John Kortink's BBC HDMI

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simonm
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John Kortink's BBC HDMI

Post by simonm » Tue Jul 24, 2018 8:55 am

Not sure if already posted on here, but I noticed that John Kortink has been building up a HDMI converter for the Beeb...
https://twitter.com/WindfallNL

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Re: John Kortink's BBC HDMI

Post by hoglet » Tue Jul 24, 2018 9:31 am

I've been watching the development of this with interest over the last 3 years. John is quite a perfectionist, so I imagine it will be very good.

It was one of the things that sparked the idea of trying to do the same in software on a Raspberry Pi.

It looks quite a nice design and uses:
- A TI 8541Y 16-bit DAC, I imagine to give a programmable input threshold to help overcome some of the Mode 7 sampling "challenges"
- An Altera MAX 10M02 FPGA doing the format conversion
- A TI TFP410 PanelBus driver to drive the HDMI interface

What's interesting is that the FPGA only has 108Kbits of memory, which is quite a small amount. For comparison, a MODE 7 frame, after character rounding, is 500x480x3 ~= 700Kbits. And a MODE 0 frame is 640x256x3 = 480Kbits.

So I would be very interested to understand how this works. Not that John is likely to ever share that. :) I can only imagine that the HDMI output format is very carefully chosen to avoid needing to buffer a whole frame, e.g. using 576i or 576p. Then it's down to your HDMI monitor to do a decent job of de-interlacing and up-scaling this to the panel resolution.

Did anyone on here sign up for one?

Has the price been announced?

Dave
Last edited by hoglet on Tue Jul 24, 2018 9:41 am, edited 4 times in total.

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Re: John Kortink's BBC HDMI

Post by BigEd » Tue Jul 24, 2018 9:42 am

Indeed, in a tweet John says 576p except for mode 7, which is 576i. It looks like he didn't get huge interest so will only do a single batch - something which could of course change. And who knows how large a batch might be.

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Re: John Kortink's BBC HDMI

Post by VincentVega » Tue Jul 24, 2018 5:55 pm

Perhaps he would have had a bigger response if he'd ventured beyond social media. I'd certainly be interested in at least one.

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Re: John Kortink's BBC HDMI

Post by BigEd » Tue Jul 24, 2018 6:09 pm

I imagine he'll put the first batch on ebay, the word will get around, and he'll get a signal of whether a second batch is worthwhile.

As Dave notes, the price isn't yet known, which will be a decider for some fraction of potential customers.

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Re: John Kortink's BBC HDMI

Post by hoglet » Tue Jul 24, 2018 7:08 pm

Last edited by hoglet on Tue Jul 24, 2018 7:14 pm, edited 2 times in total.

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Re: John Kortink's BBC HDMI

Post by BigEd » Tue Jul 24, 2018 7:17 pm

Evidently quite the challenge to pull off!

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Re: John Kortink's BBC HDMI

Post by Lardo Boffin » Tue Jul 24, 2018 7:32 pm

Very interesting project and I would be interested in one. Sadly I never venture onto social media (unless this counts?).

I thought you had to license the HDMI technology in order to use it? I noticed a Spectrum HDMI connector (https://www.sellmyretro.com/offer/detai ... trum-27558) which uses a pie zero for the HDMI part.
Last edited by Lardo Boffin on Tue Jul 24, 2018 7:34 pm, edited 1 time in total.
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Re: John Kortink's BBC HDMI

Post by colonel32 » Tue Jul 24, 2018 7:42 pm

My understanding is that the Raspberry Pi Foundation have already paid the HDMI licensing fee. By selling it as a self-assembly kit without the Pi, Ben (and presumably also Dave) does not need to pay the licensing fee a second time.
Last edited by colonel32 on Tue Jul 24, 2018 7:45 pm, edited 2 times in total.

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Re: John Kortink's BBC HDMI

Post by hoglet » Tue Jul 24, 2018 7:48 pm

HDMI Licensing does seem to be relevant to John's design...
https://www.hdmi.org/manufacturer/terms.aspx
The HDMI royalty is only payable on Licensed Products that will be sold on a stand-alone basis (i.e. that are not incorporated into another Licensed Product that is subject to an HDMI royalty). For example, if a cable or IC is sold to an Adopter who then includes it in a television subject to a royalty, then the cable or IC maker would not pay a royalty, and the Adopter television manufacturer would pay the royalty on the final product.
and
HDMI Adopters pay an annual fee of ten thousand dollars (US$10,000).
:shock:
I hope John can argue he is not delivering a product directly to consumers....

