Re: Changing nominalSampleRate considered harmful?
Re: Changing nominalSampleRate considered harmful?
- Subject: Re: Changing nominalSampleRate considered harmful?
- From: "Mikael Hakman" <email@hidden>
- Date: Tue, 22 Jul 2008 02:04:49 +0200
- Organization: Datakonsulten AB
Hello Jeremy,
The user may not know what the SR of track/video to be played next is. Also,
when playing from a playlist, different tracks may have different SR but the
user may not able or doesn't want to control the sample rate in AMS.
Just consider a user sitting in front of iTunes and for each track to be
played, he/she assesses its SR, goes to AMS panel, changes the device SR to
matching, and only then starts playing and listening to the sound. What user
experience is that?
/Mikael
On Monday, July 21, 2008 9:24 PM, Monday, Jeremy Sagan wrote:
Hello Mike,
Why not just go to the Audio MIDI Setup program in your utilities folder
and set the sample rate to what you want it to be?
Jeremy
On Jul 21, 2008, at 2:46 PM, Mike Kluev wrote:
On Mon, 21 Jul 2008 19:19:13 Lubor Prikryl DS wrote:
On 21.7.2008, at 17:39, Mike Kluev wrote:
I've noticed that neither iTunes nor QuickTime Player changes
playing rate before playing music. That means they will happily
play music/movie on, whatever rate is currently set for the
device (say, 8kHz), even if the device supports higher rates
(say 48kHz). Even after logout/restart! Is that good user
experience? How user is supposed to change the rate (e.g. if
he suddenly wants to hear better quality music)? There are no
controls for it in Sound preference panel, nor in the apps'
preferences, and average user doesn't (and shouldn't) know
what HALLab is. Is my app supposed to do the same (do not
change sample rate) because it is bad (why)?
It is the proper behavior. Core Audio is multi-client, so if one audio
application is running, the other should not automatically change
sample rate of the same device.
I am not even talking about this case. Run an app that changes
rate, quit, reboot. Run iTunes - it still uses the saved rate
(supposedly in /Library/Preferences/
com.apple.audio.DeviceSettings.plist).
For pro audio applications, a sample rate selector should be provided
in audio preferences.
For other apps, sample rate of the device should not be changed without
user's intention.
For both, you may ask Core Audio to open the device Control Panel (e.g.
Audio MIDI Setup for built in audio)
err = AudioDeviceGetProperty(mInputDevice.mID, 0, 1,
kAudioDevicePropertyConfigurationApplication, &propertySize,
&cp1location);
where user can set the desired sample rate.
That's interesting. But how does this help a user who downloaded
a third party app from the web, pressed OK in a "This app works
best at 8kHz. OK to change?" alert, played with it, then disliked
it, quitted and trashed it, then rebooted. Since then on his
movies and aiffes start to play at 8kHz and he doesn't see an
obvious way to change it back! Is this a proper behavior?!
Mike
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