Deep analysis of Windows Vista volume categories

1. Stream Volume (Stream Volume)

2. Simple Volume Volume

3. Channel volume (Channel Volume)

4. Endpoint volume (EndPoint Volume)

Because each method is a gain level (gain stage), each can be added to the audio input sample and generate the final audio output stream.

Figure 1 Audio schematic

Each WASAPI instance in the diagram represents an audio stream that is merged into an audio synthesizer (Mixer) and "flows" to the audio drive. Stream volume, simple volume, and channel volume are implemented by inserting a APO into a separate audio stream, and the endpoint volume is added to the synthesizer after a APO or is handled with hardware volume control, depending on the capabilities of the user's audio solution.

So what is the connection between these different audio controls?

Let's talk about streaming volume first. The streaming volume is a multichannel volume that works for each audio stream, allowing applications to implement relatively simple 3D effects (using multichannel streaming volume control to simulate the position of an active ball after it is bounced). You can have your application control the volume of an individual audio stream, but that's a little bit of demand.

Next is the channel volume. Channel volume is the volume of an audio session (session) that controls the volume of all audio streams in the entire session (if you remember the big Picture Post, one of the sessions contains many audio streams). Channel volume exists because there are waveoutsetvolume API because the wave volume is multichannel (stereo) volume, we have to simulate one in Wasapi. Similarly, this volume is rarely used-typically only changes the channel volume when running the System installation task (Reactiveness correction) from the control Panel, so this setting affects all applications and not just a particular application.

Again, the volume is simple. The simple volume is the volume of the audio session that controls the volume of all audio streams throughout the session. It is a unified volume and will be applied evenly to all channels. This is also how we want most applications to use volume control-because it provides a simple way to control the volume and mute state of the application, which is sufficient for most applications. This volume is actually the volume slider for each application shown in the Vista sound mixer.

Logically, you can apply the top three volumes together (but that's not true, they're actually applied at the same time) to create the final volume for each audio stream.

Finally, let's talk about the endpoint volume. As I mentioned before, the endpoint volume represents the main volume (master output) output, which acts on the last synthesized audio stream, and can play a role in the main volume control of a particular endpoint.