direto do blog:
AVCHD support in Expression Encoder 2
AVCHD (Advanced Video Codec High Definition) is a file format commonly used by the latest generation of consumer HD camcorders. It consists of an AC-3 audio stream and an AVC (H.264) video stream encapsulated into a custom MPEG2 transport stream container.
While Expression Encoder 2 does not natively support that file type, it is possible to use them if the right components are installed. More specifically, three DirectShow components are required:
After installing those 3 components, you should be able to playback the M2TS files directly in Windows Media Player as well as importing and using them within Expression Encoder 2.
Also, David Sayed posted a very nice and detailed article on one of the multiple ways to get Expression Encoder 2 to support AVCHD files: http://blogs.msdn.com/david_sayed/archive/2008/05/31/avchd-recipe-for-expression-encoder-2.aspx
But if you own a Sony or Canon camcorder, you can also take advantage of the DirectShow filters that shipped with the bundled software.