The Joys and Sorrows of Interlacing 

Well done, John! Because I WANT TO SEE image artifacts and TV flaws, I just built a 267 line, 15FPS progressive video system to show what Philo Farnsworth *might* have seen in his lab in the late 20s and early 30s. Ultimately, this project will add an actual *image dissector* tube camera section! WARNING! I make really bad videos!!! ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-zcUuoyxSJLY.html

There are several other reasons that the Twilight Zone "Videotape Episodes" look strange is because of where they where shot, CBS Television City has smaller sound stages and very different lighting then MGM where the film episodes where produced, many of the scenes had to be compressed to fit onto the CBS-TC soundstages giving them a more claustrophobic look. Also, the cameras used where the RCA TK-11 3" Image Orthicon based cameras, CBS later used the Marconi MK-VI camera which used 4.5" Image Orthicon tubes and thus had a higher resolution. Lastly, most of those shows were pretty much done "Live to tape" with the TD selecting the shots on the fly, as the freedom of editing in film did not yet exist for videotape.

Thank you for explaining this! Too many people think 60fps is a new invention, but pretty much anything that was live or taped and wasn't shot on film was shown at that high frame rate until digital cameras blew up in the 2000s. Sadly, the Internet has done a terrible job archiving old recorded content and so most old TV clips on RU-vid are in 30fps. There are even a lot of newscasts and talk shows that broadcast at 60fps but upload clips online at 30fps, with Jimmy Kimmel being one exception

I actually work in a part of the industry where 60i is still heavily used - live events and presentations. Simple reason, 1080i carries further and more stable over SDI than 60p due to bandwidth and the runs to projectors and LED displays are usually very long, and you can't cut live video to 30p because it's just less smooth enough for people to notice the difference.

A shoutout to Technology Connections! He really does have great videos. Great sense of humour too!

Further to my previous comment, I remember back in the days of camcorders (1980s) I took some video of a thunder storm, and caught some lightning. When playing it back I could see the lightning at normal speed, but when I tried to pause it, it wasn't there. When you pause a VHS it only displays one field, and the lightning was on the opposite field. It was at that point I realized that 50i does actually record 50 different images per second.

60i is not really effectively 30p. It's more of a 60p with half the resolution, which is what they originally wanted. That gives you the illusion of 30 full frames a second, but each of the two 1/60 pictures is a new frame.

Thanks! It’s great to hear someone who knows what they’re talking about. Before I became a technical writer I worked in and taught video production. People insisting that 1080p means 1080 pixels reminds me of people who think that the term “pulldown” has something to do with a mathematical conversion. I’ve read/heard people say the frame rate was “pulled down”! Even people who have lots of experience can be operating with a poor understanding of the technology. I once had a protracted “discussion” with a TV engineer turned pro video equipment sales guy who thought component video was digital.

Great video on interlacing, good to see. You and Technology Connections have presented the most info for this topic, which has sadly been lacking on youtube.

I've been watching your videos for about three years and I admire and love the way you present often complex information in a clear, easily understandable and entertaining way! As a teacher, I can only hope my lessons are as good as yours, congratulations!

Everyone take notes. He is right in every single way. There is not a single thing you can argue about this. I'm currently working on a video on how to transfer Old Tapes Properly and in a segment I write pretty much Verbatim what you discussed here. It gives me faith knowing that people like you are passing on this knowledge.

I'm getting an Internet Comment Etiquette vibe from John reading the comments. *I love it*

Thank you John. I don't know how often you hear this, but I really appreciate the amount of research that goes in on each episode you deliver. Your channel educates me in a way that many do not. I love to learn, but appreciate it most when the information is presented clear and concise. Bottom line, Filmmaker IQ makes me smarter !!

I tried to explain combing to a student a while back and I had to look on the internet to find an example. Although I don't see it anymore I always prefer a monitor rather than a TV so I can see the fields if it ever does come up again. I'm going to show this to my editing classes from now on. I already use the 24fps video. Thanks John!

