Re: Sound volume control in Matlab (Bob Masta )

Subject: Re: Sound volume control in Matlab
From:    Bob Masta  <audio@xxxxxxxx>
Date:    Wed, 13 Aug 2008 08:13:59 -0400

On 11 Aug 2008 at 18:18, Stuart Rosen wrote: > Has anyone tried to control sound volumes in Vista > through Matlab? There are extra complications over XP in > that each application window seems to have its own > volume setting (which is a good thing) but that seems to > be limited to an overarching volume control that applies > to all windows. Be very careful with volume controls in XP or Vista. Windows uses the "kernel mixer" to manipulate the digital stream so multiple applications can use the same device. It basically intercepts the data and scales it down before sending it to the D/A. The D/A thus gets the sum of all the active streams. The danger is that this is all done "behind your back"... an individual application does not know that its volume range has been shortened, or by how much. In principle you could just make sure that all other apps are fully closed before you start your desired app, but sometimes it's not clear if an app is really gone or just lurking in the background (and eating up volume range). One way to avoid this is to get a separate sound card that is used *only* for your experimental setup. My understanding is that software that uses ASIO drivers avoids the problem, by bypassing the kernel mixer. I have also heard that "kernel streaming" can be used for similar purposes. Best regards, Bob Masta D A Q A R T A Data AcQuisition And Real-Time Analysis Scope, Spectrum, Spectrogram, Signal Generator Science with your sound card!

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