Wednesday, December 21, 2005

Speex DTX denoise

The trick to get speex to "trigger" discontinuous transmission is to record 16-bit and use the --denoise flag. 8-bit recording yields too much quantization noise, so ironically one first records at a higher bitrate to get it to compress to a lower bitrate. Naive use of 16-bit recording (without denoising) does not compress so well.

speexenc -V --vbr --dtx --quality 1 --denoise foo.wav foo.spx

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