How much can you edit w/o re-encoding A/V

If you have an M2TS file (AVC+AC3), can you trim out a tiny chunk in the middle, then splice the two larger pieces back together, without re-encoding?  If so, which tools could you use for this?

I'm very new to anything remotely video-related, so assume no knowledge of existing tools.  The reason I'm asking is that if this can be done significantly more easily than re-encoding could be done, I would forgo the other possible edit which would definitely require re-encoding and just do this easy one.

I think tsMuxeR can split and join on GOP boundaries (I-frames) without re-encoding.

If you want frame-accurate editing, I believe VideoReDo can do this, and only re-encodes the edit points, leaving the rest of the video untouched.

I'm using VideoReDo right now because the cuts were not on I-frames.  I think it's re-encoding the whole stream (or else I really don't understand why it's taking so very, very long...).  Looks like Womble doesn't do AVC.