Analog video sync - Page 1
Forum section: electronics / projects

author: bopstar
author_rank: Regular Contributor
timestamp: January 24, 2018, 03:23:12 am
content: Hi i would like to know how to get two analog video signals to be synced for a analog video mixer project, i have the basic understanding of what needs to be done but don't know which way to go. should i try using a phase lock loop or make a sync generator and add that to tape machine by modding a VCR to have a SYNC in to allow video mixing from two tape drives. and if so how do i do thatKind Regards.Justin Harris

author: helius
author_rank: Super Contributor
timestamp: January 24, 2018, 03:44:58 am
content: TV studios and editing suites have a "house black" that is generated from a master device, and then fed into a Distribution Amplifier to send out to all the various equipment that needs to be synchronized. The signal consists of completely black video with sync and (usually) colorburst. However, most equipment with sync in ports will allow any kind of CVBS signal to sync with, so you can simply use the video output of one device to synchronize others.The kind of tape recorder used in these suites is called a VTR, and always has a sync (or Genlock) input. They are specifically designed to support online editing and mastering, with features like frame-accurate locate command and drop-in recording. I don't know if consumer VCRs could be modified to support genlock (seems unlikely), but they are still unsuitable for editing because they miss these other important features.I would suggest reading some white papers from Leitch or Extron to see how video synchronization works in the real world and some of the issues involved.

author: bopstar
author_rank: Regular Contributor
timestamp: January 24, 2018, 04:06:05 am
content: i knew all of that already i am asking how to mod preexisting vhs tape machines to do that (accept a house black)

author: basinstreetdesign
author_rank: Frequent Contributor
timestamp: January 24, 2018, 06:08:22 am
content: What you want to do is not impossible but none of your options are simple.To hack a VCR to accept and use a house reference requires designing and building a complicated genlock circuit and frankensteining it into the VCR circuit. This is probably the worst choice since it is so complex. A properly locked system takes into account vertical and horizontal syncs as well as chroma sub-carrier phase lock. I have built genlock systems and they generally turn out to be half a square foot of electronics (SMT, glue logic + PLLs + an FPGA + some non-trivial analog stuff, and that is if there is no uP).Just using a simple PLL to align the motor of one VCR to the vertical sync pulse of another source is simpler but much more chancy. For this you would need schematics of your machine and be able to understand in grisly detail how the circuit works and what ANY hack to it would do. Even if you get the playback motional dynamics of the PLL+slave machine to be reasonably well-behaved, the result can still be out of phase by a few lines of video. The sub-carrier phase will be random and constantly changing. What would your mixer do in this situation? I imagine the you would see half way through a wipe/dissolve one-half of the end picture is a stable source and the other half is jumping side-to-side with random/B&W colour.Another possible solution is to put a Framestore Synchronizer between one source and the mixer and reference the FS to the second (now reference) source. This is if you could find one. The only FS I can find on EBAY is only USF$50 but is non-working.It was made by Digital Processing Systems a company I knew quite well and who put out excellent stuff. They don't exist anymore, having been absorbed by Leitch who were then absorbed by Harris. A working one would still be relatively cheap (compared with new prices) these days now that analog video is effectively dead but you have to search more than I could do in 10 min.Sorry to rain on your parade, and I hope I am not making too many assumptions about your situation but I wish I could be more help.

author: drussell
author_rank: Super Contributor
timestamp: January 24, 2018, 06:45:45 am
content: My Mitsubishi HS-U55 has edit connections on it to talk to other compatible VCRs to be able to do frame-accurate editing. I've used it with other Mitsubishi and Electrohome VCRs before... You can even drop one single frame into a recording without disturbing the adjacent frames.That was pretty darn nifty back in the day.I'm pretty sure it is a relatively simple signal on the edit jacks, all the fancy stuff is already in those higher-end model VCRs from that line.

author: Siwastaja
author_rank: Super Contributor
timestamp: January 24, 2018, 06:50:16 am
content: In the professional world, genlocking became a little bit "obsolete", or at least less necessary, once the digital frame stores came around in the early 1990's. They were hugely complex and expensive back then, but now the data rates for SD video are something a $100 smartphone technology could handle!If you can't find one used, designing and building your own digital frame store would be probably a good choice. It's not easy either from scratch. But at least video ADC/DAC ICs do exist, and you can then interface them with an FPGA+SDRAM or even just a very capable microcontroller with DMA.This way, at least the result would be least iffy, giving perfect mixing, and most widely usable, with any equipment working without modifications. When you have the basics designed, it would be fairly trivial to add things like frame rate / color system conversions (PAL-NTSC) (and all those nice digital effects you can play around but don't actually want).