Actually, as long as he doesn't describe it as having a HDMI interface, he's OK. It's the term HDMI that is the licensed trademark. But then, what do I know, I'm an engineer not a lawyer!
Last edited by hoglet on Tue Jul 24, 2018 7:55 pm, edited 3 times in total.

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Re: John Kortink's BBC HDMI

Post by VectorEyes » Tue Jul 24, 2018 7:55 pm

Well, he won't be selling it with a case. I emailed him to ask about availability and express an interest, and he basically said to watch Twitter for announcements on availability!

Other points: it plugs directly into RGB port and is powered from it as well.

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Re: John Kortink's BBC HDMI

Post by hoglet » Tue Jul 24, 2018 8:13 pm

Seems to me that HDMI Licensing covers the use of the trademark, and the use of the connector, so is potentially a bit of a nightmare for projects like this. I don't think it matters whether it's in a case or not.
Last edited by hoglet on Tue Jul 24, 2018 8:13 pm, edited 1 time in total.

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Re: John Kortink's BBC HDMI

Post by cmorley » Tue Jul 24, 2018 8:21 pm

hoglet wrote:
Tue Jul 24, 2018 8:13 pm
Seems to me that HDMI Licensing covers the use of the trademark, and the use of the connector, so is potentially a bit of a nightmare for projects like this. I don't think it matters whether it's in a case or not.
Yes this is why I shelved all my HDMI projects. The low volume option is $5k/year and $1 per device sold IIRC. They actively enforce their IP and trademarks...
AFIK the end of chain device pays... so if you make modules or ICs to go in products you don't pay.

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Re: John Kortink's BBC HDMI

Post by colonel32 » Tue Jul 24, 2018 8:25 pm

Somebody was telling me you can incorportate a DisplayPort adaptor with no restrictions. And that a regular, cheap cable can do the necessary DisplayPort>HDMI conversion.
Last edited by colonel32 on Tue Jul 24, 2018 8:26 pm, edited 1 time in total.

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Re: John Kortink's BBC HDMI

Post by BigEd » Tue Jul 24, 2018 8:44 pm

AFAICT they protect the use of the logo and - just possibly - the four letters HDMI. Can anyone tell if they can in any way protect the use of the connector or the protocol or anything else? (If your product ends up including a component which has the logo on it, that could be a problem. Having a part which you add a Pi onto, or into, seems like a good solution - although you might possibly have to avoid using the four letters.)

I hate FUD around IP. It's not rocket science, but it's in the interests of rights-holders to muddy the waters and pretend it's very complicated.
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Re: John Kortink's BBC HDMI

Post by Elminster » Tue Jul 24, 2018 8:56 pm

This article was quite interesting https://www.semiconductorstore.com/blog ... -HDMI/654/

It seemed to suggest, as you say, if no mention is made of hdmi and you only used publicly available specs you could get away with it.
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Re: John Kortink's BBC HDMI

Post by danielj » Wed Jul 25, 2018 5:50 am

My reading of that was it doesn't matter whether you use the logo or not, or the latest version of the specs:
Only Adopters have access to Compliance Test Specification (CTS) that are used for compliance and certification. This is required before any HDMI product can be legally sold.

Plus the 15cent per unit royalty if you don't mention hdmi on unit/promotional material dropping to 5cents if you do...
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Re: John Kortink's BBC HDMI

Post by BigEd » Wed Jul 25, 2018 5:57 am

danielj wrote:
Wed Jul 25, 2018 5:50 am
My reading of that was it doesn't matter whether you use the logo or not, or the latest version of the specs:
Only Adopters have access to Compliance Test Specification (CTS) that are used for compliance and certification. This is required before any HDMI product can be legally sold.
Looks like FUD to me. Nothing can be required just because they say so. What they mean is that they want you to licence something, and the licence isn't valid until you pass the test suite. What they don't say is exactly what they want you to licence.

