Reduced Complexity Tree Coding of Speech in the Presence of Background Impairments

在存在背景损伤的情况下降低语音的复杂性树编码

• 批准号: 9627610
• 负责人: Jerry Gibson
• 金额: $ 24.57万
• 依托单位: Texas A&M Engineering Experiment Station
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-09-01 至 1999-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9627610&HistoricalAwards=false
• 关键词: Reduced; Complexity; Tree; Coding; Speech

Extraordinary advances in speech coding have been achieved in the past few years, with the ITU and digital cellular industries producing voice coding standards for telephony and videoconferencing with performance perhaps unimaginable even ten years ago. At rates below 12 kbits/s, however, these coders are sometimes criticized for their implementation complexity and for their difficulty in coding speech in the presence of extraneous background impairments. The complexity issue is omnipresent, but becomes increasingly important in the mobile communications environment, both in digital cellular and emerging personal communications systems, where battery power is a dominating issue. Furthermore, there are many applications being developed and proposed for packet-switched videoconferencing at various rates, where it is desirable to have voice coders implemented either wholly in software on standard platforms (Macs, PCs, Sparcs) or whose implementations do not usurp large portions of the capabilities of a DSP chip. Being able to code speech in the presence of background impairments has always been of interest, but has recently moved to the fore because of the mobile environments encountered in digital cellular mobile radio and evolving personal communications systems. Desktop applications also present a challenge for coding with background impairments, since hands-free interaction is critical and thus even some relatively quiet office environments do not have the handset to aid in rejecting the background noise. The challenge is therefore to achieve communications quality speech at 8 kbits/s with medium-to-low complexity for a variety of implementation approaches without changing background impairments into annoying artifacts. This research approaches this problem by starting with a low delay waveform following coder, called a tree coder, removing the low delay requirement and employing frequency domain based variable rate techniques, forward adaptation ideas, code tr ee adaptivity innovations, and improved perceptual weighting to reduce implementation complexity while retaining reconstructed speech quality.

在过去几年中，语音编码取得了非凡的进展，国际电联和数字蜂窝行业为电话和视频会议制定了语音编码标准，其性能在十年前可能是不可想象的。然而，在低于12 kb /s的速率下，这些编码器有时因其实现复杂性和在存在外来背景损伤的情况下难以对语音进行编码而受到批评。复杂性问题无处不在，但在移动通信环境中变得越来越重要，无论是在数字蜂窝还是新兴的个人通信系统中，电池电源都是一个主要问题。此外，有许多应用程序正在开发和建议以不同的速率进行分组交换视频会议，其中希望语音编码器完全在标准平台（mac, pc, Sparcs）的软件中实现，或者其实现不篡夺DSP芯片的大部分功能。能够在有背景障碍的情况下对语音进行编码一直是人们感兴趣的问题，但最近由于数字蜂窝移动无线电和不断发展的个人通信系统中遇到的移动环境，这一问题被提上了前台。桌面应用程序对背景干扰的编码也提出了挑战，因为免提交互是至关重要的，因此即使是一些相对安静的办公环境也没有手机来帮助排除背景噪音。因此，挑战是在各种实现方法中实现8kbits /s的通信质量语音，而不会将背景损伤改变为烦人的工件。本研究从低延迟波形跟踪编码器（称为树编码器）开始，消除低延迟要求，采用基于频域的可变速率技术、前向自适应思想、码树自适应创新和改进的感知权重来降低实现复杂性，同时保持重构语音质量。