author: John Heath
author_rank: Frequent Contributor
timestamp: January 24, 2018, 06:51:55 am
content: There could be some hope in an up scale used video mixing board used by DJs and such. In order to fade from one video to the next the two videos had to be in phase for it to look right . A ton of electronic horse power went into this to take two different videos out of phase and possibly not the same format , pal ntsc , and knit them together into one video with a band width of 10 MHz. No easy task. If you snoop around maybe you can buy one of these video mixing boards used.

author: james_s
author_rank: Super Contributor
timestamp: January 24, 2018, 10:27:18 pm
content: The Video Toaster was an incredibly popular bit of hardware back in the analog video days, once you see the various mix, wipe and fade effects you'll start to notice them in all sorts of 80s stuff. The hardware is not particularly rare, but since it's Amiga based it's almost never cheap.

author: John Heath
author_rank: Frequent Contributor
timestamp: January 24, 2018, 11:07:11 pm
content: Speaking of this I remember repairing a karaoke machine. It was some minor problem. The interesting part was the ability to change the key to sing in. If the song was in D but you are more comfortable singing in C then you change the song to the key of key to C. The odd part was a 2 minute song in D was still a 2 minute song in C . You see the problem. In order to change a song from key D to C it had to be longer than 2 minutes but in both cases the song was still 2 minutes long. To this day I still do not know how they did this? The whole song was frequency synthesizers ?

author: bopstar
author_rank: Regular Contributor
timestamp: January 25, 2018, 12:02:22 am
content: I find your respond quite weird as in the 70s analog colour video syncing was a thing that was done all analog. no digital TBS was needed just delay lines and phase lock loops

author: bopstar
author_rank: Regular Contributor
timestamp: January 25, 2018, 12:05:03 am
content: i love the video toaster

author: james_s
author_rank: Super Contributor
timestamp: January 25, 2018, 12:06:38 am
content: Many audio editing programs allow changing the pitch and speed independently. I've never actually looked into how these features work but they do. I suspect they break the sound down into small portions and then insert copies of these portions or remove bits at regular intervals to adjust the length independent of the pitch. Audacity is the software I have, it's free and I believe open source so technically you could find out.

author: BrianHG
author_rank: Super Contributor
timestamp: January 25, 2018, 12:13:23 am
content: Quote from: james_s on January 25, 2018, 12:06:38 amFor most tempo changing audio tools, like the DSP ones in Audacity, you got it correct as patents on this technique have expired in the early 2000s.For the rare FFT deconstruct/reconstruct super high quality ones, valid patents still exist, but not for much longer....

author: BrianHG
author_rank: Super Contributor
timestamp: January 25, 2018, 12:21:53 am
content: Quote from: bopstar on January 25, 2018, 12:02:22 amIn the 70s, the color analog mixing was done in YUV component analog, or, for rare blue-screen tricks like for weathermen map backdrop, it was done in RGB analog. The precision of the chroma sub-carrier was not necessary as the final full NTSC signal with the chroma was done last after the mixing console mixed all the primary video sources, with slight jitter and alignment error of each one, then superimposed a clean sync and constructed the clean full chroma mixed signal.There also existed an analog video warp and blending device, but this was done with small displays & a camera in front. See here: (Don't dream of achieving this on your own and unlike the toaster, there were no square chunks....)

author: bopstar
author_rank: Regular Contributor
timestamp: January 25, 2018, 12:29:07 am
content: I know about the Scanimate and i did make a small scale version of it using an old rear projection crt a driver board design from google and a high resolution black and white CCTV camera

author: John Heath
author_rank: Frequent Contributor
timestamp: January 25, 2018, 05:35:53 am
content: Quote from: BrianHG on January 25, 2018, 12:13:23 amFFT deconstruct then reconstruct. This is interesting. Done this way the the length of the song and the pitch of the song are separate issues. The song could be in any key but always be 2 minutes in length. I wonder how careless you could be with the exact FFT shape and still get away with it? From 10 Hz to 10 KHz would you need 10,000 samples of the FFT for a given slice of time or could you get away with 1000 samples?

