Please forgive my naivity but I have long mts files shot with a Canon HFG20 setting MXP 60i. What's the best method to extract the parts I want and render them with minimal or no loss in quality. Thanks
If you just want to trim excess fat from your clips consider checking with Canon for a utility that cuts on an I frame. It will fast frame copy everthing else. I've used the Canon Image Browser when I had a ten minute clip with 10 seconds of useful content. It's somewhat tedious for lots of clips.
Otherwise, render to something like Sony XAVC.
You could try TMPGEnc MPEG Smart Renderer or VideoReDo TVSuite. Only the frames before the first I-frame and the frames after the last I-frame would have to be re-encoded.
You can probably also do it with Vegasaur's Smart Trim feature, which uses FFmpeg under the hood, but it may not be quite frame-accurate at the ends. If you're willing to invest the time and go through some pain, you could also adapt the FFmpeg procedure I use for trimming my GH4 footage, which is a free option.