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Hot answers tagged video

47

Note how it says "330ns", a proper inductor would have a value in Henries. My guess is that this is an Analog delay line like this: Note how it has 3 connections of which one is ground which is connected to the tube and the shield. I actually came across one of these many many years ago, probably in some video equipment I scrapped for parts. At the time ...

41

It’s an early Canal+ 'pirate' box (with props to commenters who mentioned that.) The clue is the set of delay lines. Canal+ was originally based on a scrambling scheme called 'RITC Discret 1', that randomly manipulated video delay in increments of 902ns (0, 902, 1804ns). Four 470ns delay lines (those green Philips things in the photo) would give 1880ns or ...

24

The analog TV signal was originally designed to be decoded with the smallest practical number of valves (tubes). Thus about half the signal space (30% of the signal amplitude and almost 30% of the time) is dedicated solely to synchronisation pulses easily detectable by analog valve circuitry, and the picture information is left with only the other half Any ...

21

This is not an answer, but I'm not allowed to submit a "comment". As for what this component does, separate processing/filtering of video luminance and chrominance introduce different (group) delays in the two signals. This can become noticeable in the TV picture (see, for example https://www.bbc.co.uk/rd/publications/rdreport_1973_35). The delay line ...

17

The HD-15 (aka DE-15) connector for VGA connection was compatible with hand-crimping of pins to conductors of coaxial elements of the multiwire connecting cable. That practically requires a two-pin set for each of R, G, B video signals, to accommodate a signal pin and ground (coaxial shield) pin. Those signals were not logic level, and lacked the noise ...

13

As others have said, PAL and NTSC are analog and have virtually no latency. This is extremely important when flying FPV drones at high speeds. Having latency will tell you where you’ve been, not where you actually are. I have a large video/photography drone (Yuneec Q500 4K). It transmits the video digitally on 5.8 GHz using the 802.11A protocol. (Just ...

12

There are a number of problems you have here: VGA is 15 pins, not 9 RCA is composite video, not VGA IBM 5151 is neither of those, it's an old standard "MDA" (monochrome display adapter). It appears from the internet that MDA isn't a subset of VGA - you can't convert from one to the other by simple wiring. Your options are: find an old IBM 5151 ...

11

An analog video signal is basically a waveform. It's 100% time based, and one frame takes a specific length of time to transfer, since that is how long the wave is. The wave itself takes a certain amount of bandwidth, which is basically how much data is held in that wave. It's possible to reduce the amount of bandwidth required through various filtering ...

11

You can compress analog video so it uses less bandwidth, at the cost of quality: slow scan television. Used to transmit live television from the surface of the moon, in blurry monochrome. These days we can have colour HD from the surface of Mars. It's worth looking at how the various digital compression techniques work in detail, but they all rely on ...

10

You are confusing the DVI connector with the cable. That "single" analog ground is a big honking ground, but what goes into a cable? The simplest is a DVI-A cable, which usually has a VGA connector on the other end. Internally, it will carry 3 color channels (red, green and blue) and 2 sync: vertical and horizontal. And guess what? A DVI-A cable will ...

10

The green rectangles appear to be delay lines, one IC is an analog switch CD4066BE, one is a quad op-amp chip LM324DP, the yellow sticker is a MC68705 microcontroller, and the right top IC is obscured in the image. I would assume the chip is mostly likely a switch like the CD4066BE. The power side of the system has what looks to be a step-down transformer (I ...

8

Both front porch and back porch as well as horizontal pulse and color burst are sync information in the horizontal blanking period, in the analog video. The front porch it is an interval period between the end of picture information and start of horizontal pulse. The level of front porch is at pedestal (black reference) and the purpose is to set blanking ...

8

That looks like an SO239 UHF connector. That's the socket that goes with the PL259 plug. The term "UHF connector" is somewhat misleading. It was developed in the 1930s. Back then, UHF meant "over 30MHz." These days, UHF is 300 MHz to 3GHz.

7

I upvoted Nettle Creek's answer, but here is a quick explanation about why latency matters: Piloting a drone is a feedback system with you in the loop. As in any other feedback system, the usual Nyquist stability critera apply. Video latency adds lag in the feedback loop, and the effect is the same as on any other feedback system (you are the opamp): it ...

