1 00:00:00,070 --> 00:00:04,730 How do you take an existing technological standard, and make it do three times as much 2 00:00:04,730 --> 00:00:08,290 “stuff”, all the while without really changing it? 3 00:00:08,290 --> 00:00:13,629 This was the task given to RCA in developing their compatible color television system. 4 00:00:13,629 --> 00:00:17,890 A black and white television set need only know how bright part of an image is, but a 5 00:00:17,890 --> 00:00:22,050 color television needs to know how much red is in an image, how much green, and how much 6 00:00:22,050 --> 00:00:23,050 blue. 7 00:00:23,050 --> 00:00:27,060 These three combined images will appear in full color, but any one of them on their own 8 00:00:27,060 --> 00:00:29,480 wouldn’t look right on a black and white television. 9 00:00:29,480 --> 00:00:33,620 And RCA didn’t have more bandwidth at their disposal as the standards had already been 10 00:00:33,620 --> 00:00:35,370 established for black and white TV. 11 00:00:35,370 --> 00:00:39,219 They couldn’t just send three discrete images even if they wanted to. 12 00:00:39,219 --> 00:00:44,040 So they needed to take the existing television signal, and somehow add more information to 13 00:00:44,040 --> 00:00:47,880 it, and still make it compatible with existing black and white televisions. 14 00:00:47,880 --> 00:00:51,990 RCA was working towards a color television system that could do just that. 15 00:00:51,990 --> 00:00:55,571 They had gotten the fundamentals figured out on their compatible color system, and were 16 00:00:55,571 --> 00:01:01,870 competing with CBS’s field-sequential color wheel system for FCC approval in 1950. 17 00:01:01,870 --> 00:01:05,190 You can learn more about that system in the previous video. 18 00:01:05,190 --> 00:01:09,700 RCA’s system was based on the 1938 work of Georges Valensi of France. 19 00:01:09,700 --> 00:01:15,370 The National Television Systems Committee, or NTSC, chose RCA’s system as their standard, 20 00:01:15,370 --> 00:01:16,462 and they lobbied hard for its approval. 21 00:01:16,462 --> 00:01:21,910 To recap, the CBS system used a conventional black and white picture tube and camera. 22 00:01:21,910 --> 00:01:25,030 Both of which were fitted with a spinning wheel in front of them. 23 00:01:25,030 --> 00:01:29,030 The wheel contained repeating sections tinted red, green, and blue. 24 00:01:29,030 --> 00:01:33,070 If you show each color sequentially and do it fast enough, persistence of vision will 25 00:01:33,070 --> 00:01:35,689 kick in prevent you from noticing. 26 00:01:35,689 --> 00:01:39,720 Synchronize the discs between camera and receiver and you’ll get a full color image. 27 00:01:39,720 --> 00:01:42,900 But to be convincing, the color wheel has to spin very fast. 28 00:01:42,900 --> 00:01:49,700 CBS increased the field rate from the standard 60 hz to 144 hz, allowing the complete R-G-B 29 00:01:49,700 --> 00:01:52,350 image to be seen 48 times per second. 30 00:01:52,350 --> 00:01:58,049 But in doing so, they threw out any possibility of being compatible with existing televisions. 31 00:01:58,049 --> 00:02:02,740 RCA, meanwhile, was using a new type of picture tube which contained a repeating pattern of 32 00:02:02,740 --> 00:02:07,100 red, green, and blue phosphor dots in front of a shadow mask, which worked in conjunction 33 00:02:07,100 --> 00:02:12,040 with three separate electron guns in the tube to simultaneously show a red, green, and blue 34 00:02:12,040 --> 00:02:14,330 image in one device. 35 00:02:14,330 --> 00:02:17,910 These groupings are not in any way discrete pixels, which I feel bears repeating from 36 00:02:17,910 --> 00:02:19,160 my last video. 37 00:02:19,160 --> 00:02:23,300 They simply serve as a regular pattern with which the shadow mask can prevent the electron 38 00:02:23,300 --> 00:02:25,600 guns from hitting the wrong color. 39 00:02:25,600 --> 00:02:29,200 This new shadow mask picture tube was the key to compatibility. 