Clean audio file produces an extra itchy crackle sound


#1

hey guys,

I just added a clean audio file to my project and copied it 5 times.

if I listen to two of them, theyre are allways coming with crackled sound to them.
they are excact copies of the others but are making this weird extra “noise”.
I deleted, recreated etc, but didnt help.

could the problem be another audio track (of someone talking) running at the same time,
which makes the frequencies collaps somehow ?


#2

Hi rico, if you have two or more audio tracks playing at the same time, in the timeline, the playback can be very stuttery, due to the amount of processing your computer has to do. Depends on the speed of your computer, too.
If you export your video, you should find that the sound comes out without those glitches.


#3

thx for ur help !

though Im talking about the exported file which sounds crackled at the exact position of these two audio tracks


#4

Probably the other direction… rather than collapsing, two audio files playing at the same time could produce “constructive interference”. Let’s say your audio files can produce volumes that range from zero for silence to 100 for absolute loudness. If you have two audio files dumping sound at a level of 80, the two of them combined would be 160. That is higher than the max level of 100 your speakers and your digital-to-analog converter can produce, so you get distortion known as “clipping”. Shotcut has an algorithm to blend multiple audio tracks without going immediately to clipping. But if your sources are particularly loud or shrill or dynamic, then you may have to help Shotcut out by lowering the volume on one or both audio tracks using the Gain audio filter.

This is just a first guess, and I’ve simplified the details a little, but try testing this first. Could you also provide us more information, like what format your sound files are in and whether “copied 5 times” means stacked vertically on multiple tracks, or lined up horizontally in a row on a single track?


#5

OK rico, thanks for clarification. Can you be more specific? What sort of audio file? And could you post a screenshot?
Thanks!


#6

Actually, this is incorrect. It used to do that, but people complained about levels being affected outside of their control. However, you are probably correct about the reason for the crackling due to clipping.

Read here about the audio mixing and how to mitigate clipping here: https://shotcut.org/blog/new-release-1612/


#7

I just recorded a wave file of just my voice.
Although, I’m not sure the need for such a method, but I went ahead and tried it.
I wouldn’t say it’s crackled, but it would max out any speaker.
Stopped at 5 audio tracks.
5 audio tracks, 4 muted


At 5 audio tracks, 0 muted.

Click to see the other three

3 muted


2 muted

1 muted

No filters of any kind above.

Edit: Gain/Volume Filter applied to Master:
Back to about normal now.

Shotcut 18.10.08


#8

Oops, I somehow missed that release note.


#9

Good point about using an audio meter to diagnose this. @rico, if you go to the menu and turn on View > Scopes > Audio Loudness, you can play back your timeline and watch the meters to see how loud your audio is. If the “S” meter is averaging around -13 LUFS, then you are preserving sufficient headroom and you should have a good upload to YouTube. If your meters are way above or below that level (like +/-5), your audio will require the listener to adjust their volume up or down to get a comfortable level. That’s a bad thing.


#10

thx ppl for trying to help me with that, its much appraciated !!!

Not sure if this helps, but this is how the tracks are looking like:
grafik

that little audio snippet thats a little green white thats having that cracky sounds when played.
Ive even lowered the volume one with the volume filter, abd its not even “loud”, and Ive duplicated
it multiple times on that track.
the track above is a video track thats having sound. the audio from this one goes max up to -15db.

so my “feeling” is, that whenever theres audio (someone speeking in this case) on the video track
I just talked about, my little audio snippet starts to crackle. if theres no sounds in the video track above
its seems to sound clean.

does that help ? I think its obvious that somehow both tracks are interfering each other !?


#11

From the waveform on the audio clip, it appears to be already at max volume. I would use audacity to lower the volume at least 50%, save to a new WAV file. Then try the new WAV file.