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.

A low bit rate codec for AMR standard

Abstract: We describe a low bit rate speech codec based on the RCELP paradigm and designed as a candidate for GSM-AMR. The relaxation of the waveform-matching constraint in the RCELP model allows for reducing the bit rate without affecting the speech quality. New efficient quantization methods for the LSF and gain parameters coupled with some algorithmic improvements result in a high quality speech codec at bit rates as low as 4.55 kbit/s. Subjective tests show encouraging results in terms of quality and robustness under various operating conditions.

An Effective Codec Adaptation for MIH Based Vertical Handover in Heterogeneous Wireless Networks

Abstract: The explosive demands of multimedia services have been grown up to support delay-sensitive applications, e.g., VoIP and streaming using codec. When a mobile node (MN) moves across different types of networks, the codec should be effectively adapted according to the significant change of network condition, i.e., throughput and delay. Therefore, in this paper, we propose a codec adaptation for vertical handover (ACAV), aiming not only to increase throughput but also to decrease delay at MNs. Using media independent information service (MIIS), the ACAV is able to proactively estimate network conditions of the target network then determine a proper type of codec for on-going multimedia services. The simulation results show that the proposed ACAV outperforms typical codec adaptation mechanism in terms of throughput and delay by determining a proper codec for the target network.

Implementation of H.324 audiovisual codec for mobile computing

Abstract: A VLSI implementation of the H.324 audiovisual codec is described. A number of sophisticated low-power architectures have been devised dedicatedly for the mobile use. A set of specific functional units, each corresponding to a process of H.263 video codec, is employed to lighten different performance bottlenecks. A compact DSP core composed of two MAC units is used for both ACELP and MP-MLQ coding schemes of the G.723.1 speech codec. The proposed audiovisual codec core has been implemented by using 0.35 /spl mu/m CMOS 4LM technology, which contains totally 420 k transistors with a dissipation of 224.32 mW from single 3.3 V supply.

Description and evaluation of a non-DCT-based codec

Abstract: At this time, almost all (de-facto) video coding standards are DCT based. It would be wrong though to think that DCT is the only practical way to reach a reasonable compression ratio for a reasonable codec complexity. In this paper, a description of a complete hybrid codec based on OLA (Optimal Level Allocation) and HVS (Human Visual System) based classification is given. Then a performance comparison is made between this codec and an MPEG-2 like codec.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Hybrid test compression architecture using multiple codecs for low pin count and high compression devices

Abstract: This invention uses multiple codecs to efficiently achieve the right balance between compression and coverage for a given design. This application illustrates a simple example using two codecs including a high compression codec and a low compression codec. The test engineer generates a first set of test patterns using the high compression codec. If this high compression results in unacceptable fault coverage loss, the top-up patterns for additional coverage are generated using the low compression codec. The invention may use multiple codecs serially one after the other. The codecs can be of different types or parameters (such as compression ratio, debug tolerance and combinational codec versus sequential codec).