author: John Heath
author_rank: Frequent Contributor
timestamp: January 25, 2018, 06:00:49 am
content: Quote from: BrianHG on January 25, 2018, 12:21:53 amI liked that video. A throw away society. It bring to mind the day they stopped all analog TV to go digital. In one day at the stroke of midnight millions of TVs became obsolete. Thousands of clock repairmen without clocks to fix.

author: james_s
author_rank: Super Contributor
timestamp: January 25, 2018, 06:23:14 am
content: I suspect hardly anybody uses the digital OTA broadcasts either, certainly nobody I know does, a surpring number of people don't even realize you can receive HD using an antenna.At least converter boxes were available cheaply. I got one shortly after the changeover and connected it to the XBR Trinitron downstairs. I marveled over the stunning picture quality a few times then quickly realized there is nothing but garbage on TV anyway and by then all the channels had those distracting logos plastered permanently in the corner which IMO makes them unwatchable.

author: BradC
author_rank: Super Contributor
timestamp: January 25, 2018, 06:48:55 am
content: Quote from: james_s on January 25, 2018, 06:23:14 amYes, but it's the best quality garbage you've ever seen!

author: dexters_lab
author_rank: Unknown
timestamp: January 25, 2018, 09:06:42 am
content: Quote from: bopstar on January 24, 2018, 03:23:12 amas others have said, this really isn't possible with a domestic VCRsyncing two analog video sources is complex, especially if the source is tapeIt's best done digitally with a 'framestore', where multiple inputs are digitized, combined and then output as a single video channel. Quantel did this in 1975 for TV production with the DFS-3000i'd recommend just sourcing a cheap video mixer off ebay which will do this, i'd bet they are cheap as chips now and you'll save yourself a whole load of pain

author: bopstar
author_rank: Regular Contributor
timestamp: January 25, 2018, 12:29:10 pm
content: i enjoy the pain. plus i love learning about analog TTL logic. and fine ill be intrested in learning about frame stores. just please let me know where i can learn about those. also i cannot afford a any of the old video mixers of ebay. i am so poor i get all my chips from companies who are converting for DIP/through hole to SMD as liquidated stock and heaps of free sample chips from TI, Microchip, Analog Deceives etc

author: james_s
author_rank: Super Contributor
timestamp: January 25, 2018, 05:06:41 pm
content: "Analog TTL logic" is a contradiction. TTL logic is digital.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: January 25, 2018, 11:57:52 pm
content: Quote from: bopstar on January 25, 2018, 12:29:10 pmWell, fine, but why focus on this obsolete yet tremendously complex domain?A VIC-20 would be helpful as it outputs NTSC/PAL video natively and can be put into interlace mode.A university library will have many textbooks on obsolete stuff like video production. I used to hang out at Concordia University just to browse 1960s textbooks and occasional databook.

author: bopstar
author_rank: Regular Contributor
timestamp: January 26, 2018, 12:21:40 am
content: as stated i cannot afford to use modern technology and thus must use what i have and what i have is old analog equipment which in my case i wish to use to learn what i can about Analog Video. instead of just saying its to hard or ether impossible (which i know for a fact is not the case) tell me where i can learn more e.g. books, pdfs any schematic. lets forget about the VCR syncing and more to camera syncing. i make my own analog cameras with cheap CCTV modules.example of module:https://www.aliexpress.com/item/New-HD-700TVL-FPV-Mini-Analog-Camera-DC12V-CCTV-Home-Security-Video-Camera-with-Mic/32849564321.html?spm=2114.search0104.3.36.2bb48164Q8NWXT&ws_ab_test=searchweb0_0,searchweb201602_5_10065_10344_10068_10130_10342_10547_10343_10340_10548_10341_10084_10617_10616_10083_10618_10615_10307_10131_10132_5920012_10133_10313_10059_10534_100031_10103_441_10624_442_10623_10622_10621_10620_10142,searchweb201603_40,ppcSwitch_3&algo_expid=85e845c4-9f5b-47b2-ab03-30373873759a-8&algo_pvid=85e845c4-9f5b-47b2-ab03-30373873759a&priceBeautifyAB=3

author: james_s
author_rank: Super Contributor
timestamp: January 26, 2018, 02:01:22 am
content: Faced with that situation, I would be looking for used professional VCRs, I'm sure most of them have been junked by now but I'm sure there must be some sitting in storage rooms and surplus stores from all the analog TV stations that went offline.

