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Truespeech

Truespeech is a proprietary audio codec produced by the DSP Group. It is designed for encoding voice data at low bitrates, and to be embedded into DSP chips. True speech has been integrated into Windows Media Player in older versions of Windows, but no longer supported since Windows Vista. It is also the format used by the voice chat features of Yahoo! Messenger.

A Truespeech decoder was implemented in the 0.5 release of FFmpeg.