If you have Sony HD Handycam to shoot videos, and the output files are 1080i in .mts extension. I think you need transcode the HD .mts files to QuickTime DNxHD files, which is compatible to Avid. I have ever searched about QuickTime Pro, which is said to export QuickTime DNxHD, but did not find it support .mts import. Maybe some people suggested you to rename the .mts to .m2t. But it did not work.
So you may kept googling a workable solution, and hope to get through by using a Sony MTS to Avid converter, which converts the 1080i mts files to QuickTime mov. Don’t worry, Aunsoft MTS/M2TS Converter for Mac is the best Mac Sony MTS to Avid converter in the market, and it works great to export HD videos for easy editing in Avid. Below is the step-by-step guide for showing you how to convert 1080i mts to HD mov for Avid Media Composer.
Step 1. Load Sony MTS video to Aunsoft MTS/M2TS Converter for Mac.
After transferring Sony .mts videos to Apple hard drive with iMovie or directly copy from memory stick, just run Aunsoft MTS/M2TS Converter for Mac as the Mac Sony MTS to Avid converter, and click the "Add" button to load 1080i mts videos.
Step 2. Choose QuickTime MOV output format.
Click the "Format" option, and choose Adobe Premiere/Sony Vegas > MOV (AVC)(*.mov) for conversion. The Sony HD Handycam to Avid converter will transcode Sony .mts files to QuickTime H.264/AVC .mov files.
Step 3. Convert Sony MTS to MOV for Avid.
Click the convert button under the preview window, and the conversion from Sony MTS to QuickTime MOV for Avid Media Composer will start right away.
While the transcoding is finished, you can load the Sony HD Handycam videos to Avid MC for editing. The Sony MTS to Avid converter also deinterlaces AVCHD files during the conversion. You can also import the videos from Aunsoft MTS/M2TS Converter for Mac to Avid Xpress Pro.
For reviews or skills of any particular Sony HD Handycam camcorders like Sony HDR-SR10, HDR-CX350, HDR-XR520V, HDR-TG3, you can have a look at the Sony HD camcorder page.