omxplayer audio crackles after swapping uart on PI4

[eriktronics]

Hello,
I work a lot with the PI3 B+ and serial communication on it's full featured PL011 UART.
I use the 'dtoverlay=pi3-disable-bt' in /boot/config.txt to get this uart back on pin14/15 of the 40-pin header.
(Don't use bluetooth at all)
When i start omxplayer -o alsa <link of mp4> the audio is played well on the analog output mini-jack.

Now i am working with the new PI4 and also perform the above adjustments, but if i start omxplayer the analog audio is distorted/crackled.
When i comment/hide the 'dtoverlay=pi3-disable-bt' in /boot/config.txt (# dtoverlay=pi3-disable-bt } and reboot the Pi, the audio with omxplayer
on the analog output jack is okay.

I cannot figure out what the swapping of the uart's has to do with the analog audio output.

Does anyone have a suggestion on this?
Thanks in advance, erik

[eriktronics]

Got it solved.... in a way..

Instead of 'dtoverlay=pi3-disable-bt' in /boot/config.txt, one should use dtoverlay=pi3-miniuart-bt.
Somehow after this swapping of uarts to pin14/15 of the 40-pin header, the audio when starting omxplayer on the analog out jack was okay.
And Bluetooth can still be used, though it's not stable because of the clock-variation due to processor-speed.

So this is a solution I still don't know why the disabling of the bluetooth feature, 'dtoverlay=pi3-disable-bt' will distort the analog audio within omxplayer....maybe someone has a clue.

Thnx, erik