Question about 1080i

[Kevin Lewis]

I shot a 30 second promo that will be airing on TV. I shot it on a dslr at 1920x1080 30P. For HD the station prefers a file that's either 720p or 1080i. Since I shot in a progressive mode, can I actually export 1080i without a problem? I did a test of it and it looks fine. If this cant be done, how to I actually export a 1080 file that was shot in a progressive mode?

[David Heath]

Originally Posted by Kevin Lewis

Since I shot in a progressive mode, can I actually export 1080i without a problem?

Simple answer is "yes". What you are referring to is properly known as "progressive, segmented frame", or simply psf. See Progressive segmented frame - Wikipedia, the free encyclopedia

With PsF, a progressive frame is divided into two segments, with the odd lines in one segment and the even lines in the other segment. Technically, the segments are equivalent to interlaced fields, but unlike native interlaced video, there is no motion between the two fields that make up the video frame: both fields represent the same instant in time. This technique allows for a progressive picture to be processed through the same electronic circuitry that is used to store, process and route interlaced video.

And last sentence is the relevant one. With psf, the information in the original progressive signal is not changed in any way - just reordered. With progressive, the lines are in order 1,2,3,4,5,6,7 etc, with psf the data in each line is the same as before, but now the order is 1,3,5,7 etc, then 2,4,6,8 etc.

Point is that what Wikipedia then refers to as segments can be considered the same as fields in an interlaced signal and treated as such. To a transmitter etc, I and psf are the same. Difference is that all the lines in a psf frame are captured at the same time. With a true i signal the lines in each field are captured 1/60 second apart. Hence 1080psf/30 has the same "look" to motion as 1080i/30.

[Kevin Lewis]

Dave thanks for the info. Just for further clarification, I can render the 1920x1080p to 1440x1080 60i with no problem correct?

[Jeff Pulera]

Yes you can export 1920x1080 (1.0 PAR) to 1440x1080 (1.333 PAR), but can I ask why you would want to create an anamorphic file - is that what the TV station requested?

Thanks