Ubuntu – Automatically switch equalizer preset based on audio output (internal speaker or external)

equalizerheadphonespulseaudiospeakers

The facts below come from experience with Ubuntu 13.10 on a 64-bit laptop.

Context/problem: bad speakers

As many people know, laptop speakers have "highly unequal frequency response" as audio professional would say. Normal people say: "they sound very bad".

First-step solution: equalization

Equalizing provides a valuable workaround, dramatically improving sound quality with a one-time effort. For example, I installed PulseAudio Equalizer from Web Upd8.

For good results, equalization values should be chosen based on measurements, but that's another story (I could do it with Ubuntu alone though it's tricky, ask me for details).

Remaining problem: equalization curve is output-dependent

Equalization values are attached to the whole chain, though generally only the speakers are a major source of unequal response.

This means I have two equalization profiles:

one for laptop speakers (with wildly varying equalization curve)
another (much flatter curve, so disabling equalization is often acceptable) when an external stereo is plugged to e.g. a 3.5mm jack.

Current situation in practice: auto un/mute, good but insufficient

When plugging the 3.5mm jack to the external stereo, internal speakers are automatically muted and volume adjusted by the Ubuntu stack. This is good but insufficient.
When unplugging, internal speakers are automatically activated again. This is good but insufficient.

Improvement: not only auto-mute but auto-select eq curve

It would be much better to have the correct equalizer preset applied when un/plugging the 3.5mm jack. Plug the external stereo, the flat curve is selected. Unplug the stereo, internal speaker get their correction curve.

Questions

How to make a quick-and-dirty hack ? How to detect jack plug from a script ?

Regarding detecting the plugging event. I could not find documentation on the web, plus the keyword "jack" returns results regarding the jack software suite, irrelevant here. Meager starting points: sound – How to automatically change volume level when un-/plugging headphones? – Ask Ubuntu Jack detection for audio : Blueprints : Ubuntu
Regarding changing the equalizer curve I could not find any documentation about pulseaudio-equalizer-gtk. A proof-of-concept script fiddling with files then calling pulseaudio-equalizer interface.applysettings could change the settings, but the GUI wouldn't be aware.

How to make a clean setup: assign the equalization curve to internal speaker, not just plug event.

For example, say I plug a USB audio device and play audio through it. The quick-and-dirty hack would change EQ curve whenever the 3.5mm jack is un/plugged, though the audio actually continued to go to the USB audio device not the internal speaker, making eq curve change irrelevant.

In a "clean" setup, an equalization profile would be cleanly assigned to the internal speaker, making the thing more robust. Whatever the situation, it would be always (and only) applied when needed.

Is anyone working on it ? Any hint ?

Thank you for your attention.

Best Answer

Because I have a similar problem i have made a "quick and dirty" python script which uses pulseaudio's DBus-Events to detect when to activate which equalizer profile.

Installation

To use it you have to add the following line to /etc/pulse/default.pa:

load-module module-dbus-protocol

Then disable the equalizer via pulseaudio-equalizer-gtk and click on "Apply settings", now close the GUI.

Download apply-equalizer.py save it somewhere and make it executable.

Execute it as user (!). Maybe you need to install some additional python modules. Also you may want to automatically start it on login (i dont know what is the best way to do that).

Usage

The script creates per-port [1] equalizer-configurations under ~/.config/apply-equalizer and symlinks them if a device changes the output port (i.e. headphones plugged in or out).

[1]: many sound cards have different ports, e.g. one speaker-port and one headphone-port

So:

Unplug headphones.
Open pulseaudio-equalizer GUI
Customize equalizer-settings until it sounds good
"Apply Settings" will then assign the configuration you made (including if the equalizer is enabled at all) to the current port (speakers in this case)
close the GUI and repeat from step 2 for every port you want to assign (headphones not plugged in)

Now the equalizer settings get automatically adjusted whenever your switch between speakers and headphones.

Background

I had a similar problem during suspend/resume when sound would switch from HDMI TV to laptop speakers. Upon resume sound would stay on Laptop speakers and I would have to manually reset output device to TV in System Settings -> Sound.

This was one of my first annoying experiences with upgrade from Ubuntu 14.04 to 16.04 and the root was upgrade to PulseAudio 8 that comes with 16.04 LTS

After much searching I created a script called TV-sound. Although I don't plug and unplug the TV like yourself, I did some google searches and create a variation of the script to work in your situation. I've tested it and it works.

