Adaptive Multi-Rate audio codec

About: Adaptive Multi-Rate audio codec is a research topic. Over the lifetime, 1467 publications have been published within this topic receiving 19736 citations. The topic is also known as: AMR & Adaptive Multi-Rate.

Method and system for implementing codec transition for voice service

Abstract: A method and system for implementing codec transition for voice service is provided. The method comprises setting up a traffic path on a channel in response to receiving a request for a first service, the channel having capability of handling at least a first codec for the first service; determining whether the channel supports the codec transition from the first codec to a second codec, in response to receiving a request for a second service via the traffic path; and responding to the request for the second service based on results of the determining step. The method and system realize the voice codec transition seamlessly without the hard handoff to switch the channel, so as to avoid the failure of channel allocation and to lower down the call dropped rate due to codec transition.

High efficiency stereo audio compression method using polar coordinate principle component analysis for wireless communications

Abstract: High efficiency audio compression is the basic technology in audio involved multimedia communications. Downmixing and parametric coding is efficient coding scheme with wide applications in some up-to-date audio codecs such as Parametric Stereo (PS) in EAAC+ and MPEG-Surround. Principle Component Analysis (PCA) stereo coding followed this idea to map two channels to one channel with maximum energy and parameterize the secondary channel. This paper investigates the conventional PCA method performance under general stereo model with multiple sound sources and different directions, and then proposes a Polar Coordinate based PCA (PC-PCA) stereo coding method. It has been proved that when multiple sound sources exist with different directions, PC-PCA is better than the conventional PCA method when Mean to Standard deviation Ratio (MSR) is large. A stereo codec based on PC-PCA is proposed to validate the performance improvement of proposed method. Objective and subjective tests show the proposed method achieves a comparative quality and saves 50% parameter bit rate comparing with conventional PCA method, and obtains a 4–8 MUSHRA scores improvement comparing with state-of-the-art stereo codec at the same parameter bit rate.

A new sinusoidal modelling approach for parametric speech and audio coding

Abstract: In this paper we propose a new approach based on energy-adaptive matching pursuits to improve sinusoidal modelling for parametric speech and audio coding. To reduce the complexity of the algorithm, an over-complete dictionary composed of complex exponentials is used. An analysis-synthesis windows scheme that avoids overlapping is proposed. For efficient quantization of sinusoidal model parameters, a new algorithm that largely reduces the side information required by the decoder is described. Experimental results show evidence of the advantages of the proposed method to be integrated into multi-pans models for parametric speech/audio coding.

A new bandwidth extension technology for MPEG Unified Speech and Audio Coding

Abstract: In January 2012, MPEG finalized the new MPEG-D Unified Speech and Audio Coding (USAC) standard, which enables the coding of a variety of audio content at low bitrates. USAC provides low-bitrate coding by integrating a speech codec and an audio codec into a unified system. In USAC, Predictive Vector Coding (PVC) is added to Enhanced Spectral Band Replication (eSBR) to improve the subjective quality, especially for speech at low bitrates. For speech signals, there is generally a relatively high correlation between the spectral envelopes of low- and high-frequency bands. The PVC scheme exploits this by predicting the high-frequency envelopes from the low-frequency ones, with the coefficient matrices for the prediction being coded by means of vector quantization.

Perceptually Layered Scalable Codec

Abstract: Fine-grain scalable audio coding approaches, such as PLEAC [2], are flexible, can scale from low rates to lossless, and can allow the perceptual model to be updated in the decoder as additional bits are provided. They provide good perceptual quality at mid to high perceptual rates; however, they can not establish the perceptual model rapidly enough to provide good quality at very low bit rates. In this work, we combine a fine grain scalable audio codec with a good base layer audio codec. We use Windows Media Audio 10 Professional (WMA 10 Pro) [1] as the base layer coder, and use the PLEAC codec as the fine grain enhancement codec. The key to this method is to use a base layer codec that provides a very good approximation to the necessary perceptual codec, and then allows the fine grain scalable audio coder to use a simple loudness model on the difference signal. The combined codec can provide continuous scalability from the base layer codec rate all the way to lossless.