[opendtv] Re: Frames Per Second of 720P

  • From: "John Shutt" <shuttj@xxxxxxxxx>
  • To: <opendtv@xxxxxxxxxxxxx>
  • Date: Fri, 18 Jul 2008 08:36:38 -0400

The Sony brochure http://bssc.sel.sony.com/Professional/docs/brochures/mvs8000.pdf states that the switcher operates at 1080i60, 1080i59.94, and 1080i50. This is probably where the Sony rep got confused, because 1080i60 is indeed 30 unique frames per second, and 1080i59.94 averages out to 29.97 unique frames per second.

This is exactly why I don't understand the nomenclature that seemed to only come into fashion with the advent of HD, of calling 1920x1080 thirty frames per second interlaced as "i60" Read the timecode, there are 30 frames per second in the timecode, therefore it is a thirty frames per second (ignoring the 1.001 for the moment) format, and should be called "i30" which clearly states 30 fps, presented interlaced.

When recording "1080i59.94", you can frame advance through the timecode and watch the time change from 00:00:03:29 to 00:00:04:00. In contrast, with 720p59.94, you can watch the timecode change from 00:00:03:59 to 00:00:04:00.

"1080i60" looks better on paper next to "720p60" I suppose.


----- Original Message ----- From: <dan.grimes@xxxxxxxx>

I just attended a demonstration of a Sony MVS8000 production switcher. The switcher can output 720 at 59.94 P and 1080 at 29.97 I.

As I we discussed frame stores, I asked if it took 60 frames to store a one second motion clip (120 with a key) and they said no, only 30. They (multiple Sony reps) were telling me all video is 30 frames per second, no matter what the format.

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