Again, the reason he can use words like ‘about’ and ‘approximately’ is because it was all analog. Unlike digital, there were no discrete, perfectly defined packets of data in analog..
I was always fascinated by how well the screens could switch and adjust between different types of signals in real time. Especially if you had a combination TV/Monitor and you pay close attention to broadcasts or computer signals, you could notice the spacing of the scanlines change periodically.
But now we are all Digital, People say 'kind of' and "sort of". You just listen to anything now. 'kind of' and "sort of". Is uttered often. 'Sort of' and 'Kind of'. This is such a Social Media guard phrase. It's not required. It either is or isn't, did or didn't.
I had a brilliant 32inch CRT tv back in the early 2000s that I wouldn’t even hesitate to trade my 4K 55inch flatscreen to get it back. It was heavy as hell and was screwed into its own tv cabinet that was a pain in the arse to move but my god, it was awesome playing ps2 games on that thing. I had it for nearly 10 years and it still worked like brand new until i dropped the damn thing while moving house...
i know im asking the wrong place but does anybody know a trick to log back into an instagram account..? I was stupid forgot my account password. I would appreciate any tricks you can offer me!
@Axel Derek i really appreciate your reply. I got to the site thru google and im trying it out atm. Seems to take a while so I will reply here later with my results.
Back in the day, they didn't tell us, it's 576 lines or 486 lines, respectively. I was told, we've got 625 lines and across the Atlantic, they've got 525. I then computed out that with 4:3 ratio a line would have 833⅓ pixels. I had a close look at the screen, the screen was a cromaclear shadowmask, and I saw the hexagonal structure. I concluded that some lines have more pixels than others, some have 834 lines, other 833, on average 833⅓. How wrong I was. The literature I had back then didn't make things clear. Nowadays, young people have never heard about the numbers 625 and 525. They only know SD as 480 in NTSC and 576 in PAL.
Same! I keep coming back to rewatch videos...can’t wait for more content! It became one of my favorite channels almost instantly! Some collabs with other tech/video game youtubers would be awesome.
Same here, a year later. This is such great info, so professionally presented. No complaints about any aspect of the channel, unless it's that there's not a hundred times more videos haha
The VBI pulses may seem repetitive, but they are pretty important if you want a picture on your screen. Remember that television was developed using vacuum tubes and 1930s discrete components and that ancient stuff had to not only sync up with a broadcast signal, but contend with poor signals as well. A lot of NTSC's design choices come from the limits of technology at the time.
Thanks, NJRoadfan. This is definitely true. I actually cut down my script a bit and elected to omit some of this information for pacing. The limits of technology at the time were such an important, key item in the evolution of television. They certainly weren't going to change the signal every couple of years just because technology improved. The most notable instance of this, in my opinion, was the birth of composite video. I am glad you shared this comment.
This is really interesting because I remember we had a really old CRT TV with v-sync and h-sync knobs that would distort the image (and I used to play with them). Now it makes total sense why the image was distorted that way. I really loved this video ! Thanks a lot for the great explanation!
The one detail that really helped this all click home to me when it was pointed out, is that the vertical scan is constant - the electron beam is always moving down, even as it scans across each scanline. This means that the scanlines are very slightly diagonal, as the beam moves down by most of a line as it goes from left to right across the screen. This is how the half-line offset makes the interlacing work - by starting one field at the top left of the screen, and starting the second field at the top middle of the screen, the scanlines for each field gets nestled between the scanlines for the other field. This is why the total number of lines, 525, is odd.
One interested tidbit is that analog TVs didn't have pixels. The electron beam just varied in intensity as it moved left to right. So there was no definitive horizontal resolution for an analog signal. If anyone wants to learn more, the channel Technology Connections made some good videos on analog TV, and Texas Instruments has an application note about CRT displays entitled "Understanding the Operation of a CRT Monitor." With the application note number AN-656. It's a good place to start digging deeper, for those interested.
That is true, but there was a limit to horizontal resolution due to the bandwidth allowed for broadcast TV. For NTSC each channel was allotted 6Mhz, which gave a maximum of 330 horizontal lines of resolution. You could determine the horizontal resolution with a test pattern. Often one was broadcast at night in off hours. upload.wikimedia.org/wikipedia/commons/thumb/a/ad/RCA_Indian_Head_Test_Pattern.svg/1200px-RCA_Indian_Head_Test_Pattern.svg.png Until TVs had composite video inputs (and later S-video and component), that was the limitation. With composite inputs higher resolutions from connected devices could be achieved, because there was no 6Mhz bandwidth limitation. Monitors within TV studios had that capability (including some with RGB inputs) before it was available to consumers.
@@my3dviews Yup. When using baseband modulation for an RGB signal (as opposed to squeezing into an RF signal, or the limitations of a quadrature modulated color signal like composite or S-Video) your horizontal resolution was effectively infinite, limited only by the resolution of the phosphors of your display and the electronics in your display generator and monitor. This is how the ECS/AGA Amigas could do 1280 horizontal resolution in "SuperHiRes" modes on a 15Khz display.
@@my3dviews Thanks, I didn't know about the bandwidth they had for each channel. Do you happen to know what the entire bandwidth was that was dedicated to over-the-air TV in general? And the radio frequency the FCC allotted for TV related things? I was actually intending to look up info on various test patterns some time ago but forgot. So this served as a nice reminder. Great comment, man!
