iMovie 11 and AVC-HD

The Advanced Video Codec in High Definition (AVCHD) is used in today's digital camcorders. However, most editing tools still struggle to handle the bandwidth of this format. Fortunately, I found that iMovie '09 was able to use manage these files, after performing a simple conversion on the container format.

Out of my Canon camera, the files have .MTS extension. Oddly, iMovie will import them directly via the camera connection, or if the SD storage card is plugged into the computer. This works because there are extra files on the SD card that catalog the content, which iMovie uses to interpret the video. Once the files are copied to the computer, these indices aren't available and iMovie pretends not to recognize the format. Luckily, the video stream inside the MTS file is identical to that within a supported format M4V (an MPEG4 variant). Using the free ffMPEG tool, the video can be quickly stripped out of the MTS container and copied into a more compatible file format.

ffmpeg -i original_file.mts -vcodec copy -acodec aac -ab 256k output_file.m4v

This command produces a file that iMovie will read in without converting to the AIC, a much larger file and time-consuming process. Sadly, iMovie '11 objects to this format, and prefers to convert it into the AIC on Import, after all. I have found a workaround for this annoyance. Instead of using an m4v container, use the Quicktime MOV format. The command is identical, but the output extension should be .mov. Then, instead of importing the file into the iMove project, drop the file into the folder where iMovie would have placed it. On my system this corresponds to the project folder in the "iMovie Events" folder. Then, once iMovie opens the project, it will locate the new material and generate thumbnails for it automatically. After that, you can work with the source material right away.