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Why does AVCHD have to be converted to AIC 1st?

942 Views 8 Replies Latest reply: Sep 1, 2011 9:00 AM by elikness RSS
the loc-man Level 1 Level 1 (15 points)
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Jun 22, 2011 1:48 PM

Couple of questions...

 

Why does AVCHD have to be converted to AIC 1st? Is it because the hardware isn't up to AVCHD or something? I only have a Core 2 Duo 2GHz 4Gb RAM so is this enough?

 

Won't converting from AVCHD to AIC and then to an output format (which would be best for quality once editing is complete?) decrease overall quality?

 

On a side note, currently my Panasonic TZ7 does AVCHD lite 720P. I'm thinking of upgrading to a Panasonic TZ20 with AVCHD full HD 1080i. However I've heard that although 1080i is full HD its not as good as 1080p progressive. Now I'm wondering if I should buy the Sony Hx9v which has 1080p or wait till next year for a newer TZ camera which has 1080p. Is there a massive difference between 1080i and 1080p, and for that matter over my current 720p?

 

Reason I'm thinking of upgrading is I'm off to Disney Florida this year for 1st time and want best I can, so was wondering if my current TZ7 would be enough or to upgrade to a TZ20 for the video

 

Cheers 

iMovie '11
  • Dave Hardy Level 1 Level 1 (50 points)
    Currently Being Moderated
    Aug 27, 2011 5:21 PM (in response to the loc-man)

    Apple assumes that iMovie users are using some of the slower Mac machines. So everything is converted to AIC whre every frame is an I-frame so the computer has to do far less work to play back the signal. You can import directly from the camera if you record at AVCHD 60i at 60P you will need to use a converter program to bring in 60P. There are many converters in the 30-50 dollar range. However I have found that the free App  Miro Video Convertor on the Mac app store to give the best results for 60P from the Sony HX9V.

     

    All the best.

     

    Dave Hardy

  • Winston Churchill Level 10 Level 10 (81,665 points)
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    Aug 27, 2011 6:10 PM (in response to the loc-man)
    Why does AVCHD have to be converted to AIC 1st?

     

    Basically AVCHD doesn't record all the frames of a video as full frames (i-frames), it records a full frame every so often and the frames in between are made of information about the areas of the frame that have changed and a calculation so that a full frame can be recreated by comparing it with the previous frame (p-frames), this gets a little more complicated as they can also be compared with next frame too (b-frames).

     

    Since the in between frames aren't full frames they can't be edited, which is where AIC comes in. When the file is converted to AIC all the frames are recreated (as full frames) from the various types of frames in the AVCHD file, they can then be edited.

     

    Won't converting from AVCHD to AIC and then to an output format (which would be best for quality once editing is complete?) decrease overall quality?

     

    Yes and no, think of the conversion more of an expansion whereby all of the quality of the original file is maintained, hence no loss of quality. This isn't entirely true since AIC does contain compression, but the files are already large enough as AIC files to expand them to an uncompressed format would be rather ridiculous for amateur video, and the loss of quality is probably immeasurable in most cases.

     

    Is there a massive difference between 1080i and 1080p, and for that matter over my current 720p?

    That very much depends on what you are going to do with it, the difference between these resolutions can be noticeable if the videos are encoded at appropriate data rates, but if you are going to use a similar data rate to compress a 1080p file that you use for a 720p file then you won't achieve any additional quality, indeed you may actually lose some.

  • jerry kaplan Calculating status...

    Thanks for the informative reply. If I convert from AVCHD to AIC, edit in imovie 9 and burn to a DVD won't the file be too large for say an 1 hr video? Would it be better to down convert to SD, import into imovie, edit and then burn to a DVD?

     

    Jerry

  • elikness Level 4 Level 4 (2,635 points)
    Currently Being Moderated
    Aug 30, 2011 3:35 PM (in response to jerry kaplan)

    Jerry, the way iDVD works with video you export from iMovie is it looks a the runtime or length of the video then it does what it can to adjust the quality using MPEG-2 encoding to fit the video onto a 4.7GB disk. It can easily fit a 60 minute project in that space and if you need it can crunch things further and fit 2 hours into that same amount of space. It will down convert to SD anyway as the DVD frame size is 720x480 no matter what. One hour will fit on a DVD no problem.

  • jerry kaplan Level 1 Level 1 (110 points)
    Currently Being Moderated
    Aug 31, 2011 3:07 PM (in response to elikness)

    I am considering purchasing the Canon Vixia HF M400 because of it's low light ability. My wife is a singing teacher and we would like to video some lessons for sale probably as DVDs. I see that it records at 60i. Do I need to deinterlace the video at some point?

  • elikness Level 4 Level 4 (2,635 points)
    Currently Being Moderated
    Aug 31, 2011 5:19 PM (in response to jerry kaplan)

    That too will happen on import, in fact notoriously iMovie will drop one half of the interlaced lines (the old Single Field problem if you want to search for it on the Discussion Group). So iMovie will do the deinterlace whether you want it to or not.

  • jerry kaplan Level 1 Level 1 (110 points)
    Currently Being Moderated
    Sep 1, 2011 8:54 AM (in response to elikness)

    Is this good? Do I in fact want the video to be deinterlaced?

  • elikness Level 4 Level 4 (2,635 points)

    No, not really, it's the way the new iMovie works since iMovie 08 hit the market. There was a fundamental change in the design of the program itself to allow it to run well playing back and editing HD on ALL level of Macs. From entry level budget machines all the way to Mac Pro Towers. The compromise was to choose one field of an interlaced video stream and drop it. So more or less 'half' of what goes in is ignored and you get half of it out in the process of importing and editing.

     

    The stricter more demanding folks on the iMovie Discussion Group have held on to their older copies of iMovie HD 6 as a result of this as it will always import both fields of the interlaced signal (Full Field import as opposed to Single Field). The other solution is to move up to the next level of video software and that is now Final Cut Pro X, which doesn't do these behind the scenes kind of "performance optimizations" which result in less data being captured into the video editing software.

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