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How to convert progressive to interlaced

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Anette Olsen
How to convert progressive to interlaced
on Aug 7, 2013 at 10:21:44 am

I've shot a half our doc in 1080p/25 on Panasonic HMC151 (edited in Prores 422) and I have to deliver for broadcast in Prores 422 HQ (1920x1080i).


What settings do I use in Compressor to convert to interlaced?
Do I choose Top field and what about the other settings?

I haven't been able to find the exact answer in this great forum, I'll be grateful if somone can help.

PS: As for the HQ, I guess I cannot obtain the full quality, since my camera has only 8bit and not 10nti which I understand is required for Prores HQ...


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Rafael Amador
Re: How to convert progressive to interlaced
on Aug 7, 2013 at 3:36:18 pm

The standard for 1920x1080 is always Interlaced. Progressive stuff is broadcasted/streamed as interlaced., so just send the movie as it is.
To make real interlaced from progressive stuff would take very long and will degrade de picture.
rafael


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Anette Olsen
Re: How to convert progressive to interlaced
on Aug 7, 2013 at 7:34:04 pm

Rafael, what do you mean by the 'standard'? When I do the export to Quicktime from the timeline? (I use fcpX).

I read somewhere, that if the sequence is progressive it won't export to interlaced - but this is what you say?

(and how can I check if it is? The info doesn't show...)


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Andrew Rendell
Re: How to convert progressive to interlaced
on Aug 7, 2013 at 5:19:32 pm

Just putting the 1080P footage into a 1080i sequence will make it output in PSF (Progressive Segmented Frame) where the lines will be split into field one and field two. That's how progressive is usually handled. TBH, I don't know anyone who has bothered trying to fake the time separation between field one and field two anyway.

You can transfer from 8 bit to 10 bit... you won't get the full benefit of the 10 bit space but most broadcasters I deliver to will accept material originated in 8 bit at the moment.


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Rafael Amador
Re: How to convert progressive to interlaced
on Aug 8, 2013 at 1:36:13 am

[Andrew Rendell] "Just putting the 1080P footage into a 1080i sequence will make it output in PSF (Progressive Segmented Frame) where the lines will be split into field one and field two. "
No need.
You will lose one generation.
If you just interpret the file as Interlaced, it will be read field by field instead of the whole frame at once.
As I said, the standard for 1920x1080 is interlaced, so whatever the file is Interlaced or progressive, it always be read/streamed field by field.
When your camera records 1080p, the SDI puts the picture out field by field this doesn't change the Progressive nature of the picture, because both fields (upper and lower) have been generated at the same time. No between-frames motion.
Just give them the 1080p master. Their system will play it field by field.
rafael


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Andrew Rendell
Re: How to convert progressive to interlaced
on Aug 8, 2013 at 6:00:33 am

[Rafael Amador] "You will lose one generation"

What do you mean by that ?
Digital video doesn't have generation loss unless you process the pictures in some way, e.g., transcoding to a different codec.

We're both effectively saying don't change it.

I'm really only adding that I'd make it into an interlaced file myself, inside the NLE, rather than giving it to the channel as a progressive file, and that's because a couple of years ago I delivered a progressive file to a broadcaster and their playout screwed up the field order and caused a load of grief going backwards and forwards trying to apportion blame - in the end I had to hold my hands up and take responsibility because I hadn't delivered precisely what their delivery spec was.


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Rafael Amador
Re: How to convert progressive to interlaced
on Aug 8, 2013 at 7:57:18 am

[Andrew Rendell] "What do you mean by that ?
Digital video doesn't have generation loss unless you process the pictures in some way, e.g., transcoding to a different codec."

Well, you wrote: "Just putting the 1080P footage into a 1080i sequence will make it output in PSF".
In that case the sequence will be rendered and, unless your 1080P master is Uncompressed and you process Uncompressed, the movie will be recompressed. One generation lost.



[Andrew Rendell] "a couple of years ago I delivered a progressive file to a broadcaster and their playout screwed up the field order and caused a load of grief going backwards and forwards trying to apportion blame - "
if the file was Progressive, there is no way to mess up with the fields order.
it can be read as Progressive, Upper first or Lower First; Always will look progressive. Al the lines of any frame have been recorded at the same time. No motion difference between both field if read as Interlaced..
rafael


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Andrew Rendell
Re: How to convert progressive to interlaced
on Aug 8, 2013 at 8:48:13 am

[Rafael Amador] "if the file was Progressive, there is no way to mess up with the fields order."

I think you are making the mistake of assuming that play out technology is similar to edit suite technology and that the people who operate it are similarly technically adept as editors. The first one isn't true and the second can't be taken for granted.

I have seen files transmitted where the fields were wrong, so for example line 566 was above line 3 instead of below it, so to imply that that's impossible is deeply mistaken.

I learnt a long time ago to deliver precisely the specification that is requested. That's the only way for it not to be my fault when things go awry somewhere along the line.


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Anette Olsen
Re: How to convert progressive to interlaced
on Aug 8, 2013 at 9:08:33 am

Andrew and Rafael, thanx for trying to help.

I might try Rafaels suggestion of putting my progressive sequence into a interlaced sequence - only I'm working with FCP X and it doesn't seem to give the possibility of choosing...

