Ghost track

[karljones37]

Hi,
I wonder if someone could help, i have limited experience and understanding of sound processing:
I have two problems:

(1)
I am using Audacity 2.3.3 on my lap top (cant get a newer version because of the age of the laptop)
and have been successfully recording a .wav sound track to sync with recorded video over on my main Mac (Catalina)
This has been great until today.

This morning tried as usual but found that when i brought the .wav from the lap top and tried to sync it with the video in iMovie,
the sound track seems to have been compressed with regard to length and therefore always went out of sync after a second or two.

The only change i had made on the laptop was installing the FFMpeg library, from the audacity website.

(2)
Instead i tried to record the sound on my main Mac directly, using the latest version of Audacity,
in this case, when I record I get a clicking noise that over a period to time lengthens to a very distorted ghost version of the track i am recording.,

I am new to this and lost as to how to solve it, apart from reinstalling my earlier version on Audacity and not using FFMpeg, which so far seems to have solved the problem on the laptop.

Id be grateful for any suggestions.
Many thanks
karl

[karljones37]

Ok, I've looked into this further.
It seems the problem on the uptodate version of Audacity on my main Mac was down to the USB port.
Apparently, not all USB ports are equal.
The system recorded perfectly well when the mic was plugged into some ports, but horribly in others.
So this seems to solve problem (2)

If anyone know an explanation for this, i would still be grateful.
Thanks
karl

[steve]

The system recorded perfectly well when the mic was plugged into some ports, but horribly in others.
So this seems to solve problem (2)

If anyone know an explanation for this, i would still be grateful.

Possibly a difference between USB2 and USB3 ?

[karljones37]

Thanks but i think all my Mac ports are USB 3.
Maybe one is just damaged?

[karljones37]

So, I've worked on this some more.

I totally removed Audacity and the FFMpeg libraries from the laptop (MacBook Pro - OLD!)
I reinstalled Audacity 2.3.3. without the FFMpeg libraries, and all seems well.
I successfully record audio with Audacity, and video with my DSLR,
bring both across to my iMac and synchronise the two in iMovie - no problems now.

So (1) is now, not solved, but mitigated.

I'd still be grateful if anyone could hazard a guess about what the problem was.
Maybe 2.3.3 was not compatible with the FFMpegs, or maybe the laptop (about 12 years old) just didn't like them.

Thanks
karl

[steve]

The only change i had made on the laptop was installing the FFMpeg library, from the audacity website.

FFmpeg isn't used for WAV files, so I think this is a red herring.

The version of FFmpeg that you need for Audacity 2.3.3 is listed as:
RECOMMENDED download:ffmpeg_64bit_osx.pkg

when i brought the .wav from the lap top and tried to sync it with the video in iMovie,
the sound track seems to have been compressed with regard to length and therefore always went out of sync after a second or two.

If you can work out how much shorter the track is, that may give a clue to the problem. If the length is 0.91875 x the "correct" length, then the problem is almost certainly due to an incorrect sample rate.

[karljones37]

Thank you for your reply and suggestions.
I will bear all that in mind as i keep experimenting.