Volume change

[ophirpeleg]

Hey guys,
My RASPI 3 is connected to speakers with the headphone jack, and I found a way to control the volume. It was delayed when I changed the volume via the Spotify app on my PC.
Now, I connected an encoder with a button (KY-040) and controlled the volume physically.
short-press - mute / unmute
long-press - set to 0dB

Attaching here is the Python code:

import board
import digitalio
import os
import os.path
import time


def millis():
    return time.monotonic() * 1000


def long_press():
    os.system(f"amixer -c 0 set Headphone 0")

os.system(f"amixer -c 0 set Headphone unmute")
mute = False

dirPin = digitalio.DigitalInOut(board.D2)
pushPin = digitalio.DigitalInOut(board.D17)
stepPin = digitalio.DigitalInOut(board.D3)

dirPin.direction = digitalio.Direction.INPUT
pushPin.direction = digitalio.Direction.INPUT
stepPin.direction = digitalio.Direction.INPUT
volumeInterval = 50

dirPin.pull = digitalio.Pull.UP
stepPin.pull = digitalio.Pull.UP
pushPin.pull = digitalio.Pull.UP
previousValue = True

print("Welcome")
print(f"{stepPin.value} step pin value, {dirPin.value} dir pin value")
print(f"push pin value: {pushPin.value}")
is_on = True

while is_on:
    if pushPin.value == 0:
        pressTime = millis()
        time.sleep(0.2)
        longPress = False

        while pushPin.value == 0:
            if millis() - pressTime > 1000 and not longPress:
                longPress = True
                long_press()

        if not longPress:  # short press define
            if mute:
                os.system(f"amixer -c 0 set Headphone unmute")
                mute = False
            else:
                os.system(f"amixer -c 0 set Headphone mute")
                mute = True

    if previousValue != stepPin.value:
        if stepPin.value == False:
            if dirPin.value == False:
                print("Right")
                os.system(f"amixer -c 0 set Headphone {volumeInterval}+")
            else:
                print("Left")
                os.system(f"amixer -c 0 set Headphone {volumeInterval}-")
        previousValue = stepPin.value

[JasonLG1979]

Very cool but I think that it must be pointed out as a disclaimer that the software volume control in librespot is superior in every way sound quality wise then any form of hardware volume control. If sound quality is your goal don't use hardware volume control.

[JasonLG1979]

Is there another way to accomplice volume change without sacrificing sound quality?

No, not really. The best volume control for librespot is it's own software control. All internal audio processing done in librespot is done with 64 bit floating point precision with dithering when applicable (when using 16 or 24 bit output). DAC's are basically black boxes for the most part. It's impossible to know how they actually do volume control most of the time. It's also incorrect to conflate hardware volume control with analog volume control. 99.999% of the time hardware volume control just means that you're using the DAC's internal software volume control that may very well be inferior to librespot's software control.

For the headphone out on a Pi3 in particular you DO NOT want to use hardware volume control. The headphone out on Pi's is garbage. It's not even a proper DAC it's a crude PWM with a super basic analog filter. It's really not suitable for music at all. They themselves acknowledge as much and recommend leaving the hardware volume at 100% and using software volume control in whatever is making noise. A $10 USB audio dongle would be a HUGE upgrade in sound quality.

and another idea I had is to add OLED - currently displaying volume and status (if muted or not), is there a way to get what songs are playing with raspotify terminal command?

No. librespot is strictly a player. You can get silly and enable verbose logging and parse some metadata info from the logs but it's much easier to just use one of the many other projects designed for interacting with the public Spotify web API.

[JasonLG1979]

Correction:

You can use an on-event script to get some info but it's very limited and for security reasons it's not very easy with the default Raspotify service. You would basically have to write your own systemd service and disable the Raspotify service.

An example on-event python script might look something like this:

import os

if os.environ['PLAYER_EVENT'] == 'changed':
    old_track_id = os.environ['OLD_TRACK_ID']
    new_track_id = os.environ['TRACK_ID']
    # do stuff

elif os.environ['PLAYER_EVENT'] == 'started':
    track_id = os.environ['TRACK_ID']
    # do suff

elif os.environ['PLAYER_EVENT'] == 'stopped':
    track_id = os.environ['TRACK_ID']
    # do stuff
   
elif os.environ['PLAYER_EVENT'] == 'playing':
    track_id = os.environ['TRACK_ID']
    track_duration_ms = os.environ['DURATION_MS']
    track_position_ms = os.environ['POSITION_MS']
    # do stuff

elif os.environ['PLAYER_EVENT'] == 'paused':
    track_id = os.environ['TRACK_ID']
    track_duration_ms = os.environ['DURATION_MS']
    track_position_ms = os.environ['POSITION_MS']
    # do stuff

elif os.environ['PLAYER_EVENT'] == 'preloading':
    track_id = os.environ['TRACK_ID']
    # do stuff

elif os.environ['PLAYER_EVENT'] == 'volume_set':
    volume = os.environ['VOLUME']
    # do stuff

You could then use that info to get metadata info from some other lib.

[JasonLG1979]

In the above example os.environ['TRACK_ID'] is the Spotify track ID.

[JasonLG1979]

For reference:
https://github.com/librespot-org/librespot/blob/master/src/player_event_handler.rs

[giggywithit]

I'm looking for the best way to reset the volume after a period of idle, no playback. What happens is that I will listen at fairly high levels and then sometimes stop the playback and go do something. Upon returning, sometimes ill play another track and it'l be left at those high volume levels and blast when I am not prepared for it. For the moment, the only solution is to restart raspotify after a period of idle, in which I have set a start volume at a lower level.

Thoughts?