# Why Udemie’s Linux Snap Played Every Lecture in Silence

> Video played, the progress bar moved, and not a sound came out. The cause was one missing library inside the Snap sandbox, and a fallback that confinement never lets through.

- Publication: Udemie Journal (https://www.udemie.study/blog)
- Section: Engineering
- Author: Emmanuel Zenderock, Creator of Udemie
- Published: 2026-09-25 (September 25, 2026)
- About Udemie v3.6.4: https://www.udemie.study/changelog
- Canonical: https://www.udemie.study/blog/linux-snap-no-sound

## The short version

- Up to Udemie 3.6.3, the Snap build on Linux played lectures with no sound at all. Windows was not affected.
- The Snap did not contain libpulse, the PulseAudio client library, so Chromium fell back to ALSA, which strict Snap confinement does not open.
- The Snap already had the audio-playback permission. What it lacked was the library and the path to the host’s audio socket.
- Udemie 3.6.4 (September 23, 2026) ships libpulse, adds its helper library to the search path and points PULSE_SERVER at the host socket, which PipeWire answers on current Ubuntu.
- Every Linux release build now installs the Snap and refuses to publish it if any of these pieces is missing.

On Ubuntu, the Udemie Snap had no sound at all. The video ran, the progress bar moved, and the speakers stayed silent. The same lectures played with sound on Windows.

The cause turned out to have nothing to do with the player, and everything to do with the sandbox the Snap runs in. This is the story of why, and of the three lines in a shell script that fixed it in **Udemie 3.6.4**.

## What a Snap can and cannot reach

A Snap runs under *strict confinement*: the app sees its own files, its base system (for Udemie, Ubuntu’s `core22`) and only what its *plugs* allow outside. Udemie’s Snap has declared the `audio-playback` plug since its first version, in December 2025. That plug is the permission to play sound through the desktop’s audio server.

So the permission was never the problem. The question was which road the audio took to get out.

## How Chromium picks an audio output on Linux

Udemie is an Electron app, and Electron plays sound through Chromium. On Linux, Chromium sends audio to PulseAudio when it can load `libpulse`, the PulseAudio client library. On current Ubuntu releases the server behind that PulseAudio socket is **PipeWire**, through its PulseAudio-compatible server, so `libpulse` works unchanged.

When `libpulse` cannot be loaded, Chromium falls back to talking to the sound card directly through **ALSA**.

![Diagram. In 3.6.3, Chromium finds no libpulse in the snap, falls back to ALSA, and confinement blocks it, so nothing reaches the speakers. In 3.6.4, libpulse is staged, PULSE_SERVER points at the host socket, and audio reaches PipeWire's pulse server and the speakers.](https://www.udemie.study/blog/linux-snap-no-sound/audio-path.svg)

*Where the audio went. Top: the ALSA fallback that confinement blocks. Bottom: the path 3.6.4 opens. (Diagram: Udemie Journal)*

## Two missing pieces

The Snap did not contain `libpulse` at all. Chromium took the fallback, and under strict confinement the ALSA devices are not open to the app. Neither road reached the speakers, and nothing crashed or logged an error a user could see. The lecture simply played in silence.

Shipping the library was only half of it:

1. **`libpulsecommon` is hidden.** `libpulse` depends on a helper library that Ubuntu installs in a private subdirectory, `/usr/lib/x86_64-linux-gnu/pulseaudio`. Inside the Snap, the dynamic loader never looks there.
2. **The socket is one level up.** In a Snap, `XDG_RUNTIME_DIR` is the app’s own directory, `/run/user/<uid>/snap.udemie`. The PulseAudio socket lives in the real runtime directory above it, at `/run/user/<uid>/pulse/native`, where `libpulse` does not think to look.

## The fix

The Snap now stages `libpulse0` next to the libraries it already carried, with a comment so that nobody removes it by accident:

```yaml title="snap/snapcraft.yaml"
stage-packages:
  # …
  # Chromium's audio output. Without it Chromium falls back to ALSA, which strict
  # confinement does not open, and the app is silent.
  - libpulse0
```

The other two pieces live in the Snap’s launcher script, the file that sets the environment before Udemie starts:

```bash title="snap/local/launcher.sh"
export LD_LIBRARY_PATH="${LD_LIBRARY_PATH:+$LD_LIBRARY_PATH:}$SNAP/usr/lib/x86_64-linux-gnu/pulseaudio"
if [ -z "${PULSE_SERVER:-}" ] && [ -S "$XDG_RUNTIME_DIR/../pulse/native" ]; then
  export PULSE_SERVER="unix:$XDG_RUNTIME_DIR/../pulse/native"
fi
```

The first line lets the loader find `libpulsecommon`. The `if` block points `libpulse` at the host’s socket, but only when the user has not set `PULSE_SERVER` already and only when the socket really exists. On a system with no audio server, it changes nothing.

> **One launcher, not two**
>
> Before this fix, the launcher existed twice: as `launcher.sh`, and as a copy pasted inside `snapcraft.yaml`. The Snap build now installs `snap/local/launcher.sh` directly, so there is a single file to read and to change.

## How we know it works

The fix was first checked inside the confinement of an installed 3.6.3 Snap, running the new launcher with the library supplied: a Web Audio stream loaded `libpulse` and reached PipeWire. The published 3.6.4 Snap has sound again.

A silent Snap is easy to ship twice, because nothing fails loudly. So the Linux release workflow now installs the freshly built Snap and, from inside its sandbox, refuses to publish it unless:

- `libpulse.so.0` is in the Snap,
- `libpulsecommon` is in its `pulseaudio` subdirectory,
- and the launcher sets `PULSE_SERVER`.

This check confirms the files and the configuration are there. It does not play a sound, because the build machines have no speakers.

> Without libpulse there was no sound at all.
>
> (Comment in Udemie’s Snap launcher)

## If you still hear nothing

Make sure you are on **3.6.4 or later** (`snap info udemie` shows the installed version) and that the `audio-playback` plug is connected (`snap connections udemie`). If both are right and a lecture is still silent, [contact support](https://www.udemie.study/support) and mention your Ubuntu version and whether other apps play sound.

The same Snap release also fixed [hardware rendering on Linux](https://www.udemie.study/blog/linux-snap-gpu-software-rendering), which had a very similar cause: the Snap had what it needed, but was looking for it in the wrong place.