Step 1: Create script to switch audio between connected devices

We'll create a script called hotplugtv which udev calls. This same script can be called in many places though. For example, during testing I used it in lock-screen-timer where sound reverted back to Laptop during screen lock.

cd /usr/local/bin
sudo touch hotplugtv
sudo chmod +x hotplugtv
gksu gedit hotplugtv

When the editor opens with a blank screen, copy and paste the following into it:

#! /bin/bash

# NAME: hotplugtv
# PATH: /usr/local/bin
# DESC: Update pulseaudio output device when HDMI TV plugged / unplugged
# CALL: called from /etc/udev/rules.d/99-monitor-hotplug.rules
# DATE: Created Nov 26, 2016.
# NOTE: logs output using log-file
# UPDT: Dec 14, 2016 - Sometimes /sys/class/drm/card0 & sometimes /sys/class/drm/card1
#       so use /sys/class/dmcard* instead.

if [[ $(cat /sys/class/drm/card*-HDMI-A-1/status | grep -Ec "^connected") -eq 1 ]]; then
#        log-file "HDMI TV connected" ~/bin/log-hotplugtv;
        /bin/sleep 2;
        export PULSE_RUNTIME_PATH="/run/user/1000/pulse/";
        sudo -u rick -E pacmd set-card-profile 0 output:hdmi-stereo;
else
#        log-file "HDMI TV disconnected" ~/bin/log-hotplugtv;
        export PULSE_RUNTIME_PATH="/run/user/1000/pulse/";
        sudo -u rick -E pacmd set-card-profile 0 output:analog-stereo;
fi

exit 0

You will need to replace the two occurrences of rick with your own user id, ie UTF-8, etc.

I know this can be more professional with user name automatically set to a bash variable but I'm not that skilled yet :( Anyway, save the file and exit gedit.

Step 2: Create udev rules

udev monitors hotplug events when you plug in and unplug your HDMI monitor. Type the following to create a new rule.

cd /etc/udev/rules.d
sudo cp 70-persistent-net.rules 99-hotplugtv.rules
gksu gedit 99-hotplugtv.rules

NOTE: If the file 70-persistent-net.rules doesn't exist in your directory copy any other file there. We don't need the file contents, just the file permissions to ensure ours are the same.

The editor will show a bunch of irrelevant text, highlight it and delete it. Then highlight the code below and paste it into the editor:

# NAME: 99-hotplugtv.rules
# PATH: /etc/udev/rules.d
# DESC: Update pulseaudio output device when HDMI TV plugged / unplugged
# CALL: automatically called on system events
# DATE: Created Nov 26, 2016.
# NOTE: in future may requre systemd service hooks

ACTION=="change", SUBSYSTEM=="drm", ENV{HOTPLUG}=="1", RUN+="/usr/local/bin/hotplugtv"

Save the file and exit.

To enable the rule (without rebooting) we need to reload udev:

sudo udevadm control --reload-rules

Now you can plug and unplug your HDMI monitor / TV and the sound switches appropriately.

Caveat

On my system the sound automatically reverts to the Laptop speakers when HDMI is unplugged. On your system it did not. Further enhancements to the code may be required if sound doesn't go to your Laptop speakers when HDMI is unplugged. Please reply via comment below how things work / don't work out.

Quick testing in CLI

You can quickly test the code at the terminal by using:

    export PULSE_RUNTIME_PATH="/run/user/1000/pulse/";

Switch to HDMI / TV:

    sudo -u rick -E pacmd set-card-profile 0 output:hdmi-stereo;

Switch back to built in speakers:

    sudo -u rick -E pacmd set-card-profile 0 output:analog-stereo;

Remember to replace rick with your user name.
The initial export line probably isn't necessary but I've included it just to be safe.
If you have multiple sound cards, or something other than hdmi-stereo tweaks are obviously needed to find out the correct parameters before writing your script.

Deciphering your device name within PulseAudio

The code below uses the same command twice. Once when the sound is set to external HDMI TV. A second time when the sound is set to the Laptop's built in speakers. Each time you see the name PulseAudio uses:

$ pacmd list-sinks | grep -e 'name:' -e 'index'
  * index: 28
    name: <alsa_output.pci-0000_00_1b.0.hdmi-stereo>
───────────────────────────────────────────────────────────────────────────────
$ pacmd list-sinks | grep -e 'name:' -e 'index'
  * index: 30
    name: <alsa_output.pci-0000_00_1b.0.analog-stereo>

When you have multiple sound cards

Use the command aplay -l to see if you have cards greater than number 0. If so you will need to use appropriate card number in your scripts. For example:

$ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: PCH [HDA Intel PCH], device 0: 92HD91BXX Analog [92HD91BXX Analog]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: PCH [HDA Intel PCH], device 3: HDMI 0 [HDMI 0]
  Subdevices: 0/1
  Subdevice #0: subdevice #0

In the above example all card numbers are 0 with different output sources. If you have USB speakers they can have a different card number than 0.

Edit December 2, 2016

For some unknown reason the script was broken today. Above code used to read: "$(cat /sys/class/drm/card0-HDMI-A-1/status" but I had to change card0 to card1 and the code above has been revised as such. I can't explain what changed on my system other than regular Ubuntu updates since November 26, 2016.

Edit December 14, 2016

Above code needed to be switched again back to: "$(cat /sys/class/drm/card0-HDMI-A-1/status". Instead of revising code between card0 and card1 depending on boot, revise program to reference card* to capture both scenarios.