Such a great video. People’s lack of understanding of interlacing has also niggled me. I particular watching mismatched field order footage on news reports from video shot by bystanders to me is like nails down a blackboard

"False Claim" now we need at least 195 likes and we get a new Filmmaker IQ video!

A shoutout to the Editors and Motion Graphic Artists for this video! 17+ minute video and there's a review process. I understand how much credit you truly deserve!

I'm an old dude, and I remembered that I first saw 'combing' artifacts when some SD tv shows were transferred to DVD. Babylon 5 comes to mind. I might have had the DVD player going to the Trinitron in progressive connection, too. Anyway, thanks for the knowledge!

Shouts to Technology Connections. Alec deserves the praise

My Sony Handycam has an option to shoot in black and white and 60i. Good on them for showing the current generation what it was like in the '50s.

This is why any video enthusiast has to keep a good CRT around to enjoy "legacy" content properly, which will never look right on flat panels. A few of Sony's OLED professional monitors were able to do a trick to represent "true interlace", it doesn't look too bad but it's still not the same.

A good presentation. Interlacing is still in common use for broadcasting, especially for “Freesat” and “Freeview” on this side of the pond. In this case it’s 1920x1080i @25 fps. No doubt it keeps the bandwidth down to reasonable levels for transmission overground or via the satellites, weather conditions etc. Interlacing was also used for HDVi which was used for tape cameras, such as an older Canon XH/A1 which I still have; it was then possible to record about 1 hour on a miniDV tape cassette at 1480x1080i @25 fps (with the 1480 bit being anamorphic, then split into 1920 post production). All ended up being progressive when burnt onto DVD or BD.

I was born in interlace, molded by it, I didn't see progressive until I was a man!

Thank you for your time and effort in making and posting these videos. They are greatly appreciated!

Never read the comments. NEVER!

The main benefit of the PAL system (Phase-Alternate-Line) was that reducing the UHF signal bandwidth lessened the atmospheric affects on the broadcast and gave better colour stability. Indeed, my college tutor (for electronics radio and tv theory) said that the NTSC system was unkindly dubbed 'Never Twice The Same Colour'.

Happy to see shout outs to Technology Connections and Slow Mo Guys!

Thanks for another very interesting video, I had not heard of Flicker fusion threshold before, and now I have some fun nighttime reading. 30ish years ago I was in electronics school, and the reason we were told we did 50Hz in Europe while it was 60Hz in the US was because of the en.wikipedia.org/wiki/Mains_hum. I guess flicker fusion and main hum combined to help pick that frame rate. Thanks again for the video. Brian

I REALLY wish that (great) videos like this would mention an important alternative: when you're converting interlaced video to a digital format, you don't have to use the standard de-interlacing methods that reduce the effective framerate by half. There are a number of great algorithms that convert, for example, 60i to 60p, by "filling in" the missing lines of each frame with intelligent interpolations based on previous/following frames and so forth. To almost anyone's eye it looks much closer to the original, since it preserves all the temporal information that is otherwise discarded, with almost no downside. I have used QTGMC, which might be challenging for a non-tech person, but provides great results. It drives me nuts that most converters and video editing software don't have a simple way to achieve this. Just think of all the video footage that has been degraded for no good reason.

D Resolve (and I'm sure many other editing software) will deinterlace 50i footage (yes I live in Europe) to 50fps. And if you flick through frame by frame you can see that each frame is different. A man walking will be in a different position on every one of the 50 frames. So it's completely true that 50i contains 50 different images per second. The fact that these are interlaced makes no difference. When you watch 50i (or 60i) TV you are seeing motion equivalent to 50 or 60 fps. I think John's videos are great.

PAL-M earlier used only in Brazil operated at 60Hz. So what you say was applied to PAL-M too.

Another excellent video, and I'm glad that you're prepared to address controversy. Just my personal opinion, but the switch from 24p to 60p makes the image look much more realistic. However, we need to remember that this is an art form - is realistic always better? To take an extreme example, I'm sure we've all seen the trailers for the new CGI Lion King. They undoubtedly look more _realistic_ than the cell animation. Do they look _better?_

You can convert old 60i footage to 60p by just taking each field and doubling each line. The resolution is lower but you preserve the original framerate without combing. Alternatively you can dump every other frame and get 30p. But I never understand the logic of combining the fields, that's what gives you the awful combed look.

