Looking for advice on converting SD to HD with de-interlacing

[pen2paper]

Hi all, I have a new project based on a circa early 90s SD PAL broadcast intended for Blu-ray release. Master file has been provided (.mxf) which needs to be edited to length in Final Cut Pro. File is interlaced at 720x608 [4:3] which I have been advised might present some difficulties come time for replication. For consistency, we're considering a full AI upscale at some point in which the file shall need to be image-sequenced, individually upscaled frame by frame, then stitched back together.

I don't have a great deal of experience working with these types of files, but am I correct in saying that de-interlacing will result in the original 25fps being converted to 50fps?

When playing the file in VLC, selecting 5:4 aspect seems to evoke something visually more accurate to my eyes. Could this be something to do with pixel ratio? There is also a single letterbox-type black bar at the uppermost edge of the picture, which could be VBI-related, but I cannot say for sure.

Also, de-interlacing with bob/linear enabled results in far better, smooth motion. On attempting to convert the file using VLC, I can't seem to be able to force 5:4, plus the first few seconds of video are blank, though audio plays throughout. MediaInfo seemingly confirms the de-interlaced file is indeed 50fps. I've tried looking into Avisynth, but am having difficulties.

There is additional content set to feature on the disc that has been exported at 1080p 25fps. Could this also complicate things during authoring/replication?

Very grateful for any advice.

[manono]

Why on earth were you chosen to lead this project? Anyway, your first step should be to read "What is Blu-Ray".

[Bwaak]

I just educated myself on 720x608, which, apparently, is common if you want to provide extra info that goes into blanking lines. So, you would crop it to 704x576 (or 703x576, or 702x576) and treat it as your 4:3 frame (if it is indeed 4:3, not 14:9, which was common in the late 1990s for Europe).

Always deinterlace before scaling. If it is native interlaced, deinterlace into 50p. If it is prog-scan in an interlaced stream (a.k.a. PSF), then deinterlace to 25p (basically, do nothing).

If your 1080p project is square pixel 1920x1080, then the easiest way is to resize 704x576 to 1440x1080; with pixel aspect ratio 1 it will look as 4:3. Then you would drop it into 1920x1080 project, which will ensure pillarboxing. I hope you are not going to stretch it

Sometime along the lines you want to switch color from Rec. 601 to Rec. 709, I've never cared much about it myself, always relying on software doing the right conversion automatically, but other people on this board are very particular about this stuff

P.S. Considering this is a professional format being edited in FCP, I would assume that FCP knows how to handle it, aside of mandatory deinterlacing. I've never used FCP myself.

[poisondeathray]

File is interlaced at 720x608 [4:3] which I have been advised might present some difficulties come time for replication.

When playing the file in VLC, selecting 5:4 aspect seems to evoke something visually more accurate to my eyes. Could this be something to do with pixel ratio? There is also a single letterbox-type black bar at the uppermost edge of the picture, which could be VBI-related, but I cannot say for sure.

When cropping the borders, what are the dimensions of the active image area ?

I don't have a great deal of experience working with these types of files, but am I correct in saying that de-interlacing will result in the original 25fps being converted to 50fps?

Double rate deinterlacing will result in 50p - and since your VLC bob test resulted in smoother motion, likely the content was interlaced as well

There is additional content set to feature on the disc that has been exported at 1080p 25fps. Could this also complicate things during authoring/replication?

Not a problem.

But note that BD does not support 1080p50 for your main content. A BD disc will be need to be encoded & authored 1080i25 to preserve the smooth motion (this means your upscaled version will have to be re-interlaced - you discard 1/2 the spatial information - normally it's regrettable loss - but not a big loss in your case since your source files were SD to begin with), and 25p content is also encoded as 1080i25 for BD anyways - so this does not complicate authoring/replication. Native progressive encoding - 1080pN25 is not compatible with BD . The other authoring option is 720p50

[pen2paper]

If your 1080p project is square pixel 1920x1080, then the easiest way is to resize 704x576 to 1440x1080; with pixel aspect ratio 1 it will look as 4:3. Then you would drop it into 1920x1080 project, which will ensure pillarboxing. I hope you are not going to stretch it

I wonder if it actually has been stretched 5:4 for past releases... Difficult to say if I'm just used to seeing it presented that way! Perhaps, the image was stretched vertically as opposed to cropped/zoomed-in thereby giving the illusion of 5:4.