Edit: it seems they want you to license use of the trademarks and the necessary patents. In the agreement they are careful to offer independent fair terms to license these uses from the HDMI founder companies - not that this is likely to work for any small-time operator, it's a just an escape so they don't appear to be operating a shakedown. Some amateur analysis of the legalities here. For a hobbyist, the worst that's likely to happen is a takedown applied by ebay or similar marketplace. Avoiding the magic four letter word and just saying 'high definition' might be enough to avoid attention. Not selling anything with an HDMI connector on board might be safe too.
Last edited by BigEd on Wed Jul 25, 2018 6:34 am, edited 1 time in total.

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Re: John Kortink's BBC HDMI

Post by paulxtr » Wed Jul 25, 2018 6:32 am

colonel32 wrote:
Tue Jul 24, 2018 8:25 pm
Somebody was telling me you can incorporate a DisplayPort adaptor with no restrictions.
Nope, these people

http://www.mpegla.com/main/programs/dis ... Intro.aspx

will chase you for a license to use DisplayPort.
Last edited by paulxtr on Wed Jul 25, 2018 6:33 am, edited 1 time in total.

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Re: John Kortink's BBC HDMI

Post by 1024MAK » Wed Jul 25, 2018 7:59 am

:arrow: Err, use DVI-D and tell users to get and use a DVI-D - HDMI Adapter (DVI-D 25 Pin M - HDMI 19 Pin F)
Wikipedia says this...
Wikipedia wrote:DVI and HDMI compatibility

HDMI is a newer digital audio/video interface developed and promoted by the consumer electronics industry. DVI and HDMI have the same electrical specifications for their TMDS and VESA/DDC links. However HDMI and DVI differ in several key ways.
  • HDMI lacks VGA compatibility and does not include analog signals.
  • DVI is limited to the RGB color model while HDMI also supports YCbCr 4:4:4 and YCbCr 4:2:2 color spaces which are generally not used for computer graphics.
  • In addition to digital video, HDMI supports the transport of packets used for digital audio.
  • HDMI sources differentiate between legacy DVI displays and HDMI-capable displays by reading the display's EDID block.
To promote interoperability between DVI-D and HDMI devices, HDMI source components and displays support DVI-D signalling. For example, an HDMI display can be driven by a DVI-D source because HDMI and DVI-D both define an overlapping minimum set of supported resolutions and frame buffer formats.
Wikipedia wrote:HDMI implements the EIA/CEA-861 standards, which define video formats and waveforms, transport of compressed and uncompressed LPCM audio, auxiliary data, and implementations of the VESA EDID.[5][6](p. III) CEA-861 signals carried by HDMI are electrically compatible with the CEA-861 signals used by the digital visual interface (DVI). No signal conversion is necessary, nor is there a loss of video quality when a DVI-to-HDMI adapter is used.
(from here)

I'm presuming that including a DVI connector doesn’t require a licence...

Mark

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Re: John Kortink's BBC HDMI

Post by trixster » Fri Nov 02, 2018 2:46 pm

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Re: John Kortink's BBC HDMI

Post by dp11 » Fri Nov 02, 2018 3:51 pm

Looking at the Picture, it too me looks like the DAC is used to adjust the crystal frequency.

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Re: John Kortink's BBC HDMI

Post by BigEd » Fri Nov 02, 2018 4:09 pm

I think Dave has seen that there can be a slight drift as a Beeb warms up, which an extra hazard, making this quite a difficult problem to solve.

I quite like the anti-jitter tactic, as a last resort, of outputting a half-bright pixel where there's a twinkling problem due to mis-sampling.

There's no doubt that Mode 7 is the difficult one: needs a higher sample rate, and the Beeb's pixel clock is a mess.

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Re: John Kortink's BBC HDMI

Post by trixster » Fri Nov 16, 2018 3:53 pm

If you buy one of these make sure your monitor can display 576i properly first. Neither of my two monitors can - a dell 2001fp and viewsonic vp2030b - meaning mode 7 is unusable, which is not much good.
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Re: John Kortink's BBC HDMI

Post by hoglet » Fri Nov 16, 2018 5:11 pm

trixster wrote:
Fri Nov 16, 2018 3:53 pm
If you buy one of these make sure your monitor can display 576i properly first. Neither of my two monitors can - a dell 2001fp and viewsonic vp2030b - meaning mode 7 is unusable, which is not much good.
So basically it needs to be a TV then? Which would likely have a decent(ish) SCART input anyway.

