5 ms·
Yep, that's the reason! The ingenious idea of using quantum amplitude modulation unfortunately also meant that slight phase shifts--which happen easily in broad
by anyfoo 4y ago
Yep, that's the reason! The ingenious idea of using quantum amplitude modulation unfortunately also meant that slight phase shifts--which happen easily in broadcast TV--appear as color errors.
PAL fixed it by flipping the phase around every line. By subtracting the current line from the previous line, the phase error would cancel out (but is also more expensive since you need to remember the last line, in a delay line or memory[1]). So, always the same color. (But not ATSC, that's something else entirely...)
[1] Well, there wer supposedly "PAL simple" receivers in the very beginning, where no processing of the phase flip was done and your eye was supposed to average the difference out. Probably looked terrible unless you were sitting really far away...
- namibj 4y agoOld PAL typically used a quartz prism that served as a folded bulk acoustic wave delay line, using an ultrasonic transducer and exciting the low syndic range of a composite signal to get by with cheap transducer electronics.
- anyfoo 4y agoIntrigued now, where can I find more about that?
- nyanpasu64 4y agohttps://en.wikipedia.org/wiki/Analog_delay_line https://en.wikipedia.org/wiki/Analog_delay_line, https://commons.wikimedia.org/wiki/File:Us_delay_line.jpg https://commons.wikimedia.org/wiki/File:Us_delay_line.jpg
- greesil 4y agoGood god, the things people used to do because transistors weren't available, or too expensive.
- zokier 4y agoThere is not really good way of accomplishing with transistors what delay lines are used for in PAL, unless you go full digital.
- anyfoo 4y agoI guess you could take a massive amount of them, and some capacitors, and use them for sample and hold. But you already covered insanity like that by saying that there is no good way...
- deaddodo 4y agoThis is one of this things I always found funny about PAL vs NTSC arguments. There simply wasn’t a better option, at the time. Both options were engineered with limited resources to best fit their respective needs. NTSC had a better refresh rate and easier hardware integration, plus 70+ years of backwards/forwards compatibility (a 1941 NTSC B+W television set could be used to watch the series finale of Friends in 2004 using a bog standard antenna for over the air signals); PAL had almost 30 years of experience and fixed some of the major issues with NTSC (primarily the Phase signaling) and had increased resolution at the cost of refresh rates. Both were pushing analog transmission bandwidth to the limits and did admirably until digital options were available and became the norm.
- MayeulC 4y agos/quantum/quadratic/ (you got me confused for a second)
- anyfoo 4y agoUgh yeah. That comment, unlike my original one, is full of typos. I typed it out quickly on my phone, and can’t edit anymore.