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Thread: Best, highest-res, non-lossy format for archival storage of video

  1. #1

    Best, highest-res, non-lossy format for archival storage of video

    We have a slew of AVCHD files that we can't even usefully edit with our usual low-end (but otherwise reliable) video editor. In all events, we don't want to be storing AVCHD files for editing/deployment five, ten years down the road, and we're an archive, so we know that we will, in fact, be doing new clips or re-deploying those files five or ten or more years down the road as formats and standards change.

    So, what would be the best non-lossy format we could use to store files for current, and hopefully, long-term future editing? We're tentatively using avi/ntsc dv, but that is just because we're familiar with it. Ideas?

  2. #2
    If you're shooting on HD, then i strongly recommend NOT compressing files to SD. There are several output options that would reduce the file size and still retain your native frame size. The only reason you would want to shrink to SD is if you are very short on storage space, or you otherwise don't have much interest in retaining the quality of the source. AVCHD files are usually between 40 and 50 Mbps, so you can use Squeeze to cut that bitrate (data rate) in half with an acceptable amount of loss. To do that you will want to download an HD preset from presets.sorensonmedia.com and change the data rate according to the aforementioned recommendations. If you don't want any loss you can use Squeeze Pro to output to Prores (Mac only) or DNxHD in an MXF container. However these output formats will expand the file size several times larger than the original. Therefore if you like the idea of halving the file size, then you want an H.264 codec, either in Mp4 or MOV format.

  3. #3
    I this case, file size is not the issue--the issue is moving from avchd (presumably mpeg-4?) to a non-lossy format for archiving and editing. Preferably, that new file format loses none of the HD data, but is also likely to be readable by a wide variety of devices/software moving forward--it isn't clear what we'll be using five, ten, twenty years from now when we want to make new clips, or to update existing ones to take advantage of standards then.

    What is DNxHD? what is an MXF container? Sorry to be starting with so little actual knowledge. (Since yesterday I can state that not only is ntsc dv lower res, which we knew, but we seem to be able to get only 4:3, which distorts 16:9 pretty badly ;-).)

    I also know that Matroska produces files that our current video editor (Premiere Elements 10/Mac) cannot open.

    Oy.

  4. #4
    If you are unfamiliar with the codecs i mentioned before and are neither an Avid or a Final Cut user, then i suggest a quicktime codec that apple builds into that app. They give you several choices, and you can examine the entire list here:

    http://forum.sorensonmedia.com/forum/content.php?332-MOV-codecs

    From the context you have given me, i would most strongly suggest Intermediate, Animation or None. You can read about each of those on the link. After a couple tests i'm sure you'll find the codec that works best for you.

  5. #5
    Some experimentation will obviously be necessary. I've tried default Quicktime (and WebM) presets with whatever are the default codecs, and the audio and video still go way out of sync when working with these particular AVCHD mp4s. I can see where the codecs you suggest give me loss-less video; what I don't see is how to address the sync issue as well. What is/could be happening to cause what looks like AAC audio to get out of sync with the H.264 video in these AVCHD files? (When I first asked this question, I didn't realize that I had a syncing issue; I thought my only concern was to find an acceptable storage format.)

  6. #6
    Sorenson Media Tech Support Jeff_TS's Avatar
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    May 2010
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    Sometimes sync issues can be caused by a difference in the sample rate of your source file audio and the sample rate settings in your output preset.

    Which presets, specifically, are you using that are giving you the out of sync issues?
    Jeff Udall
    Tech Support Manager
    Sorenson Media
    www.sorensonmedia.com

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