Based on the information I found, it may not be possible to directly set μ-law encoding in the Vapi UI currently. While Vapi does support customizing audio encoding formats through APIs, the UI options appear limited.
For now, you can submit a feature request for μ-law UI settings at [Vapi's public roadmap board](
https://roadmap.vapi.ai/feature-requests) where they prioritize features based on user votes. In the meantime, consider implementing the encoding customization through the API integration with your Twilio setup.
Sources:
- [Vapi Support Documentation](
https://docs.vapi.ai/support)
- [Discord Discussion on Vapi Limitations](
https://discord.com/channels/1211482211119796234/1303981615344779325)