I Love the fact that any old vhs tape can be deinterlaced to 60fps, unfortunately not everyone does that to their tapes when digitizing it, idk i dont feel right when i see a video which came from a tape and is not deinterlaced into 60 progressive frames and just let it to 30 .

always so much to learn here. Thank you so much :)

Masterful presentation, well done!

Good video. Most TV studio cameras are 1080i60 because ATSC's 1080 stream was standardized at 60i for bandwidth reasons. Several people have told me that it's the same as 540p60 while some argue it's like 1080p30. Well, no, it's not. 1080i60 is notably sharper than 540p60 and the motion is notably smoother than 1080p30. That said, there's really no reason modern displays can't be tricked into showing interlaced video correctly, with 120Hz refresh rates being fairly common. Display field-1 at full brightness, reduce brightness next refresh, display field-2 at full brightness while field-1 is off, display field-2 at reduced brightness. It would be a fairly simple algorithm to implement in the TV's image processor but I suppose the manufacturers don't want to sacrifice the perceived brightness.

Nice dub at 4:34. I've had to do one or two (or six or seven) of these myself on my own show, which is always a fun little challenge... And you did it perfectly! I would not have caught it if I wasn't looking at your face when you said it. Anyway, terrific video!

I like the more depth you got into in this one, just as I liked the original. I really like shooting 60p I like that smooth "soap opera" effect coupled with the higher resolution for that "extra crispy" image.

Love your sense of humour John! I do like your "soap opera mode" that you showed in this video

i just like 60fps. I know that makes me a heathen but i like it.

100% agreed. I think a major problem has been poor software deinterlacing to create 60p from 60i. The default blending of 60i to 30p creates ghosting, then "bob" deinterlacing gets 60p but halves the resolution. Since the "Yadif" deinterlacer has been introduced in software like VLC and Handbrake, it has transformed how I see 60i sources.

John. Could you help me (and maybe several others on the web). Do you happen to know how to convert 30p exported 60i footage back whatever you want?? Basically the video is in progressive but the footage is in interlace with combing. Do you happen to know how I get it back to interlaced??

For anyone going "TL;DR": 480/60i is not the same as 480/30p or 240/30p. It's zero full frames per second. It's 60 half-frames per second. Those 60 half frames are not drawn from the hypothetical 30 full frames, each half-frame is a new image. So it's like 60fps if you turned off half the scanlines each frame. That's it. You can probably compare it to 240/60p on a frame-by-frame level, but there is much more detail in two combined frames of 480i than in two static frames of 480p as it's drawing the second half of the screen in the second frame. However those two combined frames will look slightly misaligned if there is action in them because the second frame is refreshed.

You said 59.97i...

12:10 Japanese release of the NES, called famicom in Japan, released in 1983 the NES in the US and other countries was released in 1985

Watching this at 7 in the morning before work and can't stop! This perfectly answered the question I had since I was 8 and felt there was something weird about that new BBC series (which later I realized was "filmed" with U-matic). Thank you! P.S. this vid inspired me to experiment to see if we can create a 60fps feeling in video games and real-time animation using fields, and cut the processing power in half.

love your show man learned a lot from you keep it up

50i IS 50p. Some people forget TVs “bob” the fields

Think of 60i as 60p with half the vertical resolution, Now everybody is happy. But there is a reason why some people complain about interlaced materials, they use computer players that often use wrong de-interlacing settings which reveal the nasty combing that everybody is talking about, I do capture analog video for customers and in the recent years I was forced to de-interlace the videos for them the right way using high quality commend line QTGMC program so when they play the files there will be no risks for them to see the combing in case they use the wrong player or a player with wrong setting.

