Scalable multi-rate iLBC

IEEE Trans. Audio Speech Lang. Process.

2013

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High quality speech at low bit rates makes code excited linear prediction (CELP) the dominant choice for a narrowband coding technique despite the susceptibility to packet loss. One of the few techniques which received attention after the introduction of CELP coding technique is the internet low bitrate codec (iLBC) because of inherent high robustness to packet loss. Addition of rate flexibility and scalability makes the iLBC an attractive choice for voice communication over IP networks. In this paper, performance improvement schemes of multi-rate iLBC and its scalable structure are proposed, and the proposed codec enhanced from the previous work is re-designed based on the subjective listening quality instead of the objective quality. In particular, perceptual weighting and the modified discrete cosine transform (MDCT) with short overlap in weighted signal domain are employed along with the improved packet loss concealment (PLC) algorithm. The subjective evaluation results show that the speech quality of the proposed codec is equivalent to that of state-of-the-art codec, G.718, under both a clean channel condition and lossy channel conditions. This result is significant considering that development of the proposed codec is still in early stage.Index Terms-Discrete cosine transform (DCT), internet low bitrate codec (iLBC), packet loss, scalable coding, speech coding, voice over Internet protocol (VoIP).

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Section: Packet Loss Concealmentmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Scalable Speech Coding for IP Networks: Beyond iLBC

IEEE Trans. Audio Speech Lang. Process.

2013

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“…The scalable narrowband speech codec designed specifically for IP Networks to achieve high packet-loss robustness was proposed in [1], [2]. The core layer utilizes frame-independent coding technique based on the internet low bitrate codec (iLBC) [3], [4] to achieve high robustness to packet loss.…”

Section: Introductionmentioning

confidence: 99%

“…The original iLBC operates at a fixed bit-rate of either 13.33 kbps for the frame size of 30 ms or 15.2 kbps for the frame size of 20 ms. Thus, the rate flexibility and the scalability were successfully added to the iLBC in [1], [2] in order to adapt its bit rate to the current channel conditions. The core layer codec achieved high performance whereas the speech quality improvement by adding the enhancement layer was limited.…”

Section: Introductionmentioning

confidence: 99%

Packet-loss robust scalable speech coding using the discrete wavelet transform

2014 IEEE International Symposium on Circuits and Systems (ISCAS)

2014

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This paper presents a new scalable speech codec for IP networks using the discrete wavelet transform (DWT). The scalable narrowband speech coding scheme based on the internet low bitrate codec (iLBC) was previously presented and achieved speech quality equivalent to G.718 for narrowband signals. Whereas the performance of the core layer was satisfactory, the higher speech quality by the addition of the enhancement layer which employed the modified discrete cosine transform (MDCT) was desired. We propose the utilization of the DWT instead of the MDCT to encode the core-layer coding error in the enhancement layer. The experimental simulation results show that the DWT is a promising technique to use for encoding highly non-stationary signals such as the coding error.Keywords-Discrete wavelet transform (DWT), internet low bitrate codec (iLBC), packet loss, scalable coding, speech coding, voice over Internet protocol (VoIP).

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Scalable and Multi-Rate Speech Coding for Voice-over-Internet Protocol (VoIP) Networks

Speech and Audio Processing for Coding, Enhancement and Recognition

2014