Can you use Forced Film on NTSC type movies?

[perdomot]

According to the Doom9 guide, if you run DVD2AVI and it says FILM, you can activate Forced Film to change the framerate to 23.97 but if it says NTSC, you will have to do an IVTC later. When I activate IVTC on TMPG, it takes a long time and I was wondering if I can just activate Forced Film and save some time while still getting good results? I am encoding DVD to XVCD. Thanks.

[perdomot]

Nobody has done this?

[adam]

You cannot do it. Forced film works by ignoring the RFF/TFF flags in the stream. Most NTSC DVDs are encoded at 23.976fps progressive frames and use these flags to telecine it to 29.97fps interlaced on the fly. Forced film simply avoids the telecine altogether.

But if dvd2avi reports NTSC then that means the stream is not encoded at 23.976fps but is physically encoded at 29.97fps interlaced. The only way to get 23.976fps out of this is to perform an inverse telecine. You could save many hours by doing your inverse telecine through avisynth with decomb instead. You'd get better quality too. You can still use TMPGenc for encoding.

[perdomot]

Hi Adam. That's what I ended up doing. Seems to work well. Thanks for the info.

[nocarebear]

You cannot do it. Forced film works by ignoring the RFF/TFF flags in the stream. Most NTSC DVDs are encoded at 23.976fps progressive frames and use these flags to telecine it to 29.97fps interlaced on the fly. Forced film simply avoids the telecine altogether.

But if dvd2avi reports NTSC then that means the stream is not encoded at 23.976fps but is physically encoded at 29.97fps interlaced. The only way to get 23.976fps out of this is to perform an inverse telecine. You could save many hours by doing your inverse telecine through avisynth with decomb instead. You'd get better quality too. You can still use TMPGenc for encoding.

If DVD2AVI reports NTSC, why not just encode it as NTSC and keep it at 29.97 fps? Is there a benefit to INTCing it rather than leaving it as NTSC?

[adam]

Absolutely there is a benefit. You physically are storing about 20% less frames every second, which is effectively like raising your bitrate by about that much. Secondly, you are encoding frame pictures (basically its progressive in that both fields are displayed at the same time as opposed to in sequence) which are much easier for the encoder to work with and inherantly require less bitrate. These two factors result in a much higher image.

Finally, you retain the original framerate and progressive nature of the source picture (assuming it did originate as film) which means that it can be properly played back on progressive scan devices such as pc monitors and progressive scan tvs. If you encode in NTSC (29.97fps) then it may have to be deinterlaced which kills quality.