Hi,
The PennController MediaRecorder element (which relies on, but is distinct from, the MediaRecorder API) only checks webm and ogg for audio, but Safari 14+ only references mp4 as supported, which is why you get that error
I will need to add audio/mp4 to the next release, and raise an explicit error message when no supported type is found. In the meantime, feel free to upload a copy of PennElement_mediarecorder.js to your project’s Modules folder, replacing line audio: {'audio/webm': 'webm', 'audio/ogg': 'ogg'}, with audio: {'audio/webm': 'webm', 'audio/ogg': 'ogg', 'audio/mp4': 'mp4'},. You’ll get an error about MediaRecorder being defined multiple times, but I think the experiment should still run ok
Jeremy