, Processing and Recognition
		Ubale and A. Gersho, "Multi-Band CELP Wideband Speech Coder," Proc.
		Chen and A. Gersho, "Gain-Adaptive Vector Quantization for Medium-Rate Speech Coding," Conf.
		Cuperman and A. Gersho, "Vector Predictive Coding of Speech at 16 Kb/s," IEEE Trans.
	scl.ece.ucsb.edu /html/papers_E.htm (4090 words)

	[No title] (Site not responding. Last check: 2007-11-04)
		The design of a speech coding algorithm is determined by the major requirements of high (subjective) speech quality, low bit rate, low computational complexity, high robustness against channel errors and low algorithmic delay.
		For voiced speech sounds, the periodic character of the speech signal is modeled by a long-term synthesis filter, e.g.
		The speech coding group has been working on efficient methods for the analysis and quantization of the parameters in fixed and variable rate codecs and theoretical considerations of these coding techniques.
	www.ind.rwth-aachen.de /research/speech_coding.html (3029 words)

	KTH Speech, Music and Hearing :: Annual Report 1999
		With respect to source coding, the principles of rate distortion theory, lossless (entropy) coding (Huffmann, Ziv-Lempel), scalar and vector quantization, and predictive, transform, and subband coding are presented.
		Applications of these methods to the coding of speech, audio, images, and image sequences, including the procedures found in the GSM, JPEG, and MPEG standards, are also described.
		Source coding techniques such as scalar and vector quantization, orthogonal transforms, and linear prediction are introduced and their performance is analyzed theoretically.
	www.speech.kth.se /annualreport/1999/ar-teaching.html (1411 words)

	CommsDesign - Handling VoIP Speech Coding Challenges: Part 2
		Part 1 of this article discussed the key attributes required in speech coder technology as well as challenges that the packet network creates in a speech coding architecture.
		When working on speech coding architectures, there are really five challenges that designers must tackle: error correction, adaptive wideband coding, transcoding across networks, background noise reduction, and low delay modems.
		Maximum likelihood estimation: involved an estimation of the speech envelope or the magnitude spectrum based on a statistical model of the speech and noise.
	www.commsdesign.com /design_corner/showArticle.jhtml?articleID=16505914 (2317 words)

	Low Complexity CELP Speech Coder (Site not responding. Last check: 2007-11-04)
		Other advantages of digital speech coding include the relative ease of encrypting digital signals compared to analog signals and the ability to time multiplex multiple signals on one channel.
		Code excited linear predictive (CELP) coding is a well-known technique that synthesizes speech using encoded excitation information to excite a linear predictive coding (LPC) filter.
		The speech synthesizer has the same codebook and accesses the appropriate entry in that codebook, using it to excite the same LPC filter to reproduce the original input speech frame.
	www.isr.umd.edu /ISR/accomplishments/007_CELP (1023 words)

	The CCITT G.722 Wideband Speech Coding Standard
		Speech coding with a bandwidth wider that that offered in telephony results in major improvement in represented speech quality [4, 5].
		The coding of the sub-band signal is based on a modified version of the 32kbps CCITT G.721 ADPCM speech coder.
		High quality coding with the G.722 wideband speech coder is provided by a fix bit allocation, where the low and high sub-bands ADPCM coders use a 6b/sample and 2b/sample quantizer, respectively.
	www.umiacs.umd.edu /~desin/Speech1/node3.html (633 words)

	Examples of Speech Coding (Site not responding. Last check: 2007-11-04)
		This approach partitions the sampled speech into frames (of typically 20 ms) and each frame is encoded at a rate of 8, 4, 2, or 1 kbps.
		The encoding rate to be used for each speech frame is determined by an "activity measure" selected to monitor how much energy occurs in the frame.
		In this approach the speech is also partitioned into frames, and each frame is analyzed using the DFT to determine pitch and harmonic frequencies.
	www.eecs.wsu.edu /~fischerw/speech_examples.html (222 words)

	Seminar - Voice Coding Algorithms
		Pulse Code Modulation and Sub Band Coding are examples of waveform coding algorithms while Linear Predictive Coding is an example of an algorithm that models the vocal tract.
		High quality coding with the G.722 wideband speech coder is provided by a fixed bit allocation, where the low and high sub-bands ADPCM coders use a 6 bits/sample and 2 bits/sample quantizer, respectively.
		CELP divides the speech it is to code into 30ms frames, each of which is further divided into four 7.5 ms sub-frames.
	www.nextgendc.com /seminar_voice_coding.htm (1683 words)

