2008-05-25

AVCHD support on the Mac

Editing MPEG4 needs a lot of processing power. It's highly compressed and to achieve this just a few frames contain the entire image information. In the majority of frames just the differences from previous frames as well as predictions for future frames is stored. That means that the editing software must constantly decode a lot of neighbouring frames to restore the frame you're currently working on. This is much more demanding than MPEG2 editing and even the latest Mac Pro has a hard time to do this fluidly. iMovie 08 can edit pure MPEG4 video with AAC audio natively (not AVCHD!) but forget about the scrubbing feature if you try this. Of course, over time when computers get faster this will change.

If you consider the current situation, it's nothing but clever by Apple to convert all AVCHD clips to the Apple Intermediate Codec (AIC) since you wouldn't be satisfied with the user experience of native AVCHD editing on todays computers. The AIC is a high quality MPEG2 intra frame codec that is easy to handle on all current Macs. Intra frame means that each frame is compressed individually which is very edit friendly. The conversion is not lossless but you will not see any quality loss just like you will not see a quality loss in JPEG compressed images at high quality settings. It's generally a good idea to leave the highly compressed MPEG4 codec as soon as possible.

AIC clips are QuickTime movies that can be played on Windows or OS X. The screenshot below shows the QuickTime Player info window of an AVCHD clip that was converted to the Apple Intermediate Codec by iMovie 08. As you can see the data rate is very high which ensures quality. The Dolby encoded audio of the HF100 is converted to 48 kHz uncompressed stereo audio.

The only disadvantage of the conversion is that your compact .MTS clips become much, much larger. Typically the factor is eight so a 1GB AVCHD clip will occupy 8 GB of hard disk space after conversion. An external 500 GB disk that is dedicated to video editing for instance will hold about 7 hours of AIC encoded video from the HF100.

As of May 2008 all video editing solutions from Apple convert AVCHD. iMovie 08 and Final Cut Express 4 convert to the Apple Intermediate Codec while FinalCut Pro has an additional ProRes option with even higher quality (and file size). Note that the current Final Cut Express 4 doesn't support the FXP mode of the HF100. It still uses 1440x1080 (the HDV standard) intern and scales up to full HD.

AVCHD import is only supported on Intel Macs. Users of older Macs or iMovieHD can use the utility VoltaicHD from shedworx.com

At the moment (May 2008) only the video player of Toast 9 can play .MTS AVCHD files directly.

Update November 2008: Adobe Premiere Pro CS4 allows native AVCHD editing on a Mac.

6 comments:

Thomas said...

Hi Martin,
how long does the conversion to AIC take on your mac? is it realtime or faster?

Thanks
Thomas

Martin Koch said...

Thomas, I have a Mac Pro (2.8 GHz, 1 Quad-Core Intel Xeon processor) and the conversion is approx. in real time.

Bruno Rodrigues (http://www.litux.org) said...

"At the moment (May 2008) only the video player of Toast 9 can play .MTS AVCHD files directly."

Do you mean that QuickTime can't play the .MTS files directly? How's so? isn't the iMovie import using quicktime itself?

In other words, is there a way to quickly play the videos from the SD card into the mac, or do you need to see them on the camera and/or import to imovie and then play ?

thanks for this blog

Martin Koch said...

Exactly, we can only hope Apple adds QuickTime Player playback of .mts files some day.
At the moment only the Toast Player allows watching these clips.

Thomas said...

Ok, one thing regarding the conversion time:

In final cut express 4 you can queue the import (even directly from memory cards) for a lot of clips and can start editing, as soon as the first clip is there - the remaining clips are converted one after another in the background - works like a charm (imac 2.4)
Thomas

Emilio77 said...

Hi,
does anyone have troubles playing the transcoded files? i mean... i imported my AVCHD footage from Canon hf100 into FCP6. It creates 1080i clips encoded with intermediate codec. I tried to play these clips with quick time and every camera movement is really far from being fluid. It looks like it's not able to deal with camera pan and tilt...but it makes a good job with still shooting. It's wierd because i tried to play the
m2ts files with toast 9 player...and it's really fluid.
My IMac is a new 24" dual core intel.
Any suggestion.....?

Thank you, and sorry for my english....i'm italian :-)