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Old 04 September 2016, 19:05   #1
cbmeeks
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Angry A500 to SCART to HDMI fail...

I've been trying different ways to get a modern display out of my Amiga 500. I've tried the GBS-8200. While that works, I'm not happy with the output. Perhaps it's my cable but I just don't like it.

The next solution I tried was from a video I saw on YouTube. These guys used a custom cable that converts the Amiga's video out to SCART. Then, they used an up-sampler to convert the display to HDMI. From what they showed and said, the video looked amazing.

So I set out to get the equipment. I bought this Amiga to SCART connector:

http://www.ebay.com/itm/391077101495...%3AMEBIDX%3AIT

The cable looks to be excellent quality. I haven't tested continuity but it appears to be a solid product.

Then, I bought this up-sampler:

http://www.ebay.com/itm/162081864532...%3AMEBIDX%3AIT

Notice that it has SCART IN and HDMI OUT. Which is what I want.

OK, so the parts arrived and when I tried to use them, I don't get an Amiga display.

When I use the up-sampler with no SCART plugged in, the image is a nice blue screen and it says either 720P or 1080P. And then it says "No Input". So, it appears to be outputting a signal OK.

When I plug in the SCART connector, the blue image goes away and seems to switch modes a couple times. Similar to what the Amiga does when using composite. But, that's where it ends. The display is a solid black.

I've confirmed the cables are secure and the Amiga does work.

I should mention that I am in the USA (NTSC). So, I know SCART isn't a thing over here but it seemed that SCART has all the proper RGB/sync signals brought out and it seemed to be a common solution.

BTW, a few times I did notice the up-sampler did display "NTSC" on the screen briefly. But I never get an Amiga image.

Any ideas what could be wrong?

Thanks
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Old 05 September 2016, 11:31   #2
Zetr0
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@cbmeeks

Hello there, this is quite an interesting little adaptor I may pick one of these up for a play about with =)

Now we need to isolate variables to this recipe otherwise will be going round in circles - so first up - do you know if it works with other RGB equipment?

Now, when you are taking RGB from the Amiga it doesn't have any PAL/NTSC encoding - its just component RED,GREEN and BLUE, it also requires the Vertical and Horizontal SYNC, obviously ground and Audio.

Do you hear any Audio - would you have a demo or game disk to test - I recommend Chuck Rock

Now, while I suspect it maybe because the SCART cable only provides a composite SYNC and that the HDMI adaptor might require separate Horizontal / Vertical SYNC's - to isolate this you will need to open the SCART header and take a picture of the wiring.

From that I or other can help you further.
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Old 05 September 2016, 12:42   #3
Toni Wilen
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It may also only support interlaced signal. Does it work if you switch to interlaced workbench screen?
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Old 05 September 2016, 13:12   #4
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Hmm further reading on the product -
Quote:
SKU: 51_D2000114018074

The SCART to HDMI converter is a universal converter for analog scart input to HDMI 1080p(60HZ) output. The analog to digital conversion in this module employs 10 bits maximal 162MSPS sampling, blak/white level expansion, color transition improvement, dynamic range expansion, blue stretch, auto-detect and auto-convert the composite signal to 1080p(60HZ) output. Making video come alive, delivering the sharpest, most realistic HK visuals available.
1. 10bits maximal sampling
If I am not mistaken, the Amiga ECS/OCS video is 16bit 6 bits of each R,G and B component colour - the AGA computers are 24bit with 8bits for each R,G and B component. However this might not be related to colour depth but sampling size - sadly I have no idea of what 162MSPS sampling means in this context.

2. Auto Detect / Convert Composite signal.
Does this mean that it is not COMPONENT RGB SCART but in fact Composite RCA with a SCART header?

You can test this with a small SCART to Composite RCA block - and a Composite RCA (Yellow, Red and White phono connectors) from the Amiga to the Composite RCA block plugged into this adaptors SCART port.
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Old 05 September 2016, 16:24   #5
idrougge
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Quote:
Originally Posted by Zetr0 View Post
1. 10bits maximal sampling
If I am not mistaken, the Amiga ECS/OCS video is 16bit 6 bits of each R,G and B component colour - the AGA computers are 24bit with 8bits for each R,G and B component. However this might not be related to colour depth but sampling size - sadly I have no idea of what 162MSPS sampling means in this context.
This is to be interpreted as 10 bits per channel.