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Re: John Kortink's BBC HDMI

Post by trixster » Fri Nov 16, 2018 6:41 pm

I guess so. You can force progressive for modes 0-6 by setting a dip switch on the board, and these modes look great on both my monitors but anything in mode 7 is either not displayed or looks terrible
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Re: John Kortink's BBC HDMI

Post by noggin » Fri Nov 30, 2018 10:54 pm

1024MAK wrote:
Wed Jul 25, 2018 7:59 am
:arrow: Err, use DVI-D and tell users to get and use a DVI-D - HDMI Adapter (DVI-D 25 Pin M - HDMI 19 Pin F)
Wikipedia says this...
Wikipedia wrote:DVI and HDMI compatibility

HDMI is a newer digital audio/video interface developed and promoted by the consumer electronics industry. DVI and HDMI have the same electrical specifications for their TMDS and VESA/DDC links. However HDMI and DVI differ in several key ways.
  • HDMI lacks VGA compatibility and does not include analog signals.
  • DVI is limited to the RGB color model while HDMI also supports YCbCr 4:4:4 and YCbCr 4:2:2 color spaces which are generally not used for computer graphics.
  • In addition to digital video, HDMI supports the transport of packets used for digital audio.
  • HDMI sources differentiate between legacy DVI displays and HDMI-capable displays by reading the display's EDID block.
To promote interoperability between DVI-D and HDMI devices, HDMI source components and displays support DVI-D signalling. For example, an HDMI display can be driven by a DVI-D source because HDMI and DVI-D both define an overlapping minimum set of supported resolutions and frame buffer formats.
Wikipedia wrote:HDMI implements the EIA/CEA-861 standards, which define video formats and waveforms, transport of compressed and uncompressed LPCM audio, auxiliary data, and implementations of the VESA EDID.[5][6](p. III) CEA-861 signals carried by HDMI are electrically compatible with the CEA-861 signals used by the digital visual interface (DVI). No signal conversion is necessary, nor is there a loss of video quality when a DVI-to-HDMI adapter is used.
(from here)

I'm presuming that including a DVI connector doesn’t require a licence...

Mark
Yep - the Dreambox satellite receivers used DVI-D (carrying audio) rather than HDMI for this reason, to avoid HDMI licensing issues.

It seems that John Kortink is calling it a BBC-to-DVI converter too...

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Re: John Kortink's BBC HDMI

Post by hoglet » Sat Dec 01, 2018 7:59 am

noggin wrote:
Fri Nov 30, 2018 10:54 pm
1024MAK wrote:
Wed Jul 25, 2018 7:59 am
:arrow: Err, use DVI-D and tell users to get and use a DVI-D - HDMI Adapter (DVI-D 25 Pin M - HDMI 19 Pin F)
Yep - the Dreambox satellite receivers used DVI-D (carrying audio) rather than HDMI for this reason, to avoid HDMI licensing issues.

It seems that John Kortink is calling it a BBC-to-DVI converter too...
He may be calling it BBC-to-DVI, but he's actually using a HDMI connector:
bbc2hdmi.jpg
Anyway, I'm sure the volumes will be low enough that no one will be too concerned.

Dave

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Re: John Kortink's BBC HDMI

Post by trixster » Sat Dec 01, 2018 11:43 am

Anyone interested in having mine? I have no use for it as none of my monitors seem to be compatible :(

Swap for a 2nd populated RGBtoHDMI board?!! :) :D
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Re: John Kortink's BBC HDMI

Post by rharper » Sat Jan 12, 2019 3:10 pm

Just got round to trying my BBC2DVI.
My 8" TV gave no signal and my main 19" TV gave clear text but on a vertically stripped red background.
Trying a different HDMI cable gave a wonderful clear display in all MODEs on BBC & Electron.
Expensive but excellent display.
Useful for me since the SCART, VGA, video, other HDMI connection are all used (+ with switch boxes).
Ray
Raycomp

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