IXAudio2SourceVoice::SetFrequencyRatio method (xaudio2.h)

Article
10/13/2021

Sets the frequency adjustment ratio of the voice.

Syntax

HRESULT SetFrequencyRatio(
  [in] float  Ratio,
  [in] UINT32 OperationSet
);

Parameters

[in] Ratio

Frequency adjustment ratio. This value must be between XAUDIO2_MIN_FREQ_RATIO and the MaxFrequencyRatio parameter specified when the voice was created (see IXAudio2::CreateSourceVoice). XAUDIO2_MIN_FREQ_RATIO currently is 0.0005, which allows pitch to be lowered by up to 11 octaves.

[in] OperationSet

Identifies this call as part of a deferred batch. See the XAudio2 Operation Sets overview for more information.

Return value

Returns S_OK if successful, an error code otherwise. See XAudio2 Error Codes for descriptions of error codes.

Remarks

Frequency adjustment is expressed as source frequency / target frequency. Changing the frequency ratio changes the rate audio is played on the voice. A ratio greater than 1.0 will cause the audio to play faster and a ratio less than 1.0 will cause the audio to play slower. Additionally, the frequency ratio affects the pitch of audio on the voice. As an example, a value of 1.0 has no effect on the audio, whereas a value of 2.0 raises pitch by one octave and 0.5 lowers it by one octave.

If SetFrequencyRatio is called specifying a Ratio value outside the valid range, the method will set the frequency ratio to the nearest valid value. A warning also will be generated for debug builds.

Note IXAudio2SourceVoice::GetFrequencyRatio always returns the voice's actual current frequency ratio. However, this may not match the ratio set by the most recent IXAudio2SourceVoice::SetFrequencyRatio call: the actual ratio is only changed the next time the audio engine runs after the IXAudio2SourceVoice::SetFrequencyRatio call (or after the corresponding IXAudio2::CommitChanges call, if IXAudio2SourceVoice::SetFrequencyRatio was called with a deferred operation ID).

Platform Requirements

Windows 10 (XAudio2.9); Windows 8, Windows Phone 8 (XAudio 2.8); DirectX SDK (XAudio 2.7)

Requirements

Requirement	Value
Target Platform	Windows
Header	xaudio2.h

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