12 Replies Latest reply: Jan 24, 2013 7:18 AM by Shi'an
wardyf18 Level 1 (0 points)

I would like to be able to watch all my HD video footage on my iMac, but when imported using iMovie it takes up FAR too much hard drive space.

I am importing video from a Canon Vixia AVCHD camcorder (HF21). The native .mts files on the camera are about 10GB per hour (~ 6 hrs of footage on the 64GB internal memory), but when I import the video using iMovie, they expand by around 6 times, to about 60GB per hour (that is, the .mov video files saved in iMovie Events folders are HUGE, 60GB per hour, or ~ 1GB per minute).

This seems too large to be practical; the first 6 hours of import took up ~360GB of storage - and that was only the first time I'd used the camera and imported footage! So I only get less than 2 full uses and imports of the camera's memory before my 1TB iMac is completely full (not including what is already on there).

I have started "Archive All" to save the video footage in it's raw format, but now the footage is not usable or watchable on the iMac unless I go and import it again with iMovie - where once again it expands to 6 times it's size.


Is there a solution to this? How can I make all my HD footage watchable on the iMac, retaining the full quality raw HD of the video, but not take up more than 1/3 of my 1TB hard drive each time I import from my camcorder?

If I import to iMovie, then export as a smaller file, surely I will lose quality?

I have heard it can be done with Final Cut, is that correct?


Thanks a lot.

iMac, Mac OS X (10.6.7)
  • John Cogdell Level 5 (4,605 points)

    wardyf18 wrote:


    Is there a solution to this? How can I make all my HD footage watchable on the iMac, retaining the full quality raw HD of the video, but not take up more than 1/3 of my 1TB hard drive each time I import from my camcorder?

    VLC Media Player is able to play AVCHD clips (.mts files and .m2ts). Available as a free download here:



    VLC can play the archived clips from your "Archive All" process.



  • wardyf18 Level 1 (0 points)

    Thanks John.

    Yes, I have VLC, but I should have explained more clearly - I would like to be able to edit the footage for each "event" (hundreds of very short .mts files) and export them as one movie, while retaining the quality of the footage. If I do this on iMovie the event files are huge like I explained initially.


    Thanks for your reply.

  • John Cogdell Level 5 (4,605 points)

    HD video means large files - that's the nature of the beast unfortunately. AVCHD clips are converted by iMovie on import to Apple Intermediate Codec (AIC). iMovie is not able to edit AVCHD in its native form. The AIC format allows iMovie to work efficiently at the individual frame level, as the compressed video is expanded to full frames upon conversion (in non-technical terms). Hence, much larger file sizes!


    In iMovie, if you import at the Full size (1920 x 1080), as you have noted, the file sizes balloon out to about 50 - 60 GB per hour. However, if you import as Large (960 x 540), the file sizes are around 10 - 12 GB per hour - similar to the size of the AVCHD clips from the camera. I generally import as Large (as recommended by Apple) and find that the quality is quite acceptable, but this may depend on how you are viewing the completed movie. If creating DVDs, there will be little (if any) difference, given that it will be in Standard Definition.


    Viewing my finished movies (at 960 x 540) through a Western Digital TV Live HD Media Player connected to a LCD widescreen HD TV also produces very good results. Of course, others may see things differently, as it's an eye of the beholder thing.


    If you really want to see all your movies in full HD, the best option will be to invest in extra external hard drives (prices are now quite reasonable and getting lower as we speak). I don't think there is any other way around this if using iMovie. I'm not fully up with Final Cut to be able to comment on file sizes there, but would expect a similar situation to apply there.



  • dino.a Level 1 (0 points)

    I ran into the same issue as wardyf18. After import into iMovie I did find the ability to "Optimize" the events down to "Large" (File - Optimize Video - Large (960 x540). I can confirm the file size is MUCH smaller and the loss in image quality is only noticable when you compare videos side-by-side.


    My "issue" now is that when I look in Finder (Macintosh HD > Users > <name> > Movies) I see the iMovie Events seems to house the "Large" version of the video clips in a reasonable file size. I also see a seperate iMovie Original Movies folder that houses the same video clips with very bloated file sizes. E.g., The same file in iMoive Events is 449.3 MB but in the iMovie Original Movies folder it's 1.32 GB.


    Is the iMovie Original Movies folder storing the files in the original "Full (1920 x 1080)" format?

    If so, how can I optimize this down to the "Large" format?

    Or, can I delete the videos in the iMovie Original Movies folder? What happens if I do that?



  • elikness Level 4 (2,635 points)

    I think I found a partial answer on this website;




    And it seems like the Original folder is your Full Size High def video clips prior to optimization. To Optimize go to the Event Library, highlight the Event in the Library. Then go to the File Menu > Optimize > Large Size:


    Screen Shot 2011-12-09 at 4.20.31 PM.png

    My videos aren't Full Size, so I don't have the option to choose Large in this example above, but you get the idea. You an optimize the Events Folders this way. Then you will have 1 copy @ Full and 1 copy @ Large inside of the Macintosh HD > Users > <name> > Movies folder. If you don't want the Full copy laying in the Original folder, you can delete that by just dragging it out of the Originals folder and putting it in the trash.