author: BradC
author_rank: Super Contributor
timestamp: January 26, 2018, 05:54:43 am
content: I remember talking about this in depth with a studio tech back when I was in high school.The old Ampex Quad machines had a line-store, but the VHS units needed a frame store to be able to be fed as a mixable source. Editing tape to tape wasn't so difficult and even insert editing was mechanically achievable, but getting the machine to sync up to the studio timesource in even the loosest sense was limited to the vertical sync. There was absolutely no way of getting the hsync or chroma to line up. Cut to and from tape was ok, but there was no way it was going to fade/wipe.I remember the day we took delivery of a frame store. It revolutionized production because we didn't have to dub to 2" first to give us a mixable tape source. The Quads were far more precise mechanically (having been designed for the studio) but even they needed a line store to get the sync/chroma to stay in sync.I kinda miss the old analogue stuff, but I don't miss the hour it took to warm up and line up the studio cameras before a show. The day we took delivery of the "new" Triple CCD replacements was interesting though as they had individual RGB outputs available at the controller, so we got the Dulux colour chart and some paint samples to find out which would give us the best blue key if we used the B output on one of the cameras into the desks luma-key input. and then used that to paint up some chipboard sets. Chroma key on the cheap!It would have been fun to spend more time with broadcast stuff. I kinda wished I'd gone that direction sometimes.

author: basinstreetdesign
author_rank: Frequent Contributor
timestamp: January 26, 2018, 06:55:06 am
content: Quote from: dexters_lab on January 25, 2018, 09:06:42 amDamn! I remember installing and fixing DFS-3001's back in 1978 in Toronto.I spent a week in England with the Quantel design team (and driving on the wrong side of the road) learning how to do that. The neatest part of that machine was the servo-controlled video gain pot.

author: dexters_lab
author_rank: Unknown
timestamp: January 26, 2018, 08:15:20 am
content: Quote from: bopstar on January 26, 2018, 12:21:40 amnobody is saying don't experiment with analog videobut trying to engineer domestic VCRs to synchronise themselves is just an exercise in self flagellation. In playback they just 'free-run'. There are other reasons why it will be hard and those are mechanical, it needs very precise control over the tape transport to lock playback to a reference sync. You only have to see the inside of a Betacam SP deck to realise this.if you can buy $12 aliexpress cameras then you can buy old video 'editing' systems that were very popular in the 80s and 90s, these will allow you to take two VCRs and crossfade between them and record it onto a third VCR. I am sure you'll be able to find them on ebay, flea markets, boot sales, thrift stores etc... something like this:https://www.ebay.com.au/itm/Data-Video-Integrated-Editing-Centre/263447596943?hash=item3d56b34f8f:g:kZEAAOSwoRBaWOhz

author: bopstar
author_rank: Regular Contributor
timestamp: January 26, 2018, 11:45:35 am
content: why i cannot buy that mixer unit1: its a NTSC system2: dose not ship to Australia. all the stuff that i can get to Australia costs to much.3: the reason i am asking these questions is because i am making a mixer if i buy one it will defeat the hole damn point of this projectif you properly read my last respond it dose state i don't care about syncing to tape drives anymore but more syncing camera inputs. and i have been given ccd devices for free the aliexpress thing was an example of the things i use

author: james_s
author_rank: Super Contributor
timestamp: January 26, 2018, 06:45:51 pm
content: Nobody was suggesting you buy that specific mixing unit, he posted it as an example of what to look for. There are similar units designed to work with PAL that were available in your region.

author: BrianHG
author_rank: Super Contributor
timestamp: January 27, 2018, 12:09:59 am
content: Just buy at least 2 matched Time Base Corrector units with external video sync input.You may feed any cheap VCR or any other video sources into it and you can now mix the 2 analog video outputs.It will be much harder to find a broadcast quality VCR with the feature internal, but, not impossible.

author: BrianHG
author_rank: Super Contributor
timestamp: January 27, 2018, 12:18:28 am
content: Also be careful, my old Prosumer Hi8 deck:https://www.ebay.com/itm/Sony-EV-S9000E-Hi8-Video8-Recorder-TBC-PAL/253160429393?hash=item3af1899751:g:39UAAOSwqfpZv5rSDoes have a TBC with a perfect playback time base output, however, you cannot externally synchronize the picture out to a reference sync unless you modify the deck to it's professional counterpart. Even so, it will only function during playback. Not worth the 900$us price-tag.

