I agree... 24 fps is helpful in this case. But I believe this is generally true only during the postproduction phase. In terms of distributing a final release to the public, either via digital broadcast or DVD, it seems that true 24 fps is no longer an option. Even a native 24 fps project (like one shot on film or rendered by CGI software) must be slowed down by .1% to 23.976 in order to broadcast digitally onto consumer televisions or be viewed by consumer DVDs.

I guess my question might be a little off-topic... because what I'm really wondering is why true 24 fps is part of the ATSC standard. In other words, the ATSC standard is all about digital broadcast to the masses. Since that realm appears to support only 23.976 fps, it seems superfluous for ATSC to specify 24 fps as an acceptable format, especially since there doesn't appear to be any consumer electronics capable of running at that frame rate.

This is may be a contributing factor. NTSC DVD players shows everything at 29.97 fps. If you play a 24 fps video (hollywood film movies) with the proper flags set in the media file the DVD player will insert the 2:3 pull down and automatically convert the 24fps to 29.97. You need an authoring program that supports this.

Ed B

The 24p file on the DVD will also be 23.976p, not 24.000. DVD Architects 2 and up support this.

not all projects go over air. I render video's that are meant for computers only. Stuff used for theature is 24p.

But true 24p in HDTV/DVD not an option? Why? The ATSC standards say it's an option, so it could be used somewhere. Just because it's a standard doesn't mean it SUPPORTED. You'd have to call Sony, Panasonic, etc & ask why they're not supporting it. Or perhaps they are but only in high end broadcast monitors because there is NO broadcast 24p material out there because it's all also broadcast in analog, so it's at 23.976/29.97 anyway, so why not feed it at that & just let the user/x-mitter downconvert the HD res? It's all converted to 23.976/29.97 at the end of post production. Then they'd need two different tapes, two different sattelite feeds, cost twice as much to broadcast.

Or, perhaps they are supporting it on consumer good, but again, it's not even being used because everything's converted to 23.976 anyway for analog anyway. Or 29.97.

"just because it's a standard doesn't mean it SUPPORTED"

LOL!!!

But you're right that no broadcasts are in true 24p. In fact, I beleive there are not even broadcasts in 23.976. As far as I understand, everything is broadcast in 29.97; even film-originated content is just pulled-down by 3-2 so it can go out over the airwaves as 29.97. Perhaps when analog broadcast finally comes to an end, then the broadcasts will be true 30 fps (with 3-2 pulldown of 24 fps content). But I guess even that would cause incompatibilities with existing TV and DVD equipment. Ugh. It looks like consumer electronics will be forever stuck in the rut of 29.97 until the end of eternity.

But it raises the question: what's the best way to use Vegas and DVD Architect to author a DVD of true 24 fps content? From what I've seen, the expensive Telecines at the Hollywood studios simply slow the speed of both the film and the audio each by .1%, so that both film and audio is 23.976 fps. Then they just do 3-2 pulldown to the DVD rate of 29.97. So if you started watching a 24 fps movie in a theater while also watching on a portable DVD player at the same time, the DVD player would still be playing after the projection of the movie was over.

So I'm thinking the best way to go about it in Vegas is to set the project settings to 23.976 fps, making sure that all source footage imported into the project is also 23.976 fps (and NOT 24 fps). Then render out to a 23.976 fps with 3-2 pulldown MPEG-2 file (using the DVDA template). In other words, the key seems to make sure project settings (and framerate of imported clips) are 23.976 and not 24 fps.

I wonder if that .1% slowdown of the film audio is enough to hear a difference in pitch?

Probably not, unless you have ears a heck of a lot better than mine.

I just did a brief experiment:

(1) opened a wav file on the Vegas timeline.

(2) enabled Time Stretch/Pitch Shift

(3) stretched out the wav file to 99.9% (which is 0.1% slower than original)

(4) went back into properties, saw that pitch change was about 2 cents (or 2% of a semitone).


