沒有想到speex還在持續的更新

據說微信改用了speex, 因而今天訪問了speex網站：

http://www.speex.org/

發現從08年的Speex 1.2rc1以後，在2014年12月份和2015年1月份更新了兩次

根聽說明，是說對resampler作了NEON指令的優化，我記得案桌裏面就帶有speex的resampler的NEON版本（不過仍是不如咱們本身優化的快），不知道爲何speex.org剛剛更新。

每一個codec都宣稱本身很好，好比speex說：

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 our comparison page for more.

 

對於speex 1.2 rc1的說明是：

This release adds support for acoustic echo cancellation with multiple microphones and multiple loudspeakers. It also adds an API to decorrelate loudspeaker signals to improve multi-channel performance. In the bugfix department, there are fixes for a few bugs in the echo canceller, jitter buffer and preprocessor. At this point, the API for 1.2 should be stable and only a few very minor additions are planned

是支持雙麥克回聲抵消麼？ 很想測測看效果怎麼樣。。

 

不知道和後來的codec比，好比SILK, OPUS, EVS之間的效果怎麼樣？

須要比較一下麼？