Framerates and converting to DVD

[exekutive]

This topic has been been approached from various angles, and I have successfully created DVDs from my AVIs, BUT I'm still not totally clear on the whole framerate subject.

So there are 3 standards, PAL (25 fps) which is used overseas, NTSC (29.97 fps) which is what N.American TVs operate on, and NTSC Film (23.976 fps) ... no idea what it's used for.

I'm assuming a PAL DVD won't play at home. So then what is NTSC Film and what will my DVD player and TV show? Which framerate is native to N.American DVDs?

Further, which framerate should I be choosing in the Video tab when I'm creating DVDs from an NTSC source? NTSC Film source? Is it even required to change the framerate? Obviously need to change a PAL source, but to what?

Which of these situations require the use of the Set 3:2 option? Some clarification would be much appreciated.

[jagabo]

Broadcast NTSC TV has only one standard: 59.94 fields per second. Each field consists of every other scanline of the TV screen. One field has all the odd numberd scanlines, the other has all the even numbered scanlines. You see one field at a time. You never see two fields the same time.

When this is captured on a computer consequtive pairs of fields are woven together into frames. You now have 29.97 frame per second digital video. When this is played back on a TV the frames are unwoven and displayed one field at a time -- restoring the original 59.94 fields per second.

Movies are shot at 24 frames per second. When they are displayed on TV they are first slowed down to 23.976 frames per second (1 part in 1000 slower). Then the frames are sent to the TV one field at a time in a 2:3 pulldown telecine process. Instead of each film frame becoming two fields (which would only get you up to 47.952 fields per second), or each frame becoming 3 fields (which would create 71.928 fields per second), half the frames are sent to the TV for the duration of 2 fields and half are sent for 3 fields. The end result is 59.94 (23.976 * 2.5) fields per second on the TV screen.

Generally, if your AVI source is 23.976 frames per second you should choose NTSC Film. If you AVI files are 29.97 frames per second you should choose NTSC.

[exekutive]

I see. Thanks.

Does the ffmpegx framerate video parameter set the framerate for the resulting file? And if so, both NTSC and Film will play fine on any DVD player? So I guess 3:2 pulldown is only used when working with NTSC Film sources.

When I have a PAL source, which framerate should I use?

[jagabo]

Does the ffmpegx framerate video parameter set the framerate for the resulting file?

I don't use ffmpegx so I can't say for sure what it does. I assume that if you specify NTSC film with a 23.976 fps source it will produce an MPEG file with 23.976 fps frames marked for 2:3 pulldown -- ie, instructions that tell the DVD player to perform the pulldown to create 59.94 fields per second.

And if so, both NTSC and Film will play fine on any DVD player?

That's my assumption.

So I guess 3:2 pulldown is only used when working with NTSC Film sources.

Yes.

When I have a PAL source, which framerate should I use?

That gets more complicated. PAL is interlaced just like NTSC. You see 50 fields per second on the screen. There are a few different ways to convert from PAL to NTSC.

If the PAL video is progressive (usually film sped up from 24 fps to 25 fps) the frames can be slowed down to 24 fps and 2:3 pulldown flags applied. The audio has to be adjusted slowed down by the same amount.

The progressive PAL frames can be left at progressive 25 fps and 3:2:3:2:2 pulldown flags applied to tell the DVD player how to create 59.94 fields per second from the 25 frames per second.

One frame out of every 25 can be discarded, leaving 24 fps and regular 2:3 pulldown flags applied. Audio doesn't need to be adjusted and you get one jerk every second.

One frame out of every 5 is duplicated to create 30 frames out of 25. Audio doesn't need to be adjusted but you get 5 jerks every second.

Someone who knows ffmpegx can probably tell you which method it uses.

[exekutive]

wow, complicated. let me guess, vestiges of an archaic system combined with wanting a system set up apart from the rest of the world? Honestly, who comes up with numbers like 59.94?

Anyhoo, I read this in the ffmpegx How-to's:
"To avoid audio sync problems, don't try to convert PAL into NTSC or the opposite."
I converted a PAL AVI into an NTSC DVD and it appears to play fine, audio and everything... on computer anyways .. we'll see what happens on the TV.

Oh yeah, and if someone else can confirm the part about DVD players being able to NTSC and Film framerate movies please. And howabout PAL? Does anybody know if that requires the use of a special dual-mode DVD player or is that something that they all do nowadays?

[jagabo]

Oh yeah, and if someone else can confirm the part about DVD players being able to NTSC and Film framerate movies please.

Of course they all play both normal 29.97 fps NTSC and 23.976 fps film rate NTSC. The question is what does ffmpegx do -- I assume it does something sensible with AVI files.

And howabout PAL? Does anybody know if that requires the use of a special dual-mode DVD player or is that something that they all do nowadays?

Many (most?) NTSC DVD players will not play PAL video on an NTSC TV. You have to seek that out as a feature. I've always purchased DVD players that can perform the PAL to NTSC conversion and can be made region free. And I always get DVD players that can play Divx and Xvid AVI files so I don't have to convert to MPEG 2 and master a movie DVD.

[exekutive]

Of course they all play both normal 29.97 fps NTSC and 23.976 fps film rate NTSC. The question is what does ffmpegx do

ffmpegX allows you to convert to NTSC, Film and PAL. (not sure about the methods either). Great! So that means if the source is NTSC or Film, there's no need to change the framerate when authoring to DVD. (I'm guessing you use windows and therefore different software?)

Many (most?) NTSC DVD players will not play PAL video ...

Sounds like a feature I would like too, but since it's not a 'normal' thing, I'm not going to use PAL to maximize compatibility of the DVDs I make.

Thanks again jagabo!

I still have a lot of PAL AVIs I want to put on DVD for playback here in N.America. Does anybody know the best way to encode them?