Proxy codec for AVCHD editing on iMac?

Hi there,


as I have discovered (and posted on other threads), my brand new iMac 21.5″ is unfortunately not capable of smoothly editing AVCHD footage natively (hard drive config, no hardware Mercury Engine Acceleration, etc). So I switched to transcoding into a QuickTime format…

I am coming from FCE so I have only Apple Intermediate Codec available on my computer (plus those coming with CS5.5). I also downloaded Avid’s codecs and Cineform’s. The latter won’t work for me, so I may post questions about this in a different post.

Anyhow, transcoding works fine and I can edit with smooth playback in PP BUT, of course, I get massive files. I can’t seem to find any “proxy” codecs in the list offered in AME, so I am trying to figure what kind of optimization I can do to get smaller transcoded files while still having something watchable (as a preview in PP) and giving me enough quality to edit (currently I am mostly using color correction and stabilization, on top of the usual titling, transitions, etc). Note that I replace the transcoded files by the original footage before exporting in AME to preserve the original quality.


Below, I will quote the  expansion ratio I obtain for a 130 MB 1080i60 AVCHD clip (Sony HX5V, 17 Mbps) using a 50% quality setting in AME (although the quality settings doesn’t seem to affect the final size much if at all):

Apple’s AIC: 5.2 (~120 Mbps)

Avid’s DXnHD’s 145: 7.6 (~147 Mbps)


Note that I listed this results in decreasing order of processing speed. The visual quality appears similar to my untrained eyes (on the test clip I used, at least). I haven’t tried other codecs (the list is quite long and not all of them are good for 1080i footage).

I noticed that FCP comes with a ProRes “proxy” codec with a bit rate of 45 Mbps, which would give an expansion factor of 2.6, which is a significantly smaller expansion factor (twice smaller than AIC).


Now, of course I could try transcoding in a non-QuickTime format. MPG2 comes to the mind. Its default bitrate is in the 15 Mbps! But I haven’t tried it yet in a PP timeline, so I am not sure it is any easier to edit with my iMac than the original H.264 (AVXHD) clip.


– Is it worth for me to spend $50 on Compressor to get access to this codec?

– Is there a free codec (or a combination of settings for some of the codecs coming with CS5.5) which would result in a similar expansion ratio?

– Am I asking the wrong question or missing some important points?


Thanks for any feedback.

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