Best tool for transferring Canon S10 to FCP/iMovie
Cannon’s VIXIA HF S10 is a top of the line, full HD camcorder that makes no compromises. The ease of use and superior image quality make this one of the better consumer HD camcorders on the market today.
What's more, the VIXIA HF S10 allows you to record at up to 24Mbps, the highest bit rate in AVCHD format, for the highest quality image. The VIXIA HF S10's Canon Exclusive features - such as the Genuine Canon 10x HD video lens, sophisticated Genuine Canon Face Detection capability, SuperRange Optical Image Stabilization and a host of new control and creative options - makes our Flash Memory camcorder unmistakably Canon.

"I've recently purchased the Canon Vixia HF S10 and I’m having trouble dragging and importing the AVCHD .mts videos into FCP and iMovie , these files need rendering for so long time, and the timeline becomes extremely sluggish when preview. Any solution?"
Actually, the AVCHD is highly compressed and not the iMovie and FCP friendly video format, if you wanna to edit AVCHD clips from Canon S10 in iMovie/FCP, you must convert AVCHD to the iMovie and FCP friendly video format.
By learning FCP and iMovie on google, we can find out that Apple ProRes 422(*.mov) is the best editing format for FCP, and for iMovie is the Apple Intermediate Codec(AIC)(*.mov) format. So how to make the video format conversion possible, thus, we should get a prfessional MTS Convert for Canon Vixia HF S10.
Here recommend Brorsoft MTS to iMovie Converter which i used now, it is really a very easy-to-use tool for me. OK, next please follow me up , you will make it!
Easy Guide on Converting Canon HF S10 MTS recordings to FCP/iMovie/Premiere
Step 1: Install the MTS Converter on your Mac and load your .mts/.m2ts files to it.

Step 2: Click on the Format box and select a proper format in dropdown-list.
a. You are advised to choose “Apple ProRes 422 (*.mov)”or “Apple ProRes 422 HQ (*.mov)” format for Final Cut Pro.

b. Select Adobe Premiere/Sony Vegas > MPEG-2 (*.mpg) as output format for Premiere Pro.

c. iMovie and Final Cut Express -> Apple InterMediate Codec (AIC) (*.mov) is the best format for editing Canon VIXIA AVCHD in iMovie 8/9/11.

Step 3: Click the Arrow button on the main interface to start the Canon HF S10 to FCP/iMovie/FCE/Premiere Conversion. Once the process is at 100%, then the converted video is ready for importing and editing on Mac OS X.
Other features of the Mac AVCHD Converter:
1. Joining files: Tick the box "Merge into one" on the main interface.
2. Preview: Double click on the file and you can get a preview on the converter.
3. Adjust parameters: Click Settings icon you are allowed to modify the Bitrate of Video&Audio, Video Size, Sample Rate, Frame Rate, Audio Channels, etc.
4. Crop: Edit --> Crop and you can get the imported videos cropped as you want.
5. Auto shutdown: Click Option and tick the box “Shut down the computer after conversion” before conversion starts.
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