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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07 Oct 2001
TL;DR: The speech quality of the UMTS adaptive multi-rate speech codec is investigated and relevant results are presented, showing that the speech quality is not affected appreciably by transmission errors when the FER is kept below 1%.
Abstract: We present a methodology and a tool for objective characterization of voice service quality in W-CDMA networks. Specifically, the speech quality of the UMTS adaptive multi-rate speech codec is investigated and relevant results are presented. The results show that the speech quality is not affected appreciably by transmission errors when the FER is kept below 1%. However, the codec can be operated at up to FER=7% in the highest codec mode while keeping a voice quality as good as or better than lower codec rates at lower FER.
7 citations
01 Jan 2007
TL;DR: This document updates the Enhanced Variable Rate Codec (EVRC) RTP payload formats with several enhancements and extensions, as well as discontinuous transmission (DTX) support for EVRC and EVRC-B-encoded speech transported via RTP.
Abstract: This document updates the Enhanced Variable Rate Codec (EVRC) RTP
payload formats defined in RFC 3558 with several enhancements and
extensions. In particular, it defines support for the header-free and
interleaved/bundled packet formats for the EVRC-B codec, a new compact
bundled format for the EVRC and EVRC-B codecs, as well as
discontinuous transmission (DTX) support for EVRC and EVRC-B-encoded
speech transported via RTP. Voice over IP (VoIP) applications
operating over low bandwidth dial-up and wireless networks require
such enhancements for efficient use of the bandwidth. [STANDARDS-
TRACK]
7 citations
Patent•
29 Sep 2004TL;DR: In this paper, the LSP parameters interpolated from EVRC to G.729ab were used as input to a closed-loop pitch search, and fixed codebook pulses found from a search limited to positions of EVRC fixed codebooks together with positions of target-impulse correlation maxima on the subframe tracks or full track search.
Abstract: Transcoding from EVRC to G.729ab with LSP parameters interpolated from EVRC to G.729ab, EVRC pitch used as input to G.729ab closed-loop pitch search, and G.729ab fixed codebook pulses found from a search limited to positions of EVRC fixed codebook pulses together with positions of target-impulse correlation maxima on the subframe tracks or full track search if no EVRC pulses.
6 citations
01 Jan 2004
TL;DR: This contribution reports on the work in 3GPP release 6 on the standardization of a new audio codec for mobile multimedia applications including packet-switched streaming (PSS) and multimedia messaging (MMS).
Abstract: This contribution reports on the work in 3GPP release 6 on the standardization of a new audio codec for mobile multimedia applications including packet-switched streaming (PSS) and multimedia messaging (MMS). First, the design constraints, performance requirements, test plans, selection rules were finalized for both PSS/MMS audio codecs and for the extended AMR-WB codec (AMR-WB+). The candidate codecs were as follows: MPEG4 HE-AAC codec ("AAC+1') for low and high bit-rate range, coding technologies codec ("Enhanced AAC+") for low and high bit-rate range, and Ericsson, Nokia and VoiceAge AMR-WB+ candidate codec for low bit-rate range. Next, extensive subjective listening testing was conducted. The test results showed good performance for the enhanced AAC+ and for the AMR-WB+ candidates.
6 citations
TL;DR: Simulations with various speech data show that the proposed EVRC code book search method yields voice quality equivalent to that by the standard method with only 23% codebook search load.
Abstract: An efficient enhanced variable rate codec (EVRC) codebook search method based on a two-stage search is proposed. At the first stage, a coarse codevector is selected by a fast sequential search, and at the second stage, the pulse replacement procedure is run to enhance the performance of selected codevector. Simulations with various speech data show that the proposed method yields voice quality equivalent to that by the standard method with only 23% codebook search load.
6 citations