NTSC Film SVCD mpg2 ---> Do I need to Inverse Telecine?

[darkwunder]

I have an SVCD mpg of a television show that I am trying to encode so that I can make a multi-episode DVD+R. Based on properties listed by DVD Workshop, I had assumed that it was an NTSC format mpg with a framerate of 30fps. I initially encoded the file by loading it directly into TMPGENC and using the DVD NTSC Template (with some unlocked settings). However, TMPGENC insisted on deinterlacing the mpg whether I wanted it to or not. From reading through the forums, I found out that the auto-deinterlace was occurring as a result of the PowerDVD MPEG2 codec I have installed on my computer. By frameserving to TMPGENC from DVD2AVI, I can apparently maintain the interlacing in my final mpg (which I'm assuming is desirable given that I will be watching the final DVD on a TV). This lead to my next dilemma.

When I previewed my source in DVD2AVI, the "Video Type" was listed as FILM, and the framerate was listed as 30fps. When the mpg was played, the "Frame Type" kept alternating between progressive and interlaced. I did some looking around on this site, and from what I have read, I'm assuming that my source file has had 3:2 pulldown applied at some point.

Unfortunately, I have managed to become a tad bit confused as to what this means to my encoding process. First, how do I tell if my source file has actually been "physically" converted from from 24fps to 29fps by inserting additional frames, or whether it has just had a pulldown flag applied to the header? From what I understand, if a pulldown flag has been added, the framerate is still 24fps and no extra frames were added at the time of encoding. DVD players will convert between 24fps and 30fps on the fly as the DVD is played. Should I apply the inverse telecine filter to the source file to return it to its original framerate? If I apply the inverse telecine filter to a file that is still 24fps but has had a pulldown flag written into the header, will it actually do anything? Will it reduce the quality of my output (ie. will it decimate frames)? Is there an editor to remove the pulldown flag from the header in these cases? Will that affect my audio sync?

As a test, I encoded a short portion of the file using the inverse telecine filter, and loaded it into DVD2AVI. Before applying the pulldown flag, I previewed the file. It was listed as NTSC (not FILM) at 24fps, and every frame type was listed as interlaced. After applying pulldown.exe, it was listed as FILM at 30fps, and the frame type flipped between interlaced and progressive (just like my source file). This is leading me to think that my source file is really in NTSC Film format with pulldown flags inserted into the header.

Hopefully I have managed to make some sense in my ramblings. Any insight that can be provided will be greatly appreciated.

Regards (and thanks for your patience ) ,
DW

[adam]

When dvd2avi reports the source as film, then yes it is 24fps with 3:2 pulldown flags embedded in the stream, so that it will playback at 29.97fps. When previewing in dvd2avi always ignore the framerate it reports. This is NOT reporting what your source is, it is reporting what your OUTPUT will be at the current settings. For instance, since your movie is 24fps, and you want to keep it that way, you need to turn forced film on in the video tab. DVD2AVI will now report the fps as 23.976fps and that is the output you will get. With this option enabled, dvd2avi will ignore the 3:2 pulldown flag and export your film as it is encoded, at 23.976fps. Now I suggest you encode just the video in TMPGenc at 23.976fps, with or without the 3:2 pulldown while playback option enabled. It doesn't matter because you need to use pulldown.exe anyway, so you might as well add the 3:2 pulldown flags there anyway, since TMPGenc's don't seem to work correctly with all authoring programs.

Now get pulldown.exe and the gui and in the options tab check prog_seq and prog_frames. Set prog_seq to interlaced and set prog_frames to progressive. This will get rid of that hybrid flickering between progressive and interlaced thing you notice in dvd2avi. This is how NTSCfilm SVCDs and DVDs are supposed to be encoded, with the progressive frames flag set to true and the sequence tag set to interlaced. Run the program and it will make these changes and also add the 3:2 pulldown flag (pulldown.exe calls them 2:3 flags.)

Once your done here, encode the audio to mp2 in TMPGenc and then multiplex your audio and video together into an mpg stream.

[darkwunder]

Adam,

You told me exactly what I wanted to know (and I actually understood...will wonder's ever cease ).

Thanks for your help. Regards,
DW.