The reason for the half-lines in interlacing is interesting. Horizontal scanlines aren't really exactly horizontal. They slope down slightly from left to right. The is because the vertical downward deflection of the beam continues as each line is drawn. To get interlacing a vsync happens halfway during a scanline so that the next field's lines end up starting at the level of the midpoint of the previous field's slightly sloped lines.
The algorithm suggested your channel and after several videos of well thought out content, and clearly made with love, have not been disappointed. Subscribed and eagerly awaiting more!
That was incredible! Way more thought and attention went into CRT TVs than I ever realized, but it certainly explains how heavy they were: a lot of stuff going on in there!
Displaced Gamers - JAPAN had MUSE High Difinition ANALOG TV in 1985, they had 1 channel Dedicated to MUSE Broadcasts and it was even LIVE Broadcast from the Japan Worlds Fair in 1985. the Worlds Fair also featured the Analog High Difinition TV camera and the High Difination TRINITRON Display.
Grew up with CRTs, used emulators in the mid 90's-and 2000's. Back to the original hardware and a PVM these days. It's really the best way to do it. And as mentioned in other videos, even component has its merits, so I'm looking forward to getting a nice Trinitron when I have the space.
I'm watching through your videos, having just discovered your channel. Fascinating stuff. Even though I worked with home computers since the early 80s, there are some things I still didn't know about luma, chroma and NTSC. One thing you didn't cover, however, is how live analog TV, and its recording on videotape, carries 60 intervals of motion per second even though there are only 30 full frames per second. Each field is a snapshot in time, and doesn't have to match either of the adjacent fields in the timeline. So the result looks like 60 fps even at full 480i res. Given the strobing effect of CRTs, that motion looks perfectly smooth too (unlike the sample-and-hold tech of LCDs).
It would actually be 240p, with the width of a 480p signal (i.e. 720x240). The old consoles were essentially displaying everything on the top field and ignoring the bottom one. A true 480p(720x480) signal would take more bandwidth than the typical RF connections of the day -- for color signals, at least.
The original NTSC standard was 525i (interlaced) which gave a vertical resolution of about 480, with a maximum horizontal resolution of 330 due to bandwidth limitations of the broadcast signal. There are no pixels in analog TV, just horizontal scan lines (which the number of give the vertical resolution) and horizontal resolution based on bandwidth limitations. Even today, most HD broadcasts are 1080i (interlaced), with some broadcasting in 720p (progressive scan). There are no 1080p broadcasts, but Blu-ray players and other electronic devices do use it.
Man, this is great stuff!, really interesting to see how it all works. Now I know what those dark lines with a square half way through that quickly move up are when I fist turn on my rf or composite devices, I guess the television I guess the television doesn't get all the lines right away and accidentally draws them?
It is possible it was establishing sync lock. I think my first television (1968 Color CRT) would roll the image upward and "lock" when I first powered up a console. It would happen pretty fast - like before I would get my finger off the power button/switch of the console. Thanks for your comment! I hope to make more videos like this one.
Invented in the U.K., then used in most of Europe, we had the teletext service transmitted over the air in the ‘spare line’, a service that offered hundreds of selectable pages of information without the need for a modem or computer. For some reason the US, did not make much use of the system and I believe only one cable network actually used it.
Yes, that one cable network in the US that had teletext was Superstation TBS--they carried a teletext service in the 80s and early 90s called "Electra". TBS only carried the service, it was actually originated and programmed by a company based in Cincinnati, Ohio called Taft Broadcasting (who owned a few local TV stations in the US and also the Six Flags theme parks, IIRC). Zenith and their "Digital System 3" line of TV sets were really the only brand & model of TV available in the US during Electra's era that could do teletext, although Australian company Dick Smith Electronics did offer as a kit a set-top teletext decoder through their American affiliate re-sellers, and was featured with assembly instructions in a 1985 issue of Radio Electronics magazine in the US. Electra closed down in 1993 due to the service losing money for Taft, as well as Zenith around the same time discontinuing teletext capabilities in their sets in favor of built-in closed captioning as required by the FCC at the time for TV manufacturers. Not sure why Zenith couldn't of just kept the teletext features along with CC decoding, considering the two technologies are quite similar.
Loved how you showed off Warlords for your Atari display. My favorite Atari game. It's worth noting how little time Atari games had for logic. Any and all game logic/input/sound/etc had to fit in between the horizontal and vertical blank periods. All the games had to perform the display rendering themselves in software. Part of the reason the games were so simple - you had to spend like 90% of your compute cycle just rendering the image in real-time. NES (and maybe some others prior to the NES, unsure), had dedicated graphics chips that rendered in parallel to the game doing logic for the next frame.
Před 4 lety+1
Great video. You are a bit like Technologie Connections but a bit lighter in the intensity when it comes to technical informations.
Very nice video to listen to. I love listening to information content while gaming for backgrounds noise and entertainment, and i found a new channel for that
Really old TVs some times had flop over with closed captioning signals- leading to white lines and dots at the top of the screen. The TV guy was able to fiddle with stuff in the back of the set to fix it.
7:52 - I always wondered why there was half a line missing at the bottom of the picture when a local TV station was still using analog cameras on a digital transmission, that clears it up, thank you! 11:23 - I wish there was an easy, reliable way to capture closed captions from analog video, seems to be a feature either missing or an afterthought on most capture cards :s
Very good explanation of analog video. The Atari 2600 works quite a bit differently than other videogame consoles. It can display more (or less) than 192 lines, that is just the number Atari recommends in their documentation. The programmer has almost total control over the video signal timing and it is their responsibility to set when the HBLANK and VBLANK and VSYNC signals are produced by the TIA chip. By reducing the VBLANK period, a taller game display is possible. I've achieved a stable display as tall as 230 lines, though what is possible and how much is visible outside the overscan area is largely dependent on the television. That's why a conservative 192 scanlines is recommended.
