Pal/NTSC Conversion

[Posh]

I have seen a lot of questions regarding PAL/NTSC conversions lately and the preferred method seems to be to use AVISynth AssumeFPS and Resize or Decimate. Then use besweet to convert the audio. Someone please correct me if i'm wrong but I believe this lengthens/shortens the audio and video. Well what happens if you fed the video to TMPGEnc and let it convert the video. I don't believe it would change the length of the video and then you wouldn't have to change the audio at all. Am I missing something here?

[echooff]

That is exactly how I do Pal to NTSC conversions. I don,t use cce. Mainly because of incompetence, But I almost always use Tmpegenc.

[Xesdeeni]

When you start with 25 Fps and feed it to TMPGEnc, you can choose either 24 Fps or 30 Fps outputs. If you choose 24 Fps, TMPGEnc will drop one frame every second. If you choose 30 Fps, TMPGEnc will duplicate 5 frames every second (one every 5 frames). Either way, most people notice the dropped/duplicated frames.

The other end of the spectrum is to alter the length and audio.

But there is a slightly better method that doesn't require modifying the audio and leaves the length the same. If you use AVISynth to feed TMPGEnc with the script below, you can convert 25 Fps to 60 fps (fields). There will still be replication, but instead of 4 frames being shown for 1/30 second and the 5th shown for 1/15 second, you'll have 2 frames shown for 1/30, 1 shown for 1/20, 1 shown for 1/30, and another shown for 1/20 (2:2:3:2:3). This is close to the 3:2 pulldown used for converting 25 Fps film to NTSC so it is less likely to be objectionable. And you don't have to mess with the audio at all.

The script:xxxSource("PALFilm.xxx")
LanczosResize(720,480)
ChangeFPS(59.94)
SeparateFields()
SelectEvery(4,1,2)
Weave()Be sure to set TMPGEnc to encode as interlaced.

Xesdeeni

[Posh]

Thanks for the great reply Xesdeeni! That at least cleared some of the things up for me.

I could see duplicating 5 frames every second as a possible problem. Losing 1 frame per second im not sure would be terribly noticeable but then again I haven't tried it.

One question about your script though. Does it work with progressive and interlaced PAL sources? Would it matter if your script was fed into CCE or TMPGEnc?

[Xesdeeni]

I have always felt that dropping frames was much more noticable than replicating them...but all of this is EXTREMELY subjective.

If the PAL source is interlaced, you will get the best quality by deinterlacing first. See my Standards Conversion page (http://www.geocities.com/xesdeeni2001/StandardsConversion) for a slightly modified script.

The script should work with CCE or TMPGEnc. Just be sure you encode interlaced.

Xesdeeni

[daehkcid]

Do you lose quality by doing this?

[Xesdeeni]

Do you lose quality by doing this?By doing what? Deinterlacing? Converting from PAL->NTSC?

Xesdeeni

[daehkcid]

Converting PAL/NTSC.

[Xesdeeni]

Even the most expensive standards converters lose quality somewhere. But whether you will see the loss is subjective.

[Speaking in general of standards conversion, not including compression issues of decode and re-encode.]

If you are converting 25 Fps -> 23.976 Fps, no-one will see any loss. However, they may hear a problem with the audio, since it must be slowed down. If you are converting 23.976 Fps -> 25 Fps, there will be slightly less vertical resolution than a native PAL image would have, so it's possible some people will see that. And again, the speedup of the audio may be noticable. The vertical resolution issue applies to all NTSC -> PAL conversions.

If you convert 25 Fps/50 fps -> 59.94 fps, what you see will depend on which method you choose. Using the above-referenced technique, I prefer ChangeFPS(), but smooth panning shots will show a "bump." ConvertFPS() will introduce a "jutter," which is caused by interpolation of multiple fields. This is the method most inexpensive hardware converters use, so much converted video we see will have this problem (I see this artifact on foreign video shown on the evening news almost every day). If we had an expensive motion estimation device, almost any video would convert without artifacts you could see...but those cost big $$$. In all these cases though, you will not touch the audio, so there will be no loss there.

Xesdeeni

[daehkcid]

Really not worth it. I'd rather go rent areal NTSC then converting :) Thnx for the info!