which field is first?

[kinglerch]

I'm a little confused on interlacing with regards to which field is first. I have 25fps progressive I want to pulldown to 30fps interlace, so I made a script like this:

SeparateFields()
SelectEvery(10, 0,1, 0,3, 2,5, 4,5, 6,7, 8,9)
Weave()

That turns: Aa Bb Cc Dd Ee
Into: Aa Ab Bc Cc Dd Ee

Which is the smoothest possible 3-2-3-2-2 pattern....but is this TFF or BFF? I would have thought TFF but this is jerky and BFF conversion looks smooth. What am I missing?

[Gavino]

It's BFF, since that's what Avisynth assumes by default.
If you want TFF, add AssumeTFF() before the call to SeparateFields().

[jagabo]

AviSynth assumes BFF.

Note that that will give you 30 fps, not 29.97 fps. You'll be better off with:

ChangeFPS(60000,1001) # duplicate frames
SeparateFields() # convert to fields
SelectEvery(4,0,3) # decimate to 59.94 fields per second
Weave() # weave to 29.97 fps

[kinglerch]

I assumed that when I chose field "0" that it was the top field and then field "1" that meant the bottom field...so I was choosing the field order TFF by 0,1 etc...this is not the case?

[jagabo]

I assumed that when I chose field "0" that it was the top field and then field "1" that meant the bottom field...so I was choosing the field order TFF by 0,1 etc...this is not the case?

No. AviSynth assumes the video is bottom field first. So after separate fields field 0 is the bottom field, field 1 is the top field, etc.

[poisondeathray]

If you are doing this for DVD, another option is DGPulldown

[manono]

If you are doing this for DVD, another option is DGPulldown

Right, I was wondering myself about the point of this little exercise. What he's asking doesn't make much sense to me.

[kinglerch]

Going from 25fps progressive to 30fps interlaced can be done any number of ways. My field combination yields a 3-2-3-2-2 pattern with 4/6 "progressive" frames, which is the cleanest possible conversion. I don't know if DGPulldown does the pulldown this way, so I used a 3 line AVISynth script. What's not to make sense?

[poisondeathray]

The benefit of using TFF/RFF flags, is that you can encode as progressive . This yields better quality instead of encoding interlaced and having to encode 20% more fields for nothing

(It's the same idea as 3:2 soft pulldown for 24p sources - encoding interlaced means you encode 25% extra content , which of course will yield lower quality)

[jagabo]

Going from 25fps progressive to 30fps interlaced can be done any number of ways. My field combination yields a 3-2-3-2-2 pattern with 4/6 "progressive" frames, which is the cleanest possible conversion. I don't know if DGPulldown does the pulldown this way, so I used a 3 line AVISynth script. What's not to make sense?

If you use DgPulldown you can encode as 25 fps progressive MPEG 2 then use DgPulldown to add pulldown flags to tell the player how to make 59.94 fields per second. That gives the best quality for DVD. And is within spec.

[kinglerch]

This is an HD film transfer to blu-ray, so 30 fps is within spec too. But how the pulldown is achieved is important, and 25->30 can be done many different ways. I *think* my script is the smoothest possible. DGPulldown could use the same pattern, but I don't know.

[poisondeathray]

This is an HD film transfer to blu-ray, so 30 fps is within spec too.

Can you clarify what you mean? Your final goal is blu-ray? or the source was blu-ray and the final goal is for DVD?

You mentioned 25fps progressive source?

[kinglerch]

The source is a 16mm 25fps film, goal is blu-ray. I can do this in 25fps as-is for PAL, and 30fps for NTSC with some interlacing.

[manono]

This is an HD film transfer to blu-ray, so 30 fps is within spec too. But how the pulldown is achieved is important, and 25->30 can be done many different ways. I *think* my script is the smoothest possible. DGPulldown could use the same pattern, but I don't know.

You could always try a small piece and find out. Then you'll see it does use the same pattern. Four of six frames progressive and the other two interlaced. There are at least two reasons why the use of DGPulldown is preferred. One has already been mentioned - encoder efficiency. Not only are you encoding 20% more frames, but with those additional frames being interlaced and with interlacing being more difficult to encode (needing more bits for the same quality as compared to a progressive frame), you'll be losing something like 30% of the quality (for the same file size) as compared to just encoding the original progressive frames. The other reason is that you'll be at the mercy of the deinterlacer in your player and/or TV set and using a deinterlacer always results in a drop in quality, no matter how good it is. It's always preferred to encode progressive whenever possible. We're all assuming you're encoding in MPEG, and not AVC or VC-1.

[poisondeathray]

The source is a 16mm 25fps film, goal is blu-ray. I can do this in 25fps as-is for PAL, and 30fps for NTSC with some interlacing.

Not exactly - strictly speaking 25FPS progressive isn't compliant for blu-ray - even for "euro" models . It doesn't conform to blu-ray specs.

Usually what is done for "euro" BD releases are it's either encoded as 50i interlaced (this is what BBC typically does) , or encoded as progressive with "fake interlaced" flag

I don't know if dgpulldown will work for hd sources, and most people would use AVC for encoding, not mpeg2 (There is a dgavcpulldown, but that is only 3:2 cadence)

The other options are resampling the fps , or even doing a slowdown to 24fps (audio & video) .

I don't know if all blu-ray players can handle 3:2:3:2:2 pulldown correctly . Personally I think 24p is probably the "safest" choice for a BD release

[manono]

Not exactly - strictly speaking 25FPS progressive isn't compliant for blu-ray - even for "euro" models .

Sure, but (assuming MPEG2), he can take his progressive 25fps source and encode it as interlaced, can't he? As is usually done with PAL DVDs? And by the same token I don't see why he can't encode it at 25fps and then apply DGPulldown to output interlaced 29.97fps.

I don't know if dgpulldown will work for hd sources

I don't see why not, since MPEG-2 is MPEG-2. He says, never having tried himself. But the included doc doesn't seem to restrict it to certain resolutions.

I think I also agree with you that now we know it's to be for Blu-Ray, the best might be to slow the video and audio to 24p and encode for AVC.

[poisondeathray]

Not exactly - strictly speaking 25FPS progressive isn't compliant for blu-ray - even for "euro" models .

Sure, but (assuming MPEG2), he can take his progressive 25fps source and encode it as interlaced, can't he? As is usually done with PAL DVDs? And by the same token I don't see why he can't encode it at 25fps and then apply DGPulldown to output interlaced 29.97fps.

That's what the 2nd line says, that's how 25p sourced BD's (like BBC produced material) are typically done in 50Hz areas

Usually what is done for "euro" BD releases are it's either encoded as 50i interlaced (this is what BBC typically does) , or encoded as progressive with "fake interlaced" flag

The danger with 60Hz North American BD setup is deinterlacing, and subsequent loss of quality . There are test discs that check the various cadences and patterns , and some forums report the results . Many "lower quality" imported models from China etc.. do not support exotic patterns , but 24.0pN and 23.976pN (native) is supported across the board on all BD players and I think would be the "safest"