My recollection is that the notion of 480i was born with the notion of digital TV and DVDs. Before that I don't recall anyone ever saying "480i", it was just NTSC.
This extra res is also a thing in current digital signals. Also google "Scanline sync". That's the best vsync alternative we have cause it eliminates vsync input lag.
Think of the electron beam as a pen, which has momentum when it moves. When the line ends, it still has the momentum from moving to the right for so long, so it literally has to slow down, go to the left for awhile to return to the beginning, turn around again, and start moving right for the next line. The H-sync interval accomidates this. Also, it was never just 525 and 625, there was a bunch of bespoke TV systems which all worked more or less the same way, but with different settings. The BBC used 405 lines for awhile, and the 525 line system was *originally* a 441 line system that then got upgraded. The first BBC TV broadcasts were 30 lines, mechanically scanned. It later got tweaked into a 32 line system that oldschool hams sometimes used over shortwave. Incidentally, the mechanical systems theoretically didn't need an H-sync pulse, as the mechanical scanners were able to start new lines instantaneously due to their geometry.
Funny that you mentioned KHOU Channel 11 from Houston. Right before they aired Dallas, we'd watch the Dukes of Hazzard on Friday nights on the same channel.
Sometimes a defect in the video amp could cause the otherwise blanked retrace lines to become visible. Or could be caused by what was known as "poor grid cutoff" characteristics in the cathode Ray tube.
Amazing work! Really amazing! How long does it take to make a video like this? Btw I was actually considering pausing this to make a sandwich, and then you said it. No joke. :)
there's just something so interesting about learning why the most mundane things work... like, who ever thinks "huh, i wonder how this 30 year old TV works?", yet here i am, spending 15 minutes of my life learning about it
Interesting trivia, because of the way the Atari 2600 controlled the video output (with the game itself control the HSYNC and VSYNC to an extent) it's possible to create an interlaced image. It has been done with real hardware as a proof of concept around 2001, but I'm not sure if any games actually use it.
If you got two stations on the same channel, you could see the VBI, and even some picture. Stations were offset by 10KHz, so you’d get a beat in the audio and video. I got a few faraway station IDs that way. Some VHS recordings on CZcams have it.
Actually, the vertical hold process typically starts at the bottom (visible if you can see the bottom of the raster), then the rest of the bar is drawn on it's way up, including the other half of the sync process. On an older TV (70s, back), you can see this with adjusting brightness, and contrast, as well as the retrace lines with vertical hold slightly off-sync. You can also view the copyright protection on DVDs/Tapes as well, as the beam always is drawing (it uses the black portions as "Blanking" the physical image, as that technology didn't exist then). It draws a pair of 4 black, and super-black boxes in the vertical bar retrace region. When this happens, you can see the white parts fade in, and out of the image on the upper-left of the display, because the older TVs didn't blank the raster at any point.
The aspect that isn't really explained here is how a half scanline can cause a shift in the field position: It's because the horizontal lines aren't actually perfectly straight, but due to the horizontal waveform, slightly bend to the next field position.
I had a general idea of how this worked, but never knew the magic number(s). I do recall using the 640x400 interlaced mode on my Amiga and getting a headache.
On the second pass (odd lines) the tv is drawing the video fields of the next frame, not the current frame. Interlaced video is sacrificing vertical resolution for temporal resolution.
In what context? Interlaced video has multiple options. You can use it to scanline-in a second field that illustrates some of the same frame as the previous field or use it to move forward in time and provide part of a new frame.
Front door back porch vertical blanking horizontal blanking 2 fields a frame....wow I'm glad I still engineer for the media. Such a history of technology......no sync pulse acts like a blurry picture.
This is where the copy protection company "Macrovision" got its name. The protection occurs within the horizonal "blanking bar" between the frames by intermittently adding white blocks that only allow the video signal to go to your TV. If you attempt to record that bar, the resulting intermittent blocks cause the contrast (luma) to fall below standard interfering with it.
This was fun to watch... Now for the headache, it's analog, there is no autoadjust of the electron beam, it was fixed timing setup at manufacturing by setters with a screwdriver and in fact you can also say the beam always runs the full lines, just it does a blank travel in interleaved mode and could perfectly run non interleaved (though it would cause some glitches and flickering visible and that's why TV were interleaved) With time and wear, the pulse could unsync, barely visible if not a slightly blurry or deformed image because the beam is a bit too high, too low on the tv grid or the speed of it isn't right. This is then you know your tv tech is a master or just crappy one! And add more... broadcast standard, NTSC, PAL or SECAM
Thats why for me it was always worth the extra money to use monitors instead of consumer TV's. A good monitor allows adjustments of all features and timings manually.
Late to the party, but I had to observe: So, the reason that we have these scanline filters for our retro games is that they were always only drawing to field one? Because they were doing the '240p' signal, the horizontal lines were only ever drawing the odd lines (sorta), skipping the even lines (again, sorta. I understand we're using digital terms to try to describe analog processes) by setting up another field one frame? And those blank even lines gave us the lined images that we remember so fondly? Mind blown.