	Speech Coding (Site not responding. Last check: 2007-11-04)
		Digital speech coding is done to obtain the objective of efficient storage and transmission of the speech signal.
		This type of coding is done in speech, music, etc. It has a high bit rate, approximately 50 kbps and possess a good quality.
		Parametric coding:- Aim of coding is to extract or derive a limited number (10 - 20) of relatively slowly varying characteristic parameters of the speech signal and represent them as a bit stream.
	www.eng.usf.edu /~lazam2/Project/Coding/speech_coding1.htm (198 words)

	comp.speech Frequently Asked Questions - part 2/3
		ADPCM is the next family of speech coding techniques, and does exploit this redundancy by using a simple linear filter to predict the next sample of speech.
		At the decoder a regular set of pulses for voiced speech or white noise for unvoiced speech is passed through the linear filter and multiplied by the gain to produce the speech.
		The algorithm is based on analysis-by-synthesis predictive coding with vector-coded excitation, in which the excitation signal is optimized by minimizing the perceptually weighted error between the original and synthesized speech.
	www.faqs.org /faqs/comp-speech-faq/part2 (4997 words)

	Speech Coding
		"Speech Coding" is the term used for algorithms or devices whose purpose is to decrease the bit rate for transmission of a digital speech signal across a digital channel.
		As with all other coding systems, a speech coding algorithm has two primary parts, the "Encoder", located at the transmitting or the source end of the system, and a "Decoder", located at the receiving or the sink end of the system.
		The purpose of this WWW page is to give an idea of the workings of some speech coding algorithms and also demonstrate their applicability.
	www.eas.asu.edu /~speech/sp_cod.html (326 words)

	Speech Coding (Site not responding. Last check: 2007-11-04)
		Adaptive filters are at the heart of most speech coding techniques, such as linear predictive coding (LPC), which is required for low bit rate communication.
		The basic idea behind LPC is that a speech sample can be approximated as a linear combination of past speech samples.
		Therefore, by minimizing the MSE between the actual speech samples and the predicted ones, an optimal set of weights for an all-pole (synthesis) or all zero (analysis) digital filter can be determined.
	freespace.virgin.net /sanjeev.sarpal/speech_coding.htm (493 words)

	comp.speech Frequently Asked Questions - part 1/3
		Linguistic Data Consortium (LDC) The LDC was established to broaden the collection and distribution of speech and natural language data bases for the purposes of research and technology development in automatic speech recognition, natural language processing and other areas where large amounts of linguistic data are needed.
		Speech waveforms, spectrograms, pitch traces etc can be displayed, edited and processed in X windows and Openwindows (versions 2 and 3).
		Speech and Hearing Research Group, University of Sheffield, UK http://www.dcs.shef.ac.uk/research/groups/spandh/world/misclink s.html Links to sites in the UK, USA, Europe and the rest of the world.
	www.faqs.org /faqs/comp-speech-faq/part1 (9990 words)

	Wiley::Digital Speech Transmission: Enhancement, Coding and Error Concealment
		Digital speech transmission techniques play an important role in these applications, all the more because high quality speech transmission remains essential in all current and next generation communication networks.
		Enhancement, coding and error concealment techniques improve the transmitted speech signal at all stages of the transmission chain, from the acoustic front-end to the sound reproduction at the receiver.
		Advanced speech processing algorithms help to mitigate a number of physical and technological limitations such as background noise, bandwidth restrictions, shortage of radio frequencies, and transmission errors.
	www.wiley.com /WileyCDA/WileyTitle/productCd-0471560189.html (325 words)

	Educational MATLAB Speech Coding Software
		Speech coding or compression is the field concerned with compact digital representations of speech signals for the purpose of efficient transmission or storage.
		For each frame processed by the selected algorithm, users are able to view a time-domain signal representation and a frequency-domain signal representation for both input and output speech.
		Most of the speech coders rely upon a source-system signal representation, which is realized as a combination of an excitation sequence (lower vocal tract) and a digital filter (upper vocal tract filter).
	www.eas.asu.edu /~speech/education/educ1.html (442 words)

	DataCompression.info - Speech (Site not responding. Last check: 2007-11-04)
		Nellymoser is the leading provider of proprietary speech and audio software technology and solutions in the areas of compression, modification, synchronization and conversion.
		This is reputed to be C source code for a GSM codec.
		This is supposed to be a 2.4 Kbps LPC speech codec.
	datacompression.info /Speech.shtml (2714 words)

	comp.speech WWW site
		This site provides a range of information on speech technology, including speech synthesis, speech recognition, speech coding, and related material.
		This site is mirrored at several other WWW sites around the world (Australia, UK, Japan and USA) and the information is also available in a plain text format.
		The comp.speech ftp site is an excellent repository of speech technology information, software and resources.
	www.speech.cs.cmu.edu /comp.speech (375 words)