author: bopstar
author_rank: Regular Contributor
timestamp: January 27, 2018, 03:10:54 am
content: I dont want to be buying anything. just making it all from scratch, i dont intend on using any VTR's anymore just wanting to sync to live video feeds from two cameras

author: BradC
author_rank: Super Contributor
timestamp: January 27, 2018, 03:19:40 am
content: Quote from: bopstar on January 27, 2018, 03:10:54 amMost "common" syncable cameras (like CCTV with sync inputs) will frame sync. You'll still need to deal with horizontal sync and chroma. Hsync isn't so hard in a camera if it's an old one with lots of discretes as you can modify it with a pll on the horizonrtal. New asic based cameras are not so easy. Chroma sync is another whole ball of wax.That's why old studio cameras had all sorts of wizardry in the control units to compensate for delays and cable lengths and a very specific and accurate master sync generator.Nobody here is trying to discourage you but you need to pay heed to these technical issues unless you want to spend many hours in front of a soldering iron which is likely to lead to disappointment.If you limit your aspirations to black and white then you'll have much better luck with a diy solution.

author: bopstar
author_rank: Regular Contributor
timestamp: January 27, 2018, 04:20:44 am
content: ok ill do black and white for now. what do you think i should do. i have some old CCD cctv caneras i was given ages ago. it has a Complex multi pin dc in and a BNC Composite out, i have about 4 of these cameras but only want to fade/mix between two of them

author: bopstar
author_rank: Regular Contributor
timestamp: January 27, 2018, 04:22:27 am
content: also if someone knows of any analog video cookbooks that teach how to generate basic video with discreet components and stuff, i would love to read it. something that goes into how to build up a circuit

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: January 27, 2018, 04:32:50 am
content: It's "discrete", not "discreet".http://www.swtpc.com/mholley/RadioElectronics/TV_Typewriter.htm

author: bopstar
author_rank: Regular Contributor
timestamp: January 27, 2018, 04:43:20 am
content: that is not what i was talking about

author: bopstar
author_rank: Regular Contributor
timestamp: January 27, 2018, 04:44:41 am
content: The CCTV camera i have is a jai cv m50. which is a black and white camera with SYNC Input

author: BradC
author_rank: Super Contributor
timestamp: January 27, 2018, 04:48:09 am
content: Quote from: bopstar on January 27, 2018, 04:20:44 amMost old CCTV cameras can either be synced to the 24vac power input, or have an extra input for a composite sync signal. The sync is only generally designed to be accurate enough to prevent frame roll when switching between sources on an analogue monitor, but it'll be a starting point for you.Older cameras with line lock often had a pot to adjust the phase to ensure you could sync them as accurately as possible.Check the data on the cameras you have to see if they have an available sync methodology.

author: BradC
author_rank: Super Contributor
timestamp: January 27, 2018, 04:49:38 am
content: Quote from: bopstar on January 27, 2018, 04:44:41 amIt was common to put a quality analogue camera in the rack with no lens and a cap on to provide relatively distributable black/sync source.

author: bopstar
author_rank: Regular Contributor
timestamp: January 27, 2018, 04:51:44 am
content: don't quite know what that is. main reason for why i am asking for links to documentation and books

author: BradC
author_rank: Super Contributor
timestamp: January 27, 2018, 05:15:32 am
content: Quote from: bopstar on January 27, 2018, 04:51:44 amThe manual for the camera is quite comprehensive. Don't need to register to download it, just click the download link under the registration info.

author: bopstar
author_rank: Regular Contributor
timestamp: January 27, 2018, 05:36:24 am
content: the pdf lacks information on the sync input

author: BradC
author_rank: Super Contributor
timestamp: January 27, 2018, 05:43:52 am
content: Quote from: bopstar on January 27, 2018, 05:36:24 amNo it doesn't. It gives you the details for both H & V sync (HD & VD), the jumpers to enable/disable and even timing diagrams and amplitude requirements. The only thing it doesn't do is spell out how the H & V are related, but you can get that info from anything that explains basic genlocking.You have several of the cameras, why not designate one a master and configure it to *output* the HD/VD sync, and use that to slave the other cameras?

author: bopstar
author_rank: Regular Contributor
timestamp: January 27, 2018, 07:12:57 am
content: i will