I have a question, I understand that sync signals help stabilize the image, but what's the actual physical process of "locking" to the sync? I was always confused about this. Does the electron beam never stop moving? or does it finish the lines before the sync signals stops and "waits" for the sync signal before proceeding? If it never stops moving, how does the beam adjust when it receives the sync signals?
I love these older "technology" videos a lot, including the Luma and Chroma videos, but they sadly seem to have mostly died with that Chroma video. I get why; the view count on the "game code" videos seem higher, so it makes sense to focus on those. Not that they're bad, I just wish we could have more of a mixed bag.
The Amiga computer is the only computer really designed to control, and display correctly on, a CRT TV. Even so the 625 line PAL standard can only have 576p maximum output to the TV/monitor.
An Amiga is be ridiculously slow at 576p, and I have an AGA chipset. Though the highest it can output to a TV is 576i, for any higher you'd need a VGA monitor. The highest I've seen is 1024x768 on a VGA monitor, though if you have enough chip RAM and the right drivers you could go higher. 1024x768 was an interesting experiment, but it was genuinely too slow to be usable you could see each line being drawn onto the screen in real time.
@@fattomandeibu You are getting confused, I am talking about the fact that on a PAL 625i signal input from RF that all CRT TVs accepted the Amiga can only output 576/625 maximum lines the PAL signal allows per frame/two fields. This is not about resolution in total, it's about the reserved 50 lines used for things like Teletext or NICAM stereo sound broadcast through the RF signal in areas not even the Amiga chipset can access under any circumstances. No machine except specialist CRT TV engineer equipment can, but the Amiga accesses the most by far compared to any other system with RF output.
So for it drawing the same field for 240p the reason why we have crt filters in emulators that create black lines every 2-4 lines? That would make sense if it's drawing the field in the same place as the 2nd field never gets drawn and there would be a casual gap in the picture
13:10 cool, I always was wondering about those colorful dots on the bottom on the Sega display :D in PAL region we see them :P another fuck PAL situation :D haha
Again, the reason he can use words like ‘about’ and ‘approximately’ is because it was all analog. Unlike digital, there were no discrete, perfectly defined packets of data in analog..
I was always fascinated by how well the screens could switch and adjust between different types of signals in real time. Especially if you had a combination TV/Monitor and you pay close attention to broadcasts or computer signals, you could notice the spacing of the scanlines change periodically.
That broadcast data like the CC was discreet however, if not totally “digital”
@Ronnie Deacon I just love these fake conversations that are supposed to trick people into your scam!
But now we are all Digital, People say 'kind of' and "sort of".
You just listen to anything now. 'kind of' and "sort of". Is uttered often.
'Sort of' and 'Kind of'. This is such a Social Media guard phrase. It's not required. It either is or isn't, did or didn't.
CRT TV’s were some of the most awesome machines ever invented.
That invention changed human life style.
That lady in the photo is pretty awesome, too. Who is she?
exactspace I think dialup was the coolest thing. Sending all of that data over POTS with machines that test the lines by themselves? Neato
1440p @ 80-85hz with 0-2ms latency in 2003 so yeah they were!
I had a brilliant 32inch CRT tv back in the early 2000s that I wouldn’t even hesitate to trade my 4K 55inch flatscreen to get it back. It was heavy as hell and was screwed into its own tv cabinet that was a pain in the arse to move but my god, it was awesome playing ps2 games on that thing. I had it for nearly 10 years and it still worked like brand new until i dropped the damn thing while moving house...
This channel deserves more attention than it's getting.
i wanted to subscribe after i read this but i already am subscriber lol
i know im asking the wrong place but does anybody know a trick to log back into an instagram account..?
I was stupid forgot my account password. I would appreciate any tricks you can offer me!
@Frederick Tristan Instablaster :)
@Axel Derek i really appreciate your reply. I got to the site thru google and im trying it out atm.
Seems to take a while so I will reply here later with my results.
@Axel Derek It did the trick and I now got access to my account again. I am so happy:D
Thanks so much, you saved my account :D
Back in the day, they didn't tell us, it's 576 lines or 486 lines, respectively. I was told, we've got 625 lines and across the Atlantic, they've got 525.
I then computed out that with 4:3 ratio a line would have 833⅓ pixels. I had a close look at the screen, the screen was a cromaclear shadowmask, and I saw the hexagonal structure. I concluded that some lines have more pixels than others, some have 834 lines, other 833, on average 833⅓. How wrong I was. The literature I had back then didn't make things clear.
Nowadays, young people have never heard about the numbers 625 and 525. They only know SD as 480 in NTSC and 576 in PAL.
Oh i get it now.
CRTs are magic.
No, it is just "sufficiently advanced technology". A common misconception. ;)
I just discovered your channel earlier this week. It's become one of my favorites. Keep it up man!
Thanks, mrandostrike. Your comment means a lot. I’ll do my best!
Same! I keep coming back to rewatch videos...can’t wait for more content! It became one of my favorite channels almost instantly! Some collabs with other tech/video game youtubers would be awesome.
Would expect at least 100k subs for quality, content and age of this channel... CZcams's algorithm is a endless miracle to me!
Same here, a year later. This is such great info, so professionally presented. No complaints about any aspect of the channel, unless it's that there's not a hundred times more videos haha
The VBI pulses may seem repetitive, but they are pretty important if you want a picture on your screen. Remember that television was developed using vacuum tubes and 1930s discrete components and that ancient stuff had to not only sync up with a broadcast signal, but contend with poor signals as well. A lot of NTSC's design choices come from the limits of technology at the time.