40 00:02:29,200 --> 00:02:33,220 If all three electron guns ran at the same intensity relative to each other it would 41 00:02:33,220 --> 00:02:37,360 function exactly the same as an ordinary black and white television, making an image using 42 00:02:37,360 --> 00:02:40,050 a repeating pattern of horizontal lines. 43 00:02:40,050 --> 00:02:44,400 But if you control them independently, the picture tube can now make a full color image 44 00:02:44,400 --> 00:02:49,220 on its own, while still building the image in fundamentally the same fashion as a standard 45 00:02:49,220 --> 00:02:50,220 television. 46 00:02:50,220 --> 00:02:55,090 However, RCA’s color system required a more complicated camera with three separate video 47 00:02:55,090 --> 00:02:59,590 tubes, each of which was behind a filter to provide it only with red, green, or blue light. 48 00:02:59,590 --> 00:03:03,650 The three separate image components provided by the tubes were combined and encoded in 49 00:03:03,650 --> 00:03:07,930 such a way that the transmitted signal appears to be a black and white transmission. 50 00:03:07,930 --> 00:03:12,470 A black and white TV would display a perfectly acceptable image from these transmissions. 51 00:03:12,470 --> 00:03:16,740 But a color television set could recover the color information from the camera using some 52 00:03:16,740 --> 00:03:17,740 clever tricks. 53 00:03:17,740 --> 00:03:22,130 Now, I’m going to do my best at describing how NTSC color is encoded. 54 00:03:22,130 --> 00:03:26,670 It’s very technical and hertz to think too much about, so I’m going to tell you some 55 00:03:26,670 --> 00:03:31,650 basic info and do my best to explain how it allows the TV to form a color image from an 56 00:03:31,650 --> 00:03:33,690 apparently black and white transmission. 57 00:03:33,690 --> 00:03:37,870 The beauty of NTSC color was how it dealt with the outputs of the three separate camera 58 00:03:37,870 --> 00:03:38,870 tubes. 59 00:03:38,870 --> 00:03:42,900 Instead of deal with them directly in an RGB encoding scheme, the outputs from the tubes 60 00:03:42,900 --> 00:03:48,550 were used to create two separate intermediary signal components: luminance, a brightness 61 00:03:48,550 --> 00:03:51,740 component, and chrominance, a separate color component. 62 00:03:51,740 --> 00:03:55,420 The luminance part of the signal was created by adding together the red, green, and blue 63 00:03:55,420 --> 00:03:57,300 channels from the camera. 64 00:03:57,300 --> 00:04:00,760 This would be compatible with existing black and white televisions, as it was simply a 65 00:04:00,760 --> 00:04:02,880 measure of overall brightness. 66 00:04:02,880 --> 00:04:07,090 The most genius part of NTSC color was that the chrominance component was almost completely 67 00:04:07,090 --> 00:04:09,920 hidden using some clever encoding methods. 68 00:04:09,920 --> 00:04:14,200 No extra bandwidth was required because by using a little math, a color television can 69 00:04:14,200 --> 00:04:18,970 derive the chrominance component from within the luminance component itself. 70 00:04:18,970 --> 00:04:20,720 So first, some methodology. 71 00:04:20,720 --> 00:04:24,820 The luminance signal is created by adding together the the R, G, and B components from 72 00:04:24,820 --> 00:04:27,530 the camera in this ratio. 73 00:04:27,530 --> 00:04:29,450 Luminance is referred to as Y. 74 00:04:29,450 --> 00:04:35,080 Chrominance is conveyed as two signals, I and Q. I is created by taking 60 percent of 75 00:04:35,080 --> 00:04:39,190 the Red signal, subtracting 28 percent of the Green signal, and further subtracting 76 00:04:39,190 --> 00:04:41,570 32 percent of the Blue signal. 