	Amazon.com: Speech Coding and Synthesis: Books: W.B. Kleijn,K.K. Paliwal (Site not responding. Last check: 2007-11-04)
		The fields of speech coding and synthesis have developed rapidly over the last decade.
		Topics such as the effect of cross channel errors on coded speech and the determination of a proper pitch contour for synthesized speech are included.
		Both readers unfamiliar with the fields of speech coding and speech synthesis as well as those already working within the areas, will find the book of interest.
	www.amazon.com /Speech-Coding-Synthesis-W-B-Kleijn/dp/0444821694 (700 words)

	Speech Coders from Encore (Site not responding. Last check: 2007-11-04)
		Encore offers a choice of robust speech coding algorithms for applications that require real-time codecs with good voice quality at bit-rates significantly lower than either 64 KB/s PCM or even 32 KB/s ADPCM.
		Apart from the speech coders being available as programmable DSP implementations on Texas Instruments' TMS320C54x, TMS320C55x, TMS320C62x, and TMS320C64x Series of DSPs, Encore can also port these coders to customer's target processors.
		Having gained abundant experience in developing Speech coders on various DSPs, Encore can also provide those speech coders which are not on its present list should the customer have such a requirement.
	www.ncoretech.com /speech (122 words)

	Speech Coding - Training by TRA (Site not responding. Last check: 2007-11-04)
		Course content explains how voice is digitized in traditional Pulse-Code Modulation, the difference between the North American mu-law and the European A-law coding, how speech is compressed and affects the Mean Opinion Score, how Linear Predictive Coders achieve balance between speech quality and deficiency, and other speech coding fundamentals.
		Students looking for a thorough technical introduction to speech coding will find this course a wise choice.
		The course provides a high-level look at the entire telephone network providing a solid baseline for deeper study of speech coding, transmission, switching and signaling.
	www.tra.com /pages/product.cfm?id=TEL121 (317 words)

	Speech Coding (Site not responding. Last check: 2007-11-04)
		Often the speech is bandlimited to between 200 and 3400 Hz, and is sampled at 8 kHz.
		An ideal speech codec will represent this speech with as few bits as possible, while producing reconstructed speech which sounds identical, or almost identical, to the uncoded speech.
		Of course in practice there is always a trade-off between the bit rate of the codec and the quality of its reconstructed speech.
	www-mobile.ecs.soton.ac.uk /speech_codecs (253 words)

	Wiley::Digital Speech: Coding for Low Bit Rate Communication Systems, 2nd Edition
		Speech Coding Algorithms: Foundation and Evolution of Standardized Coders (Hardcover)
		This Second Edition continues to provide the fundamental technical background required for low bit rate speech coding and the hottest developments in digital speech coding techniques that are applicable to evolving communication systems.
		Written by a well-known, highly respected academic, this authoritative volume will be invaluable to practising engineers, network designers, computer scientists and advanced students in communications, electrical and electronic engineering.
	www.wiley.com /WileyCDA/WileyTitle/productCd-0470870087.html (295 words)

	TechOnline \| Techniques for Real-Time DSP Implementation of Speech Coding Algorithms
		Over the last few years, a great deal of effort has been spent in developing methods of coding digital speech signals for applications such as mobile communications, transmission of speech over the Internet, and mass storage by call centres of recorded telephone conversations.
		However, in order to achieve lower and lower bit rates while maintaining an acceptable quality of speech, speech coding algorithms are becoming increasingly sophisticated and more demanding in terms of the number of calculations required per second.
		Therefore, there is a continuous need for efficient implementation of speech coding algorithms on digital signal processors (DSPs).
	www.techonline.com /community/tech_group/dsp/tech_paper/39749 (219 words)

	WIDEBAND SPEECH CODING (Site not responding. Last check: 2007-11-04)
		Higher bandwidths than that of the 300 to 3400 Hz telephone bandwidth result in major subjective improvements in represented speech quality [3, 4].
		A bandwidth of 50 to 7000 Hz not only improves the intelligibility and naturalness of speech, but adds also a feeling of transparent communication and eases speaker recognition.
		Audio and video teleconferencing where broadened bandwidth(50-7000 Hz) provides improved sound quality,more presence of the speaker, and a more realistic rendering of the actual sound in a room.
	www.umiacs.umd.edu /~desin/Speech1/node2.html (156 words)

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