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The volume state may be briefly displayed on the screen every time a sound is played through the speakers of a DisplayPort or HDMI-connected external monitor

Symptoms

Consider the following scenario:

  • You have a Windows 7 or Vista PC that is connected to an external display using a DisplayPort or HDMI cable. 
  • The external display has built-in speakers.
  • The display's speakers are set as the default audio playback device in Windows.
  • You are running an on-screen display (OSD) application that displays the volume level or screen brightness state whenever there is a change in levels.

In this scenario you may notice that whenever audio is played through the external display's speakers, the OSD application will appear for a couple of seconds and display the volume level.  The expected behavior is that the application should only display the volume state when the volume is changed or muted.

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Cause

Windows is notifying the application every time a new audio stream is created for some types of digital audio streams, regardless if the audio volume has changed or not.

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More Information

In Windows 7 Service Pack 1 and earlier, IAudioEndpointVOlumeCallback::OnNotify is called every time the software volume control is inserted into the audio path.  Application developers can mitigate this issue by checking if the endpoint has a software volume control and if they find one, track the volume so they can ignore volume notifications where the volume has not changed.

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Keywords: kb

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Article Info
Article ID : 2554573
Revision : 1
Created on : 1/7/2017
Published on : 5/18/2011
Exists online : False
Views : 76