7

At worst the recording device will saturate (and the camera element may be damaged), but the playback device will only generate an intensity that it is capable of. There is no danger to vision that would not normally be present with the playback device.

7

The width of the HSYNC signal was 6 us, out of spec of 2.8 ... 5.3 us for AD725. The mother circuit had the location to source this signal (as video processor outputs 4.7 max, and prolongation of the pulse was introduced down the circuit), and I reused this signal. Now circuit works properly in both NTSC and PAL mode. Small dot crawling and ripple exists, ...

7

I found the answer to this some time ago, posting it here in the hope it will help others. The reason 1 byte is sent immediately on enabling DMA, is because a DMA request (DRQ) is still active from the last time that TIM8 ran. TIM8 keeps running and raising DRQ signals, even after all the bytes in the buffer have been written and DMA stops. TIM8 is gated ...

7

Unfortunately, they are all important. Including cable shields. Except maybe the UTIL and CEC lines if you don't need the features they provide.

6

For PAL, used in Europe, part of Africa, part of South America, Asia and Australia, the number of scan lines is 625. For NTSC, used in most of the Americas and Japan, the number of scan lines is also an odd number, 525. This answer discusses the latter, as I cannot find a definitive answer why PAL uses an odd number of lines. The National Television ...

6

If you are interested in how digital video is sent there are a number of current standards which are relevant. As you mention VGA it is worth focusing on digital signalling designed to work between device and screen, rather than broadcast standards. Right now there are three standards for consumer devices and each has an excellent Wikipedia article: DVI, ...

6

Since you're using fairly low frequencies, this will be straightforward but tedious. What you'll need to do is to divide each channel into 3 segments - left,horizontal center and right, and bottom, vertical center and top. Then feed the 9 combinations (permutations, actually) to your 9 monitors. You make the 6 segments using op amps. Let's say, just for ...

6

It is not practical to resolve an NTSC or PAL type analogue video data into a digital format using a typical microcontroller A/D converter. The equivalent pixel density of the analogue signal is 13.5 MHz and if you want to retain any type of ability to realize the color of the pixels you would be having to oversample the analogue signal at something on the ...

6

Aside from what Justme wrote (accept their answer, it's correct and the critical point here): HDMI's data lines are really high-speed. That's easy to imagine: assume you have 1920×1200 px screen you want to feed at 60 fps. That makes 138.24 million pixels a second. Each of these have 8 bit on each color channel, and then there's 8b/10b-encoding, so that you ...

6

Setup, or pedestal, was a 'feature' that helped engineers align the raster on the monitor: it made an active video extent visible by turning up the brightness. When's the last time you did that? Never. So the later PAL and SECAM standards didn't use it. PLUGE is used instead. Setup requires that the video be 'squished' to allow for the 7.5 IRE added to it ...

5

EDID is used, among other things, to query the monitor for the timings it would like. It isn't used to transmit any video information. I guess it's been so long that no one remembers, but VGA monitors back in the day had adjustments for the image location on the CRT. You could move it left or right, up or down, or scale it horizontally or vertically. More ...

5

It looks to me that your DVD player is outputting YPbPr component video instead of RGB. If you look at the pinout listing on Wikipedia, you'll see that pin 11 carries either green for RGB, or luminescence (Y) for YPbPr. (It also notes that the YPbPr mode is a non-standard extension.) I'd check your DVD player menus to see if you can change the output mode. ...

5

Because the video is baseband. That means that it is NOT modulated onto a VHF or UHF carrier. You are asking to take the audio modulated onto a HF carrier and combine it with the baseband video signal. And then to demodulate the audio back into baseband at the other end of the cable. That has the deadly combination of costing more, plus being lower quality. ...

5

If you are looking for accuracy and (more probably) avoiding reflections then the $50\:\Omega$ oscilloscope inputs will need a $75\:\Omega$ feed-thru terminator of some kind. You can buy them or make them. The T connector I'm sure you are familiar with. But you can see the T, the termination, and both hooked together here: Also, you will really wish you ...

5

You'll want an old-school RF modulator: https://en.wikipedia.org/wiki/RF_modulator. These were common in the days prior to baseband composite inputs on TVs. They basically are an upconverter-in-a-box: they take the composite signal and upconvert it to the VHF broadcast band so that it looks like an over-the-air signal to the TV. You simply tune to the ...

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