NTSC -> PAL same movie length?

[busta3396]

The way I used to convert ntsc to pal was through ffmpegx then I would have to use another program to convert the audio to 25 fps as well, however what I use now is first mac the ripper to rip the main film onto the computer, then I use a small program someone wrote that uses dvd author to convert the vob file to pal, the process takes about an hour. When it is done I get an image with the new video which is 25 fps and the audio is perfectly in sync and is the same length as the original ntsc video, is this possible? so going from 30 fps to 25 and keeping the audio in perfect sync and not changing the video length, i dont understand but it seems like it is working. My only fear is that perhaps it is really ntsc but just tricks the computer into thinking it is pal, but then why would it take so long to convert, any ideas? Thanks

[goat]

The length of the movie does not change .... just the frame rate.
Converting PAL to NTSC the software copies some of the frames to make 29.9 frames/sec
Converting NTSC to PAL I guess it just removes some of the frames to 25 frames/sec

Its still the same second either way you go; 1 sec (29.9 frames) = 1 sec (25 frames)

Thats my understanding of the conversion process.

[Alex_ander]

There are mainly 2 different methods optimized either for 1)telecined sources (movie converted from 24 to 30 by combining repeated frames in proper order) or 2)TV sources originally shot at 29.97 framerate. Using 1) (24 is assumed 25fps in the end) gives a 4% shorter PAL output and you have to adjust audio length.
You have to choose a conversion method depending on your source to prevent jerky motion in the result of framerate conversion. The optimal Avisynth scripts are also different for progressive and interlaced sources.

[Anonymous5394]

I just posted an exact post. Im like busta396 never thought it possible to have same film length. Always assumed if you change from NTSC to PAL or reverse that 4% time diffrence would occur in every case!

[Herve]

I just posted an exact post. Im like busta396 never thought it possible to have same film length. Always assumed if you change from NTSC to PAL or reverse that 4% time diffrence would occur in every case!

NTSC exists in 2 flavours: NTSC FILM ("24"fps) and NTSC VIDEO ("30"fps)
when you convert NTSCFilm<->PAL, you should change the length to preserve frames contents and keep quality (±4%)
when you convert NTSCVideo<->PAL, you should re-create the frames for a better smoothness (no need to change the length)

(my personal opinion: PAL is more cool to handle than NTSC )
bye

[manono]

Always assumed if you change from NTSC to PAL or reverse that 4% time diffrence would occur in every case!

It occurs in most cases, but far from all cases. Sometimes the conversion is done by fieldblending to make a blurry mess, and the length stays the same. One advantage of doing a film to PAL conversion this way (about the only one, because the video winds up looking pretty bad) is that the original audio can be used, so no higher pitched and speeded up audio. About 95% of the DVDs I see these days (classic Indian films on NTSC DVD) have been field-blended from PAL sources, so even though NTSC they still have that out-of-pitch PAL audio on them. The worst of both worlds.