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Forums Broadcasting Refresh Rate, Progressive Scan & Electrical Current

  • Refresh Rate, Progressive Scan & Electrical Current

     Jared Leo updated 8 years, 1 month ago 1 Member · 1 Post
  • Jared Leo

    July 23, 2012 at 1:30 am

    I don’t think there’s a better section for this. Excuse me if so.

    When you’re viewing progressive footage on a TV that’s locked to a 60hz refresh rate, you’re seeing the frames refresh multiple times correct?

    Figuring out 30fps at a 60hz refresh rate is easy – it’s just doubling each frame. Does that mean we see 24p frames 2.5 times each though?

    Why do some TVs have both a 60hz and 59.94hz option?

    I’m hearing that the 60hz rate on some TVs is actually 59.94hz, and that they round it to 60 only in text to not confuse you. I believe we backed the refresh rate down slightly due to NTSC color and this has got me confused. In the oldschool B&W NTSC days we had 30fps and 60hz – perfectly divided. If there’s now a refresh rate of 59.94, wouldn’t there be some extremely slight sync issue since 59.94 isn’t locked exactly to our 60hz AC electrical current supply?

    They say progressive footage requires double the bandwidth. I thought that only your *TV* refreshes those frames in a video, like from a DVD. Does this mean that in a progressive DVD or bluray, multiple copies of the frames are in the vob files? Or does your TV handle that? Or maybe your DVD player employs a special telecine process and brings it up to match with the 60hz rate.

    I can understand ‘double the bandwidth’ in a progressive broadcast – that would mean broadcasting 60 images per second instead of fields, if it does indeed work where it has to broadcast the frames plus its repeated copies. But why not figure out a way to broadcast only single frames and let everyone’s TV do the refreshing work? I’m curious as to how DVDs and blurays hande this.

    PS: I wonder what it’s like seeing *actual* 24 frames per second, like directly from a film projector without the shutter. We’re used to seeing it displayed differently on our TVs and monitors.

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