Thanks, NJRoadfan. This is definitely true. I actually cut down my script a bit and elected to omit some of this information for pacing. The limits of technology at the time were such an important, key item in the evolution of television. They certainly weren't going to change the signal every couple of years just because technology improved. The most notable instance of this, in my opinion, was the birth of composite video.
I am glad you shared this comment.
Ah! I was wondering why those sync pulses were needed in the first place!
And also for PAL and SECAM, through their use of similar technology to address NTSC's flaws.
This is really interesting because I remember we had a really old CRT TV with v-sync and h-sync knobs that would distort the image (and I used to play with them). Now it makes total sense why the image was distorted that way. I really loved this video ! Thanks a lot for the great explanation!
The one detail that really helped this all click home to me when it was pointed out, is that the vertical scan is constant - the electron beam is always moving down, even as it scans across each scanline. This means that the scanlines are very slightly diagonal, as the beam moves down by most of a line as it goes from left to right across the screen. This is how the half-line offset makes the interlacing work - by starting one field at the top left of the screen, and starting the second field at the top middle of the screen, the scanlines for each field gets nestled between the scanlines for the other field. This is why the total number of lines, 525, is odd.
I love these videos man, great work as always. I don't know what it is in our nerd brains that makes this stuff so interesting, but I love it.
Thanks, Robby! Your comment means a lot to me. I hope to have more videos like this one soon!
One interested tidbit is that analog TVs didn't have pixels. The electron beam just varied in intensity as it moved left to right. So there was no definitive horizontal resolution for an analog signal.
If anyone wants to learn more, the channel Technology Connections made some good videos on analog TV, and Texas Instruments has an application note about CRT displays entitled "Understanding the Operation of a CRT Monitor." With the application note number AN-656. It's a good place to start digging deeper, for those interested.
That is true, but there was a limit to horizontal resolution due to the bandwidth allowed for broadcast TV. For NTSC each channel was allotted 6Mhz, which gave a maximum of 330 horizontal lines of resolution. You could determine the horizontal resolution with a test pattern. Often one was broadcast at night in off hours. upload.wikimedia.org/wikipedia/commons/thumb/a/ad/RCA_Indian_Head_Test_Pattern.svg/1200px-RCA_Indian_Head_Test_Pattern.svg.png
Until TVs had composite video inputs (and later S-video and component), that was the limitation. With composite inputs higher resolutions from connected devices could be achieved, because there was no 6Mhz bandwidth limitation. Monitors within TV studios had that capability (including some with RGB inputs) before it was available to consumers.
@@my3dviews Yup. When using baseband modulation for an RGB signal (as opposed to squeezing into an RF signal, or the limitations of a quadrature modulated color signal like composite or S-Video) your horizontal resolution was effectively infinite, limited only by the resolution of the phosphors of your display and the electronics in your display generator and monitor. This is how the ECS/AGA Amigas could do 1280 horizontal resolution in "SuperHiRes" modes on a 15Khz display.
Well you had the dot pitch/TVL of the actual display and the frequency of the signal itself both contributing to the resolution.
@@my3dviews Thanks, I didn't know about the bandwidth they had for each channel. Do you happen to know what the entire bandwidth was that was dedicated to over-the-air TV in general? And the radio frequency the FCC allotted for TV related things?
I was actually intending to look up info on various test patterns some time ago but forgot. So this served as a nice reminder. Great comment, man!
@@doltBmB Can't say I'm familiar with dot pitch or TVL. Definitely gonna look those up.
The reason for the half-lines in interlacing is interesting. Horizontal scanlines aren't really exactly horizontal. They slope down slightly from left to right. The is because the vertical downward deflection of the beam continues as each line is drawn. To get interlacing a vsync happens halfway during a scanline so that the next field's lines end up starting at the level of the midpoint of the previous field's slightly sloped lines.
The style of these videos makes it so much easier to understand
This is the best explanation on how CRT/tube TVs work in displaying the picture based on data.
Great visual and technical explanation! Especially on the half lines and how it makes the video interlaced (or not).
I just found your channel last month right around the time i started working with video signal, and then you start making videos on em, great videos.
The algorithm suggested your channel and after several videos of well thought out content, and clearly made with love, have not been disappointed. Subscribed and eagerly awaiting more!
Great job! I loved it! I deal with so much AVC and MPEG2, that this review of CRT tech is a refresher.
That was incredible! Way more thought and attention went into CRT TVs than I ever realized, but it certainly explains how heavy they were: a lot of stuff going on in there!
Displaced Gamers - JAPAN had MUSE High Difinition ANALOG TV in 1985,
they had 1 channel Dedicated to MUSE Broadcasts and it was even LIVE Broadcast from the Japan Worlds Fair in 1985.
the Worlds Fair also featured the Analog High Difinition TV camera and the High Difination TRINITRON Display.
625/576 line analog video in europe was great as we had wonderful teletext, that i could check news, betting, etc. on the TV!
We still have teletext in Finland :P But obviously it haven't been analog since 2007
Great Video, never seen the inner workings of the blanking intervals. I learned several things from this video. Keep it up!
Found your channel today and already watched about 6 videos of yours. Great content! Subscribed!
Thanks, Rodrigo! I am glad you are enjoying it and hope you continue to enjoy it as I release future videos! I welcome your feedback.
