speech codec

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speech codec

Also called a "voice codec" or "vocoder," it is a hardware circuit that converts the spoken word into digital code and vice versa. It comprises the A/D and D/A conversion and compression technique (see G. standards). If music is encoded with a speech codec, it will not sound as good when decoded at the other end.

Specialized for Voice
A speech codec is an audio codec designed for human voice. By analyzing vocal tract sounds, a recipe for rebuilding the sound at the other end is sent rather than the soundwaves themselves. The speech codec is able to achieve a much higher compression ratio, which results in a smaller amount of digital data for transmission. When telephones were first digitized in the early 1960s, they generated digital streams of 64 Kbps (see PCM). Since then, speech codecs have reduced voice to as little as 5 Kbps and less. See audio codec, sampling, codec examples and codec.
References in periodicals archive ?
Speech coding is the process of obtaining a compact representation of speech signals for efficient transmission and/or storing in digital media [1]-[3].
Subsequent chapters discuss mathematical representations (pitch-synchronous spectral analysis methods and waveform recovery) and applications in speech and voice technology, including voice transformation and speech coding, recognition, and synthesis.
POLQA supports the latest HD-quality speech coding and network transport technology with higher accuracy for 3G, 4G/LTE and VoIP networks.
Among their topics are sampling theory, waveform coding and quantization, linear predictive coding, vector quantization for speech coding applications, and signal processing in voice-over-Internet protocol systems.
He conducted research in various speech and audio processing, speech coding, and voice systems applications at AT&T Bell Laboratories and AT&T Labs until his retirement from AT&T in May 2008.
TELECOMWORLDWIRE-4 April 2007-NTT DoCoMo develops speech coding technology for mobile phones(C)1994-2007 M2 COMMUNICATIONS LTD http://www.
The ESPrit 3G offers a built-in telecoil that permits wireless access to hearing-aid-compatible telephones and allows listeners to connect to sound systems in public venues with assistive listening devices; the Whisper setting, which improves the audibility of soft and moderate speech; 54 hours of battery life; and all three Nucleus digital speech coding strategies--ACE[TM], CIS, and SPEAK--designed to allow users to hear clearly in all environments.
Voxware Inc, the speech and audio compression firm from Princeton, New Jersey, is heading off in a new direction, and has agreed to sell off its speech coding technologies to Ascend Communications Inc for around $5.
Also discussed were applications in text-to-speech technology, large vocabulary speech recognition, interactive audiotex, interactive voice response, speech I/O interface for super workstations, military speech communications and applications, office automation, automating operator services using speech technology, factory/industrial automation, voice verification and security, emerging information services, Canadian activities, military R&D to operational environments, banking/brokerage, voice mail/voice messaging, international activities, software tools for technology development and application, neural networks, consumer products, speech coding, PC voice-based systems, Outbound technology, and information providers, services, products, and users.
The patent was granted to SPIRIT for multilayer, scalable, packet loss-resilient speech coding technology for IP-networks.
Chapters are provided on spectral transformations, filter banks for spectral analysis and synthesis, stochastic signals and estimation, linear prediction, quantization, speech coding, error concealment and soft decision source decoding, bandwidth extension of speech signals, single and dual channel noise reduction, multi-channel noise reduction, and acoustic echo control.