Enhanced Variable Rate Codec B
- Enhanced Variable Rate Codec B
Enhanced Variable Rate Codec B (EVRC-B) is a speech codec used by CDMA networks. EVRC-B is an enhancement to EVRC and compresses each 20 milliseconds of 8000 Hz, 16-bit sampled speechinput into output frames of one of the four different sizes: Rate 1 - 171 bits, Rate 1/2 - 80 bits,Rate 1/4 - 40 bits, Rate 1/8 - 16 bits.
In addition, there are two zero bit codec frame types: null frames and erasure frames, similar to EVRC. One significant enhancement in EVRC-B is the use of 1/4 rate frames that were not used in EVRC. This provides lower average data rates (ADRs) compared to EVRC, for a given voice quality.
The new 4GV Codecs used in CDMA2000 are based on EVRC-B. 4GV is designed to allow service providers to dynamically prioritize voice capacity on their network as required.
The Enhanced Variable Rate Coder (EVRC) is a speech codec used for cellular telephony in cdma2000 systems. EVRC provides excellent speech quality using variable rate coding with 3 possible rates, 8.55, 4.0 and 0.8 kbit/s. However, the Quality of Service (QoS) in cdma2000 systems can significantly benefit from a codec which allows tradeoffs between voice quality and network capacity, which cannot be achieved efficiently with the EVRC.
An upgrade of the EVRC vocoder, known as EVRC-B, was recently introduced by 3GPP2. The EVRC-B speech codec is based on the 4GV concept and is the newest and most advanced speech codec for cellular applications. In addition to the Relaxed Code Excitation Linear Prediction (RCELP) used by EVRC, EVRC-B uses Prototype Pitch Period (PPP) approach for coding of stationary voice frames and Noise Excitation Linear Prediction (NELP) for efficient coding of unvoiced or noise frames. Using NELP and PPP coding at 2.0 kbit/s provides EVRC-B with superior flexibility in rate assignment, allowing it to operate at several operating points, each with a different trade-off between speech quality and system capacity. EVRC-B will replace EVRC as the main speech codec for cdma2000 and its first network commercial deployment is planned to start in 2007. A wideband extension, EVRC-WB, will provide speech quality that exceeds regular wireline telephony and its standardization process is planned to be completed at the summer of 2007.
Wikimedia Foundation.
2010.
Look at other dictionaries:
Enhanced Variable Rate Codec — (EVRC) is a speech codec used in CDMA networks. It was developed in 1995 to replace the QCELP vocoder which used more bandwidth on the carrier s network, thus EVRC s primary goal was to offer the mobile carriers more capacity on their networks… … Wikipedia
EVRC — Enhanced Variable Rate CODEC (EVRC) est un format de compression audio utilisé dans les réseaux CDMA. Il a été développé en 1995 pour remplacer le codec voix QCELP qui consommait plus de bande passante sur les réseaux de téléphonie. Le premier… … Wikipédia en Français
EVRC — Enhanced Variable Rate Codec (Computing » Telecom) * Evercel, Inc. (Business » NASDAQ Symbols) … Abbreviations dictionary
List of codecs — The following is a list of codecs. Audio codecs Non compression formats * Audio Interchange File Format (AIFF, container format) * Resource Interchange File Format (RIFF, container format) * WAV – Microsoft WAVE format (format supports… … Wikipedia
Audioformat — Ein Audioformat ist ein Datenformat, das den Aufbau einer Audiodatei oder eines Audiodatenstromes beschreibt. Inhaltsverzeichnis 1 Allgemein 2 Datenreduktion oder Datenkompression 3 Liste gängiger Audioformate … Deutsch Wikipedia
SMV — Saltar a navegación, búsqueda SMV son las siglas de Selectable Mode Vocoder. Constituyen una de las versiones de codificadores de voz en radiotelefonía. Contenido 1 Introducción 2 Antecedentes de la codificación CDMA 3 Codificador … Wikipedia Español
Selectable mode vocoder — o SMV es un estándar de codificación de voz de tasa de bits variable, usado en redes CDMA2000.[1] SMV usa distintos modos de operación que son seleccionanos en base a las características de la voz usada como entrada. Constituyen una de las… … Wikipedia Español
усовершенствованный кодек речи с переменной скоростью передачи — Вокодер с переменной скоростью передачи, разработанный компанией Motorola. Средняя скорость передача 8,5 кбит/с (IS 127). [Л.М. Невдяев. Телекоммуникационные технологии. Англо русский толковый словарь справочник. Под редакцией Ю.М. Горностаева.… … Справочник технического переводчика
усовершенствованный кодек с переменной скоростью (передачи) — (МСЭ R F.757 3). [http://www.iks media.ru/glossary/index.html?glossid=2400324] Тематики электросвязь, основные понятия EN enhanced variable rate codecEVRC … Справочник технического переводчика
усовершенствованный речевой кодек с переменной скоростью передачи — вокодер с переменной скоростью передачи — [Л.Г.Суменко. Англо русский словарь по информационным технологиям. М.: ГП ЦНИИС, 2003.] Тематики информационные технологии в целом Синонимы вокодер с переменной скоростью передачи EN enhanced… … Справочник технического переводчика
