SCART Confused (sync signal) -RESOLVED w/extended solutions. - Page 1
Forum section: electronics / projects

author: Oneminde
author_rank: Regular Contributor
timestamp: April 11, 2016, 08:29:56 pm
content: Intro.Lets start with the reason for me writing this thread. I am working on designing/building an ultimate arcade machine and I picked up a 32" 16:9 CRT SONY Trinitron TV (SD CRT) made in 2005, so one of the last and this one have not been used for years, so near mint. The model is;SONY KV-32FQ86E.so this is the model I will use in my arcade (RetroPie). So basically, I will use a Raspberry Pi 3 as the computer (ROM emulator), connect the HDMI port to a converter (HD to SCART) and connect to the TV. So any game console issue is redundant in terms of video signal. The goal is to understand which composite video signal the TV accepts or work via.The Issue.I stumbled upon a YT channel called: My life in gaming, and they have a video series about RGB and Sync [RGB103 :: Demystifying RGB & Sync - MY LIFE IN GAMING]. Basically, there are different ways of showing the signal on a TV and it is this bit that is kinda confusing when I am reading some info on the different RGB & Sync types available in conjunction with what info is available in theService Manualfor the TV. So lets start with component video sync.Component video sync / Composite Video (RGB Video).First we have the obvious, red, green and blue is sent via its own cable, then there is theRGB Sync-on-Composite. If we look at S-Video, that one useSync-on-Luma + Chromafor image, YPbPr Component Video useSync-on-Luma + Pb + Prcompared to SCART which useRed + Green + Blue + Sync-on-Compositeand it is this that make SCART superior compared to S-Video and YPbPr. But as that is not enough, there is alsoComposit Sync / CSYNC.Composite Sync haveRed + Green + Blue + H+V Sync[Horizontal + Vertical Sync]. Combines horizontal and vertical synchronization onto one pair of wires. When used in RGB connections, four separate signals are sent (Red, Green, Blue, Sync).So we have Sync-on-Composite and Composite Sync, out of these two, the Composite Sync is the one to have/use. Apparently, Sync-on-Composite introduce artefacts (chequerboard patterns) overlay on the video. Composite Sync / CSYNC does not, so a much cleaner signal. CSYNC is also known as Raw Sync / Pure Sync and Boosted Sync.Here is a list of all the sync types.Separate sync:Uses separate wires for horizontal and vertical synchronization. When used in RGB (i.e. VGA) connections, five separate signals are sent (Red, Green, Blue, Horz. Sync, Vert. Sync).Composite sync:Combines horizontal and vertical synchronization onto one pair of wires. When used in RGB connections, four separate signals are sent (Red, Green, Blue, Sync).Sync-on-green (SOG): Combines composite sync with the green signal in RGB. Only three signals are sent (Red, Green with Sync, Blue). This synchronization system is used in - among other applications - many systems by Silicon Graphics and Sun Microsystems through a DB13W3 connector.Sync-on-luminance:Similar to sync-on-green, but combines sync with the luminance signal (Y) of a color system such as YPbPr. This is the synchronization system normally used in home theater systems.Sync-on-composite:The connector carries a standard composite video signal along with the RGB components, for use with devices that cannot process RGB signals. For devices that do understand RGB, the sync component of that composite signal is used along with the color information from the RGB lines. This arrangement is found in the SCART connector in common use in Europe and some other PAL/SECAM areas.The SCART.Looking at the pins of the scart cable, pin-7 is blue, pin-11 is green, pin-15 is red and pin-20 is sync.On page 4 in the SM;Scart 1 or AV1; 21-pin Euro Connector (CENELEC STANDARD): Inputs for Audio and Video signals. Inputs for RGB. Outputs of TV video and Audio Signals.Scart 2 or AV2; 21-pin Euro Connector; Inputs for Audio and Video Signals. Inputs for RGB. Outputs of TV Video and Audio signals. (Monitor Out).Scart 3 or AV3; 21-pin Euro Connector: Inputs for Audio and Video Signals. Inputs for S-Video. Outputs for Video and Audio signals. (selectable), Smartlink Interface.On page 6 in the SM;Here I can see the 21-pin layout and feature and as far as I can see, only AV1 have connected RGB pins while AV2 & AV3 is not connected (open). Remembering that SYNC is carried over pin-20, here SONY writes:Video input: 1V +/- 3dB, 75 ohm, positive sync 0.3V (-3 + 10dB). AV1: Pin-16: Blanking input (Ys signal) if that mattersPage 42 show a schematic called:C Board Schematic Diagram [R-G-B Out)which has dedicated RGB channels connected to the picture tube - I think this is called a "Neckboard" and is located on the tube itself.Page 44 shows the:J Board Schematic Diagram [AV Scart I/O Switching and Socketswhich display the SCART input, here, only AV1 have RGB + Video In clearly marked on the schematic but AV2 also have RGB + Video In connected on the SCART as well, just not marked on the schematic.Basically,this is itin terms of information regarding Sync-on-Composite and Composite Sync.The Question.Based upon information available, what SYNC type is used in my SONY?- EDIT -This thread have been resolved. See answers bellow.

