Volume "100" is +4dB and clips audio when using HDMI output

[DavidGA]

I have my Pi4 running Moode (6.7.1 2020-07-22) connected to my receiver using HDMI. Because it's a digital output I have my volume control set to "Disabled (0dB output)".

I thought it was working fine but I noticed that on a lot of tracks, there was distortion that sounded like clipping.

I ssh'd into the pi and ran alsamixer, and noticed that alsamixer is reporting "HDMI [dB gain: 4.00]".

So that will be the problem then.

I set volume control to "Hardware" and was frustrated to find that volume 85 correponds to -0.26dB, and volume 86 corresponds to +0.05dB. There is no volume level that corresponds to 0dB.

Is there any way to configure Moode to just spit the decoded bits out of the HDMI port, and not attempt any volume adjustment at all?

[Tim Curtis]

IIRC its the Raspberry Pi firmware that adds +4dB to both the Headphone and HDMI outputs but I don't remember why its done.

Theres a Max ALSA volume setting in Audio Config that you can use to approximate the 0dB point but since ALSA scale is 0 - 100 (percentage) it may not map perfectly into your audio devices dB range.