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Sophia rev.C - DVI board


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#51 Fox-1 / mnx OFFLINE  

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Posted Fri Apr 20, 2018 1:49 AM

Quoted from that particular item description:

 

"This cable does NOT integrate or extract the digital audio into or from the HDMI portion of the cable. It instead is a convenient cable bundle that includes an ANALOG source and destination connection in the same cable harness."



#52 tane OFFLINE  

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Posted Fri Apr 20, 2018 10:19 AM

DVI Video and Left/Right Audio (RCA) to HDMI Converter

 

https://www.mycablem...t_detail&p=5743

 

PDF Specifications

 

With this device should work on a modern TV.


Edited by tane, Fri Apr 20, 2018 10:23 AM.


#53 tane OFFLINE  

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Posted Fri Apr 20, 2018 11:35 AM

Some basic questions about resolutions: The first post says that now it's available 2: 1536×960 (16:10) and 1280×1024 (5:4), and a 4:3 and 16:9 are planned.

 

As the games were in a different aspect ratio (5:3), I expect a small black border will be shown like the first topic video, instead of changing the aspect ratio of the image (stretched image), and someone else asked the same in posts ago, and the answer was 'it depends of the monitor', and a reprogramming is possible with some presets (cores). As far as now there isn't enough information or an easy guide to do that, and just to be curious about if there is any plan to do that, which I think should be a must for a properly working with several different monitors.

 

The previous question arises because what happens with a big resolution screen like 3840×2160 (16:9): Will the image be automatically scaled 1:1 to fit the screen as much as possible?, or will be a small image in the center with large black borders at the 4 sides?, or will be a stretched image loosing its aspect ratio?

 

Hopefully a 16:9 resolution (1920×1080) will available soon, as it will work with modern size screens.



#54 TheMontezuma OFFLINE  

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Posted Fri Apr 20, 2018 12:12 PM

DVI Video and Left/Right Audio (RCA) to HDMI Converter

 

https://www.mycablem...t_detail&p=5743

 

PDF Specifications

 

With this device should work on a modern TV.

 

Nice (as long as it does not introduce additional delay).

 

The previous question arises because what happens with a big resolution screen like 3840×2160 (16:9): Will the image be automatically scaled 1:1 to fit the screen as much as possible?, or will be a small image in the center with large black borders at the 4 sides?, or will be a stretched image loosing its aspect ratio?

 

Hopefully a 16:9 resolution (1920×1080) will available soon, as it will work with modern size screens.

 

This aspect ratio is already supported with the resolution 1600x900 (you need to tell Simius which resolution you would like to order).

 

More info:

https://translate.go...pl-1vtRrIMzJWKg

 

SOPHIA keeps the original ratio of the Atari screen (by adding black borders), so a circle remains a circle.

 

What happens with the 1600x900 picture depends on your Monitor / TV.

My LG TV rescales the video to its native 1920x1080 resolution.


Edited by TheMontezuma, Fri Apr 20, 2018 12:17 PM.


#55 mytek ONLINE  

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Posted Fri Apr 20, 2018 12:48 PM

Have you tried it out?

I don't think you can inject audio to the HDMI this way...

 

Apparently not, my mistake for not researching this better  :( . As already pointed out it appears to be simply a parallel cable carrying audio information, so no use for getting from analog audio into the digital format required in HDMI. Be nice if someone came up with a cable that did an active conversion.

 

 

The device that tane found looks to be the ticket, although at nearly $50 it's a bit on the pricey side. Good find none the less  :thumbsup:  :) .



#56 Brentarian OFFLINE  

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Posted Sun Apr 22, 2018 5:46 PM

The device that tane found looks to be the ticket, although at nearly $50 it's a bit on the pricey side. Good find none the less  :thumbsup:  :) .

Monoprice has it for $29.99. https://www.monopric...duct?p_id=8124#

Nice (as long as it does not introduce additional delay).

Latency is what I fear also. If somebody tries one, please let us know.

#57 towmater OFFLINE  

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Posted Sun Apr 22, 2018 7:27 PM

Looks like Monoprice has an Earthday discount code, so I pulled the trigger, I'll find out if there's much stick latency in 3-6 days... of shipping latency.



#58 jc13 OFFLINE  

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Posted Mon Apr 23, 2018 11:17 AM

I snagged one as well - reviews of it on Amazon weren't that positive though.  Nothing about latency, more about hardware failure.



#59 Brentarian OFFLINE  

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Posted Mon Apr 23, 2018 7:04 PM

Brentarium also reported good results under 1280x1024 on a Dell 1905FP.


Correction on that. I just tried PAL on the 1905FP and it says CANNOT DISPLAY THIS VIDEO MODE. So, the Dell 1905FP apparently only supports NTSC.

#60 towmater OFFLINE  

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Posted Wed Apr 25, 2018 9:30 PM

The Monoprice audio+DVI to HDMI combiner arrived, and works beautifully. Not only is there no detectible latency (It's probably not doing much in the way of conversion) but it also inexplicably fixed a problem where my HDMI monitor would blank out occasionally with the raw Sophia signal.



