What happens to an avchd video imported into iMovie 10.0.6

Discussion in 'Digital Video' started by stauffec, Nov 20, 2014.

  1. stauffec macrumors newbie

    Joined:
    Nov 20, 2014
    #1
    I'm trying to understand what iMovie is doing. Basically, I have a panasonic gh2 with hack to increase the bitrate. Regardless, it stores the videos in avchd format. When I import it into iMovie, I see the video in the Movie Library/Original directory as h.264 encoded, which surprises me because some people said it should stay as avchd or prores. Can anyone confirm? Also, I'm wondering what format I'm actually editing the file in when I'm using iMovie. Where is that file located? Does anyone know? My concern is I'm losing image quality.
     
  2. Small White Car macrumors G4

    Small White Car

    Joined:
    Aug 29, 2006
    Location:
    Washington DC
    #2
    I don't know what iMovie does these days so I can't fully answer your question, but I CAN tell you that you don't have to worry about losing quality.

    If iMovie is converting the video it's basically doing it for performance reasons. Back when it converted files to AIC (and when Final Cut Pro X converts them to Pro Res) the main goal is to take it from an inter-frame compression format to an intra-frame format. This is nicer to your hard drive and processor but shouldn't really change the quality of the video in any way.

    Now, I don't know what iMovie is up to these days. Maybe they gave up on AIC and just let you edit AVCHD directly now. Or maybe not. The point is, do't worry about it either way. (For quality reasons, anyway. If you're having playback performance issues that's another discussion.)
     
  3. stauffec thread starter macrumors newbie

    Joined:
    Nov 20, 2014
    #3
    Thanks

    Thanks for your post. One of the points of concern I had was when I looked at the "original" file in that directory, it said it was h.264 codec (instead of avchd), but what was stranger was that the bitrate was listed as 24mbps. This was disconcerting because I'm using a hack that should give me 80-100mbps. So I am nervous it is transcoding it to h.264, but dropping the bitrate. So even though AIC should have a difference, it's "base file" if there is such one actually has dropped the bitrate. The other possibility is my hack hasn't been working, and therefore is using the standard 24mbps on the GH2. I think this actually may be more likely.
     
  4. Small White Car macrumors G4

    Small White Car

    Joined:
    Aug 29, 2006
    Location:
    Washington DC
    #4
    Keep in mind that AVCHD is a form of h.264. While a camera menu or a video-editing program may identify it as AVCHD it's entirely possible that an OS or file-viewer may default to just calling it the generic h.264 even when it is AVCHD.

    Try opening one of the movie files in the VLC app and hitting command-i and going to Codec Details: Stream 0

    I see here that it's telling me h.264 - MPEG-4 - AVC. (Which is accurate, if a bit wordy and redundant. It is all of those things, technically.) So it's giving me more detail than other programs do.
     

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