Re: Setting volume levels?
Re: Setting volume levels?
- Subject: Re: Setting volume levels?
- From: Howard Moon <email@hidden>
- Date: Thu, 26 Jun 2003 13:14:58 -0700
Oh! well, that explains the LARGE difference. I assumed it was just
normal rounding error, but the took a second look and saw how big that
difference was. Simple rounding error would have resulted in something
more like 0.5899956 (just picking a number out of a hat, not an
experimental result there :-)) Of course, the same kind of theory
applies, but the HAL is apparently even LESS able to give you exact
results than the RAM on your computer.
-Howard
On Thursday, June 26, 2003, at 12:55 PM, Jeff Moore wrote:
The reason why is that the hardware provides a range of discreet
values which the HAL normalizes out to be between 0 and 1. So if you
set a value that is "between" a pair of hardware steps, the HAL floors
it to the nearest hardware step.
On Thursday, June 26, 2003, at 12:08 PM, Jim Dolan wrote:
If I run the following code - why do I get different values in the
last line?
It does not matter what value I feed in, I always get something less?
I
thought maybe it was ramping but the value always seems to be less
than, no
matter which direction I change the volume to.
// Set the new level
Float32 fVolume = 0.59;
Float32 fVolume2 = 0.0;
UInt32 dataSize = sizeof(Float32);
AudioDeviceSetProperty( iDeviceID, NULL, actualChannel, isInput,
kAudioDevicePropertyVolumeScalar, sizeof( Float32 ), &fVolume );
AudioDeviceGetProperty( iDeviceID, actualChannel, isInput,
kAudioDevicePropertyVolumeScalar, &dataSize, &fVolume2 );
printf( "Volume: %f %f\n", fVolume, fVolume2 );
Volume: 0.590000 0.586691
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--
Jeff Moore
Core Audio
Apple
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