Tvheadend

I can build the latest TVHeadend 4.3-2051~g0ff96106a in Ubuntu 22.04.1 on a Pi 4.

I was not able to install the library: libavresample-dev because it is no longer available for Ubuntu 22.04.1
Instead it has been replaced with libswresample-dev and TvHeadend builds fine with this.
The configure script gives me this information:

checking for pkg libswresample >=2.1.100 ...      ok (detected 3.9.100) 
checking for pkg libavresample >=3.0.0 ...        fail (detected <none>)

However when I use the build option:

--enable-libav

I get ENDLESS error/warning messages in the build output:

Package libavresample was not found in the pkg-config search path.
Perhaps you should add the directory containing `libavresample.pc'
to the PKG_CONFIG_PATH environment variable
No package 'libavresample' found

When I use the build option:

--disable-libav

I don't get ANY of those error/warning messages in the build output:

I'm interested to know what is going on here. I've tried reading and googling but it's complicated!
Is this explanation close at all?
--> These warnings happen because when you build TVHeadend with --enable-libav support you also build ffmpeg along with libav and the code for these depends on the libavresample-dev library.

The truth is even though TVHeadend builds OK for me with --enable-libav I have not tested if the transcoding is working so maybe it doesn't?!

Is there a way to stop those error/warning messages and why exactly are they generated?

Any help or explanation much appreciated.

Flex