Can someone quickly clear this up for me - PAL to NTSC

[tarrickb]

Hello,
I've done these sorts of conversions in the past and need to convert another PAL DVD to NTSC, however i've gotten a little confused. If someone could explain the answers to the following it would be of GREAT help.

1. If I have PAL progressive source, can I not just slow it down to 23 fps (including the audio) then enode with TMPENC with the 3:2 pulldown (changing the resolutions of course).

2. Why is it that when using the tutorial by FulciLives (https://forum.videohelp.com/viewtopic.php?t=300144), you must de-interlace if there is a PAL interlace source?

3. Is the only advantage of using DGPulldown that you don't have to re-code the audio?

I'm just trying to understand some logic behind all of the steps.
That's all!
Thanks for your time.

[dphirschler]

I don't know about John's tutorial, but I will say this. I frequrntly encounter progressive source in PAL which is interlaced. It's not telecined, or anything like that. Both halves of the frame come in successive fields. So what I need to do is decomb which reassembles the fields into frames. No need to telecide though. Then I slow down to 23.976 (including the audio).

PAL video (25i) is a different story though.


Darryl

[jagabo]

1. If I have PAL progressive source, can I not just slow it down to 23 fps (including the audio) then enode with TMPENC with the 3:2 pulldown (changing the resolutions of course).

Yes, you can just slow it down to 23.976 and apply 3:2 pulldown flags.

2. Why is it that when using the tutorial by FulciLives (https://forum.videohelp.com/viewtopic.php?t=300144), you must de-interlace if there is a PAL interlace source?

Your 23.976 fps frames have to be progressive for 3:2 pulldown to work properly. In an interlaced frame the two fields come from different times. 3:2 pulldown will display some of the fields in the wrong temporal order if you leave the video interlaced. Say you have a frame with two fields and it is top field first (TFF). The top field is the picture that was taken first, the bottom field is the picture that was taken second. They should be displayed in that order. But with 3:2 pulldown, during the "3" phase the top field will be displayed on TV first. Then the bottom field (this is fine, it's the correct temporal order). But then the top field will be displayed again, running backwards in time.

3. Is the only advantage of using DGPulldown that you don't have to re-code the audio?

Yes. If your PAL source comes from 24 fps film (that was sped up to 25 fps) you have the disadvantage that you're not restoring the original frame rate.

[Guest34343]

3. Is the only advantage of using DGPulldown that you don't have to re-code the audio?

No. It also has the advantage that the video is left as encoded at 25fps, which means you can have better quality for the same bit budget, compared to a traditional conversion. Also, if you ever need the original progressive frames again, you can recover them from the NTSC disc (by using Ignore Pulldown Flags in DGIndex).

[tarrickb]

Thanks for the clarification guys!
That was all I needed and am now on my way

[jagabo]

3. Is the only advantage of using DGPulldown that you don't have to re-code the audio?

No. It also has the advantage that the video is left as encoded at 25fps, which means you can have better quality for the same bit budget, compared to a traditional conversion.

Better than performing 3:2:3:2:2 pulldown and encoding as interlaced. Not better than slowing down to 23.976 fps and encoding progressive with 3:2 pulldown flags.

[tarrickb]

would the slowing down method produce better quality output???

[jagabo]

Only very slightly since it's only 4 percent fewer frames per second. So you could use 4 percent less bitrate and have the same quality, or the same bitrate and have slightly higher quality. On the other hand, the sound quality will get worse since you have to make it 4 percent slower.

[tarrickb]

ahh...understood.

I think i would prefer a 4% degradation in video compared to audio (not to mention the time saved not having to slow things down).
Thanks again for all of the responses.