NTSC 23.976/29.976??

[andyg]

Hi guys. Am having some serious problems converting at the moment. My burned disks keep jumping when played on my standalone - video slows down and audio carries on resulting in de-sync, then video goes fast to catch up with audio. Am trying different encoder at present in the hope that it's TMPGEnc not liking the source file since it plays fine in media player.

Anyway, this is my question: We use PAL in UK and NTSC is the norm for USA but why do they have 23.976 and 29.976?? My DVD player will play NTSC disks and so when I encode I keep the same framerate 23.976>23.976, 25>25 and so on but should I be converting from 23.976 to PAL? I ask this because the new encoder I am using tells me that I am making an invalid VCD stream using 23.976 - says for NTSC it should be 29.976. I am wondering if this is what's messing around with my DVD player and causing those jumps/skips.

[sterno]

My understanding is that NTSC standard is 29.97fps, and films are shot at 23.97fps. For video transfers they run the film through a telecine machine to convert it to 29.97fps. Most North American DVDs today keep the video at 23.97fps and the DVD players internally convert it to 29.97 before they send it to the TV. The benefit is that they can get better quality at a given file size because there are fewer frames to be encoded. 23.97fps is commonly called "NTSCFilm" (that's why tmpgenc has NTSC and NTSCFilm templates), and it should work fine for VCD/SVCD.

If your video is alternately speeding up and slowing down like that in a set-top player but working on the PC I would first suspect the media. I assume that you're using the standard templates in tmpgenc - my DVD player doesn't like VBR MPEG1, and I see that kind of behavior when I try encoding MPEG1 with 2-pass or CQ VBR modes.

I also noticed a few problems like that on my SVCDs - I saw the same problems in the same places no matter what disc I used. I found that it would go away if I disabled the "enable padding" option (which you can only do if you're using VBR) or enabled the "close GOPs" option.

[spaceman]

If you want to keep a nice smooth framerate with 23.976fps code is under the 1st tab(video) in tmpgenc you will notice the text encode mode check it so it says 3:2 pulldown when playback(you may have to unlock the template to check this box) then go up to framerate you will now notice a new framerate is available 23.976(internally 29.97) so check this and hey presto encode and enjoy......spaceman

[adam]

spaceman 3:2 pulldown is only used for SVCDS, he's making VCDS.

andyg, there is nothing wrong with a vcd encoded at 23.976fps. It fully complies with the VCD standards but that doesnt necessarily mean your pal tv/dvd player can properly play it.

See a file encoded at 23.976fps is normally telecined in real time as it plays to 29.97fps, which the ntsc standard requires. If you have a pal dvd player with an ntsc mode then it will then convert this signal to what is called ntsc 50Hz, basically just an ntsc signal modified to play on a pal system. My guess is that either your dvd player simply does not do real time telecines on VCDs well, unfortunately there are a number of players like this, or the conversion from ntscfilm=>ntsc->pal is just too much for your player.

The best thing for you to do would be to convert your ntscfilm (23.97fps) material to pal yourself.