I can barely hear a 10 cent change, so a 2 cent change would be unnoticeable to me.


As for the inclusion of 24fps in the ATSC standard:

I took part in many of those early standards-setting meetings at SMPTE locations both in LA and in Washington DC. I can remember that it was sorta like cat-herding: it's very difficult to keep everyone in the same room let alone move them along in a certain direction. It was obvious early on that so many companies had so many vested interests that it would be impossible to agree on a single standard, which is why there are multiple standards.

Early on, Sony wanted to filmmakers to start shooting with HDTV gear that they had developed at great expense. Since everyone knew that 24fps was a horribly slow framerate, Sony had hoped that Hollywood would finally get on board the 60i express. Hollywood wouldn't budge. Horrible or no, they argued that 24fps contributed to the "film look" that everyone was already used to.

So in short the 24fps standard is there to provide compatibility with film already shot at 24fps.

Incidentally, our little company proposed a production format called "HDPro" at the Montreaux (Switzerland) IBC conference back in 1988. We suggested using the Sony/NHK camera/VTR technology of the time to capture 1500 lines at 24fps. We argued that 1500 easily downconverted into both the 1125 US/Japan HD standard and the 1250 European proposal. What I was too stupid to realize at the time was that Europe wanted nothing that gave any encouragement to the Japanese standard, so supporting something that everyone could use was an idea that was DOA. Oh, well, I enjoyed the trip to Switzerland...

Movies in PAL land run at 25fps and no one notices so 24/23.976 isn't an issue.

Yes all film in NTSC land runs at 23.976 and is broadcast at 60i with pulldown. You can author a DVD at 24fps with no pulldown encoded into the vision. Playback devices may or maynot insert pulldown on playback. It does save a lot of space on the DVD, that's where it's usefull.

Bob.

I can imagine how frustrating that must have been!

From my perspective, I guess the most frustrating part of the ATSC standards is the .1% shift between the integer rates (24, 30, 60) and the old NTSC rates (29.97 and its variants 23.976 and 59.94). In other words, its not the 3-2 pulldown that's the sore spot, but its the .1% difference in speed that really seems to complicate things.

For example, I still don't know of a way to work in Vegas at true 24p and then export to MPEG-2 for use in DVD Architect. The best I can figure is to work in Vegas at 23.976 and make sure all imported video is at this framerate. But since I work a lot with animation and CGI at true 24fps, I'd really prefer to work in the Vegas timeline at true 24fps and then just "press a magic button" to export it all to NTSC DVD. If NTSC was true 30fps, this would be easy. But because of the .1% playback rate difference, it doesn't work.

i've rendered computer video (still frame sequences) that were recorded @ 30fps to 29.97 & it worked fine. If it is all CGI then it shouldn't me MUCH of a problem. :)

What I did was change the media framerate to 29.97. Didn't seem to be a problem for the several minutes of CGI I had at 30fps.

farss,

What happens when 2-3 pulldown is not encoded by Vegas into the MPEG-2 file? I noticed that the 24p DVD Architect MPEG-2 template is 23.976 with 2-3 pulldown. But if I change the setting to plain-old 23.976 (without the 2-3 pulldown), DVD Architect will still import this file without recompression. It appears to play fine on my set-top DVD player, too. But I don't really know if I've gained anything or just caused myself potential problems by doing things this way.

Yeah, that's basically what I do right now, except I render animations at 24 fps and then import the animated sequence into Vegas as 23.976 fps (with a project setting of 23.976 fps, too). Then I render this with the DVD Architect 24p MPEG-2 template and author in DVD Architect. For the most part, it works just fine. But it's just downright annoying that I cant work with a native 24 fps project setting in Vegas if I wish to output for video or DVD, i.e., I'd really prefer to have a true 24 fps timeline in my Vegas project.

Some rendering programs, like 3DS MAX, for example, don't even allow non-integer framerates like 23.976 fps.

