telecined VHS and field order

[geowharton]

I was reading an old post about feild order (https://forum.videohelp.com/viewtopic.php?t=257631&highlight= ). it said "VHS doesn't have a field order". Does this mean that the info on the tape is in whole frames and transferred that way? Doesn't the telecining interfere with this?

I'm trying to understand a little more about what is happening when I capture from VHS. I've read all the info on 100fps.com and some others about 50Hz, 60Hz, film, etc. Because I had understood that NTSC was bottom field first, why my card captures TFF is a puzzle. If the vid is telecined, then wouldn't it be neccessary to play the fields in the same order?

I guess the short question is How can video with no feild order be telecined comming out of the VHS for my NTSC TV?

[jagabo]

Television is broadcast, VHS records, and TVs display as a series of alternating top and bottom fields -- it is neither TFF nor BFF.

It is the capture device that puts pairs of fields together into frames and hence creates the field order. If the device starts with a top field and then adds the next the frame is TFF. If the device starts with a bottom field then adds the next it's BFF.

[mikiem]

As jagabo wrote, but chiming in re: telecine...

If broadcast video content originated at something other then NTSC 29.97 (normally film at 24p), then additional frames were/are created to get to 29.97 & that process is telecine.

If you read up on this you'll see reference to pulldown flags etc. With cable & sat nowdays the content might be originally mpg2 with pulldown flags added, which is *very* basically a fake telecine as on many DVDs. If you capture it however, for all intents and purposes you have telecined video.

IVT (Inverse Telecine) tries to get rid of these extra frames.

An NTSC Std. TV refreshes every other line of the display, alternating odd and even lines, just short of 60 times a sec.. When it refreshes all the even numbered lines, there's just no data for the odd numbered lines, & vice versa. But, your PC monitor can't easily display a line of no data To make things work easier, all the lines are put together by your capture hardware into one assembled frame.

Often there's movement (something moving on screen) between the moment one set of lines is shown and when the 2nd set is displayed. Deinterlace tries to very basically merge the two, forming a frame that ideally is a better individual picture, often blurring the difference (when it exists) between lines.

Now when you work with captured video, you have to specify which field was recorded 1st in a frame, because of that motion that occurs between the two. When/if it comes time to go back to analog (i.e. to a std. TV), the even and odd lines are again counted, & assuming there are at least 480 of them, split into 2 fields.

[edDV]

See if this helps you understand
http://www.dvdfile.com/news/special_report/production_a_z/3_2_pulldown.htm

[geowharton]

Thank you all! This clears it all up. And edDV, the site was very helpful.