If you're trying to ingesting Sony NEX footage in FCP but to no avail, or find some of the audio from the mts clips is missing, a best solution is encoding H.264/AVC video to Apple ProRes 422 before importing the Sony NEX footage to Final Cut Pro.
Why convert H.264 to Apple ProRes Codec: ProRes is a line of intermediate codecs developed by Apple Inc, especially for use in post production of Final Cut Studio. For Final Cut Pro, Prores is simpler to decode than distribution oriented formats like H.264. Media files not optimized for Final Cut Pro are suggested to encode to Apple Prores codec before ingesting.
How to convert H.264 to Apple ProRes Codec
The workflow is easy and straight-forward with Pavtube Mac AVCHD to Final Cut Pro Converter, which converts Sony NEX-F3, NEX-5N, and NEX-7 footage to Apple ProRes .mov as well as various other video formats.