77 00:04:41,570 --> 00:04:47,750 Q is created by taking 21% of the red signal, subtracting 52% of the green, and then adding 78 00:04:47,750 --> 00:04:50,180 31% of the blue. 79 00:04:50,180 --> 00:04:54,190 Yes this is all confusing and I don’t even want to try and work out how these ratios 80 00:04:54,190 --> 00:04:59,430 fit into each other but the fact of the matter is so long as the TV set can see I and Q, 81 00:04:59,430 --> 00:05:04,270 it can bring back the original RGB values seen in the camera by applying a bit of analog 82 00:05:04,270 --> 00:05:07,490 algebra to the known luminance, that’s Y. 83 00:05:07,490 --> 00:05:12,240 With I and Q signals, a television can use the same ratios the camera did to produce 84 00:05:12,240 --> 00:05:17,640 I, Y, and Q to bring back R, G, and B, and it will then be able to adjust the output 85 00:05:17,640 --> 00:05:21,910 of the three electron beams in order to follow the original RGB ratios the camera picked 86 00:05:21,910 --> 00:05:22,910 up. 87 00:05:22,910 --> 00:05:27,120 If the television doesn’t see I and Q, it will simply fire all three electron guns with 88 00:05:27,120 --> 00:05:29,760 the same intensity to produce only black and white. 89 00:05:29,760 --> 00:05:32,200 Now for the REALLY complicated bit. 90 00:05:32,200 --> 00:05:34,380 You might have asked where I and Q are coming from. 91 00:05:34,380 --> 00:05:36,450 He keeps talking about these apparently nonexistent values! 92 00:05:36,450 --> 00:05:38,220 What is he going on about?! 93 00:05:38,220 --> 00:05:42,590 Well, I and Q are hidden within the luminance component. 94 00:05:42,590 --> 00:05:47,950 Using a process called QAM, or quadrature amplitude modulation, the luminance component 95 00:05:47,950 --> 00:05:54,200 can serve as a vessel for I and Q. To actually extract them, the luminance carrier is multiplied 96 00:05:54,200 --> 00:05:58,930 by a 3.579545 MHz reference signal. 97 00:05:58,930 --> 00:06:03,480 The phase of this signal is used in determining the hue of the color, so it was critical that 98 00:06:03,480 --> 00:06:08,660 the television receive a perfectly timed reference of this frequency from the transmission itself, 99 00:06:08,660 --> 00:06:10,980 otherwise the hue would be all wrong. 100 00:06:10,980 --> 00:06:15,670 Just before each line, in the back porch as it’s called, is the colorburst. 101 00:06:15,670 --> 00:06:18,290 This is a brief transmission of that carrier. 102 00:06:18,290 --> 00:06:22,600 The television set’s own crystal oscillator will lock onto and synchronize with the carrier 103 00:06:22,600 --> 00:06:25,240 to ensure the colors are decoded correctly. 104 00:06:25,240 --> 00:06:28,970 The colorburst doesn’t actually include any color information, but it’s vital to 105 00:06:28,970 --> 00:06:32,110 the television’s ability to correctly extract the color. 106 00:06:32,110 --> 00:06:36,580 If the television sees the color burst, it will begin demodulating the I and Q signals 107 00:06:36,580 --> 00:06:41,600 with the help of that crystal oscillator, now in a phase-locked loop with the colorburst. 108 00:06:41,600 --> 00:06:44,900 Actually, this is easier to explain in graph form. 109 00:06:44,900 --> 00:06:47,520 A black and white television signal looks like this. 110 00:06:47,520 --> 00:06:51,540 These low points are the horizontal blanking intervals between the lines, and this squiggly 111 00:06:51,540 --> 00:06:53,390 bit is the part you see. 112 00:06:53,390 --> 00:06:57,030 The brief section between the blanking interval and the start of the visible portion is called 113 00:06:57,030 --> 00:06:58,780 the back porch. 114 00:06:58,780 --> 00:07:02,830 Along the visible portion, the higher the line goes, the brighter the image is drawn 115 00:07:02,830 --> 00:07:03,940 on the screen. 116 00:07:03,940 --> 00:07:07,820 Remember, the image is made of lines, which can you learn more about, here. 117 00:07:07,820 --> 00:07:13,320 Now, a color transmission looks nearly exactly the same, but this little squiggle, the colorburst, 118 00:07:13,320 --> 00:07:16,750 is tucked in just before the line in the back porch. 119 00:07:16,750 --> 00:07:21,250 This colorburst is simply the carrier that I and Q are modulated on. 120 00:07:21,250 --> 00:07:26,300 The carrier is suppressed during transmission except for during the colorburst, which eliminates 121 00:07:26,300 --> 00:07:30,350 most of the interference between the chrominance and luminance signals, allowing a black and 122 00:07:30,350 --> 00:07:32,280 white television to display the image. 