Think of modifying the boot logo image of this phone. This is another mod discussed in the mi 9 forum (https://forum.xda-developers.com/Mi-9/themes/mi-9-splash-boot-image-creation-script-t3952572). It works for our phone too!
It made my audio problem worse before I flash this audio can be fix by pressing vibrate silent but after I flash this no audio at allTo everyone having sound issues w/ video lags, fellow Abaddon suggested his fix in another thread:
In Magisk, flash "Audio Modification Library" and then "Audio Compatibility Patch" and follow the steps
press any volume button when prompted for test.
It will ask "do you want to skip audio_policy patching?"
-press VOL DOWN as NO
-select VOL UP as NEW LOGIC
It will next ask "if you like to skip notification helper remover?"
-select VOL DOWN as NO
Select fix method
-select VOL DOWN to REMOVE VOLUME LISTER LIBRARY
it will next ask if you "would like to skip USB policy patching"
-any option will do. up to you
it will next ask for a lib workaround
-select VOLUME DOWN as NO (recommended)
This worked for me.