Camtasia Studio screen recording software allows users to offer their own recordings (.trec sessions) to several other multimedia formats - including the common AVI video, which is more or less what trec to avi conversion represents.
You can do that by accessing production wizard screen and selecting output as AVI, which should allow you to convert trec to avi in Camtasia. The MP4 format is a preferred choice for export though, because you can get your videos in higher quality / smaller file size compared to AVI. It's worth mentioning that you have really no alternative here, it is not possible to convert trec to avi without Camtasia.Open TREC file Open AVI file
A screen capture and video editing software