[SOLVED] Anyone explain this to me please?

[dippy]

Hi

New boy here!

Running RPI4 with IQAudio DAC+

I see this  when viewing the audio information;


[*]Encoded at 16 bit, 44.1 kHz, Stereo FLAC
[*]Decoded to 16 bit, 44.1 kHz, Stereo, 597 kbps
[*]Output rate 24 bit, 44.1 kHz, Stereo, 2.117 Mbps
[*]Output mode ALSA Direct (hw)
[*]Output chain MPD -> hw -> Device


The track was ripped from CD using fre:ac so the first 2 lines make sense.....

[*]Why has the "output rate" apparently been upscaled?
[*]Am I missing a setting to stop the upscaling?


Thanks

D

[Nutul]

Hi

New boy here!

Running RPI4 with IQAudio DAC+

I see this  when viewing the audio information;


[*] Encoded at 16 bit, 44.1 kHz, Stereo FLAC
[*]Decoded to 16 bit, 44.1 kHz, Stereo, 597 kbps
[*]Output rate 24 bit, 44.1 kHz, Stereo, 2.117 Mbps
[*]Output mode ALSA Direct (hw)
[*]Output chain MPD -> hw -> Device


The track was ripped from CD using fre:ac so the first 2 lines make sense.....

[*]Why has the "output rate" apparently been upscaled?
[*]Am I missing a setting to stop the upscaling?


Thanks

D

[*]

I think it depends of the bit-depth supported by your dac. Mine for instance (an audio card, to be honest) supports only S32_LE, so now that I am playing a 24/88.2, I see, instead:

Encoded at  24 bit, 88.2 kHz, Stereo FLAC
Decoded to  24 bit, 88.2 kHz, Stereo, 2.601 Mbps
Output rate  32 bit, 88.2 kHz, Stereo, 5.645 Mbps
Output mode  ALSA Direct (hw)
Output chain  MPD -> hw -> Device

[Tim Curtis]

The Audio info popup should list the formats supported by the DAC.

For example for an Allo Boss DAC

Code:

AUDIO DEVICE
DeviceAllo  Boss DAC
Mixer name  Digital
ChipBurr    Brown PCM5122
Interface   I2S
Formats     S16_LE, S24_LE, S32_LE
Platform    Pi-3B+ 1.3 1GB

[bitlab]

De decode line is about the bandwith from the Flac file. The bandwidth in pcm from 16b/44.1 a lot more (2 bytes * 2 channels * 44100 samples p/s).

And if you didn't forced 24bit, maybe you are using software volume?
I thought (@Tim Curtis can you confirm or deny this ? ;-) ) if software volume is used, MPD uses 24bit.

[Tim Curtis]

De decode line is about the bandwith from the Flac file. The bandwidth in pcm from 16b/44.1 a lot more (2 bytes * 2 channels * 44100 samples p/s).

And if you didn't forced 24bit, maybe you are using software volume?
I thought (@Tim Curtis can you confirm or deny this ? ;-) ) if software volume is used, MPD uses 24bit.

You have a good memory!

Yes, MPD software volume will force 24 bit.

The OP has an IQAudio DAC+ which should support Hardware volume.

[dippy]

De decode line is about the bandwith from the Flac file. The bandwidth in pcm from 16b/44.1 a lot more (2 bytes * 2 channels * 44100 samples p/s).

And if you didn't forced 24bit, maybe you are using software volume?
I thought (@Tim Curtis can you confirm or deny this ? ;-) ) if software volume is used, MPD uses 24bit.

You have a good memory!

Yes, MPD software volume will force 24 bit.

The OP has an IQAudio DAC+ which should support Hardware volume.

OP here.

CORRECT I was using software volume.
Changed to HW....and now this looks sensible to me.


[*] Encoded at 16 bit, 44.1 kHz, Stereo FLAC
[*]Decoded to 16 bit, 44.1 kHz, Stereo, 337 kbps
[*]Output rate 16 bit, 44.1 kHz, Stereo, 1.411 Mbps
[*]Output mode ALSA Direct (hw)
[*]Output chain MPD -> hw -> Device

...I know the docs said to use hardware  (I did read the docs  ) but it made no sense to me as I don't have a "hardware" (physical) volume control on the RPi/DAC
Or is that not what it means?
The help for volume setting says;
- Hardware: Use audio device on-board volume controller.
- Software: Use MPD software volume routine (32 bit float with dither).
- Fixed (0dB output): Assumes external analog or digital volume controller is used.

So does it mean the volume control capability built into the "DAC Hardware" rather than a physical volume control?

D

[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.

[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)?

[Always_In_The_Moode]

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

[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.