Speech bandwidth extension (BWE) refers to widening the frequency bandwidth range of speech signals, enhancing the speech quality towards brighter and fuller. This paper proposes a generative adversarial network (GAN) based BWE model with parallel prediction of Amplitude and Phase spectra, named AP-BWE, which achieves both high-quality and efficient wideband speech waveform generation. The proposed AP-BWE generator is entirely based on convolutional neural networks (CNNs). It features a dual-stream architecture with mutual interaction, where the amplitude stream and the phase stream communicate with each other and respectively extend the high-frequency components from the input narrowband amplitude and phase spectra. To improve the naturalness of the extended speech signals, we employ a multi-period discriminator at the waveform level and design a pair of multi-resolution amplitude and phase discriminators at the spectral level, respectively. Experimental results demonstrate that our proposed AP-BWE achieves state-of-the-art performance in terms of speech quality for BWE tasks targeting sampling rates of both 16 kHz and 48 kHz. In terms of generation efficiency, due to the all-convolutional architecture and all-frame-level operations, the proposed AP-BWE can generate 48 kHz waveform samples 292.3 times faster than real-time on a single RTX 4090 GPU and 18.1 times faster than real-time on a single CPU. Notably, to our knowledge, AP-BWE is the first to achieve the direct extension of the high-frequency phase spectrum, which is beneficial for improving the effectiveness of existing BWE methods.

翻译：语音带宽扩展（BWE）旨在扩展语音信号的频率带宽范围，提升语音质量使其更清晰丰满。本文提出一种基于生成对抗网络（GAN）的BWE模型，通过并行预测幅度谱与相位谱（命名为AP-BWE），实现高质量且高效的宽带语音波形生成。所提出的AP-BWE生成器完全基于卷积神经网络（CNN），采用具有相互交互的双流架构，其中幅度流与相位流彼此通信，分别从输入的窄带幅度谱与相位谱中扩展高频分量。为提升扩展语音信号的自然度，我们在波形层面采用多周期判别器，并在频谱层面分别设计了一对多分辨率幅度判别器与相位判别器。实验结果表明，针对目标采样率为16 kHz和48 kHz的BWE任务，所提出的AP-BWE在语音质量方面达到了最先进的性能。在生成效率方面，由于采用全卷积架构与全帧级操作，AP-BWE可在单张RTX 4090 GPU上以实时速度的292.3倍生成48 kHz波形样本，在单CPU上以实时速度的18.1倍生成。值得注意的是，据我们所知，AP-BWE是首个实现高频相位谱直接扩展的方法，这有助于提升现有BWE方法的有效性。