Re: convert kAudioSessionProperty_CurrentHardwareOutputVolume to dB value
Re: convert kAudioSessionProperty_CurrentHardwareOutputVolume to dB value
- Subject: Re: convert kAudioSessionProperty_CurrentHardwareOutputVolume to dB value
- From: Roman Thilenius <email@hidden>
- Date: Tue, 17 Jul 2012 02:35:03 +0200
do you use a FS cosine or a FS sqare?
a cosine is not exactly the optimal material to measure power. :)
On Jul 17, 2012, at 2:08 AM, Kevin Dixon wrote:
So it seems that kAudioSessionProperty_CurrentHardwareOutputVolume
returns arbitrary volume units instead of linear gain.
For example when i get the value 0.711712, I convert to dB with
20.0f * log10(volume)
returning ~ -2.95 dB.
However when I measure a 0dB FS tone from my headphone output, with
the volume at 0.711712, the observed power is more in the neighborhood
of -16dB
Can anyone clarify this situation? It is imperative that I know the
actual attenuation so my algorithm can react correctly.
Thanks in advance
-Kevin
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