Major Bug Discovered

[schmidtbag]

As a disclaimer, this bug is reproducible 100% of the time, but it's a little complicated to explain and extremely specific. Please bear with me.

About a half year ago, I got a SPDIF compatible 5.1 receiver. At the time, I was using I think VLC 2.0.8, and surround worked pretty flawlessly through SPDIF. I don't watch movies often, but there was a time when I went to watch one, with version 2.1.0, and the sound wasn't working, at all. The receiver acknowledged there was a surround sound signal and even set up the channels accordingly, but there was no sound coming out. I spent several hours trying to figure it out and google searching the problem, as well as workarounds, but none of them worked. I tried deleting my VLC configuration folder and re-apply my settings, but the problem persisted. The best I could do was play the movie in stereo.

Today, though, I had enough and wanted to get this problem out of the way for good. This time, I decided to take things 1 step at a time. Here's how I discovered the bug:
First, I deleted the ~/.config/vlc folder. Then, I ran VLC and opened a .ac3 speaker test. It was in stereo, but it was playing - I expected this. So, I went to the advanced audio settings and the first and only thing I did was enable "Use S/PDIF when available". I re-played the audio file, and surround worked! To be sure everything was cool, I closed VLC and opened the file again - surround still worked. Great!
BUT
Here's where the bug occurs:
Any time I open the "Simple" preferences and navigate between more than 1 section (meaning, Audio, Video, Subtitles / OSD, etc.) and save, 5.1 channel sound stops working. It does NOT matter whether or not I changed anything - it will always permanently fail SPDIF surround; SPDIF stereo still works. When I mean permanently, I mean I can undo all changes and it still doesn't work.

So to walk you through a way to reproduce the error:
1. Delete the ~/.config/vlc folder
2. Open VLC and enable the "Use SPDIF when available" checkbox
3. Go back to "Simple" settings
4. Click on the "Video" tab
5. Click on the "Input / Codecs" tab
6. Click save, then close VLC
7. Open VLC, play a surround sound file, and it won't work. Skip steps 3, 4, and 5, and it will work fine. It doesn't matter which tab you go to in steps 4 and 5, you just need to click on 2 or more tabs.

Just to clarify, if I only move to ONE section under "Simple" settings, make any changes I want, and save, I get no issues at all. The problem also doesn't seem to occur if I move between sections under the Advanced settings.

I also found another cause for the problem - any time I change the "Output Module" (under the Audio secion), surround permanently fails. I'm not sure if this applies to Windows users.

For some system info:
Arch Linux 64 bit
ALSA (I tried Pulseaudio, but that had its own set of issues)
Realtek ALC889
VLC 2.1.2
No ~/.asoundrc, no /etc/asound.conf

[Rémi Denis-Courmont]

This looks like a bug in the Qt4 preferences dialog.

[schmidtbag]

I'm thinking it's the VLC backend as well as the preferences dialog. The settings I set in the preferences dialog are correctly preserved because they do actually work. Maybe switching between the different tabs is adding extra fluff that the VLC backend can't read, and somehow manages to mute the surround. Remember, the 5.1 audio is actually being received, but it can't be heard.