    As the Link at the top of this message indicates you can also optimize on Import of the video and save some space by converting it to Large as it imports. Then you don't have 2 copies inside your Movies folder (1 original, 1 optimized)

  • mvmum Level 1 (0 points)

    Did you decide on a good solution wardyf18?  I am having the same problem and feel very stuck-- I have several HD video cards that are full of footage but after putting a few video clips on my computer (which has a 750GB hard drive), my hard drive is nearly full.  It seems like I'd need a whole truckload of external hard drives. 


    I was just curious to see if you had found a solution you are happy with as I'd love to be able to access and edit the clips and stop buying more video cards (and make highlight films so my family can actually enjoy the videos, the whole reason we bought the camera and new computer), as I don't currently feel comfortable with any storage option. 


    Thanks for any help!

  • lucian35 Level 1 (0 points)

    I need help when I import video from my canon camcorder which is 10 gb to imovie its making it 50gb way to large....I'm not interested in editing video maybe later down the road....I just want to be able to import video as is from camcorder and view it on my macbook....

  • mvmum Level 1 (0 points)

    lucian 35, I am in the same boat-- ideally I'd love to do some editing but right now I also just want to know that all my footage is safely backed up and be able to watch it and eventually be able to share parts of it with family via Vimeo, Facebook, etc.  I can't figure out how to save it on my computer or external hard drive (much less view it) without  importing into iMovie and can't figure out how to make it save in a smaller format. 


    Does anyone know why the video size blows up so much bigger when imported?  Any ideas on how to bypass iMovie and still save and view the video on a Mac? 


    Perhaps I should buy a cheap PC just for video purposes-- so so frustrating to have bought the Mac with its great promise only to find it lacks the capacity to handle HD video in any reasonable way. 


    Thanks so much to anyone for advice!

  • lucian35 Level 1 (0 points)

    mvmum, I have spent so much time trying different things and nothing is working....It is driving me crazy...


    I heard that imovie 8 imported video as AVCHD as the original without making the file huge....

  • AppleMan1958 Level 7 (27,415 points)

    See this post for an explanation of why the files get bigger. iMovie 08 also converted AVCHD to Apple Intermediate Codec on import.



  • wardyf18 Level 1 (0 points)

    mvmum - In short, no, but I'm going to try the "Large" optimize option as described above next time I import. But it still makes me wonder why I got such a great camera with great picture quality at such a high resolution and bitrate, only to have to optimize it down to a smaller picture size so the files sizes are reasonable. But...if you can watch it, and like John Cogdell says above it is still good quality picture, well maybe that's enough.

    John also explained above why the files expand to ~6 times their size on import.

    In terms of backing up your footage, use the "Archive All" function in iMovie Import. It keeps all your footage in it's original size and format, it's just a bit more tricky to watch it all, especially if you want to watch on a tv (VLC works on the computer). If you want to access & edit them, import them into iMovie and do what you need to do - then export it, and delete the iMovie project (which will have been blown up to about 6 times the original file size - like we discussed earlier).


    John - do you think the "Large" format would stream and display adequately over an Apple TV? I understand Apple TV is limited to 720p, so Large may not show up as well as a 720 picture. Eh...I'll do some experimenting.

    Happy new year.

  • Shi'an Level 1 (0 points)

    Thank you AppleMan1958 for that link to your earlier post. I have spent way to many hours tonight trying to work out why Nanna's Christmas video clips off her new JVC suddenly filled my HD. iMovie warned me that an hour of video at full would take 40GB. Gross underestimate lol.

    I have decided I will import as large just to off stuff to DVD or quicktime format for the family then dump the iMovie Event in the trash and do an archive of all the footage to keep it for future editing. I'm lucky to have an external raid as the backing up of externals just starts becoming expensive in redundant backup drives.

    I would be very cautious of using DVD's for backup as I have seen them fail too easily after a only a few years.


    wardyf18 - My understanding is that importing on the Large setting gives you 960x540 resolution which isn't as good as the 1280x720 supported by older Apple TV's but I havn't noticed much difference in recent testing.

    I believe the newest Apple TV will support 1080 on H.264 format but if you are playing MPEG4 it only supports 640x480 anyway. As a lot of my older stuff was converted to MPEG4 for iTunes so I now realise most of what I watch is only 640x480


    mvmum - after hours of reading tonight I have come to the realisation that a Mac actually handles the editing of HD video pretty well but ADVHC is just not a good editing codec. Converting a 'group of pictures' codec to a 'full frame' codec is going to give you a large file on any system. Unfortunately a 'full frame' codec appears to definately be the best way to edit and anything that edits a 'group of pictures' codec like ADVHC has other quality problems.


    Thanks all for your discussion and advice.