IMFSimpleAudioVolume interface

Controls the master volume level of the audio session associated with the streaming audio renderer (SAR) and the audio capture source.

The SAR and the audio capture source expose this interface as a service. To get a pointer to the interface, call IMFGetService::GetService. For the SAR, use the service identifier MR_POLICY_VOLUME_SERVICE. For the audio capture source, use the service identifier MR_CAPTURE_POLICY_VOLUME_SERVICE. You can call GetService directly on the SAR or the audio capture source, or call it on the Media Session.

Members

The IMFSimpleAudioVolume interface inherits from the IUnknown interface. IMFSimpleAudioVolume also has these types of members:

• Methods

Methods

The IMFSimpleAudioVolume interface has these methods.

Remarks

To control the volume levels of individual channels, use the IMFAudioStreamVolume interface. The IMFAudioStreamVolume interface is supported by the SAR only.

Volume is expressed as an attenuation level, where 0.0 indicates silence and 1.0 indicates full volume (no attenuation). For each channel, the attenuation level is the product of:

• The master volume level of the audio session.

• The volume level of the channel.

For example, if the master volume is 0.8 and the channel volume is 0.5, the attenuaton for that channel is 0.8 × 0.5 = 0.4. Volume levels can exceed 1.0 (positive gain), but the audio engine clips any audio samples that exceed zero decibels. To change the volume level of individual channels, use the IMFAudioStreamVolume interface.

Use the following formula to convert the volume level to the decibel (dB) scale:

Attenuation (dB) = 20 * log10(Level)

For example, a volume level of 0.50 represents 6.02 dB of attenuation.

Requirements

See also

Media Foundation Interfaces

Streaming Audio Renderer