Interlaced to progressive done correctly

[EDV]

I've been given some footage shot on miniDV ( Sony VX2000 camera ) to edit and publish online. I am wondering what the correct way of processing this footage is. Using After Effects to edit the footage captured in Premiere.
My understanding is that the Sony VX2000 at 25fps ( PAL camera ) shoots interlaced footage. Is this correct? After Effects seems to read the AVI files as 720 x 576 interlaced. In the "Interpret Footage" dialog box, the files default to D1/DV Pal 1.09 ( does that mean interlaced? )

Now, my target video will be viewed on LCD computer screens so, I guess my target output is square pixels?
And that means the default resolution now becomes 788 x 576 ?
Assuming the AVI was left unchanged as I imported it ( square pixels option should be ignored? ), and PAL DV square pixels is the selected output, the image should not look stretched in any way. But I read that now 10 pixels should be cropped left and right to make 788 x 576 become 768 x 576 ? So that means framing your shots with this in mind? Wow. Not as straight forward as I would have imagined...

 

[EDV]

??

 

[GrahamH]

Basically, yes.

According to this site - http://lurkertech.com/lg/pixelaspect/ - you need to apply a 59/54 horizontal scale to convert the file to 786.7 x 576, and then crop that to 768x576.

(You'll also want to deinterlace the footage for online viewing, but that's really a separate issue ... the same scaling and cropping would be needed even if your footage was progressive.)

There are various avi and mpg codecs that will let you save and play a 768x576 square pixel video, however strictly speaking those are not "DV"-specification codecs.

 

[Andrius Simutis]

Wow. I just realized how much I've forgotten about analog formats and SD in general. Actually, it's more like recovered from traumatic experiences in analog SD video.
1.09 refers to the pixel aspect ratio. Old TVs (at least here in NTSC land) had slightly rectangular pixels. Computer NLEs could compensate the output to the square pixel display for this while editing and Photoshop had a switch to toggle back and forth for doing graphics. Depending on the content I'm not really sure how much this will show up when played back in square pixel format. Best thing to do is try a quick test with some of it or the add a circle graphic over your footage on your DV timeline and export it. See if it's noticeably squished on playback on the delivery format. If it's unacceptably squished, then you'll need to scale it when you output it.
The other thing I'd look at is what the delivery spec is and work towards that when it's time to export. If you're not recording this back to DV tape, then why stick with that format for final export? What I mean is that the dimensions of the captured video may be irrelevant to the final output.

 

[David Jimerson]

Your VX2000 shoots and records 50i, so yes, it's interlaced. If you deinterlace it, it will become 25p.

I would disable frame blending and export as 25p. What format depends on your delivery requirements.

 

[EDV]

Thanks people. Toggle aspect ratio also works in AE to display the correct aspect ratio. So how exactly do I "deinterlace" interlaced footage in AE? Is it just a matter of choosing 25fps as your output? I just noticed AE gives you a number of frame rate choices for PAL D1/DV Square Pixels, not just 25.

 

[David Jimerson]

Anything other than 25 or 50 will not be "PAL."

PAL actually refers only to the SD (576) standard; technically, HD is not PAL.

But what remains true is that PAL is 50i; 25i and 50i are exactly the same thing -- 50 interlace fields per second.

25p -- 25 true progressive FRAMES per second, is not technically PAL, but it can be contained within PAL by splitting the 25 frames into 50 fields. (This is 2:2 pulldown.)

Any other frame rate, anything not 25 or 50, is not PAL, and the footage will require resampling, frame-dropping, or both in order to be conformed to it. You don't want this.

 

[EDV]

Thanks David. Maybe I can see how that 24p DVD might be worth a look now. So what AE refers to as 25 fps is 25i or 25p then? Or do I need to choose "50 fps" to get 25p ? I thought 25 fps was the only logical choice ( for square pixels output ) but I also thought the VX2000 was a progressive scan camera. I also read that an interlaced camera footage is best viewed on an interlaced display just like a progressive scan camera footage is best viewed on a progressive scan display. This means interlaced to progressive conversions ( or the other way around ) would be less than ideal and may result in loss of quality.

 

[drapeama]

So how exactly do I "deinterlace" interlaced footage in AE?

This might be a good start for you:
[video]http://www.videocopilot.net/tutorial/deinterlace_in_ae/[/video]

So what AE refers to as 25 fps is 25i or 25p then? Or do I need to choose "50 fps" to get 25p ?

If you load your footage in AE, and drop it into a composition, the composition should adjust to the clip automatically.
I'm not an expert with PAL material, but with NTSC videos if it's interlaced, the drop frame option won't be greyed out. If it's progressive, it'll remain greyed out as in your attachment:

 

[David Jimerson]

Thanks David. Maybe I can see how that 24p DVD might be worth a look now.

It really does explain the difference between interlaced and progressive, and what all those frame rate numbers mean, including why "25i" and "50i" are the same thing, while 25p is totally different, and the only true 25 fps rate.

So what AE refers to as 25 fps is 25i or 25p then?

Could be either. Depends on what the field order is.

If it's "none (progressive)," then it's 25p. If it's "lower field first" or "upper field first," then it's interlaced, so it's 50i.

The problem is that engineers called 50 fields per second "25 fps" or "25i" a very long time ago, even though it really isn't 25 fps in any real or visual sense, and it's still around today. And now we have actual 25 fps -- 25p -- but calling it all "25" is hopelessly confusing.

This kind of stuff is exactly why I created the 24p & Frame Rates tutorial. It explains all of this, though it starts with NTSC-based frame rates first.

Or do I need to choose "50 fps" to get 25p ?

No, 25p is 25 fps, progressive (field order "none").

The thing is, your VX2000 footage is not 50p or 25p, it's 50i.

I thought 25 fps was the only logical choice ( for square pixels output )

The pixel shape doesn't have anything to do with frame rate, or being interlaced or progressive.

I also read that an interlaced camera footage is best viewed on an interlaced display just like a progressive scan camera footage is best viewed on a progressive scan display.

Both true.

This means interlaced to progressive conversions ( or the other way around ) would be less than ideal and may result in loss of quality.

Well, when you convert anything to anything, you lose something. However, if you stay in 25 or 50 (instead of any of those other choices), you'll compromise less.

 

[Andrius Simutis]

I'm not an expert with PAL material, but with NTSC videos if it's interlaced, the drop frame option won't be greyed out. If it's progressive, it'll remain greyed out as in your attachment:

Drop frame is only a counting method for NTSC frame rates and not necessarily an indication of interlacing. You can have interlaced or progressive Drop Frame footage in NTSC. Because NTSC video runs at either 23.98 fps or 29.97 fps instead of 24fps/30fps, if you run the video long enough and count every whole frame, the time code at the end won't match the real time on a clock that the video has been running. This is an issue for TV shows where the lengths need to be exact, and conversely an issue for encoding where you want to have a consecutive whole frame number for every frame.
The solution was to create two ways to count the same video. Non Drop Frame counts every frame of the video in order. Drop Frame drops a frame every so often so that the time code matches the clock.
To see this in action on your NLE, park the playhead at the end of a 1 hour long video on your 29.97 fps timeline and switch the timecode from DF to NDF. The timecode number will change even though the video is still the exact same length!
PAL doesn't have drop frame because every frame is consecutively numbered so there is no drift from timecode to real time.