Postman, help me understand how 59.94 TC can be read at 29.97!

[Eric Seaberg]

So we've got lots of HD video decks recording 1080i @ 59.94. Our SSL C200 is setup to run at 29.97 DFTC ref'd to video black (59.94). I don't have any problems having the SSL read serial TC and would assume it will also read LTC, so are the HD decks really laying 59.94 TC and, if so, how is it readable by a non-HD reader?

Thanks....

[DIAFXMX]

Sorry to jump in.
1080i/59.94 decks spit out 29.97 TC. Both serial, and LTC.

59.94/2 = 29.97

[Eric Seaberg]

Well, that's what I figured, but I can't find anything in the Sony docs that confirms this.

I guess since it works I shouldn't question it, eh?


Thanks for the reply, DIAFXMX.

[DIAFXMX]

I had to prove it to myself by plugging the output of the SWR5800 into a destripalyzer!!!

[Craig F]

It works, had a tape last spring that was suppose to be 23.976 but was 59.94 instead.
Changed Pro Tools to 29.97 and no problems.

[Postman]

Sorry I'm late to the party!

There is no such thing as timecode at higher frame rates. Nothing above 30fps was ever defined, AFAIK. All manufacturers are now using 1/2 frame rate LTC for frame rates above 30. I don't think this will ever change, instead LTC will simply fall out of use over time.

There is nothing to prevent an adaption of SMPTE/EBU LTC standards for frames rates above 30, some readers might even read and display it but they would think the deck is in forward or reverse wind.

[Eric Seaberg]

Thanks guys... ALL of you. I think what was really confusing me was that on the display of our HD decks it says something like "2F 59.94 1080". What I'm going to assume this is meaning is "2 fields @ 59.94 of 1080" based on some info found on Wikipedia and SMPTE's site.

1080P is, from what I can tell, running at 24FPS, right?

You are right, I believe, in that as we get further into 2k and 4k images, timecode as we know it will disappear, at least drop-frame. In fact, from what I've been reading, HD doesn't need to be drop frame at all, EXCEPT for the fact that there's still down-conversion to SD required.

I know this is WAY OFF TOPIC, but I knew you guys would have some good answers. Thanks again for clearing out the fog for me.

[DIAFXMX]

Yes, 1080i is interlaced, meaning 2 field.

You are right, I believe, in that as we get further into 2k and 4k images, timecode as we know it will disappear, at least drop-frame. In fact, from what I've been reading, HD doesn't need to be drop frame at all, EXCEPT for the fact that there's still down-conversion to SD required.

Correct, once SD is completely gone, 29.97 can disappear.
Digital can be 30.

[Postman]

"P/p" is progressive. "I/i" is interlaced. The number indicates how many lines of pixels are per frame. For us in the USA, 1080 can come as 30 or 24 fps, while 720p can come as 60, 30, or 24fps, as chosen by the broadcaster. I don't think anyone is doing 720p/60, but it is defined. The thing that makes this messy is that "interlaced" is really talking about fields per second, not frames. There are two fields per frame of video, so 1080i/59.94 is really only 29.97 frames per second. (Similar to good 'ol NTSC) And, each field has 1/2 the total number of lines, 540 lines per field. Two fields together contain 1080 lines. OTOH, 1080p/29.97 is also 29.97 frames per second. 720p/59.94 is actually 59.94 frames per second. Confusing? You bet.

[Eric Seaberg]

AAAAAAAAAAAAHHHHHHHHHHHH!!!!!!!!!!! (head explodes, here)


Anyone remember the movie SCANNERS?

(Thanks again, postman)