Nam-Suk Lee

Low latency audio coder design for bluetooth and bluetooth low energy

Wireless audio service attracts increasing attention both in mobile and in home audio market. For high quality audio service especially on wireless network, the audio codec with low latency is indispensable since the latency prevents a user from being immersed in the service. This paper presents a low latency audio coder design with a short length window. Side effects due to the short length window are mitigated by the proposed coding tools such as pitch coding and low frequency masking threshold control. The audio quality assessed by the objective and subjective manners shows that the proposed design outperforms the well-known commercial codec.

Method and apparatus for encoding envelopes of harmonic signals and method and apparatus for decoding envelopes of harmonic signals

Provided are a methods and apparatuses for encoding/decoding an audio signal to efficiently encode/decode a harmonic envelope. The method of encoding an audio signal includes performing harmonic analysis with respect to an input signal to determine harmonic parameters with respect to harmonic signals; correlating the amplitudes of the harmonic signals to signals in a time domain instead of signals in a frequency domain; applying a time-frequency transformation operation to the amplitudes in the time domain to generate time-frequency transformed values in the frequency domain; and encoding the time-frequency transformed values. When expressing a harmonic envelope, the amplitudes of the harmonic signals are regarded as signals in the time domain so as to perform a time-frequency transformation and only a part from among the transformed values is selected to be encoded. Therefore, sound quality is not affected and coding efficiency greatly improves.

Low latency audio coder design for high quality audio service on server-client environment

Low latency audio coding attracts increasing attention among high quality communication applications such as video conferencing system and server-client media applications such as cloud computing based interactive A/V service. This paper presents a low latency audio coding scheme which can achieve both low delay and high subjective audio quality at the same time. In order to guarantee low delay, the proposed coding system incorporates low overlap window while preserving the window size as same as that of conventional (AAC) long window. The supplementary signal processing tool is incorporated to enhance the audio quality. The proposed coding scheme achieves the delay of 24ms in 48 kHz and the MUSHRA score which is comparable to that of commercialized AAC.