24 fps to 29.97 fps ?

[Mike99]

How is 24 fps converted to 29.97 fps for proper viewing without any hiccups?

I understand 23.976 fps +3:2 pulldown = 29.97 fps and there is no problem. Is that correct?

But 24 fps +3:2 pulldown is not 29.97 fps. So what does my stand alone DVD player do in order to output a correct NTSC video?

I’ve never had a problem watching any DVDs or Blu-ray discs. Maybe there is some small jerkiness, however I never noticed it. When reading about building a Home Theater PC some people experience jerkiness depending on which graphic card is used. That means there must be a way to go from 24 to 29.97 fps. But all the information I come across keeps mentioning using 3:2 pulldown with 24 fps.

Can a 24 fps sourced DVD be converted to a perfect 23.97 fps, or is there always going to have some jerkiness?

[aedipuss]

24fps is 23.976 just like 30 is really 29.97. so ivtc is how it's converted. true 24fps isn't in the dvd spec.

[Mike99]

I'm trying to figure out what the 24fps "bug" is with some HTPC graphic chips that I frequently see mentioned. If nothing is 24fps then there should be no problem. I'll admit I'm confused & have been trying to figure out what is the problem.

[jagabo]

True 24 fps video can be output as 59.94 fields per second (ie, 29.97 fps) using the same 3:2 pulldown as 23.976 fps. Except one field out of every 501 is skipped. Ie, one frame that would normally be is output as 3 fields is output as 2 fields instead. That makes up for the difference between 24 fps and 23.976 fps.

[Mike99]

jagabo,

If a true 24 fps video is converted to 23.976 fps before a commercial DVD is made, is the same process used? IOW the DVD is created with a skipped field every 501 fields?

If someone was able to notice any jerkiness it would be visible no matter what. Is that correct? Or is it virtually impossible for the human eye/brain to notice this missed field?

A lot of what I read talks about 1080p 24fps Blu-ray discs. And one of the reasons newer LCD HDTVs use 120 Hz refresh rates is because this is a multiple of 60 and 24. In this case does a Blu-ray player output a true 24 fps, or are they playing a numbers game & it is actually outputting 23.976 fps?

[manono]

If a true 24 fps video is converted to 23.976 fps before a commercial DVD is made, is the same process used? IOW the DVD is created with a skipped field every 501 fields?

Nothing is ever skipped when going from 24fps to 23.976fps. It's just slowed down a touch.

If someone was able to notice any jerkiness it would be visible no matter what. Is that correct?

Many NTSC people don't notice the jerkiness that 3:2 pulldown creates. I don't. PAL people, not being used to it, sometimes find NTSC DVDs with the 3:2 pulldown annoyingly jerky.

If a Blu-Ray disc says it's 24p, it's real 24fps. It'll be played as a multiple of that on the TV set (depending on the refresh rate of the set)

[Cornucopia]

No, most (nearly ALL) Hollywood/US & Japanese releases are actually 23.976fps masters encoded that way to BluRay. UK/European release are mainly TRUE 24fps masters encoded that way to BluRay. On an NTSC system player (not counting 24p/Cinema modes), they output at 59.94 or 119.88fps. NEVER true 60/120fps.
So true 24fps sources have to have a 1000/1001 slowdown (which either the player or the TV must provide, usually the player) in realtime, OR there may be some occasional "hiccups" for those devices that aren't built to accomodate.

Scott

[manono]

No, most (nearly ALL) Hollywood/US & Japanese releases are actually 23.976fps masters encoded that way to BluRay.

No? Have you never heard of the drop_frame flag? Some (most?) may be true 23.976fps, but by no means all. I was answering Mike99's speculation that unique frames or fields might be dropped when going from 24 to 23.976fps. And Mike99 was talking about both Blu-Ray and DVD.

they output at 59.94 or 119.88fps. NEVER true 60/120fps.

Yeah, so? I didn't say they were integer multiples. If it's a true 24fps blu-ray, then of course it won't play completely smoothly on an NTSC TV set as every so often one of the frame multiples will be dropped. On a 60Hz set it's playing slightly jerky anyway. On a 120Hz set, where it would play smoothly at 23.976fps (each frame being repeated 5 times), if it's really 24fps one frame gets dropped every so often.

So true 24fps sources have to have a 1000/1001 slowdown (which either the player or the TV must provide, usually the player) in realtime, OR there may be some occasional "hiccups" for those devices that aren't built to accommodate.

OK, so you do know about the drop_frame flag. Why'd you contradict me then? I see nothing to contradict. I know nothing about Blu-Rays so I don't know whether or not the flag can be used for them

[Mike99]

It appears that in order to accurately play a true 24fps Blu-ray disc you need an HDTV that supports 24fps.

I would like to clarify message #6 regarding slowing down 24fps to 23.976fps. I'm presuming that is just for a standard DVD, is that correct?

And that a true 24fps Blu-ray disc would drop frames if displayed on an "old" HDTV that does not support 24fps, is that correct?