#61 jc13 OFFLINE  

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Posted Thu Apr 26, 2018 7:03 AM

That’s great news - are you going to try to install it permanently inside?


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#62 towmater OFFLINE  

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Posted Thu Apr 26, 2018 7:55 AM


That’s great news - are you going to try to install it permanently inside?
 

 

I didn't think about that, it would need to a very short DVI cable, or a gender changer, or swapping out the little board hanging off the Sophia. Or perhaps a lot of soldering fine wires.


Edited by towmater, Thu Apr 26, 2018 7:57 AM.


#63 jc13 OFFLINE  

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Posted Thu Apr 26, 2018 8:09 AM

 

 

 

I didn't think about that, it would need to a very short DVI cable, or a gender changer, or swapping out the little board hanging off the Sophia. Or perhaps a lot of soldering fine wires.

 

 

 

I was thinking about a new little board or removing the DVI port and wiring a cable up directly to the Monoprice adapter - I ordered a few of the connectors to match the Sophia side of the DVI connection and it's only 10 wires to solder. Seems like a fun way to waste some time...  :)



#64 Spaced Cowboy OFFLINE  

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Posted Thu Apr 26, 2018 8:27 AM

The Monoprice audio+DVI to HDMI combiner arrived, and works beautifully. Not only is there no detectible latency (It's probably not doing much in the way of conversion) but it also inexplicably fixed a problem where my HDMI monitor would blank out occasionally with the raw Sophia signal.

 

 

It's almost certainly doing nothing in the way of conversion (HDMI and DVI signals are compatible, with HDMI being a superset of DVI), but it'll have to re-mux the signal, which implies a decoding, and then a re-encoding. Since this is digital, and happening at wire speed, you're not going to lose image quality, and there's no frame-buffer or anything that ought to introduce lag. 

 

Basically it's almost certainly [serial data x4]--->[decode-chip]===>[parallel data]===>[encode-chip]--->[serial data x4], where the [encode chip] also has a digital audio feed so it can mix in the audio. Here's the kicker.... If you re-encode the data, you have to re-time it, and the hardware to re-time the signal is what is solving your blanking-out. It's presumably outputting something your monitor prefers to that of the native Sophia output.

 

[technical aside]

Both HDMI and DVI transmit using a TMDS (transition-minimised differential signalling) pair for each of red, green, blue and clock. You get up to 16-bits of R,G,B (although it's usually 8-bit), with each clock pulse having a width of 10 pixel-data clocks (ie: the clock runs 10x slower than the pixel data). This is used to encode the RGB data into something called 8b10b, so each 8 bits of data actually takes up 10 bits on the wire. This is the 'transition minimised' part, and it makes the line robust against transmission errors. The differential signalling is also important to this - you can typically run a TMDS line for ~70 feet or so if you need to.

[/technical aside]

 

Simon



#65 towmater OFFLINE  

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Posted Thu Apr 26, 2018 9:39 AM

That’s great news - are you going to try to install it permanently inside?
 

 

You've inspired me, rather than order connectors, I've just torn apart the DVI cable, and it looks like a fairly simple job to whack-off a gender changer. (I think that's how EEVblog would state it.)

2018 04 26 08.34.07


#66 jc13 OFFLINE  

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Posted Thu Apr 26, 2018 11:06 AM

 

You've inspired me, rather than order connectors, I've just torn apart the DVI cable, and it looks like a fairly simple job to whack-off a gender changer. (I think that's how EEVblog would state it.)

 

 

Nice!  Here's a pic of the add on DVI board connector with signals (I think :) ).  It looks like the 5V connection from the Sophia feeds 5V and HotPlugDetect on the DVI each through a 4.7 ohm resistor, but I haven't tested any of that yet. I was just going to make a board with an HDMI connector on it instead of the DVI due to the size of the connector, but now I'm going to try to get the Monoprice device in the mix.

 

Screen Shot 2018-04-26 at 12.56.42 PM.png



#67 TheMontezuma OFFLINE  

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Posted Thu Apr 26, 2018 1:34 PM

Since this is digital, and happening at wire speed, you're not going to lose image quality, and there's no frame-buffer or anything that ought to introduce lag. 

Basically it's almost certainly [serial data x4]--->[decode-chip]===>[parallel data]===>[encode-chip]--->[serial data x4], where the [encode chip] also has a digital audio feed so it can mix in the audio.

 

Although it doesn't buffer complete frames, it still needs a buffer and introduces some latency, doesn't it?



#68 Spaced Cowboy OFFLINE  

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Posted Thu Apr 26, 2018 2:23 PM

 

Although it doesn't buffer complete frames, it still needs a buffer and introduces some latency, doesn't it?

 

 

I doubt it. 

