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.

All assembly implementation of G.729 Annex B speech codec on a fixed point DSP

Abstract: A lot of effort has been spent over the last few years in the development of digital speech coding methods and their subsequent standardization. Algorithms have evolved which provide good quality speech at sub 8 kbps bit rates although at a much higher computational expense. DSP processors have also improved with time providing specific signal processing functionalities aiding in easier codec implementations along with lower power consumption at higher clock speeds. Software development tools and compilers have also improved although they still do not work well in high volume, low cost systems. The cost of development tools may also be prohibitive for nonvendors and at times high level code conversion tools may not be present at all. This paper describes techniques and approaches commonly used to realize such systems where the codec implementation in all assembly is necessary. The specific codec implemented was International Telecommunication Union (ITU-T) G.729 Annex B. The techniques described in this paper are applicable to any other speech codec.

Packet loss concealment for sub-band codecs

Abstract: Packet loss concealment systems and methods are described that may be used in conjunction with a Bluetooth® Low-Complexity Sub-band Coding (LC-SBC) codec or other sub-band codecs, including but not limited to an MPEG-1 Audio Layer 3 (MP3) codec, an Advanced Audio Coding (AAC) codec, and a Dolby AC-3 codec.

A robust low rate voice codec for wireless communications

Abstract: The design, implementation and performance of a high quality low bit rate speech codec for wireless communication is presented. The codec is based on the CELP model. Generalized analysis-by-synthesis, algebraic fixed codebooks, and multistage LSF techniques are used, resulting in robustness to transmission errors and high quality across changing speech levels and background noise conditions. The bit allocations for the quantization of LSF, pitch and the excitation are chosen in a mode specific manner based on a robust mode classification scheme. A 4.8 kb/s version has been implemented and subjective tests show speech quality that is equivalent to or better than most cellular standard codecs. Performance is also consistent across speech levels and transmission errors.

Integrated echo canceller and speech codec for voice-over IP(VoIP)

Abstract: A method includes operating an integrated echo canceller and speech codec for voice-over internet protocol. An apparatus includes an echo canceller and a speech codec, wherein the speech codec includes a decoder and an encoder, and wherein the echo canceller and the speech codec are integrated for voice-over-internet protocol.

A steganography scheme in a low-bit rate speech codec based on 3D-sudoku matrix

Abstract: Redundant information of low-bit rate speech is extremely small, thus it's very difficult to implement large capacity steganography on the low-bit rate speech. Based on multiple vector quantization characteristics of the Line Spectrum Pair (LSP) of the speech codec, this paper proposes a steganography scheme using a 3D-sudoku matrix to enlarge capacity and improve quality of speech. A cyclically moving algorithm to construct 3D-Sudoku matrix for steganography is proposed in this paper, as well as an embedding and an extracting algorithm of steganography based on 3D-Sudoku matrix in low-bit rate speech codec. Theoretical analysis is provided to demonstrate that the concealment and the hidden capacity are greatly improved with the proposed scheme. Experimental results show the hidden capacity is raised to 200bps in ITU-T G.723.1 codec. Moreover, the quality of steganography speech in Perceptual Evaluation of Speech Quality (PESQ) reduces no more than 4%, indicating little impact on the quality of speech.