Asterisk.org: Developer Documentation (28 Oct 2009)

Wed Oct 28 15:49:24 2009

## Asterisk developer's documentation

# CODEC Configuration

## codecs.conf

    [speex]
    ; CBR encoding quality [0..10]
    ; used only when vbr = false
    quality => 3

    ; codec complexity [0..10]
    ; tradeoff between cpu/quality
    complexity => 2

    ; perceptual enhancement [true / false]
    ; improves clarity of decoded speech
    enhancement => true

    ; voice activity detection [true / false]
    ; reduces bitrate when no voice detected, used only for CBR
    ; (implicit in VBR/ABR)
    vad => true

    ; variable bit rate [true / false]
    ; uses bit rate proportionate to voice complexity
    vbr => true

    ; available bit rate [bps, 0 = off]
    ; encoding quality modulated to match this target bit rate
    ; not recommended with dtx or pp_vad - may cause bandwidth spikes
    abr => 0

    ; VBR encoding quality [0-10]
    ; floating-point values allowed
    vbr_quality => 4

    ; discontinuous transmission [true / false]
    ; stops transmitting completely when silence is detected
    ; pp_vad is far more effective but more CPU intensive
    dtx => false

    ; preprocessor configuration
    ; these options only affect Speex v1.1.8 or newer

    ; enable preprocessor [true / false]
    ; allows dsp functionality below but incurs CPU overhead
    preprocess => false

    ; preproc voice activity detection [true / false]
    ; more advanced equivalent of DTX, based on voice frequencies
    pp_vad => false

    ; preproc automatic gain control [true / false]
    pp_agc => false
    pp_agc_level => 8000

    ; preproc denoiser [true / false]
    pp_denoise => false

    ; preproc dereverb [true / false]
    pp_dereverb => false
    pp_dereverb_decay => 0.4
    pp_dereverb_level => 0.3

    [plc]
    ; for all codecs which do not support native PLC
    ; this determines whether to perform generic PLC
    ; there is a minor performance penalty for this
    genericplc => true