25fps to 29.97 problems

Praesto wrote on 7/24/2003, 10:57 PM

hi,

I have a problem with rendering a video captured at 25fps to 29.97fps, the video tends to break up at certain points during the render process.

Are there certain settings that I must adjust?

thanks

Comments

TheHappyFriar wrote on 7/24/2003, 11:33 PM

I know that for NTSC 24fps, when it's converted to 29.97 every 4th frame is duplicated (you can see this is you capture a movie into Vegas. It's pretty cool). That's an extra 6.5fps. So, if you add a frame dublicated every 5th frame you should be ok. That is probely the ony way you can do it. Or you can try converting it to 24fps, then to 29.97. that might work better.

Praesto wrote on 7/24/2003, 11:50 PM

thanks friar,

i've reverted back to vegas 3.0, it doesnt' have that problem as compared to vegas 4.0.

CrazyRussian wrote on 7/25/2003, 12:26 AM

TheHappyFriar, I dont think you're correct here (about duplicated 4th frame). I rember seeing a post by Sonic stating that it only appears that 4th frame is duplicated, but if you switch preview to "Best" you will see that Vegas does not duplicate frame it bulds a new one. Search this form for Sonic's posts and you'll find it.

farss wrote on 7/25/2003, 6:38 AM

I've been doing a lot of PAL to NTSC conversions, so far I just cannot make it go wrong, I'm using VV 4.0c if that means anything but Idon't recall any changes in that area of the code from 4.00 to 4.00c that would affect that area.

I guess you haven't turned resampling off?

TheHappyFriar wrote on 7/25/2003, 7:48 AM

The 4th frame duplication is something that studios use. The ony way to see it though is to find something made in 24fps (like movies, older TV shows, etc.) then view them frame by frame. At the station I work at we have Bonanza on DVCPro and you can see the 4th frame duplication. I always thought it was a mistake until I read that is how some hardware mpg encoders convert from 24fps to 29.97. Super Sampling should work though. Don't know why it was giving problems with that.

mikkie wrote on 7/25/2003, 9:30 AM

"At the station I work at we have Bonanza on DVCPro and you can see the 4th frame duplication. I always thought it was a mistake until I read that is how some hardware mpg encoders convert from 24fps to 29.97. "

If of interest, outside of broadcast, stuff like a set top DVD player does the same thing, & in my experience can be more accurate then the pull-down flags in an mpg2 that say render this video at 29.97i, and then set the order for field duplication (where it gets interesting as you invariably get some fields holding longer then others). Happily Vegas 4c seems an exception and works well. The guide on telecine at doom9.org isn't bad, and this http://www.cs.tut.fi/~leopold/Ld/FilmToVideo/ and this http://www.zerocut.com/tech/pulldown.html might be of interest.

"Super Sampling should work though. Don't know why it was giving problems with that. "

All unsubstantiated alas, just a guess re: how it works, VV4c does supersampling extremely well, and the core code for it is built into the way VV4c works. The same procedures are used when altering fps etc. as are used with supersampling, and so what might appear harder telecine &/or interlace artifacts in VV3 and other apps appears softer and maybe more blurred in 4c. Anyway, whenever I read that version 3 does something better/sharper etc. then 4, that's how I'd explain it, as I've never encountered any prob, especially when the result is viewed on a TV. As farss noted, not resampling often helps.

To the original prob posted, think the easiest way I've read, when length isn't absolutely critical, is set the clip playback to 24, then if going to mpg2, use the pulldown flags in the Vegas encoder. Otherwise, every time I've gone from 23.976 to 29.97 in VV4c haven't seen the least prob.