Bug 452192

SUMMARY

Could not hear Dolphin playing audio/video files in the Preview panel, the issue was due to Dolphin unexpectedly setting its volume to 0%. The issue is compounded by the lack of obviousness on how to fix the issue, versus older versions of Plasma Desktop.


STEPS TO REPRODUCE

1. In Dolphin, make the Information panel visible if not already (press F11). Make sure that the Preview option is enabled (right-click in empty select in empty space of Information panel and enable the Preview option)
2. Select an .mp3/audio or video file. The issue is best noticed with a video file that has audio.
3. In the Preview pane, click the play button.

OBSERVED RESULT

If the Dolphin audio setting is set to 0% then there will be no audio for the previewed file.

Clicking on the speaker icon in the system tray for the audio volume shows that the output devices are in a normal, audible range, yet there is no place to see where Dolphin's volume is changeable. 

Upon further investigation in a non-intuitive way, going to the System Settings -> Audio and scrolling to the bottom of the page, and only if Dolphin happens to be playing a file in the Preview pane, a "dolphin:audio stream" entry becomes visible. This can have a 0% value, which effectively mutes Dolphin's Preview playback. 

In my case, it is unclear how Dolphin's audio was set to 0%. 


EXPECTED RESULT

Should hear the file's audio being played or some way to figure out how to fix it. This is most noticed with video files because we can see that the video is being played yet there is no audio.

We were able to diagnose my system and determine that sound was audible in other programs like VLC but not from Dolphin's preview panel. And only digging into System Settings -> Audio at a fortuitous moment revealed the issue.

In older versions of Plasma Desktop in the Audio Volume system tray popup window, there was an "Applications" tab that displayed the individual volume settings for all applications that are currently playing audio. For some reason this tab is now absent, at least in my KDE neon system, and it makes it hard to discern the issue.

This is being submitted as a bug because this could easily trip up non-technical folks.

SOFTWARE/OS VERSIONS

Operating System: KDE neon 5.24
KDE Plasma Version: 5.24.4
KDE Frameworks Version: 5.92.0
Qt Version: 5.15.3
Kernel Version: 5.13.0-39-generic (64-bit)
Graphics Platform: X11
Processors: 8 × Intel® Core™ i5-8250U CPU @ 1.60GHz
Memory: 7.6 GiB of RAM
Graphics Processor: Mesa Intel® UHD Graphics 620

ADDITIONAL INFORMATION