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MPD volume mixer type
#1
Hi there,

Currently (v7.2.1) in the MPD volume mixer there are two (besides fixed out) options for volume control:
1. Hardware
2. Software

In which, if any, cases is it preferable to use a software volume mixer to an available hardware volume control implementation?
Also, will the hardware mixer still have bit perfect audio out, or is it necessary to use the fixed out for this?

For context I'm using a Topping D30Pro USB DAC.
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#2
If the audio device has its own physical volume control then use "Fixed (0dB output)" for bit-perfect volume output from moOde. The "Software" option would also yield bit-perfect output if moOde volume is set to 100. Make sure the device's physical volume control is really low when first using these settings.

The "Hardware" option will make use of the on-chip hardware volume controller in the device. If the device's own physical volume control also uses this controller then I'm not sure what would happen. I'd be extremely careful with this setting!
Enjoy the Music!
moodeaudio.org | Mastodon Feed | GitHub
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#3
Quote:The "Hardware" option will make use of the on-chip hardware volume controller in the device. If the device's own physical volume control also uses this controller then I'm not sure what would happen. I'd be extremely careful with this setting!

I'm definitely not an expert in this, so take this with a grain of salt, I might be flat out wrong.

Given that pretty much every modern USB DAC uses UAC2, and this protocol has volume settings. I'd imagine that the alsa hw volume mixer is using these controls for volume (assuming it's using UAC2). I doubt it'd be using more low-level firmware specific controls, as this would mean implementing device specific drivers.
The point being, it's expected in the USB UAC2 spec, that you can control volume on the device using these volume metadata controls.
So assuming, the spec is sanely implemented and the USB DAC has a (digital) volume knob, there are two possibilities:
1. The device has two independent volume controls which get multiplied.
or
2. The device has a single global volume control that can be properly controlled both through UAC2 and the internal control.



With this in mind, could you elaborate why one should worry about using the "Hardware" volume mixer option if it's supported?
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#4
One caution would be if your device uses an analog volume control and moOde is configured for Hardware volume. Then you have two separate volume controls in the pipeline.

IIRC USB Audio devices can implement hardware volume using the controller in the USB chip, the DAC chip or via an analog volume control.

What happens if you set moOde to Hardware volume and change the volume using the volume knob on the device?
Enjoy the Music!
moodeaudio.org | Mastodon Feed | GitHub
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#5
(05-08-2021, 01:02 PM)Tim Curtis Wrote: One caution would be if your device uses an analog volume control and moOde is configured for Hardware volume. Then you have two separate volume controls in the pipeline.

IIRC USB Audio devices can implement hardware volume using the controller in the USB chip, the DAC chip or via an analog volume control.

What happens if you set moOde to Hardware volume and change the volume using the volume knob on the device?

From all I can tell, it works fine with two separate chained volume controls.
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