Copying 2:3 pulldown video ?

[Mike99]

My understanding is that when playing a 23.976 fps DVD, the DVD player uses 2:3 pulldown and outputs 29.97 fps for viewing on NTSC TV. What happens if you copied such a DVD using a composite or S-video connection between 2 DVD players? If you looked at the copy on your PC using MediaInfo, would it indicate 29.97 fps?

More to the point, how would you determine the frame rate of a LaserDisc? If the LD was 23.976 fps, the player would have to convert to 29.97 fps at it’s output. If I made a DVD copy of this in order to check the info, MediaInfo would indicate 29.97 fps, correct? And if the LaserDisc was 29.97 fps then the DVD copy would also be 29.97 fps. IOW MediaInfo could not tell the difference in this scenario & I would have no way of knowing what the LD really is. Is that correct, or does MediaInfo somehow indicate 2:3 pulldown was used?

[manono]

All NTSC DVDs output interlaced 29.97fps. Maybe the majority of film DVDs have been encoded as progressive 23.976fps with pulldown applied, maybe others have been encoded as interlaced 29.97fps with the telecine encoded into the video. MediaInfo always indicates 29.97fps. Better for you might be to check the DVD with GSpot. The ones encoded as progressive 23.976fps with pulldown will show as 23.976 Pics/s, 29.970 Frames/s, and 59.940 Fields/s. The hard telecined ones will show 29.970 Pics/s, 29.970 Frames/s, and 59.940 Fields/s.

As far as I know, laser discs are always hard telecined and thus 29.97fps. Only after a reencode with an IVTC performed can you return it to 23.976fps. There's no soft pulldown on laser discs or VHS tapes.

[Mike99]

All NTSC DVDs output interlaced 29.97fps. Maybe the majority of film DVDs have been encoded as progressive 23.976fps with pulldown applied, maybe others have been encoded as interlaced 29.97fps with the telecine encoded into the video.

I hear what you are saying but I am a little confused. If all NTSC DVDs are interlaced, how can "film DVDs have been encoded as progressive 23.976fps with pulldown applied"? Does that mean that 23.976fps with pulldown only works with progressive? I'm not challenging what you are saying, I just don't understand.

[jagabo]

The only thing that travels over composite and s-video is interlaced video -- 59.94 fields per second. It will always record as 29.97 fps.

DVDs can be recorded with 23.976 fps (or any other rate between 19.98 and 29.97) progressive frames with flags that tell the DVD player how to produce 59.94 fields per second for composite or s-video output.

[manono]

I hear what you are saying but I am a little confused. If all NTSC DVDs are interlaced, how can "film DVDs have been encoded as progressive 23.976fps with pulldown applied"?

All NTSC DVDs output interlaced 29.97fps (or 59.94 fields per second). They may have been encoded as progressive 23.976fps, but the pulldown applied tells the player how to output the 59.94 fields per second - which fields are to be repeated and in what order they're all to be played.

This is why MediaInfo always says NTSC DVDs are 29.97fps and also why I suggested using GSpot for the purpose of better explaining what you have.

[edDV]

...
More to the point, how would you determine the frame rate of a LaserDisc? If the LD was 23.976 fps, the player would have to convert to 29.97 fps at it’s output. If I made a DVD copy of this in order to check the info, MediaInfo would indicate 29.97 fps, correct? And if the LaserDisc was 29.97 fps then the DVD copy would also be 29.97 fps. IOW MediaInfo could not tell the difference in this scenario & I would have no way of knowing what the LD really is. Is that correct, or does MediaInfo somehow indicate 2:3 pulldown was used?

All NTSC Laserdiscs were analog composite video "encoded" to pits that could be "decoded" by laser back into analog video. By analog composite video, I mean just as broadcast with 3.58 MHz subcarrier carrying the color information. The format performance was very similar to 1" Type C broadcast videotape so quality "could be" far superior to VHS/Betamax (color under) or even Betacam SP which recorded in components but had restricted luma bandwidth.

In the NTSC system all "film" source was field repeated 2:3 as telecine so the TV display didn't need to know if the source was 29.97 fps or 23.976 fps, it all looked like 29.97 fps (59.94 fields per sec) to the TV.

Digital component DVD had more output options. Default for analog composite or S-Video out was 29.97 fps regardless of whether the source disc was 29.97 or 23.976 progressive. The progressive flag informed the player if the source was film rate. Progressive DVD players could be set to output analog component or HDMI as 59.94 frames per second where any 23.976 or hard telecined source could be processed as 23.976 progressive, then frame repeated 2 frames then 3 frames to 59.94 fps progressive.

A "60Hz" progressive capable TV could display this directly. A "120Hz" progressive TV would first remove the 2/3 frame repeats, then display each 23.976 frame with 5x repeats to 119.88 fps, or optionally, it would apply a frame interpolation algorithm to smooth the motion.

NTSC Blu-Ray players did the same but some included a 23.976p/24p output option for HDMI so that film progressive source could be passed as is to a "24p" capable TV. The TV would then repeat frames 5x to 119.88 Hz or optionally apply frame interpolation.