I finally found a channel to give me the answers. Not noly FPS and delays, but explanation. Love it
Very interesting video. Keep up the good work!
Good job and thank for sharing. It's valuable info after all
Fantastic video, thank you so much!
I would appreciate it if you added Closed Caption.
And thanks to you, I've learned how overscan works.
Done. Want to give it a try?
@@DisplacedGamers Sure.
1:02 gotta admit I was expecting it to hit the top left corner.
Love the video!!!
excelent work. solid information. subscribed. +1 for the keen 4 music
Your videos are my cup of tea. Nerdgasms abound!
Thanks, Nathan!
Bets video on the subject. Subscribed!
Really cool and well done
This is just awesome!
J.R. Ewing what a blast from the past. Lol Great video man.
Grew up with CRTs, used emulators in the mid 90's-and 2000's. Back to the original hardware and a PVM these days. It's really the best way to do it. And as mentioned in other videos, even component has its merits, so I'm looking forward to getting a nice Trinitron when I have the space.
Followed the link from RetroRGB. This was great info.
Thanks, TV’s Ben! Glad you stopped in!
That 80s VHS demonstration is such an eye opener.
I'm watching through your videos, having just discovered your channel. Fascinating stuff. Even though I worked with home computers since the early 80s, there are some things I still didn't know about luma, chroma and NTSC. One thing you didn't cover, however, is how live analog TV, and its recording on videotape, carries 60 intervals of motion per second even though there are only 30 full frames per second. Each field is a snapshot in time, and doesn't have to match either of the adjacent fields in the timeline. So the result looks like 60 fps even at full 480i res. Given the strobing effect of CRTs, that motion looks perfectly smooth too (unlike the sample-and-hold tech of LCDs).
Yeah! Sports in particular are great for this. Another interesting topic is framerate conversion from film (24 fps) to NTSC.
Interlacing could be thought of as an early form of video compression in this way.
I'm subscribed !!! Fantastic Video. I love Crt Technology. Today i have a mini collection of Crt projectors !!!!! Thanks for the video !
I've always wondered how CRT TV's functioned. Had no idea "480p" has been around since the 40's, that's amazing!
It would actually be 240p, with the width of a 480p signal (i.e. 720x240). The old consoles were essentially displaying everything on the top field and ignoring the bottom one. A true 480p(720x480) signal would take more bandwidth than the typical RF connections of the day -- for color signals, at least.
@@thebeetalls makes sense... The first time I saw true 480p on CRT was around 2005 on PS2 with an S-Video cable
The original NTSC standard was 525i (interlaced) which gave a vertical resolution of about 480, with a maximum horizontal resolution of 330 due to bandwidth limitations of the broadcast signal. There are no pixels in analog TV, just horizontal scan lines (which the number of give the vertical resolution) and horizontal resolution based on bandwidth limitations.
Even today, most HD broadcasts are 1080i (interlaced), with some broadcasting in 720p (progressive scan). There are no 1080p broadcasts, but Blu-ray players and other electronic devices do use it.
You should advertise your channel. This type of great content must dominate CZcams.
Awesome video.
I'd love to see more info about how game consoles use the blanking intervals or overscan to let the cpu run operations.
Significantly more complex than I expected!
Man, this is great stuff!, really interesting to see how it all works.
Now I know what those dark lines with a square half way through that quickly move up are when I fist turn on my rf or composite devices, I guess the television I guess the television doesn't get all the lines right away and accidentally draws them?
It is possible it was establishing sync lock. I think my first television (1968 Color CRT) would roll the image upward and "lock" when I first powered up a console. It would happen pretty fast - like before I would get my finger off the power button/switch of the console.
Thanks for your comment! I hope to make more videos like this one.
Invented in the U.K., then used in most of Europe, we had the teletext service transmitted over the air in the ‘spare line’, a service that offered hundreds of selectable pages of information without the need for a modem or computer. For some reason the US, did not make much use of the system and I believe only one cable network actually used it.
We had Teletext Here in new Zealand, it was quite handy in its time
Yes, that one cable network in the US that had teletext was Superstation TBS--they carried a teletext service in the 80s and early 90s called "Electra". TBS only carried the service, it was actually originated and programmed by a company based in Cincinnati, Ohio called Taft Broadcasting (who owned a few local TV stations in the US and also the Six Flags theme parks, IIRC).
Zenith and their "Digital System 3" line of TV sets were really the only brand & model of TV available in the US during Electra's era that could do teletext, although Australian company Dick Smith Electronics did offer as a kit a set-top teletext decoder through their American affiliate re-sellers, and was featured with assembly instructions in a 1985 issue of Radio Electronics magazine in the US. Electra closed down in 1993 due to the service losing money for Taft, as well as Zenith around the same time discontinuing teletext capabilities in their sets in favor of built-in closed captioning as required by the FCC at the time for TV manufacturers. Not sure why Zenith couldn't of just kept the teletext features along with CC decoding, considering the two technologies are quite similar.
We still have teletext in Finland
@@Pasi123
it's still running in Iceland too.
i think the reasoning is that there is a need for an alternative if accessing the internet is impossible.
@@Pasi123 here in Germany we still have Teletext too
You get a like an sub just for the Dallas footage.
Ha!
Loved how you showed off Warlords for your Atari display. My favorite Atari game.
It's worth noting how little time Atari games had for logic. Any and all game logic/input/sound/etc had to fit in between the horizontal and vertical blank periods. All the games had to perform the display rendering themselves in software. Part of the reason the games were so simple - you had to spend like 90% of your compute cycle just rendering the image in real-time.