NTSC and PAL are color norms, but number of lines and frame/field rate were defined in the B&W time. Hence, compatible color. The original norm (and basis of the color) are still called CCIR B/G for 625/50 and CCIR M for 525/60, and there are more of them, some obsolete, for different specifications for resolution, video bandwidth, audio carrier, and modulation type (positive/negative, AM or FM)

Dude you’re a freaking genius. I don’t care what anyone says

Combing artifacts are not inherent to deinterlacing interlaced content, that only happens if you merge the two interlaced fields (half-frames) into one progressive frame. Inherently, however, _some_ visual compromise is always involved in interlacing. For example, it is also possible to display each half-frame as its own frame, which gives you smooth 60fps motion, but half the vertical resolution and the scene “bobbing” very slightly up and down every frame, or to discard all the odd or even frames, which gives you 30fps motion and half the vertical resolution, but no combing or bobbing. There are also algorithms that try to achieve 60fps with full resolution, but since they have to guess, filling in missing information, they can make mistakes etc.

Woah how did u get get 60 and 24 fps in the same video??? Please share

It's funny how you mentioned those specific Twilight Zone episodes because they reminded me so much of earlier Doctor Who episodes, which would explain so much.

In defense of the comment section: Interlacing isn't easy to understand and most people who think they do, don't.

Sadly you didn't mention deinterlacing. Of course it's "just software hocus-pocus", but it does work pretty well. There are a ton of different algorithms implemented in e.g. VLC player, I've found Yadif 2 to work the best. To activate it, right click on the video->video->deinterlacing->on/automatic. Then right click again->video->deinterlacing mode to set the algorithm. You can alter those permanently in the settings CTRL+P->video. Of course it won't be as sharp as the original, but give it a try! Also if the video is stored as progressive despite really being interlaced (e.g. if you digitised an old video and set the export to progressive) it wont work. There are example pictures (no videos sadly) on the vlc deinterlacing page: wiki.videolan.org/Deinterlacing/#Examples

Extremely well done! The metronome demo was excellent and conclusive.

can you make a video about how much the motion blur due to 24p compared to 60p effects the perceived resolution?

I really don't notice the difference when watching. If I slow down I see that 60p has more pictures than 24 or 30. 720p looks great to me. 1080 and 4k aren't really necessary. For me the only real difference is the size of the files and the time it takes me to download, upload, and edit. I do believe that the quality differences are there, but I just don't notice them.

Love this vid, nice one Jon

Hellow I would like some help I hope what I am about to say will make sense... I have canon 7d mk ii and atoms shogun flame... via HDMI the 7d send a 1080 50i and 50p signal then when I change setting on the 1080i 50i I can get it to 25p and gives a 2:2 pull down. And whn delivering I need to deliver in MXF XDCAM 50 1080i 25i I hope that makes sense Now my question is whn I shoot in 25p and edit in final cut as a 25i and export it as 25i will I loose any quality? What impact will it make on the footage? Please assist?

Thanks. Good history/future lesson. Probably I don't really need to know this, but one of the joys of RU-vid is learning stuff you have no real need of----right now, but might somewhere down the road.

How does it have 1080 vertical lines. Shouldnt that be horizontal or 1920 vertical lines instead

Stupid question: why don't we show TV shows now-a-days at 60 frames (fields?) per second instead of 30? So you don't see comb artifacts. Or do we do that already? Do you see the fields alternating then, just like on your TV w/ the metronome in slow motion?

Wait a minute--there is a discrepancy in your discussion. It has to do with transferring film to tv. It wasn't a 3-2 drop down, it was, and still is 4 frames plus one repeated frame. Watch a movie, filmed at a full 24 fps. Take a look at it frame by frame. You will see 4 different frames in a sequence followed by a repetition of the 4th frame. No one notices that repetition because it happens so quickly. I realized it when I was editing a film to video conversion.

Ok; I was going to write a comment about how I was so glad you made this video because so many people nowadays fail to understand that 30p is NOT THE SAME as 30i and doesn't look like live TV (which looks the way it does because of the 60 interlaced fields per second), but then, after you spent all that time explaining it... You told people they could shoot in 30p if they wanted the NTSC look. wat. 30p is only 6 frames away from 24p and looks very similar to 24p... As you had PREVIOUSLY mentioned, they're going to need 60 fields or 60 progressive frames per second (or greater) to get that live look. I don't understand why you would say that right after explaining why that ISN'T the case.

