Recording Opus calls file format

I have SIP 48kHz Opus calls working ans I can register with automon as a DTMF featuremap.
Basically, it is recording my calls in a .wav format with 8kHz 16bits. So my records are really poor.

I can see in the supported file format there is not opus:

raspberrypi*CLI> core show file formats
Format     Name       Extensions          
------     ----       ----------          
g729       g729       g729                
g726       g726-16    g726-16             
g726       g726-24    g726-24             
g726       g726-32    g726-32             
g726       g726-40    g726-40             
ilbc       iLBC       ilbc                
g723       g723sf     g723|g723sf         
h264       h264       h264                
h263       h263       h263                
siren7     siren7     siren7              
slin       ogg_vorbis ogg                 
siren14    siren14    siren14             
gsm        gsm        gsm                 
adpcm      vox        vox                 
gsm        wav49      WAV|wav49           
g722       g722       g722                
ulaw       au         au                  
alaw       alaw       alaw|al|alw         
ulaw       pcm        pcm|ulaw|ul|mu|ulw  
g719       g719       g719                
slin16     wav16      wav16               
slin       wav        wav                 
slin192    sln192     sln192              
slin96     sln96      sln96               
slin48     sln48      sln48               
slin44     sln44      sln44               
slin32     sln32      sln32               
slin24     sln24      sln24               
slin16     sln16      sln16               
slin12     sln12      sln12               
slin       sln        sln|raw             
31 file formats registered.

So what is the best format to record opus calls ? And how can I set it ?
Thank you

slin48, if you really want to record music well.

Hi david, thank you for your reply.
But how/where can I change this format ?