How Can I set WriteTranscode Yes

I want to set WriteTranscode:yes also ReadTranscode. Is ıt posible or Asterisk set this dynamically.
When I execute > core show channel PJSIP/2888-00002bf8 command output beloong:
CLI> core show channel PJSIP/2888-00002bf8
– General –
Name: PJSIP/2888-00002bf8
UniqueID: AST-1457347750.11273
LinkedID: AST-1457347750.11273
Caller ID: 2888
Caller ID Name: SIP TEST
Connected Line ID: 6025
Eff. Connected Line ID: 6025
DNID Digits: (N/A)
Language: en
State: Up (6)
NativeFormats: (g729|ulaw|alaw|g722)
WriteFormat: ulaw
ReadFormat: g729
WriteTranscode: No
ReadTranscode: No
Time to Hangup: 0
Elapsed Time: 0h0m27s
Bridge ID: 2a5b9fa2-f334-4d46-aae0-eebb9d57390e
– PBX –
Context: macro-isy-vm-dial
Extension: s
Priority: 4
Call Group: 1024
Pickup Group: 1024
Application: Dial
Data: PJSIP/6025,20,tr

Thanks for your replies.

That is Yes when an application or the bridging sets up a transcoding path. It’s not something you can configure to be on.