NES (and maybe some others prior to the NES, unsure), had dedicated graphics chips that rendered in parallel to the game doing logic for the next frame.
Great video. You are a bit like Technologie Connections but a bit lighter in the intensity when it comes to technical informations.
I love that Neon graphic / visual nod to 80's and 90's. ☘️👍
Well explained.
Very nice video to listen to. I love listening to information content while gaming for backgrounds noise and entertainment, and i found a new channel for that
When you bought 'pay-per-view porn' in the 80's you were buying horizontal sync pulse.
If you had a good tv, you could fuck with the manual adjustments and sometimes see a free boob. I was a kid in the 80's, don't judge me.
That scrambling of the video was called Gated Sync Pulse.
When I was young, I remember boys talking about how that waited for a few frames to be visible.
@@rich1051414 Hey man, sometimes your only other option was the Sears catalog. Times were tough. No shame in it.
And they didn’t scramble the audio at all! ‘Watched’, or rather ‘listened’ to, _Superman II_ a dozen times this way as a kid!
Really old TVs some times had flop over with closed captioning signals- leading to white lines and dots at the top of the screen. The TV guy was able to fiddle with stuff in the back of the set to fix it.
7:52 - I always wondered why there was half a line missing at the bottom of the picture when a local TV station was still using analog cameras on a digital transmission, that clears it up, thank you!
11:23 - I wish there was an easy, reliable way to capture closed captions from analog video, seems to be a feature either missing or an afterthought on most capture cards :s
Yeah, I've always wondered also while watching old cartoons on CZcams why the bottom of the picture had half of a missing line.
I kind of wish you had covered Teletext as well. One of the most fascinating uses of the spaces left by vertical blanking!
Very good explanation of analog video. The Atari 2600 works quite a bit differently than other videogame consoles. It can display more (or less) than 192 lines, that is just the number Atari recommends in their documentation. The programmer has almost total control over the video signal timing and it is their responsibility to set when the HBLANK and VBLANK and VSYNC signals are produced by the TIA chip. By reducing the VBLANK period, a taller game display is possible. I've achieved a stable display as tall as 230 lines, though what is possible and how much is visible outside the overscan area is largely dependent on the television. That's why a conservative 192 scanlines is recommended.
So that's how it works! Wow thanks for sharing! Right on dude! B)
My recollection is that the notion of 480i was born with the notion of digital TV and DVDs. Before that I don't recall anyone ever saying "480i", it was just NTSC.
This extra res is also a thing in current digital signals.
Also google "Scanline sync". That's the best vsync alternative we have cause it eliminates vsync input lag.
the green vertical line within the horizontal sync pulse was the color burst signal.
Think of the electron beam as a pen, which has momentum when it moves.
When the line ends, it still has the momentum from moving to the right for so long, so it literally has to slow down, go to the left for awhile to return to the beginning, turn around again, and start moving right for the next line.
The H-sync interval accomidates this.
Also, it was never just 525 and 625, there was a bunch of bespoke TV systems which all worked more or less the same way, but with different settings. The BBC used 405 lines for awhile, and the 525 line system was *originally* a 441 line system that then got upgraded. The first BBC TV broadcasts were 30 lines, mechanically scanned. It later got tweaked into a 32 line system that oldschool hams sometimes used over shortwave.
Incidentally, the mechanical systems theoretically didn't need an H-sync pulse, as the mechanical scanners were able to start new lines instantaneously due to their geometry.
Funny that you mentioned KHOU Channel 11 from Houston. Right before they aired Dallas, we'd watch the Dukes of Hazzard on Friday nights on the same channel.
Sometimes a defect in the video amp could cause the otherwise blanked retrace lines to become visible. Or could be caused by what was known as "poor grid cutoff" characteristics in the cathode Ray tube.
Amazing work! Really amazing! How long does it take to make a video like this? Btw I was actually considering pausing this to make a sandwich, and then you said it. No joke. :)
Great video. You forgot to mention the chroma burst located in the horizontal blanking interval.
Thanks, David! I decided to leave it out in favor of a future video.
When you already know your stuff but you still watch the video because it's enterteining as heck.
For an expanded lecture(?) on CRT TV, check out Technology Connections extensive series on the history of television.
there's just something so interesting about learning why the most mundane things work... like, who ever thinks "huh, i wonder how this 30 year old TV works?", yet here i am, spending 15 minutes of my life learning about it
Interesting trivia, because of the way the Atari 2600 controlled the video output (with the game itself control the HSYNC and VSYNC to an extent) it's possible to create an interlaced image. It has been done with real hardware as a proof of concept around 2001, but I'm not sure if any games actually use it.
Gotta love that Seaquest on the Atari! []
If you got two stations on the same channel, you could see the VBI, and even some picture. Stations were offset by 10KHz, so you’d get a beat in the audio and video. I got a few faraway station IDs that way. Some VHS recordings on CZcams have it.
Most 8 bit computers had processors that could run in parallel with the video hardware dumping screen data to the CRT.
Actually, the vertical hold process typically starts at the bottom (visible if you can see the bottom of the raster), then the rest of the bar is drawn on it's way up, including the other half of the sync process. On an older TV (70s, back), you can see this with adjusting brightness, and contrast, as well as the retrace lines with vertical hold slightly off-sync. You can also view the copyright protection on DVDs/Tapes as well, as the beam always is drawing (it uses the black portions as "Blanking" the physical image, as that technology didn't exist then). It draws a pair of 4 black, and super-black boxes in the vertical bar retrace region. When this happens, you can see the white parts fade in, and out of the image on the upper-left of the display, because the older TVs didn't blank the raster at any point.