Quote:
Originally Posted by Zetr0 View Post
2. Auto Detect / Convert Composite signal.
Does this mean that it is not COMPONENT RGB SCART but in fact Composite RCA with a SCART header?
That would explain why it works with the Sega. The Sega doesn't offer any pure sync signal; only composite video doubling as sync.
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Old 05 September 2016, 23:25   #6
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Hey folks

The SCART->HDMI adapter linked in the first post only works with Composite SCART, not RGB SCART. I've tried two and neither worked, then I noticed that some of the ebay listings to actually say it's for Composite SCART.

Instead, try one of these, they both work:

http://www.ebay.com/itm/Scart-HDMI-t...4AAOSwygJXg3Hw

http://www.ebay.com/itm/HDMI-to-SCAR...4AAOSwGvhUBXps

Edit: I should say that I know a few people who use the former, and are perfectly happy with it. Mine was producing noisy output, so I binned it and bought two of the latter and they both work perfectly (one on my Vampire'd A600, the other on my A4000, both are PAL machines if that helps)

Edit edit: I also thought I might mention that if you find yourself wanting to switch between various devices, e.g. multiple SCART->HDMI adapters from Amigas, and their RTG outputs, I have been very pleasantly surprised by this HDMI switcher: http://www.ebay.com/itm/5-Port-1080P...oAAOSw0fhXlbg4

Edit edit edit: Ok, last edit, I promise. I think it's pretty likely that with any of these things, because they're so cheap, there will be units that work well, and units that work poorly. It's also entirely possible that the converter linked in the first post is available in various forms that all look the same, some of them supporting RGB, some not.

Last edited by cmsj; 05 September 2016 at 23:31.
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Old 06 September 2016, 09:46   #7
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@cmsj

Quote:
Originally Posted by cmsj View Post
Hey folks

The SCART->HDMI adapter linked in the first post only works with Composite SCART, not RGB SCART. I've tried two and neither worked, then I noticed that some of the ebay listings to actually say it's for Composite SCART.
I had my suspicions thanks for confirming them =)

Quote:
Originally Posted by cmsj View Post
Both of these claim composite SCART not component RGB - in fact the latter reads as though it converts HDMI to Composite via a SCART output LOL.

Quote:
Originally Posted by cmsj View Post
Edit: I should say that I know a few people who use the former, and are perfectly happy with it. Mine was producing noisy output, so I binned it and bought two of the latter and they both work perfectly (one on my Vampire'd A600, the other on my A4000, both are PAL machines if that helps)
Good to read of another V600 in the fold

Quote:
Originally Posted by cmsj View Post
Edit edit: I also thought I might mention that if you find yourself wanting to switch between various devices, e.g. multiple SCART->HDMI adapters from Amigas, and their RTG outputs, I have been very pleasantly surprised by this HDMI switcher: http://www.ebay.com/itm/5-Port-1080P...oAAOSw0fhXlbg4
I have been looking at one of these - cheers for the link - just save me $10!

Quote:
Originally Posted by cmsj View Post
Edit edit edit: Ok, last edit, I promise. I think it's pretty likely that with any of these things, because they're so cheap, there will be units that work well, and units that work poorly. It's also entirely possible that the converter linked in the first post is available in various forms that all look the same, some of them supporting RGB, some not.
Indeed, purchasing from the Asian markets can be cheap and exciting since some products are just not made here in Europe - however it is ALWAYS a good thing to ask the seller questions before purchase =)
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Old 06 September 2016, 11:05   #8
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Quote:
Originally Posted by Zetr0 View Post
[B]Both of these claim composite SCART not component RGB - in fact the latter reads as though it converts HDMI to Composite via a SCART output LOL.
Ugh. It is possible I selected eBay links too quickly.

For reference, these are the actual things I bought:

https://www.amazon.co.uk/dp/B00ABOB1NU/

http://www.ebay.co.uk/itm/172160857081
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Old 06 September 2016, 16:24   #9
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Thanks to everyone for their replies.

Unfortunately, I don't own any native SCART equipment so I cannot test with other machines.