In any case, I don't see this problem as a shortcoming of Vegas. On the contrary, if Vegas and DVD Architect weren't so good at accomodating all these different framerates then life would be really, really difficult.

DVD Architect WILL recompress if you render as 23.976p without the "2-3 pulldown" added.

It's important to remember, though, that it's not really adding pulldown in the same way pulldown is added if you render to DV. It's still a 24p file. What it's doing is adding pulldown FLAGS to the data so that the player knows how to add pulldown when playing the file on a 60i display.

Hi David,

Ah, yes, you're right. I just rendered a 23.976 MPEG-2 in Vegas without the 2-3 pulldown, imported to DVD Architect, and went into the optimize dialog... and it indicated the file was going to be recompressed. Ok. That makes me feel better then... I'll be sure to use the 2-3 pulldown option in the future.

I suppose... it makes sense. Like you said, the MPEG-2 file doesn't actually store all those reduntand fields. At the same time, an NTSC device does not support 23.976 framerates. So the DVD player has to duplicate the reduntant frames of the 2-3 pulldown "on the fly" in order to make the video stream play at the proper framerate of 29.97. But I suppose a "dumb" DVD player might not know to do this if the MPEG file does not contain the 2-3 pulldown flag. For example, it might just give up and say "I don't know how to play 23.976."

As an example, one of these days I know one of the animators is going to use a sound file in 3DS MAX to sync his 24 fps animation (he can't animate at 23.976 in MAX). When this inevitable day comes, I'll have to not only import the animation at 23.976 (which is easy: just choose the framerate in the clips properties), but I'll have to actually have to resample the audio file used by the animator... I'll have to stretch it by .1% before I import into the Vegas project. Otherwise the sync between what the animator worked so hard for will be lost.

This begins to get complicated in a larger project, trying to manage which audio files need to be resampled on import and which do not. It would be so much nicer to just have a true 24 fps timeline in Vegas. That way all media (including audio that the animator used for sync) gets imported at original framerates.

But in this "worst case scenario," I take heart that -- in theory -- I should be ok. For example, I *could* create a true 24 fps timeline project in Vegas, import all the animation and audio, and then edit in true 24 fps. When it comes time to master to DVD, I could render the video and audio into separate files. Then I could create a new 23.976 Vegas project and import the rendered video and audio. For the video track, I would just change its framerate to 23.976 in the clip's properties. For the audio, I could stretch the time by .1%. Then I could render this 23.796 project with the DVD Architect 24p settings and make the NTSC DVD.

The only downside to this approach is it will require rendering the whole project twice. Additionally, the first render of the video should most likely be to uncompressed frames to avoid double-compression. So it will require lots of disk space. But at least it seems possible.

Well, no DVD player knows how to play it if the flags aren't there -- and all DVD players can read the flags.

Ok. That's encouraging. Honestly, I don't know enough about the DVD spec to know what formats DVD players are required to support. I was guessing that if a DVD player saw that the framerate was 23.976 fps it might be "smart" enough to allow proper playback on a 29.97 video display by adding 2-3 pulldown on the fly. But if the 2-3 pulldown flags are supported by all DVD players, then I guess that's even better because it doesn't leave room for "interpretation" by a "smart" or "dumb" DVD player. :)

Every Hollywood movie is laid to disc as 24p; has been so almost from the beginning.

Specifically, you mean 23.976 with the 2-3 pulldown flags, right?

Well, yes. I'm just saying, you've watched a lot of 24p DVDs over the years and probably a couple of different players..

I've always known Hollywood DVDs were 24 frames per second. But what I didn't know was exactly how that was encoded on the DVD into the MPEG-2 file. So to learn that it has always been 23.976 fps with the 2-3 pulldown flags (so the DVD player can insert redunandt fields "on the fly" and playback at 29.97), this is the part I wanted to make sure I was understanding from you clearly.

I think you have solved your problem, but you still might want to look at a similar thread I started just a little over a month ago:

23.976 DVD encode all wrong