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Equipment How much HD can fit on a HDD?

Discussion in 'Photography, Art & Design' started by l3v1ck, 13 Jun 2009.

  1. l3v1ck

    l3v1ck Fueling the world, one oil well at a time.

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    Okay, I've narrowed my camcorder search down to two.
    One has a 80gb HDD and claims "up to" 33 hours
    The other has a 120gb HDD and claims "up to" 50 hours.

    Obviously this "up to " estimates are complete crap as I want to use the highest possible quality settings for HD so the things I film look good.
    How long can hard drives of that size record the highest quality HD for ?
    The cameras are both Sony.

    Thanks in advance.
     
  2. smc8788

    smc8788 ...at least I have chicken

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    It would depend on what the highest quality settings are for each camcorder (i.e. 720p/1080p). In any case, you should be able to find some info somewhere for each camcorder on what bit rate the highest quality setting records at (most record to AVCHD format), and you should be able to work out how many hours worth of video you can record from that. I assume the quoted figures from Sony would be for the lowest quality settings.

    E.g. for 24 Mbits/sec bit rate AVCHD files = 86400 Mbits/hour = 10800 MB/hour = 10.54 GB/hour

    So for:

    80GB HDD = 7.6 hours
    120GB HDD = 11.4 hours

    Assuming that both camcorders record at the same bit rate in their highest quality setting.
     
  3. l3v1ck

    l3v1ck Fueling the world, one oil well at a time.

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    I found this burried in the specifications.
    Assuming that 16 Mbps is the highest recording quality, that's 57600Mbps/hour = 7200MB/hour = 7.03 GB per hour

    120GB HDD = 17.1
    80GB HDD = 11.4

    Does that sound about right to you?

    Is 16 Mbps quite low for a modern camera or will that be okay?
     
  4. ch424

    ch424 Design Warrior

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    AVCHD is just mpeg-4, so 16Mbit should be ok for home use. I've seen some footage from AVCHD cameras and the limiting factor is their lens/sensor quality, not the compression. Considering how easy it is to increase the bitrate, you can bet that Sony/Panasonic/whoever made sure it wasn't going to limit the overall quality of the camera.
     
  5. smc8788

    smc8788 ...at least I have chicken

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    Yeah that sounds right, I just used the 24Mbps bit rate as an example as that is the highest available in the AVCHD format.

    Anyway, 16Mbps should be fine as most of the competition use bit rates around that as it seems to be optimal for a decent balance between high quality and decent length of recordings.

    Even Sony's highest-end cameras don't offer 24Mbps recording, as they still use the H.264 main-profile 4.0, rather than the high-profile 4.1 which allows the 24Mbps bit rate. Some of the higher end cameras from Canon and (I think) JVC use the 4.1 profile and offer 24Mbps recording, although I'm not sure of the benefits this provides.

    Some Canon cameras also offer a full progressive video mode (as opposed to interlaced), but I think in the majority of cases it's not that beneficial in terms of image quality.
     
  6. supermonkey

    supermonkey Deal with it

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    As ch424 said, AVCHD uses mpeg-4 AVC/H.264 compression. H.264 is an excellent compression method; you'll find a lot of companies using it for a variety of commercial purposes. We were looking at a "Makito" encoder from Hai-Vision a couple weeks back, and we dialed down the compression to 3Mbps, and the video held up quite well on the 60" plasma display. If I recall correctly, we had it running at around 6Mbps, and it looked every bit as good as HDV at 27Mbps. Granted, it's not an apples-to-apples comparison (the Makito to a consumer camcorder), but it just goes to show how well H.264 will hold up under heavy compression.

    So yes, 16Mbps will be fine for just about anything you need.

    -monkey
     

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