However, I suspect it is the composite conversion and not the RGB conversion is the issue.

I may look into purchasing one of the other converters one day.

But, on a different note, I decided this weekend to see if I could build an NTSC converter like the A520. I went by these schematics:

http://www3.telus.net/narmi/schematic.png

I was surprised how good the image looked! In fact, I decided to use the S-Video portion on my 1084S and it was incredible.

I am working now to tidy up the board. I built it on a breadboard and there was some interference but at least I'm going to have color video now. Especially since my A520 died.

:-D
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Old 06 September 2016, 18:11   #10
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Quote:
Originally Posted by Zetr0 View Post
1. 10bits maximal sampling
If I am not mistaken, the Amiga ECS/OCS video is 16bit 6 bits of each R,G and B component colour - the AGA computers are 24bit with 8bits for each R,G and B component. However this might not be related to colour depth but sampling size - sadly I have no idea of what 162MSPS sampling means in this context.
ICS/OCS/ECS use 4 bit per component and 12 bit in total for RGB, AGA use 8 bit per component and 24 bit in total for RGB, ADC in HDMI converter use 10 bit per component and 30 bit for RGB, 162 MSPS means that video signal is massively oversampled as such overal quantization noise is reduced (so 10 bit converters + oversampling should give almost perfect conversion from analog to digital domain - usually for high speed ADC ENOB is way lower than specified bit resolution - oversampling and higher ADC resolution are workaround to have more than 8 bit real life resolution).
ECS and AGA video bandwidth is way over 27MHz.
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Old 07 September 2016, 11:44   #11
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Quote:
Originally Posted by pandy71 View Post
ICS/OCS/ECS use 4 bit per component and 12 bit in total for RGB,
Its 12bits Zee..... you know this....


Quote:
Originally Posted by pandy71 View Post
AGA use 8 bit per component and 24 bit in total for RGB, ADC in HDMI converter use 10 bit per component and 30 bit for RGB, 162 MSPS means that video signal is massively oversampled as such overal quantization noise is reduced (so 10 bit converters + oversampling should give almost perfect conversion from analog to digital domain - usually for high speed ADC ENOB is way lower than specified bit resolution - oversampling and higher ADC resolution are workaround to have more than 8 bit real life resolution).
ECS and AGA video bandwidth is way over 27MHz.
Thank you my friend, this explains quite a bit indeed!
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Old 07 September 2016, 15:06   #12
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Quote:
Originally Posted by pandy71 View Post
ICS/OCS/ECS use 4 bit per component and 12 bit in total for RGB, AGA use 8 bit per component and 24 bit in total for RGB, ADC in HDMI converter use 10 bit per component and 30 bit for RGB, 162 MSPS means that video signal is massively oversampled as such overal quantization noise is reduced (so 10 bit converters + oversampling should give almost perfect conversion from analog to digital domain - usually for high speed ADC ENOB is way lower than specified bit resolution - oversampling and higher ADC resolution are workaround to have more than 8 bit real life resolution).
ECS and AGA video bandwidth is way over 27MHz.
The 165MHz figure is the maximum pixel clock frequency supported by the HDMI specification. It's not the sampling frequency of an analogue video to HDMI converter.

Typically analogue video would be sampled at 13.5MHz. A composite video decoder might oversample at 27MHz before reducing the data rate to 13.5MHz.
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Old 08 September 2016, 12:38   #13
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Quote:
Originally Posted by mark_k View Post
The 165MHz figure is the maximum pixel clock frequency supported by the HDMI specification. It's not the sampling frequency of an analogue video to HDMI converter.

Typically analogue video would be sampled at 13.5MHz. A composite video decoder might oversample at 27MHz before reducing the data rate to 13.5MHz.

Depends on HDMI version as such Pixel Clock can be higher than 165MHz.

AD converter may use oversampling (such as Analog Devices NSV technology - this will improve overall converter linearity and reduce quantization noise - important for high bit depth video).

As minimum Pixel Clock allowed by HDMI is 25MHz then SD video is usually oversampled 2 - 4 times, 13.5MHz video need special DVI/HDMI mode to not violate interface limitation - pixel are repeated twice or four times automatically in HDMI transmitter and decimated in same fashion in HDMI receiver.
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