New post-processing techniques for low bit rate celp codecs

Vaillancourt, Tommy; Salami, R.; Jelinek, Milan

doi:10.1109/icassp.2015.7179105

Cited by 3 publications

(2 citation statements)

References 5 publications

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“…To enhance the perceptual quality at low bitrates, modern speech codecs employ post-filters [3,4,5,6]. Post-processing the coded speech is conceptually similar to most speech enhancement techniques aiming to attenute or amplifiy frequency components with a bad or good signal-to-noise ratio, respectively.…”

Section: Introductionmentioning

confidence: 99%

Enhancement of Coded Speech Using a Mask-Based Post-Filter

Korse

Gupta

Fuchs

2020

ICASSP 2020 - 2020 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP)

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The quality of speech codecs deteriorates at low bitrates due to high quantization noise. A post-filter is generally employed to enhance the quality of the coded speech. In this paper, a data-driven postfilter relying on masking in the time-frequency domain is proposed. A fully connected neural network (FCNN), a convolutional encoderdecoder (CED) network and a long short-term memory (LSTM) network are implemeted to estimate a real-valued mask per timefrequency bin. The proposed models were tested on the five lowest operating modes (6.65 kbps-15.85 kbps) of the Adaptive Multi-Rate Wideband codec (AMR-WB). Both objective and subjective evaluations confirm the enhancement of the coded speech and also show the superiority of the mask-based neural network system over a conventional heuristic post-filter used in the standard like ITU-T G.718.

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Section: Introductionmentioning

confidence: 99%

Enhancement of Coded Speech Using a Mask-Based Post-Filter

Korse

Gupta

Fuchs

2020

ICASSP 2020 - 2020 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP)

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“…Partners: Imec, Televic, Cochlear, and Qorvo. various speech-model based methods such as Linear Predictive Coding (LPC), Long Term Post-Filter (LTPF), and pitch enhancement filters were proposed [5], [6], to emphasise the harmonic structure during enhancement.…”

Section: Introductionmentioning

confidence: 99%

Bitrate-Informed Coded Speech Enhancement Model

Zhao,

Madhu

2024

2024 International Conference on Electronics, Information, and Communication (ICEIC)

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Enhancing speech processed by lossy codecs can significantly improve the resultant signal quality, providing a richer listening experience while reducing listening fatigue. Since there are a multitude of codecs, each supporting several bitrates, deep-learning-based solutions typically train networks in a codecspecific manner and use multi-condition training for each codecspecific network, to improve generalizability for the different bit-rates. In contrast, we propose a bitrate-informed model for improving the inter-bitrate generalizability of the model for coded speech enhancement. The well-known Convolutional Recurrent U-Net Speech Enhancement (CRUSE) encoder-decoder model is selected for the enhancement, however, we propose modifying only the initial few layers of the encoder, to introduce bitrate dependency. The rest of the network is shared for all bitrates. Evaluation is carried out on two contemporary codecs: the Bluetooth low complexity communication codec plus (LC3plus) and the 3GPP adaptive multi-rate wideband (AMR-WB) codec. The experimental study shows that using bitrate-informed layers improves generalisation capability. More importantly, this only causes a small increase (< 1%) in model footprint and no increase in the computational cost. Further, to provide better insights into where such bitrate-informed layers can be useful, we propose using the histogram of the ideal training target masks. The radically different histograms at the different bitrates for LC3plus codec indicate a stronger benefit with the bitrateinformed model -which is also seen in the instrumental metrics. This paper lays the foundation for further work on bitrate and codec-informed models -allowing for the development of a single, universal model for coded speech enhancement.

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Improvement of the post-processing algorithm in AMR-NB speech codec

Hou

Zhao

2021

Procedia Computer Science

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New post-processing techniques for low bit rate celp codecs

Cited by 3 publications

References 5 publications

Enhancement of Coded Speech Using a Mask-Based Post-Filter

Enhancement of Coded Speech Using a Mask-Based Post-Filter

Bitrate-Informed Coded Speech Enhancement Model

Improvement of the post-processing algorithm in AMR-NB speech codec

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