AVCHD footage is approximately 2 Mb per second which is pretty good compression, especially for HD content. Unfortunately, you can't edit raw AVCHD .mts files on a Mac, even though iMovie 08 and Final Cut Express 4 both claim to "natively" support AVCHD. What they actually support is transcoding of AVCHD footage from the camera to Apple Intermediate Codec (AIC) format on import. AIC files are optimized for realtime editing and they take up about 8 Mb per second* of footage, which uses up disk space pretty quickly.

* These numbers are just based on my personal observations, and compression ratios vary due to the variable encoding rates, but they are in the ballpark for my Sony HDR-CX7 camcorder capturing AVCHD footage at 960 x 540 resolution through iMovie 08.

I've been experimenting with editing footage from my Sony HDR-CX7 HD Camcorder in iMovie 08. It seems that some people are having problems getting the camcorder to work properly with iMovie 08 and here is the process that is working for me.

Importing footage directly from the camcorder

• Connect the dock to the Mac with the USB cable.
• Place the camcorder in the dock and power it on.
• You should see a menu asking which method you'd like to use to connect the camera.
• Press the Computer button.
• The Memory Stick icon should appear on the Finder desktop.
• Launch iMovie 08
• iMovie with automatically detect the camcorder and prompt you to import video.

I've been a a fan of hard drive camcorders ever since I purchased a JVC Everio GZ-MG50 a couple of years ago. The convenience of not dealing with tapes plus instant random access to the footage really made the recording and editing process more streamlined. However, the quality of the MPEG-2 video was not as good as DV and most mainstream video editing applications seem to have a hard time dealing with MPEG-2.

Thus, it was a nice surprise to see that iMovie 08 supports editing of all the major video formats outside of DV such as MPEG-2 and newer formats such as AVCHD (Advanced Video Codec High Definition) and the MPEG-4 standard H.264.

I've found that recompressing standard definition video with MPEG Streamclip to H.264 format yields much smaller files: on the order of 1/20 the size of DV footage and 1/3 the size of MPEG-2. There is very little, if any, quality loss evident in the video re-encoded as H.264 and I'm quite happy to use this format moving forward since it appears to be the format that is gaining acceptance across the board, e.g., Flash 9 and YouTube are both supporting H.264 these days.

I'm in the process of converting my old DV and MPEG-2 footage to H.264 using MPEG Streamclip. It's time consuming, but it yields tremendous savings in disk space.