Slow playback when importing 1080i film

[flybaba]

Hi! Ive been searching around in a great lot of forums, but I have not yet find the answer I'm looking for. I have got a Canon Legria HF200 (1080i) videocamera and a MacBook late 2009.

When I import the video that i have recorded into iMovie (I don't know any other ways - it's AVCHD format) the MacBook warns me that if I'll import in full resolution (1080i) this will might result slow playback on my computer. Why? When i preview the files before I import them the video plays perfectly fine. If I import them to my laptop and then view them they turn out to be played really slow and unclear. Would this be a problem with the way iMovie imports the file, or my hardware? Could it be that my HDD is to slow? This has annoyed me for months, please help!

 

[spinnerlys]

As iMovie and many other and more sophisticated editing applications don't work directly with AVCHD footage, which uses an MPEG-4 codec variant, and need to transcode (change format/container and encoding) it to a format like .mov using a codec like Apple Intermediate Codec (AIC), the data rate (KB or MB/s) rises, the resulting file of that transcoding process gets bigger.

One hour (60 minutes) encoded with AIC take up 42GB (1080i50) to 49GB (1080i60) of HDD capacity (link). Thus the data rate per second is 12 to 14 MB/s, which is not much, but if you use the internal laptop HDD in your MacBook for storing and using the footage, which is also used by the Operating System (OS) and the applications, you will experience a slow down. Depending on what MacBook you have, get an external HDD to store your transcoded video onto to work with it, and preferably buy an HDD with a Firewire interface, if your MacBook has it too. If not, only USB is your choice, but it should work there too.

 

[flybaba]

Thanks for a great explanation! I already do have an external harddisk, I'll try it out with that one. You wouldn't all by chance know any other way to import the AVCHD files to my MacBook? Because I very often edit films when I'm not at home and it's a bit annoying to have to bring my external HDD everywhere I go with my camera and computer. For editing i use Final Cut Express.

Thanks!