So my question remains, if Compressor can be used to convert from progressive to interlaced?


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Rafael Amador
Re: How to convert progressive to interlaced
on Aug 8, 2013 at 3:58:53 pm

[Anette Olsen] "I might try Rafaels suggestion of putting my progressive sequence into a interlaced sequence "
I haven't suggested that.
Things are more simple.
rafael


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Anette Olsen
Re: How to convert progressive to interlaced
on Aug 8, 2013 at 4:49:06 pm

But you wrote this: "Just putting the 1080P footage into a 1080i sequence will make it output in PSF"
what did you mean by that then?


And is that possible in FCP X?


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John Heagy
Re: How to convert progressive to interlaced
on Aug 8, 2013 at 9:35:01 pm

You can simply alter the metadata in your 25p movie from progressive to interlaced using Digital Rebellion's QuickTime Edit.


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Rafael Amador
Re: How to convert progressive to interlaced
on Aug 9, 2013 at 1:31:58 am

[Anette Olsen] "But you wrote this: "Just putting the 1080P footage into a 1080i sequence will make it output in PSF"what did you mean by that then?"
I was just repeating Andrew's text.
What John suggest is a very good idea.
With just a click, you flag the movie as Interlaced. No reprocessing.
rafael


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Carl V. Spurner
Re: How to convert progressive to interlaced
on Jul 24, 2014 at 11:50:39 pm

You blokes never answered Anettes' question and hijacked her post which was an attempt to get an answer to solve her issue.

Anette, here is a link to get crystal clear vision in interlaced format from a progressive file:

http://library.creativecow.net/articles/solorio_marco/interlacing_progressi...

This will take time but a solution none the less.

A simple rule is:

Television requires - Interlaced

Film, Web, DVDs requires or works best with - progressive.

It helps to know where your product will end up before your begin your field production.



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Ht Davis
Re: How to convert progressive to interlaced
on Feb 14, 2015 at 2:06:37 am

You're all close... ...But most aren't answering the question, only offering their own work around.

Here's what guys who actually present playable media do...

Remembering that the biggest factor in "Motion" quality is frame rate, and the second biggest is field order, you have to think about what you are getting when you actually render out your project.

Any NLE is going to allow you to set up a Timeline that is based on Frame rate, not field order (they don't care about field order ON THE TIMELINE ITSELF); but there is a Preview video created (a proxy file that you can size to your hearts content and format to your liking) that does worry about field order, as it will be what you see when you play back your effects. When you render out the final project, you typically want to keep the frame rate of your timeline, but occasionally you can just use your preview video if the quality is to your spec. This means you want to choose your timeline based on frames, but choose your preview based on your output spec so you can get an idea of what your product will look like.

For 60p source-->start with 60i preview, at full Frame Size (1080). If you have to output a disc, You may want to leave it at 60p, but use 720p target for preview. You could, at the end, nest your final in another timeline, same frame setting for the timeline, but set the preview to 30i with full size and see if that still suits you. If so, go with it.

For 30p Source-->stick to 30p output for online or computer based playback. You can squeeze this into blu-ray with x264 plugin or handbrake and freex264 (FFMPEG)... ...But you are best off using 30i transcode for 1080 preview, and then set up a new timeline with a 720p preview, and see which you like the best across all screens (Put a compressed preview or transcode onto usb and playback on tv).

For 24p, remember not to move around too much, and you should be able to go right to 1080p blu-ray, or full frame youtube, but you will lose more quality at that sizing. You may want to shift to 720p target, if for no other reason than that you want to use less data rate while keeping fine edge quality. Scaling up from that is easier to do at the screen than on the server where it is stored.

I like to use uncompressed for source, and occasionally proxy, as playback on a computer looks better. Rendering out several work areas and playing through to see my work is the only way I've been able to get it done with a macbook pro 2.16ghz core2duo and an older geforce 8600m with 256mb vram and 4gb ddr2.

side note:
If you do any slo-mo, you really want a camera where the frame rate is really high, like 60p, but you want to be able to cut it down to 24p. This is called a pulldown. Since 60 and 24 both have several common factors (1,2,3,4,6), the frames can be reprocessed to 24p with better results than with 60 to 30 ( 1,2,3,5,10). The first 4 factors are perfectly inline, and only 1 apart, where with 30, there are only 3 1 apart factors. Rendering to a slower rate yields that, for a number of frames, there is a number of sections, and those sections must have so many frames. Divide 60 by 4, you get 15, divide 24 by 4 you get 6. At this point, it may look mismatched. But take a closer look... ...In the end you get this: for every 5 frames at 60fps, there are 2 at 24fps. This would typically drop 3 of the frames. If you know where to drop these 3 frames, you can, effectively, slow the motion, and recode it to 60 frames by simply reconstitution of the motion from those dropped frames, or by stretching the time it takes to play 5 frames, so that only 2 frames are played. That's 40% speed! Less than half-speed, so just over double the time. 60fps becomes 60frames every 2.4seconds, or 24fps. By stretching the frames over more time, you can reinterpolate the motion and slow it down. Put a 60fps, slow it to 24 and then render the section to a 60fps preview. You'll see it in a 60p\i container, but the bits that define what is actually playing should show the drop in frame rate. This will still output just fine from any encoder, to any container with a 60frame.


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