123 00:07:32,280 --> 00:07:37,090 A color TV, though, will use this colorburst to synchronize its own crystal oscillator. 124 00:07:37,090 --> 00:07:41,260 Once it’s locked on, the television set’s oscillator will recreate the carrier. 125 00:07:41,260 --> 00:07:45,370 Imagine the colorburst continuing on throughout the entire process. 126 00:07:45,370 --> 00:07:51,160 The TV will then use its own generated carrier to complete the task of demodulating the color. 127 00:07:51,160 --> 00:07:55,270 As the three electron beams fly along the face of the tube, the circuitry multiplies 128 00:07:55,270 --> 00:07:59,730 both the sine and the cosine of the carrier wave with the luminance value, which will 129 00:07:59,730 --> 00:08:02,270 now provide the I and Q values. 130 00:08:02,270 --> 00:08:06,639 Then the derived I and Q values, along with the original Y value are passed through a 131 00:08:06,639 --> 00:08:11,420 matrix circuit applying the ratios we learned earlier, which will then spit out the original 132 00:08:11,420 --> 00:08:14,220 RGB values encoded by the camera. 133 00:08:14,220 --> 00:08:19,130 With this recovered, we finally have the ability to mix the three electron guns separately 134 00:08:19,130 --> 00:08:21,080 into a coherent RGB output. 135 00:08:21,080 --> 00:08:25,310 Now, limited bandwidth meant that the resolution of the chrominance component is not as high 136 00:08:25,310 --> 00:08:26,930 as the luminance. 137 00:08:26,930 --> 00:08:31,310 In effect, the picture is still mostly monochrome but with gobs of loosely-applied coloring 138 00:08:31,310 --> 00:08:33,029 thrown on top. 139 00:08:33,029 --> 00:08:37,460 Think of it as the ratio of the three electron beams--thus the apparent color--being locked 140 00:08:37,460 --> 00:08:42,360 in by the color signal over large chunks of the line, but still with the ability to in 141 00:08:42,360 --> 00:08:46,890 unison change intensity, and thus brightness, along with the luminance signal. 142 00:08:46,890 --> 00:08:51,020 We’re much more sensitive to changes in brightness than in color, so the image would 143 00:08:51,020 --> 00:08:52,790 seem completely natural. 144 00:08:52,790 --> 00:08:57,380 In fact, many digital formats such as MPEG-2 exploit our eye’s poor color detection in 145 00:08:57,380 --> 00:09:02,570 a similar way, dedicating more data to brightness than color to allow for compression. 146 00:09:02,570 --> 00:09:07,171 Anyway, I’m really not going to elaborate further on QAM because oh my goodness there’s 147 00:09:07,171 --> 00:09:11,120 a lot of math involved but if you’re intrigued I cordially invite you to visit some links 148 00:09:11,120 --> 00:09:12,440 down below. 149 00:09:12,440 --> 00:09:16,600 But to finish our story we started with the last video, when the FCC had given the go-ahead 150 00:09:16,600 --> 00:09:22,610 for CBS’s color wheel system in 1950, RCA’s color wasn’t working too well. 151 00:09:22,610 --> 00:09:27,339 In fact at the beginning of the “competition”, they were still pursuing a three tube optical 152 00:09:27,339 --> 00:09:31,240 system, but they were investing heavily in their replacement system using a shadow mask 153 00:09:31,240 --> 00:09:32,240 CRT. 154 00:09:32,240 --> 00:09:37,180 Regardless, the image quality from the CBS system was far superior to what RCA and others 155 00:09:37,180 --> 00:09:40,550 could muster at the time with their early shadow mask offerings. 156 00:09:40,550 --> 00:09:45,290 RCA fought very hard to get approval for their system, but it didn’t come. 157 00:09:45,290 --> 00:09:48,580 But two things happened to make sure they would eventually succeed. 158 00:09:48,580 --> 00:09:50,950 First was the reformation of the NTSC. 159 00:09:50,950 --> 00:09:54,640 The National Television Systems Committee created the original black and white television 160 00:09:54,640 --> 00:09:59,660 specifications, and having seen RCA’s work on a compatible color system coming down the 161 00:09:59,660 --> 00:10:03,200 pipeline, they got back together and worked hard to try and get the FCC to approve this 162 00:10:03,200 --> 00:10:04,730 new system. 