How could any one think 60p =pixels duh I learned in high school interlacing vs. Progressive any movie editor witch is what class I was in that is 1st day stuff.

Well explained! :D but.. I just have to ask this: Was the *focus* of the camera a bit off or was the soft look intentional? Because the background looks sharper than you. btw, I prefer 30fps over 24fps especially for average web videos, not necessarily for the higher frame rate. It's actually the amount of *motion blur* which is a bit *too much* for my eyes here (assuming you stick to the 180° shutter rule). The thing is: RU-vid videos where people explain things are very close to TV shows from a content type point of view. Basically: You pretty much look like some person who is hosting the tonight show or something if you know what I mean. *You are not making videos that look like something from a movie*. The type of content in a video is a key factor! To me it feels like you prefering 24fps is the equivalent of another common thing people do to make videos more filmic/ cinematic: Slapping on some nice and big cinemascope/ black bars without thinking why and what kind of effects it has. *That's why I'd recommend: Try 30fps or just change the shutter speed of your camera and check your focus!*

A funny anedocte is that Rod Serling purposefully chose some of the worst scripts to the videotape episodes, so that it maybe would be easier for him convince the network to come back to shooting on film. And Rod Serling's vocal delivery of the introduction in The Lateness Of The Hour also seems so completely rushed and phoned-in. The big exception is The Night Of The Meek. It's one of the most beloved Twilight Zone episodes, and the DVD commentary even says that maybe shooting on tape helped with the sincerity and simplicity of such a low-key, charming and heartwarming Christmas episode. Though one can still think that the episode would be even better if it was shot on film. Videotape was simply so severely limiting, simple and cheap in all aspects, the frame rate being only one of the problems. I will add that while 24FPS is part of the traditional cinematic look, there is obviously much more that also makes a video look cinematic. Many youtubers (not you) think that 24FPS is enough to make a video cinematic, while many 30FPS videos are actually pretty cinematic. On another matter, I will talk about one of your points from one of your other videos, when you say that comparing 24FPS and 60FPS side-by-side is not right. I agree, and I think it's so because when one frame rate is blatantly higher than another, watching them side by side can give the illusion that the lower frame is choppier than it actully is. The video below, comparing the same animation in 24FPS, 12FPS and 8FPS, is a good example. Watching the 12FPS animation right after 24FPS is really jarring. But the exact same 12FPS animation looks perfectly fine when watched right after 8FPS animation. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-0r3d2eMw8Ws.html Also, higher frame rates in animation truly follow the law of immensely diminishing returns, as these video comparisons below show very well. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-o2WBBgqV21s.html ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-RdGwTIhEsIU.html ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE--ZnxYYABLww.html We don't really need higher frame-rates in animation. Anyone who thinks otherwise really needs to look at this awesome and buttery smooth animation chase scene from Richard Williams' The Thief And The Cobbler (that film has plenty of examples of GOAT animation). ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-Usf5vtaYDI0.html And art is very subjective. Higher frame rates aren't objectively mean better or worse, the only objective thing about them is that they have a higher number of frames per second! Though Richard Williams, in his book The Animator's Survival Kit, was always a huge defender of animation in 24FPS as much as possible (Williams was always obssessed with animation being as smooth as possible), he also says that there are many animators who actually think that 12FPS in many instances can look better than 24FPS, and he mentions Art Babbit, one of Richard Williams' own biggest mentors, as one example of such, even though Williams still doesn't agree with Babbit's view. I also highly recommend this video below. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-YtYpif-dLjI.html Cheers! I wish you the best!

Brilliant! Thanks!

5:15 If the p in resolution really meant pixel then interlace wouldn't make sense because it would also be pixels

9:10 So that's what Windows and DaVinci Resolve were doing to my Canon Vixia's footage. I assure you it looks 60fps!