author: ericloewe
author_rank: Unknown
timestamp: April 12, 2016, 09:56:49 am
content: Everything seems to point to sync-on-composite. What's the source of your doubt?You only need one SCART connection, presumably, and the TV provides at least one that accepts RGB, which is presumably SCART-standard RGB. If you're lucky, it provides support for other things like VGA sync, but don't count on it.

author: Oneminde
author_rank: Regular Contributor
timestamp: April 12, 2016, 11:23:14 am
content: Quote from: ericloewe on April 12, 2016, 09:56:49 amIts not a doubt, rather "what the heck is used" ... he he. Since there are two versions used in SCART, knowing if it is sync-on-composite or composite sync is interesting. There is no mentioning of either and no sync mentioned for pin-20, only video in, I can't figure out how or where to check for that specific info.

author: Gyro
author_rank: Super Contributor
timestamp: April 12, 2016, 11:25:59 am
content: Simple answer, if it is SCART then is HAS to support composite sync on pin 20, it's not optional. Even in the most basic non-RGB supported case, Composite video on pin 20 naturally includes composite sync.Edit: If you really want the official spec. you need to find a copy of EN 50049-1.http://fr.meric.free.fr/Articles/articlesba/stsurtvplat/Scart/BS_EN_50049-1%20Peritelevision%20connector.pdf

author: Oneminde
author_rank: Regular Contributor
timestamp: April 12, 2016, 12:40:39 pm
content: Quote from: Gyro on April 12, 2016, 11:25:59 amEN 50049-1: page 5:Video in, pin-20: Impedance: 75V - Difference between white level and synchronizing level 1V (±3 dB). [Y signal is the blanked luminance signal plus the synchronization signal plus data signals (when present).This sounds likeSync-on-luminancesince "Difference between white level and synchronizing level". But it could also mean:CSYNC over Luma.CSYNC over Luma(above) andComposite Sync / CSYNC(bellow)@Gyro:In the end, is it fair to say that it is CSYNC over Luma since: [R+G+B] + [Sync (V+H) + Luminance info (contrast difference in picture)]?

author: Kilrah
author_rank: Unknown
timestamp: April 12, 2016, 01:16:57 pm
content: Why not just connect the Pi's CVBS out directly and ditch the converter?

author: Gyro
author_rank: Super Contributor
timestamp: April 12, 2016, 01:26:32 pm
content: QuoteYes, apart from in RGB mode where the R,G,and B pins are respective Luma. But composite sync is always on pin 20 regardless.Note however:Most Set top boxes etc continue to put out Composite video to pin 20 so that a non-RGB equipped display will still get a picture. RGB monitors don't care, they just take the sync info.For RGB Video signals level is 0.7V p-p. For Composite video it's 1V p-p (0.7V of luminance and 0.3V of negative sync. Composite sync on it's own is 0.3V p-p.@Kilrah: That's what I'd be tempted to do.

