Topic
Enhanced Variable Rate Codec
About: Enhanced Variable Rate Codec is a research topic. Over the lifetime, 357 publications have been published within this topic receiving 4842 citations. The topic is also known as: EVRC.
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13 Sep 1998
TL;DR: The design techniques for very low power consumption were applied to the speech codec in a personal digital cellular phone and their effectiveness was verified.
Abstract: As technology advances offer small size and light weight in mobile telecommunication equipment, low power techniques become important elements. This paper describes the design techniques for very low power consumption, solving hardware implementation issues. Basically they were applied to the speech codec in a personal digital cellular phone and their effectiveness was verified.
2 citations
19 Apr 1994
TL;DR: A low bit-rate speech codec has been developed and the speech coder employs a PCELP (CELP with pulse codebook) algorithm, which uses a pulse-train excitation codebook to enhance the quality of voiced speech.
Abstract: A low bit-rate speech codec has been developed. The speech coder employs a PCELP (CELP with pulse codebook) algorithm, which uses a pulse-train excitation codebook to enhance the quality of voiced speech. The computational complexity for the pulse codebook search is greatly reduced by using truncated impulse responses of a weighted synthesis filter. An improved Viterbi decoding method using error detecting code information instead of tail bits has also been developed to increase the effective error-correction coding rate. A 5.6 kb/s speech codec has been implemented by incorporating the PCELP speech coding algorithm with the improved Viterbi decoding. Formal listening tests show that the synthetic speech quality of this codec is equivalent to that of 5.4-bit /spl mu/-law PCM in the absence of channel errors. >
2 citations
06 Mar 1998
2 citations
25 Jun 1992
TL;DR: A half rate speech/channel codec intended for the TIA technology assessment is described and its performance is presented.
Abstract: A half rate speech/channel codec intended for the TIA technology assessment is described. The requirements for this assessment are an overall bit rate of 6.4 kbps and a frame size of 40 msec. The codec design and its performance is presented. >
2 citations
01 Jan 2016
TL;DR: A method to estimate two codec-related parameters that used to calculate the E-model, which are called equipment impairment factor \( I e) and packet loss robustness factor \( Bpl \) of the non ITU-T codec are proposed.
Abstract: The aim of this research is to the improve performance of the E-model, which is one of the most successful non-intrusive speech quality prediction models for voice communication over a packet based network. However, the E-model still has limitations. The calculation method of the E-model is restricted to a set of voice codecs from ITU-T. This paper proposes a method to estimate two codec-related parameters that used to calculate the E-model, which are called equipment impairment factor \( I_{e} \) and packet loss robustness factor \( Bpl \) of the non ITU-T codec. The process to estimate both parameters uses a curve fitting method to calculate \( I_{e} \) values from PESQ results under various levels of network packet loss. The set of \( I_{e} \) and \( Bpl \) of eight narrowband codecs (G.711, G.729, GSM, AMR, iLBC, Speex, Silk, and Opus) are presented. Statistical analysis was also performed for model validation. The results show that the E-model with our I e and Bpl parameters achieved a good accuracy and a good correspondence with PESQ MOS among the eight codecs.
2 citations