163 00:10:04,730 --> 00:10:09,140 This very much annoyed the FCC because they had already given permission to CBS to proceed. 164 00:10:09,140 --> 00:10:12,810 However, the Korean War threw CBS’s plans under the bus. 165 00:10:12,810 --> 00:10:17,290 The National Production Authority declared that color television production must cease 166 00:10:17,290 --> 00:10:24,080 on November 20th, 1951--exactly one year after permission was granted to begin color broadcasts. 167 00:10:24,080 --> 00:10:28,860 And in the meantime, the NTSC and RCA remained hard at work improving their new compatible 168 00:10:28,860 --> 00:10:30,030 color system. 169 00:10:30,030 --> 00:10:35,850 By 1953, the shadow mask CRT was sufficiently developed and was producing excellent results, 170 00:10:35,850 --> 00:10:40,029 and funny enough it was one of CBS’s subsidiaries that made the first breakthrough. 171 00:10:40,029 --> 00:10:44,270 It became obvious that CBS’s sequential color wheel system didn’t make any sense 172 00:10:44,270 --> 00:10:48,820 whatsoever if compatible color was producing similar results. 173 00:10:48,820 --> 00:10:55,240 In March of 1953, CBS testified before congress that they were abandoning their color TV efforts, 174 00:10:55,240 --> 00:10:58,680 afterwhich time the ban on producing color televisions was lifted. 175 00:10:58,680 --> 00:11:04,779 The NTSC restarted their efforts for FCC approval, and it was granted to them on December 17th, 176 00:11:04,780 --> 00:11:05,779 1953. 177 00:11:05,800 --> 00:11:10,700 The first nationwide color transmission of the new compatible system occurred on January 178 00:11:10,700 --> 00:11:15,240 1, 1954, a broadcast of that year’s Tournament of Roses parade. 179 00:11:15,240 --> 00:11:19,490 In the US, color TV wouldn’t really take off for about 10 years. 180 00:11:19,490 --> 00:11:24,399 Early color sets were insanely expensive, costing about as much as a new car, and their 181 00:11:24,399 --> 00:11:27,870 vacuum tube electronics were very finicky. 182 00:11:27,870 --> 00:11:30,800 These color TVs required lots of patience. 183 00:11:30,800 --> 00:11:34,390 Though it’s amazing to me that this amount of complexity could even be achieved with 184 00:11:34,390 --> 00:11:36,330 1950s technology. 185 00:11:36,330 --> 00:11:40,000 But the fact was, most TV programming was still in black and white. 186 00:11:40,000 --> 00:11:45,200 It wasn’t until 1965 that the majority of TV broadcasts were in color. 187 00:11:45,200 --> 00:11:50,040 Until that point, owning a color TV was a luxury that only rarely saw its true value. 188 00:11:50,040 --> 00:11:56,920 It wouldn’t be until 1972 that color TVs outsold black and white units in the US. 189 00:11:56,920 --> 00:11:59,140 And now, some odds and ends. 190 00:11:59,140 --> 00:12:01,140 Actually, later, some odds and ends. 191 00:12:01,140 --> 00:12:05,040 I hate to do this, but I’ve found over 10 minutes of stuff that I want to talk about. 192 00:12:05,040 --> 00:12:09,190 I’m sorry, this was supposed to be two parts, but it’s getting longer still. 193 00:12:09,190 --> 00:12:14,330 In the next video, I’ll touch on the differences between NTSC and PAL, we’ll go over chroma 194 00:12:14,330 --> 00:12:20,680 dots and color restoration, Guillermo Gonzalez Camarena’s dubious invention, the 29.97 195 00:12:20,680 --> 00:12:24,529 frames per second nonsense we deal with here in the States, and more. 196 00:12:24,529 --> 00:12:28,300 Thanks for watching, and thanks for putting up with another cliffhanger. 197 00:12:28,300 --> 00:12:31,290 If you like this sort of video and are new to the channel, why not subscribe? 198 00:12:31,290 --> 00:12:35,430 I’d also like to thank all of my Patreon supports for keeping this channel possible, 199 00:12:35,430 --> 00:12:38,110 especial these folks who get their name in lights. 200 00:12:38,110 --> 00:12:41,700 You can support this channel and help keep these videos coming more frequently. 201 00:12:41,700 --> 00:12:45,600 Patreon Supporters have allowed me to 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