Speex

Speex:一个针对音频的免费编解码器

概要

Speex是一个开源/自由软件专利免费的音频编码格式。Speex开源项目是通过专有的音频编解码器降低进入音频处理的门槛。另外，Speex能够很好地适应互联网应用，这是目前大多数编解码器所不具备的。最后，Speex是GNU项目的一部分，具有BSD许可。

技术

Speex是基于CELP设计且压缩声音的比特率范围从2到44 kbps。

Speex的一些特性包括：
窄带（8千赫）、宽带（16千赫）和超宽带（32千赫）在同一比特流中的压缩
强度立体声编码
数据包丢失隐藏
可变比特率操作（VBR）
语音活动检测（VAD）
非连续传输（DTX）
固定点端口
声学回声消除器
噪声抑制
注意，Speex具有许多其他编解码器所不具备的功能，如强度立体声编码，在相同的比特流的多采样率一体化（嵌入式编码）和一个VBR模式；浏览更多请点击链接。

Speex: A Free Codec For Free Speech

Overview

Speex is an Open Source/Free Software patent-free audio compression format designed for speech. The Speex Project aims to lower the barrier of entry for voice applications by providing a free alternative to expensive proprietary speech codecs. Moreover, Speex is well-adapted to Internet applications and provides useful features that are not present in most other codecs. Finally, Speex is part of the GNU Project and is available under therevised BSD license.

The Technology

Speex is based on CELP and is designed to compress voice at bitrates ranging from 2 to 44 kbps. Some of Speex's features include:

• Narrowband (8 kHz), wideband (16 kHz), and ultra-wideband (32 kHz) compression in the same bitstream
• Intensity stereo encoding
• Packet loss concealment
• Variable bitrate operation (VBR)
• Voice Activity Detection (VAD)
• Discontinuous Transmission (DTX)
• Fixed-point port
• Acoustic echo canceller
• Noise suppression

Note that Speex has a number of features that are not present in other codecs, such as intensity stereo encoding, integration of multiple sampling rates in the same bitstream (embedded coding), and a VBR mode; see ourcomparison page for more.