Issue with mp4 + separate wav audio

ELAN user interface seems buggy with regards to volume control, it does not respect the “mute” button (on mp4 audio) and makes practical annotations quite hard.

Setup: ELAN 6.4, Windows 10 (rev. 22H2) running on Thinkpad T-series laptop (tested with two different units), MP4 files + separate wav files (extracted from mp4 for higher accuracy on playback / future praat usage or sometimes because of audio preprocessing cleanup).

In practice, the current workflow is that annotations are started with a regular trimmed mp4 from camera (but any standard video works for problem replication, e.g. search for downloadable version sample_960x400_ocean_with_audio.mp4 as links are not allowed for new users). Then, audio is extracted from MP4 with VLC as 16-bit uncompressed PCM. These are loaded to ELAN, but the audio playback is really buggy. Platform/OS has VLC player library selected for highest accuracy / best all-round file type compatibility.

Issues:
-initial steps: mp4 audio is muted (listed as first track / master), wav audio as solo under Controls tab. No audio is heard, unless either the track-specific or global volume slider is slightly changed during playback (e.g. 100 => 98 is enough). However, following pause/play the issue resets, the slider has to be again changed slightly.
-mp4 audio is heard through even though it’s muted / set manually to 0, creating a eerie echoing sound (mp4 audio and wav are slightly off-sync)

Workaround:
-changing the order of WAV/MP4 slightly helps with the situation, after setting WAV as the first track (master media) the volume control only needs to be changed once after opening the file, not following every play/pause action. However, dual audio track playback is still an issue
-best case: use WAV as first “master” file and MP4 with audio removed as secondary (e.g. ffmpeg -i file.mp4 -an -codec copy file-no-audio.mp4)

Changing media framework under Preferences doesn’t seem to have much effect. It seems very much like ELAN user interface bug. Any chance of tackling with this issue in some new release? There’s some sort of workaround even now, I’m happy to hear other options as well (other than changing to MacOS/Linux; we’re currently somewhat stuck with Windows).

Hello,
I can reproduce the problem when the VLC based player is selected, but as far as I have seen so far, the volume mechanism seems to work well with the JMMF and JavaFX based players (with .mp4 and .wav). I’ll try a bit more, but this seems to be specific to the VLC based player.

The (standalone) VLC player is a very versatile player and I understand why many people like it a lot. But embedded in ELAN (via a Java-to-native bridging interface), it is really not the most accurate player.
I don’t know yet where the source of the volume problem is; maybe in our code interacting with this bridging software, or maybe on a lower level. If it is in our implementation, we’ll try to improve it in the next release.

-Han