The aspect that isn't really explained here is how a half scanline can cause a shift in the field position: It's because the horizontal lines aren't actually perfectly straight, but due to the horizontal waveform, slightly bend to the next field position.
I always wondered what the heck was going on when I had to play with the Vsync button on the VCR to get the image to stop blink shifting up
I had a general idea of how this worked, but never knew the magic number(s). I do recall using the 640x400 interlaced mode on my Amiga and getting a headache.
I did paused the video and made a sandwich.
Awesome content! 🔥
On the second pass (odd lines) the tv is drawing the video fields of the next frame, not the current frame. Interlaced video is sacrificing vertical resolution for temporal resolution.
In what context? Interlaced video has multiple options. You can use it to scanline-in a second field that illustrates some of the same frame as the previous field or use it to move forward in time and provide part of a new frame.
@@DisplacedGamers apologies I was talking in the context of video (say live from a camera), not games or computer graphics.
Front door back porch vertical blanking horizontal blanking 2 fields a frame....wow I'm glad I still engineer for the media. Such a history of technology......no sync pulse acts like a blurry picture.
This is where the copy protection company "Macrovision" got its name.
The protection occurs within the horizonal "blanking bar" between the frames by intermittently adding white blocks that only allow the video signal to go to your TV. If you attempt to record that bar, the resulting intermittent blocks cause the contrast (luma) to fall below standard interfering with it.
"Now is a good time to pause the video and make a sandwich."
Well, I think I will! *pause*
most 240p consoles seem to use 524 lines... but I've noticed that my n64 puts out 526, interesting stuff
This was fun to watch...
Now for the headache, it's analog, there is no autoadjust of the electron beam, it was fixed timing setup at manufacturing by setters with a screwdriver and in fact you can also say the beam always runs the full lines, just it does a blank travel in interleaved mode and could perfectly run non interleaved (though it would cause some glitches and flickering visible and that's why TV were interleaved)
With time and wear, the pulse could unsync, barely visible if not a slightly blurry or deformed image because the beam is a bit too high, too low on the tv grid or the speed of it isn't right. This is then you know your tv tech is a master or just crappy one!
And add more... broadcast standard, NTSC, PAL or SECAM
Thats why for me it was always worth the extra money to use monitors instead of consumer TV's. A good monitor allows adjustments of all features and timings manually.
Late to the party, but I had to observe:
So, the reason that we have these scanline filters for our retro games is that they were always only drawing to field one? Because they were doing the '240p' signal, the horizontal lines were only ever drawing the odd lines (sorta), skipping the even lines (again, sorta. I understand we're using digital terms to try to describe analog processes) by setting up another field one frame? And those blank even lines gave us the lined images that we remember so fondly?
Mind blown.
❤
I have a question, I understand that sync signals help stabilize the image, but what's the actual physical process of "locking" to the sync? I was always confused about this. Does the electron beam never stop moving? or does it finish the lines before the sync signals stops and "waits" for the sync signal before proceeding?
If it never stops moving, how does the beam adjust when it receives the sync signals?
Television magic, got it.
I love these older "technology" videos a lot, including the Luma and Chroma videos, but they sadly seem to have mostly died with that Chroma video. I get why; the view count on the "game code" videos seem higher, so it makes sense to focus on those. Not that they're bad, I just wish we could have more of a mixed bag.
What was the additional data in the Dallas broadcast (that wasn't the closed captions)?
For the algorithm. ✊
The Amiga computer is the only computer really designed to control, and display correctly on, a CRT TV. Even so the 625 line PAL standard can only have 576p maximum output to the TV/monitor.
An Amiga is be ridiculously slow at 576p, and I have an AGA chipset. Though the highest it can output to a TV is 576i, for any higher you'd need a VGA monitor.
The highest I've seen is 1024x768 on a VGA monitor, though if you have enough chip RAM and the right drivers you could go higher. 1024x768 was an interesting experiment, but it was genuinely too slow to be usable you could see each line being drawn onto the screen in real time.
@@fattomandeibu You are getting confused, I am talking about the fact that on a PAL 625i signal input from RF that all CRT TVs accepted the Amiga can only output 576/625 maximum lines the PAL signal allows per frame/two fields. This is not about resolution in total, it's about the reserved 50 lines used for things like Teletext or NICAM stereo sound broadcast through the RF signal in areas not even the Amiga chipset can access under any circumstances. No machine except specialist CRT TV engineer equipment can, but the Amiga accesses the most by far compared to any other system with RF output.
*And love my Super Nintendo sir!* ❤️ ❤️ ❤️
small note, if you send 2 different fields per frame you can achieve 60fps using 480i instead of the usual 30fps that the format was designed for.
I understood at least half of this
Who's the model you've used in the example image?
how could be so complicated the way of the analog TV works back to an era were the electronics were far less developed than now?
So for it drawing the same field for 240p the reason why we have crt filters in emulators that create black lines every 2-4 lines? That would make sense if it's drawing the field in the same place as the 2nd field never gets drawn and there would be a casual gap in the picture
13:10 cool, I always was wondering about those colorful dots on the bottom on the Sega display :D in PAL region we see them :P another fuck PAL situation :D haha