Is there any way to convert 1080i 60 to progressive 1080 60fps? Dont want to lose quality neither 60fps

I play FPS game with Interlace resolution on 19”inc LED 60hz Screen and SET TIMING TO CRT Format then 75hz By overwrite it’s E-EDID accidentally but the result is beyond 60hz monitor their has no input lack at all. Thanks you for your video my doubt is clear.

You are quite correct here. I hope this gets watched by all.

Curses you with your accurate and well delivered information. 😂😂😂

10:53 so no one is talking about the magic that you aligned each field of the 60i CRT screen with each frame of the video. no rolling scan lines, no half image.

I always thought, assumed, each field was from the SAME image. Thanks!!!

But we are not playing back at 60fps? You may have recorded part of the video at 60fps, but this export is in 30fps. The section where you switch does look smoother than the rest, but that has more to do with the fact that you likely shot the rest in 24fps and edited in either 60 or 30fps, thus duplicated the 24 material to reach 30fps. I enjoyed the video, but am curious if I missed something?

You only see combing when viewing interlaced video on a non-interlaced display because the software tries to combine the separated interlaced frames. blending them together.

This was awesome!!!

Dude! Your videos are the best, thanks so much for making these videos

Let me ask you something. I actually support interlacing since I discovered 50i is literally 50 vertically half frames. Now I’m thinking, in the world of film anamorphic lenses were or are used which on the horizontal side (mostly) has less detail than vertical. My point is: if it’s possible to convert 50i to 50p with vertically half the information, why don’t we keep doing that if films also do that?? On the other side, it’s a ongoing war of better imagequality between resolution versus framerate.

Excellent content as usual. I haven't noticed any editing slip-ups this time :)

Gotta say - your videos in 60i/p looked way better! Wish you'd shoot the channel that way :) Love your work MPEG encoders that handle interlaced fields compress fine and don't interpret combining as noise. I used to record TV with my capture cards in the late 90s with that method so as to not lose any motion resolution. I used to record in interlace and then playback via S-Video out to my CRT

On a related matter, are there any plans on a video about the Vidfire system that is used (at least here in the UK) to restore old shows to their original look? I'd be interested to learn more about that. In connection to this I think your viewers might also be interested to learn how the BBC have been able to restore colour to shows where only black and white backup copies survive (not colourisation but extrapolating the actual original colour info). It's fascinating and incredibly ingenious!

at 13:59 the color correction changes

Im'm still using crt with interlaced resolution @120i to 160i

Billy Lynn's long half time walk is my favorite 4K bluray ! And now I want more HFR movies !

Technology Connections... sometimes the guy doesn't get his facts right, though. Out of that little detail, another wonderful video!

glad you gave a shout out to Technology Connections! love your channel and I am big into SD video art.

lol, someone actually thought the p was for pixels?

If anyone can please answer. For low light sports, should I use 24p or 60i? If the answer is 60i should I use 1/60 or 1/125 shutter speed?

I think we can agree on that 60p has a more realistic look (life-like) compared to 24p which instead allows for the imagination to fill in the blanks to some extent. The question is if it is always better to use 24p for feature films/movies, or would some movies benefit from a more realistic look? For example movies based on true/real events might benefit from 60p, while purely fictional movies such as SciFi might benefit from 24p? Since 60p is superior to 24p for most other media forms (computers, games, documentaries, etc) it would be strange if there was not a place for 60p also in movies, when the story/style allows for it (not considering technical limitations of e.g. cinema projectors, or more time-consuming editing and CGI etc).

Just watch everything with your 2i

Your tongue in cheek sarcasm aimed at stupid people is infinitely funnier than your "special fx" gag.

4:47 Was that an audio desync or a really smooth audio edit to fix a mistake when reading the number 94?

Thanks for this great video! All this time I was shooting in 25p. So if I shoot in 24p my work will look like film? will 1 frame make such a difference?

On my DVD copy of Super Mario Bros, there is ONE scene (the climax, as the Dinosaur world and the real world start combining) where all of a sudden, it's a Interlaced image with terrible combing. It's really odd because the entire film is fine (well... it's Super Mario Bros, but you know what I mean).