A1 Audio Track Volume Fluctuations with V1 Video Track

[Neuner]

I have clips of video in V1 that I’ve accompanied with music in an audio track A1. For some of the video clips, I’ve removed the audio track and with others, I’ve left it in to give ambience.

Everything plays/views as it should with the Player Preview.

Watching the video after exporting it, the music track volume fluctuates as it plays along. The volume for the music, A1, greatly decreases when a video clip with sound is shown and then jumps back up when a video clip without sound is shown.

It’s not subtle, others viewing it have really noticed it and said it’s annoying.

I’ve tried various export settings but it remains the same;

Export settings;
Video - mp4, 1920x1080, 59.94, progressive, Deinterlacer Best, Bilear Good, libx264, Constant Bitrate 12M, GOP 60
Audio - stereo, 44000hz, aac, avg bitrate 96k

The max audio level for all of the music, A1, is between -10 and -15. Some of the video clip audio is between -5 and -10.

Hopefully I’ve explained it in a way you can understand. I have no idea what would be causing this since it previews fine before export.

Is there a way of making the Audio Track A1 a priority or to normalize it?

Thanks!

[Austin]

What version of Shotcut are you using, and what operating system? Shotcut has handled audio mixing in different ways over the years. If the Shotcut version is several years old, there was a window of time where tracks were proportionally summed together which would create the ducking effect you’re hearing. Using the latest version would fix that immediately.

Also, are there any Compressor or Limiter filters involved, particularly on the Output or Master track?

[Neuner]

I have version 22.04.25. Qt vs 5.15.2.

Don’t know what you mean by compressor or limiter filters. The ones I’m using are; gain (varies per song, -5 to -15), fade audio in and fade audio out.

[Austin]

What happens if audio is exported at 192kbps or higher?

[Neuner]

It’s the same which is why I’m so confused. I did a different codec like h264 and 300 GOP, VBR and Constant Bitrate and still always the same.

Exported files ranged in sizes of 1.5Gb to 22Gb and no differences. Very odd.

Found some clips where it didn’t happen but I can’t figure out what is different. Same camera with audio.

[Neuner]

Okay, happy to say that I think I found the problem.

I reviewed the audio frequency range of both the music and video clips in which the issue occurred and the video clips had a very low and prominent, inaudible, Mhz noise to them.

I used the High-Pass Audio filter on each of those to cut off the noise and exported the file. The music no longer fluctuates in volume so I’m happy.

I’m just assuming that the low frequency was overwhelming the audio spectrum, diminishing the volume of the music track somehow.

In a separate issue, I need to find out why those clips had the low Mhz noise to begin with.

Thank you for your time and effort in trying to help me with this.

[Austin]

Good find! Sounds like there may have been destructive interference between sound sources that are out of phase and canceling each other.