What is SPX?
SPX is the file extension for Speex, an audio compression format for speech. This patent-free easily available format has specifically been designed with the aim to providing an alternative to the expensive speech codecs. Speex is available under BSD license. Speex is a lossy format targeted at VoIP (Voice over IP), and not at cell phones as most other speech codecs are. This means that Speex is adapted to Internet applications and has certain features not available in other speech codecs. Some of Speexs features include: • Designed for narrowband (8 kHz), wideband (16 kHz), and ultra-wideband (32kHz) in the same bit stream. • Encoding controlled by parameters of 0 to 10. • Variable complexity for different noise levels. • Variable bit rate (VBR) allowing for adaptation to different sound qualities. • VAD (Voice Activity Detection) detects whether sound is speech or background sound for Speex to encode accordingly. • DTX (Discontinuous Transmission) stops transmission when background s