author: Oneminde
author_rank: Regular Contributor
timestamp: April 12, 2016, 03:59:03 pm
content: Quote from: Kilrah on April 12, 2016, 01:16:57 pmCVBS is just composit video - one cable, same as we used on the NES back in the day. Even S-Video is better than CVBS. But CVBS would be simpler yes

author: Oneminde
author_rank: Regular Contributor
timestamp: April 12, 2016, 04:03:33 pm
content: Quote from: Gyro on April 12, 2016, 01:26:32 pmand as we recall, pin-20 on the SONY is positive sync 0.3V.Okay then, thanks for clearing up my question. This makes the tread resolved. Thanks a million Gyro

author: Kilrah
author_rank: Unknown
timestamp: April 12, 2016, 06:00:36 pm
content: Quote from: Oneminde on April 12, 2016, 03:59:03 pmI doubt anything is really better after going through a potentially dubious converter.

author: Oneminde
author_rank: Regular Contributor
timestamp: April 12, 2016, 08:04:36 pm
content: Quote from: Kilrah on April 12, 2016, 06:00:36 pmNon conversion biased ? Well, it all depends, but composite video / RCA will always fall short in quality. If the circuit layout and components are top notch, then there should not be a problem, but I do get what you mean. Chose a dubious converter and you are left with well, composite video results. So, HDMI ->  -> SCART only makes sense if you use quality equipment and why wouldn't one do that. The simplest path is always the least amount of components, allowing the signal to travel more or less freely.I'm working on that - I will see what I can dig up as a solution. Stay tuned- EDIT -I might have an unusual solution, but until then. I checked a HDMI to SCART which is suppose to be a good one ... supposedly. Bad news is that it puts out CVBS + Stereo Audio and CVBS = composite videoso while this device is a nice solution and will work, its no good for me.Link:http://www.freetv.ie/hdmi-to-scart-converter.htmlalso sold on amazon:http://www.amazon.co.uk/Composite-Converter-Adapter-Blu-Ray-specification-HDMI-SCART/dp/B00NAT0W2Y/ref=pd_sim_201_1?ie=UTF8&dpID=41-aFy32hrL&dpSrc=sims&preST=_AC_UL160_SR160%2C160_&refRID=00QYBSC74HF7D37RQCYATo rank quality, it is as follows:1. Best: HDMI2. Slightly Better: RGB Scart3. Better: Component such as YUV, YIQ, YPbPr and YCbCr4. Good; S-Video5. Okay; Composite (Yellow cable or RCA)6. Basic or worst: Coaxial (RF)Raspberry Pi is HDMI out, so best, then I will have RGB Scart in and it is between these two points I might have a very unusual solution - on standby to learn if it actually works.

author: Oneminde
author_rank: Regular Contributor
timestamp: April 13, 2016, 07:50:17 pm
content: Here is the solution.

author: Kilrah
author_rank: Unknown
timestamp: April 14, 2016, 04:42:16 am
content: I'd really be interested in a comparison between this and direct CVBS connection. Yes in theory it's got better potential, in practice I doubt it has any noticeable impact.

author: Oneminde
author_rank: Regular Contributor
timestamp: April 14, 2016, 02:54:55 pm
content: There IS a noticeable difference. Its not so much a question of if but rather do one care. It is pixel peeping to an extent since the composite vs s-video vs component vs RGB deals with getting as much details out of the game(s) as possible. Going from composite to RGB is a huge difference while going from s-video or component to RGB is far less visible, the argument of what one need is more or less redundant for everything above component. But if and when you have the option to go for RGB (standard via RGB SCART and hardware config for NTSC), why wouldn't one choose the best ?Here is a picture and bellow a video showing the difference between RGB and Composite.SNES - RGB vs. Composite Video Comparison- EDIT -Basically all arcade machines are RGB by default.