When cropping the borders, what are the dimensions of the active image area ?

Looks to be around 775x565 - that's cropping a few pixels of soft edge, too.

Thank you, Bwaak and poisondeathray. It is very important to me that the heart of the presentation is preserved (no filmizing, etc), but this notion of AI upscaling intrigues me. After de-interlacing, could the upscaled image sequence be interpolated/re-timed in mind to go progressive?

Would Avisynth be the best way forward in terms of de-interlacing? So many recommendations! Thanks again

[poisondeathray]

When cropping the borders, what are the dimensions of the active image area ?

Looks to be around 775x565 - that's cropping a few pixels of soft edge, too.

Ideally you'd want to examine some known objects, shot straight on, such as tires, a circular clock, etc... to determine the actual aspect ratio of the content. That would dictate what other fixes are required

After de-interlacing, could the upscaled image sequence be interpolated/re-timed in mind to go progressive?

I don't understand the question ; or what do you mean by "progressive" ?

It's considered "progressive" content ( well, interpolated) once it has been deinterlaced . Double rate deinterlacing transforms each field to a frame. In general, a deinterlacing algorithm attempts to fill in the missing scan lines using various interpolation algorithms .

If you meant timing, "50p" is easily retimed to "25p" by dropping 1/2 the frames. There are other methods to interpolate in between , or intermediate points if you wanted to retime to say 24p such as optical flow and machine learning algorithms

Would Avisynth be the best way forward in terms of de-interlacing?

Not necessarily; it depends on the source and scenario - but there are many options and settings in avisynth (it's very versatile, and customizable) , and often there are tradeoffs in terms of details, smoothness, temporal artifacts, spatial artifacts. There is no "best" at everything

In the scenario of machine learning upscalers - it depends on how the algorithm used handles deinterlacing artifacts (e.g. aliasing, jaggies - because those errors are going to be upscaled and magnified), and how it handles noise. Those tend to be the 2 major issues these days with "AI" scalers. e.g. If you're using one that fails miserably on source noise, you have to pre filter appropriately. It takes a lot of time and testing to get ideal results. Often you have mix several of them , composite parts, and post filter appropriately - because machine learning scalers often make mistakes - sometimes severe ones (eg. you might have to photoshop some manual fixes on a few frames)

If you want "easy" set and forget - I would avoid machine learning at this point. Even conservative algorithms can make mistakes. In general, for "AI" upscaling - Lots of upside, lots of downside - ie. risky unless you go over everything closely

[pen2paper]

If you meant timing, "50p" is easily retimed to "25p" by dropping 1/2 the frames. There are other methods to interpolate in between , or intermediate points if you wanted to retime to say 24p such as optical flow and machine learning algorithms

Basically, yes - given that, in any event, the file will require de-interlacing at some stage, I am keen to explore the possibility of converting the main interlaced feature to progressive ahead of any potential AI upscale, but I am concerned this might distract from the original presentation - particularly in terms of smooth motion. If at all possible, I hope to retain the appearance of the master file simply running in VLC at the aforementioned decomb/aspect ratio settings.

I am also mindful of the additional 1080p content we hope to include alongside on the same disc - am I right in saying that all media has to be the same settings on a single BD? So, in this instance, everything would be encoded at either 50i, or 25p?

And yes, the AI programme is producing some encouraging results so far - ideally, that process would be on a shot-by-shot basis, and to tweak as we go.

[poisondeathray]

Basically, yes - given that, in any event, the file will require de-interlacing at some stage, I am keen to explore the possibility of converting the main interlaced feature to progressive ahead of any potential AI upscale, but I am concerned this might distract from the original presentation - particularly in terms of smooth motion.

"Distract" in what way ? If you watch "25i" content on a modern display, it gets deinterlaced to 50p on the fly anyways. ie. it looks similar to VLC "bob" , or yadif 2x

Or are you referring to deinterlacing artifacts being distracting ?

I am also mindful of the additional 1080p content we hope to include alongside on the same disc - am I right in saying that all media has to be the same settings on a single BD? So, in this instance, everything would be encoded at either 50i, or 25p?

