XAudio2 Volume and Pitch Control
This topic describes XAudio2 volume and pitch control.
Volume levels are expressed as floating-point amplitude multipliers between -XAUDIO2_MAX_VOLUME_LEVEL and XAUDIO2_MAX_VOLUME_LEVEL (-224 to 224), with a maximum gain of 144.5 dB. A volume of 1.0 means there is no attenuation or gain; 0 means silence; and negative levels can be used to invert the audio's phase. Two inline functions are provided in XAudio2.h to convert between volume units: XAudio2DecibelsToAmplitudeRatio and XAudio2AmplitudeRatioToDecibels.
You can apply a volume level to the audio at several points as it flows through the XAudio2 graph:
- All voice types apply an overall volume level to their input, which they control using the IXAudio2Voice::SetVolume method. In submix and mastering voices, the overall volume level is applied just before the voice's built-in filter and effect chain. In source voices, the overall volume level is applied after the voice's built-in filter and effect chain.
- Voices apply a per-channel volume level to their output, which they control using the IXAudio2Voice::SetChannelVolumes method. The per-channel volume level is applied just after the voice's final sample rate conversion, and before it is sent to other voices.
- Every connection between one voice and another has a table of levels used to send audio from each source channel to each target channel, which is controlled using the IXAudio2Voice::SetOutputMatrix method.
Pitches are expressed as input rate/output rate ratios between 1/1,024 and 1,024/1, inclusive. A ratio of 1/1,024 lowers pitch by 10 octaves, while a ratio of 1,024/1 raises it by 10 octaves. You can only use the IXAudio2SourceVoice::SetFrequencyRatio method to apply pitch adjustments to source voices, and only if they were not created with the XAUDIO2_VOICE_NOPITCH flag. The default frequency ratio is 1/1: that is, no pitch change. Two inline functions are provided in XAudio2.h to convert between frequency ratios and semitones: XAudio2FrequencyRatioToSemitones and XAudio2SemitonesToFrequencyRatio.
- Volume and Pitch Control
- XAudio2 Programming Guide
- How to: Change Voice Pitch
- How to: Change Voice Volume