Q: Settings for CCE SP for non-interlaced 29.970fps NTSC

[FulciLives]

Hello

I know how to set up CCE SP if I have a progressive 23.976fps NTSC source.

I now how to set up CCE SP if I have an interlaced 29.970fps NTSC source.

But I have a non-interlaced 29.970fps source.

So I'm confused hehehe

Any help is appreciated

- John "FulciLives" Coleman

[FulciLives]

I just wanted to clearify some of the points I'm confused about ...

1.) Should I use M=3 N/M=4 or M=3 N/M=5
2.) Should I check mark the option UPPER FIELD FIRST
3.) Should I check mark the option PROGRESSIVE FRAME FLAG

I've never encoded a 29.970fps source that was deinterlaced so that is why I'm so confused. I've only done interlaced 29.970fps or progressive/non-interlaced 23.976fps

- John "FulciLives" Coleman

[adam]

If its progressive, regardless of framerate, then always check the progressive frames option and zigzag scan order and leave the top field first option unchecked.

For 23.976fps sources always use M=3 N/M=4.
For 29.976fps sources I believe you can get a way with M=3 N/M=5 and still be compliant. Using M=3 N/M=4 would definitely be compliant but would be less efficient.

[FulciLives]

For 23.976fps sources always use M=3 N/M=4.
For 29.976fps sources I believe you can get a way with M=3 N/M=5 and still be compliant. Using M=3 N/M=4 would definitely be compliant but would be less efficient.

In the past I've always used the following:

M=3 N/M=5 ---> 29.970fps interlaced NTSC
M=3 N/M=4 ---> 23.976fps non-interlaced/progressive NTSC

I just am unsure WHAT the setting means and I am unsure if the setting is due to frame rate difference or the difference between interlaced/non-interlaced.

Hence my confusion as to which one to use for non-interlaced 29.970fps source material.

Also I didn't realize that you could use M=3 N/M=4 for 29.970fps interlaced. I thought it was only for 23.976fps NTSC and yeah I'm in the USA so I never do PAL encoding.

- John "FulciLives" Coleman

P.S.
Thanks Adam I appreciate it

[adam]

Ok, here's what I know. The N/M setting adjusts the length of the GOP. Look at the frame sequence up top and see how it changes. The / represents the end of the GOP. By increasing it from 4 to 5 it increases the GOP length from 12 to 15.

Interlaced vs progressive has nothing to do with the GOP settings requirements, its all about framerate. If you are NTSC, or more specifically, encoding at 29.97fps then you are limited to 18 frames per GOP. For PAL, or 25fps, its 15 frames per GOP.

So here's what I think... You basically treat 23.976fps like 25fps. Even though its going to be played back at 29.97fps, you are physically only encoding ~24 frames per second.

I think I've read that optimum GOP length is equal to half of your framerate. Which is why most encoders give you the option of 12 (closest possible to half of PAL's 25fps) and 15 (half of 30). I guess there needs to be room for fluctation in there, maybe for scene changes and what not I really don't know, but that's why they don't expressly use 15 and 18.

There's never any risk of non-compliance with using too small of a GOP, which is why 29.97fps at N/M=4 will work, its just less efficient than N/M=5...which I believe is perfectly compliant.

Longer GOPs result in better quality. Imagine if there is redundant information on frames 1 and 19. With a GOP length of 18, both of those redundant frames are stored in 2 separate units. Each gets taken care of by their own I-frame. With a GOP length of 19 they are both stored in the same unit, within the same I-Frame. The longer your GOP the more redundant frames get grouped into each unit, but then that increases the burden on the decoder which is why the DVD standard has its set limits.

[FulciLives]

Thanks for that Adam ...

It sounds like M=3 N/M=5 is fine for 29.970fps NTSC be it INTERLACED or NON-INTERLACED/PROGRESSIVE.

I actually already started a small test encode of a section of the source using M=3 N/M=4 so when that is done I'll re-do it with all the same settings except I'll do M=3 N/M=5 and see if the two look any different.

As I've said before I have always used M=3 N/M=5 for INTERLACED 29.970fps NTSC without any issues on playback (or warnings from TMPGEnc DVD Author).

So when it is all said and done I will probably use M=3 N/M=5 on the final encode.

- John "FulciLives" Coleman

[thor300]

May i ask, when encoding 23.976 progressive, is there any difference when setting the progressive option in CCE compared to when doing it in pulldown.exe with the -prog_frames switch?
i also use M=3 N/M=4 when encoding 23.976, i thought its only for avoiding too long GOPs when later applying 2:3 pulldown, so i would also use M=3 N/M=5 for a 29.97 progressive.

[adam]

May i ask, when encoding 23.976 progressive, is there any difference when setting the progressive option in CCE compared to when doing it in pulldown.exe with the -prog_frames switch?

The effect will be the same. If you set progressive in CCE you probably don't have to set the prog_frames flag in pulldown because it will be set already...of course it doesn't hurt anything if you do it.

i also use M=3 N/M=4 when encoding 23.976, i thought its only for avoiding too long GOPs when later applying 2:3 pulldown, so i would also use M=3 N/M=5 for a 29.97 progressive.

Correct. Just go by the framerate.