Different titles can have different settings on a single BD

In this instance everything is encoded at "25i" ("50i" is the same thing, different naming convention) for BD compatibility . 25p encoding is not supported by the BD standard. To be clear, the 25p content is encoded at 25i; and the 50p content is re-interlaced to 25i and encoded at 25i (essentially convert frames to fields by dropping 1/2 the scanlines, it's normally lowpassed too for professional distribution - essentially vertically blurred to minimize line twitter - but that's a "cost" of using interlaced distribution) . From an SD upscale, I bet 720p50 would usually look better, because you're not lowpassing it, and it's not being deinterlaced by the display. Marketing wise, "1080" is used more often because it's a larger number

[pen2paper]

"Distract" in what way ? If you watch "25i" content on a modern display, it gets deinterlaced to 50p on the fly anyways. ie. it looks similar to VLC "bob" , or yadif 2x

Sure, I did consider that. I'm just concerned that dropping any data might affect the motion in some way. During testing, different de-interlacing modes in VLC produce quite different results - sometimes with a judder, which I would hate to introduce here. I guess it's just a question of figuring out the most appropriate software to de-interlace, then. That, and to crop, and change aspect ratio, which I'm not sure how best can be achieved in Final Cut Pro.

The AI upscale is currently set to increase everything to full HD, so ideally, that's what I'm aiming for.

[Bwaak]

In this instance everything is encoded at "25i" ("50i" is the same thing, different naming convention) for BD compatibility .

BD standard, updated for UltraHD, allows 1080p25 and 1080 at 50p/60p with HEVC. When consumer camcorders capable of shooting 1080 at 50p/60p appeared around 2010, their footage initially was not playable on domestic BD players, but within a year most popular brands made it playable. Practically, I bet it is supported by most players, even non-UHD ones. But from the point of view of the standard, this officially became available only with UHD. Most people will not understand a UHD disc which is not 4K.

I have never understood why they did not allow it from the start, the trend towards 50p/60p as origination/mastering/archival format became apparent in the late 1990s, EBU and the BBC recommended using 1080p50 whenever possible back then. Even more puzzling that 720p25 is still not officially allowed.

[poisondeathray]

When consumer camcorders capable of shooting 1080 at 50p/60p appeared around 2010, their footage initially was not playable on domestic BD players, but within a year most popular brands made it playable.

Yes, as a file, through USB, not as an authored BD .

1080p50/59.94 requires L4.2 AVC, and that is "illegal" for BD

Practically, I bet it is supported by most players, even non-UHD ones.

Definitely not as a authored BD disc, nor will any strict authoring tool allow it

Back then, a subset of AVCHD allowed for 1080p50/59.94 authoring, but with a maxrate of 28Mb/s. But only BD players that have "AVCHD 2.0" compatible label would play it. The original BD players which were "AVCHD" compatible would not

[Bwaak]

Yes, as a file, through USB, not as an authored BD.

Authored AVCHD disc (hi-def on DVD media). I tried 18, 24 and 28 Mbps, the latter was unstable, 24 worked on a Panasonic I believe, 18 Mbps worked on Panasonic and Sony. The official limit for AVCHD discs is 18 Mbps no matter resolution or frame rate. I agree, it is not a very compatible format for distribution, maybe just for family stuff. Both 1080p60 and 720p25 worked.

[poisondeathray]

The 18Mb/s is due to the transfer rate of DVD media .

AVCHD 2.0 28Mb/s works ok with BD media on all AVCHD 2.0 BD players - It's still a mediocre compromise, but the only way you could get 1080p50/59.94p authored on disc back then

These days, hardly anyone cares about optical media. Probably 90% of the real authoring/post houses have gone out of business

Anyways, the OP wrote "replication", so if he really meant that - you need to follow strict specifications to the letter, strict authoring tools (many you can't even get anymore, because optical disc is almost obsolete) , and create a BDCMF image. It's not like "burning" a blu-ray for home use

[pen2paper]

Anyways, the OP wrote "replication", so if he really meant that

I certainly did! Project shall be professionally authored and replicated. Just doing my utmost to learn as much about the process ahead of time, for the best possible result. Any recommendations regarding the de-interlacing software? I'm thinking 720p 50fps might be the way to go for the SD main feature. Thank you so much again for the good advice.