[Bobby Hall]

Since progressive TVs show progressive frames and a film movie from a progressive DVD player will be shown at 24fps, that got me wondering about how DVDs are displayed with other types of players and TVs used.

Regarding a 24fps movie DVD:

Will playing that movie on an interlaced DVD player on an analog TV show the movie at 30 fps (60 fields per second)?

How many fps will the movie be displayed at with an interlaced DVD player on a progressive TV? Will the TV remove the repeated fields and display 24 fps?

Obviously using a progressive player and progressive TV will display at 24 fps, but what about a progressive player with an analog (interlaced) display? Will it show 24 fps or use the 2-3 pulldown flags and display at 30 fps? And if it’s 30 fps, is it showing complete frames or is it actually 60 segmented frames per second (showing the odd lines of one frame for 1/60 of a second and then the even lines of the same frame for 1/60 of a second)?

[Bobby Hall]

Thanks for all the info. I was curious, why are DVDs encoded with the 29.97 frame rate instead of the field rate? If digital video is recorded at 59.94 fields per second and also shown on analog TVs at 59.94 fields per second, what’s the point in taking an extra step and encoding them to a frame rate if they’re just going to be displayed as a field rate later on? When movies first started to be edited digitally, was there some type of requirement that 24 fps movies had to be converted to 29.97 for editing?

[Bobby Hall]

Dave, when I asked if a 24fps film on a DVD is really 24 frames or 48 interlaced fields, I was using the term “interlaced” to mean progressive segmented frames (never heard that term till you used it). I understand that the two fields of a progressive frame represent the same instance in time. So what I meant to ask was, is the file on the DVD 24fps, or is it actually 48 segmented frames per second? If the file is 24 fps, then wouldn’t that mean the DVD has flags that tell the player to split up those frames into segmented frames (two fields per frame representing no change in time), and then displaying those 48 segmented frames using 2-3 pulldown?

Also, if I have a DVD of a tv show that was shot with video, this means it was shot 60 fields per second, right? And when put on a DVD, it combines those fields into 30 fps. So in this case, the two fields of a frame are different instances of time. So wouldn’t this make each frame blurrier than a 24p frame? If you pause a 24p file, you’re seeing an entire frame of a still moment in time. And when you pause a 30i frame, you’re seeing two interlaced fields recorded 1/60 of a second apart, right?

[Bobby Hall]

Thanks Dave and Nick!

I thought DVDs were interlaced (480i) and don’t store progressive files. Is this not true? Is there really a 24p file on the DVD (I’m using whole numbers for the sake of simplicity) or is it really 48 interlaced fields with flags to do 2-3 pull down? If there really is a progressive file on there, why aren’t DVDs called 480p instead of 480i?

And when I’m ripping DVDs in MPEG Streamclip, should I uncheck “interlaced scaling”? And what about the “deinterlace” option?

[Bobby Hall]

Also, I’ve been reading different articles about this subject and now I’m not so sure what’s going on. I looked at the frame rates of several of my my movie DVDs (originally 24fps movies) in MPEG Streamclip and it said all of them were 23.976 fps. But I also read some articles that said movies put on DVD aren’t actually 23.976 fps but are really interlaced into separate fields. And that all NTSC DVDs are 480i and are displayed at 29.97 fps.

Now, when MPEG Streamclip is telling me the movies are 23.976, does this mean it’s just telling me the frame of the video file before it was actually put on the DVD? Is it really 29.97fps (or 59.94 fields per second) and the 23.976 is just info about the video before put on a DVD? Or is the actual movie file 23.976 on the DVD and the DVD has flags that tell a DVD player to split the film into fields, which would be 47.952 fields per second (23.976 x 2), and then it also has flags to tell the player to do 2-3 pulldown?

I’m not sure, but I think what’s happening is that during the telecine process, the 24fps movie is slowed down to 23.976fps, and then it’s split up into fields, achieving 47.952 fields per second, and this video file is what’s put on the DVD. And the DVD has flags telling the player to do 2:3 pulldown. So this would mean non-progressive DVD players are 60hz, right?

When I play a DVD on my Blu-ray player, it says 1080/60p, 48 khz. So, this tells me that the player is upscaling the 480i content to 1080, using 2-3 pulldown to convert the 23.976fps to 29.97 fps (59.94 interlaced fields), and then combining each of those fields into single frames, and having each one on the screen twice so that it’s now 60 fps. But then the 48hz thing throws me off. I thought 48hz means it’s just refreshing the screen 48 times per second, twice the rate of 24 fps. When I click through a movie frame by frame, it takes 24 clicks to go one second. So why does it say 60p if each second is actually 24 frames? Is it doing pulldown, and then reversing it or something? What does it mean if my player is 60hz and the Blu-ray player is 48hz?

[Bobby Hall]

Thanks Nick. If I rip a DVD using mpeg streamclip and the movie is 23.976, does that mean it’s progressive? Or is it really interlaced and I should check “deinterlace video” if I’m working in a progressive timeline?

And when would someone use “interlaced scaling”?

[Bobby Hall]

Just a couple other questions. If the NTSC decided to lower the bandwidth to allow for color video, why didn’t they decrease the bandwidth used for audio so that video could still be at 30fps?

And when slowing down film from 24fps to 23.976 and video from 30fps to 29.97, does that change the pitch of the audio at all, or is the pitch the same and just the length different?

[Bobby Hall]

Thanks for your help everyone!

[Bobby Hall]

Thanks Nick. When you say rip it at its original frame rate, do you mean the 23.976 rate or the original 24 film rate?

[Bobby Hall]

Thanks Jerry and Dave!

So if I rip a 24 fps movie DVD, I should rip it at 23.976 to have the frame rate that’s stored on the DVD? If I rip it at 24 fps, will it slightly speed up the movie to make it the exact same length as the original film? And is there any downside to doing this? Would that technically alter the audio pitch at all?

Also, in case I want to use the footage in a 29.97 fps timeline in FCP, would I rip the 24 fps DVD footage at 29.97? Or would that just create duplicate frames?