[SOLVED] Anyone explain this to me please?

[Tim Curtis]

This is a great thread and explains why I get the below no matter what type of volume control I use, presumably because the external DAC (a Topping d50s) supports S32_LE, SPECIAL, DSD_U32_BE. I've therefore gone back to the fixed 0db output!

Encoded at 16 bit, 44.1 kHz, Stereo FLAC
Decoded to 16 bit, 44.1 kHz, Stereo, 940 kbps
Output rate 32 bit, 44.1 kHz, Stereo, 2.822 Mbps
Output mode ALSA Direct (hw)
Output chain MPD -> hw -> Device

DSP OPERATIONS
Resample rate Off
Selective rate Off
Resample quality Off
Crossfade 8 seconds
Camilla DSP Off
Volume type Fixed (0dB output)

AUDIO DEVICE
Device D50s
Mixer name D50s
Interface USB
Formats S32_LE, SPECIAL, DSD_U32_BE
Platform Pi-4B 1.5 2GB

Don't worry about the bit depth being zero-padded from 16 to 32 bits. This operation preserves the original 16 bits of audio data and maintains "bit-perfectness".

[Mattt]

Hopefully not a silly question but why does the kbps or Mbps rate increase from decoded to output? Where is the extra data coming from?
Is the file still compressed after being decoded?

[Nutul]

Yes. Thats what it means. Linux audio provides low level access to device options such as on-chip or on-board volume controllers.

There are other options in moOde for physical volume controllers for example Rotary Encoder or USB Volume Knob.

I am curious... now, what is the actual difference between Hardware (or, like it writes on my machine, Null) and Fixed (0dB output)?

Audio Config "Volume type"

Hardware: MPD requests audio device on-board volume controller to perform volume calculation.
[b]Software: [/b]Perform volume calculation using MPD software volume algorithm.
Fixed (0dB): MPD outputs 100% (0dB) volume level. This corresponds to MPD mixer_type "none".
https://mpd.readthedocs.io/en/latest/use...io-outputs
Null: MPD creates a fake mixer. This is useful for implementing an external volume control.
https://mpd.readthedocs.io/en/latest/use...rnal-mixer

Note that "on-board" volume controllers can be implemented in the DAC chip itself or in the USB chip. Which one is used depends on implementation.

For example in some implementations where the volume controller on the DAC chip is superior to the one on the USB chip the USB chip is programmed to proxy volume commands to the volume controller on DAC chip. This would be something like a DAC with an XMOS USB chip and an ESS DAC chip with its "Hyperstream" volume controller.

I understand that all of these volume paths remain in the digital domain, so having the 100% / 0dB output no matter how, is the way to go for an analog volume.

I do not see Hardware as an option in my settings (maybe this applies only for the HATs, don't know), just Software, Fixed and Null. So far I have always used Software, but the volume reel in moOde has always been left at the maximum, hence I assume it has always been as if I had chosen Fixed (0dB), right?

P.S.
The links to the MPD documentation lead both to a 404 redirected page ;-)

[Tim Curtis]

Yes. Thats what it means. Linux audio provides low level access to device options such as on-chip or on-board volume controllers.

There are other options in moOde for physical volume controllers for example Rotary Encoder or USB Volume Knob.

I am curious... now, what is the actual difference between Hardware (or, like it writes on my machine, Null) and Fixed (0dB output)?

Audio Config "Volume type"

Hardware: MPD requests audio device on-board volume controller to perform volume calculation.
[b]Software: [/b]Perform volume calculation using MPD software volume algorithm.
Fixed (0dB): MPD outputs 100% (0dB) volume level. This corresponds to MPD mixer_type "none".
https://mpd.readthedocs.io/en/latest/use...io-outputs
Null: MPD creates a fake mixer. This is useful for implementing an external volume control.
https://mpd.readthedocs.io/en/latest/use...rnal-mixer

Note that "on-board" volume controllers can be implemented in the DAC chip itself or in the USB chip. Which one is used depends on implementation.

For example in some implementations where the volume controller on the DAC chip is superior to the one on the USB chip the USB chip is programmed to proxy volume commands to the volume controller on DAC chip. This would be something like a DAC with an XMOS USB chip and an ESS DAC chip with its "Hyperstream" volume controller.

I understand that all of these volume paths remain in the digital domain, so having the 100% / 0dB output no matter how, is the way to go for an analog volume.

I do not see Hardware as an option in my settings (maybe this applies only for the HATs, don't know), just Software, Fixed and Null. So far I have always used Software, but the volume reel in moOde has always been left at the maximum, hence I assume it has always been as if I had chosen Fixed (0dB), right?

P.S.
The links to the MPD documentation lead both to a 404 redirected page ;-)

Links fixed :-)

Hardware volume only appears in the dropdown if the audio device indicates that it has a hardware volume controller 
i.e., has an ALSA simple mixer control listed in amixer with front left/right Playback volume.

Code:

pi@sig:~ $ amixer -c 2
Simple mixer control 'Revolution ',0
 Capabilities: pvolume pswitch
 Playback channels: Front Left - Front Right
 Limits: Playback 0 - 127
 Mono:
 Front Left: Playback 104 [82%] [-23.00dB] [on]
 Front Right: Playback 104 [82%] [-23.00dB] [on]
Simple mixer control 'Revolution ',1
 Capabilities: pvolume pvolume-joined pswitch pswitch-joined
 Playback channels: Mono
 Limits: Playback 0 - 127
 Mono: Playback 127 [100%] [0.00dB] [on]
pi@sig:~ $

For Software or Hardware volume types when knob is set to 100 it's equivalent to Volume type set to Fixed (0dB). 

If you are using a downstream physical volume control then "Fixed (0dB)" is the appropriate setting.

[TheOldPresbyope]

@Nutul

An aside -

The links in Tim's original reply #10 are correct as they stand. I suspect you're clicking on the elided links in a post which quotes Tim's reply. That elision is a "feature" of this forum software.

Regards,
Kent

[Nutul]

@Nutul

An aside -

The links in Tim's original reply #10 are correct as they stand. I suspect you're clicking on the elided links in a post which quotes Tim's reply. That elision is a "feature" of this forum software.

Regards,
Kent

Yes, you're right: nice "feature" indeed :-D