 

The TMDS data is essentially packet-switched, with packets being defined for video, audio, I2C-traffic (called DDC), etc. etc. As a packet comes in, its data will be de-serialised, sent over the decoder's output parallel bus as video R,G,B + extra-control-lines, and immediately re-serialised into a valid packet. The only latency introduced is the SERDES implementation, and we're talking nanoseconds at most here, more likely picoseconds.

 

I mean, if you're being literal, then yes there's *some* latency, in as much as there's some latency as it gets transmitted over a wire as well, but for all practical purposes there ought to be zero latency. We normally define latency as relative *to* something, and since the entire signal is being transformed (without buffering), there's nothing for any delay to be relative to. If you prefer, you could imagine it as introducing a delay akin to extending the wire by another 1m of cable - sure that adds some more picoseconds to the delay, but since the entire signal has that delay, it's not "latent". Also, a delay of tens of picoseconds generally isn't important :)

 

There's a lot more bandwidth on the signalling bus than is used by any of the video resolutions that we're transmitting here, so we don't delay the signal by adding audio, the audio packets will just be intermixed into spare slots as an audio packet. The HDMI spec actually goes into this, and defines 'data island' areas where audio (for example) can be interspersed within the signal - typically within the horizontal front-porch (the part of the signal at the start of each horizontal scan-line that is not displayed on the screen). There are also other data-islands defined at the top of the screen, as well as control-periods wherein data packets are used to identify which data-islands contain which data (amongst other things). You'll find the HSYNC and VSYNC info in the data island packets as well.

 

FWIW, video is the acknowledged "master stream" on an HDMI link, with audio only being generally transmitted with an accuracy to its associated video frame, so the audio will trickle in as the video frame progresses down the screen. There is sufficient slack ahead of the video frame that the first scanline's audio can be transmitted then, and enough space per scanline for another dollop of audio. 

 

Overall, HDMI can carry a massive amount of audio (IIRC it's 8 x 192kHz 48-bit channels, way more than we would ever need), and it can carry video (even at the lower LBR rate) to show video at 1920x1280x24-bit @ 60Hz. Then you've got HBR (high bit-rate) which can go much further. The carrying-capacity of a single HDMI link is at least 165 million pixels/second, with every version of the spec increasing that...



#69 jc13 OFFLINE  

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Posted Fri Apr 27, 2018 10:55 AM

The Monoprice audio+DVI to HDMI combiner arrived, and works beautifully. Not only is there no detectible latency (It's probably not doing much in the way of conversion) but it also inexplicably fixed a problem where my HDMI monitor would blank out occasionally with the raw Sophia signal.

 

I received mine today and had no luck at all.  I could get it to work on my PC, but it didn't like the Sophia output at all.  Mine is 16x9 and it outputs at 1600x900 according to the monitor - is yours maybe running a different core?  Unrelated to the Monoprice box, I also have issues sometimes going into the U1MB setup - screen displays for a minute and then goes black with the monitor thinking I don't have an input connected.  I wonder if there is a better / more compatible core for the Sophia that my monitor and the Monoprice box would behave better with.



#70 towmater OFFLINE  

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Posted Sat Apr 28, 2018 12:59 AM

 

I received mine today and had no luck at all.  I could get it to work on my PC, but it didn't like the Sophia output at all.  Mine is 16x9 and it outputs at 1600x900 according to the monitor - is yours maybe running a different core?  Unrelated to the Monoprice box, I also have issues sometimes going into the U1MB setup - screen displays for a minute and then goes black with the monitor thinking I don't have an input connected.  I wonder if there is a better / more compatible core for the Sophia that my monitor and the Monoprice box would behave better with.

 

I didn't have enough info to make a decision, so I asked Simius to recommend, and he (or she) chose 1536x960



#71 jc13 OFFLINE  

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Posted Sat Apr 28, 2018 4:30 AM

 
I didn't have enough info to make a decision, so I asked Simius to recommend, and he (or she) chose 1536x960


Exactly what I should have done...


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#72 tane OFFLINE  

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Posted Sat Apr 28, 2018 9:42 AM

So at this time the Monoprice works with 1536×960 but not with 1600×900 ?



#73 jc13 OFFLINE  

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Posted Sat Apr 28, 2018 1:18 PM

So at this time the Monoprice works with 1536×960 but not with 1600×900 ?


Only two data points so far, but I couldn’t get a sync on the input with the 1600x900 Sophia.


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#74 tane OFFLINE  

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Posted Sat Apr 28, 2018 2:21 PM

Only two data points so far, but I couldn’t get a sync on the input with the 1600x900 Sophia.

 

Only 2 data points = 2 resolutions ?



#75 jc13 OFFLINE  

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Posted Sat Apr 28, 2018 3:55 PM

 

Only 2 data points = 2 resolutions ?

 

 

Yeah - that's what I meant.  The only posts I've seen about it are towmater 's at 1536x960 (that worked) and mine at 1600x900 (that didn't).


Edited by jc13, Sat Apr 28, 2018 3:56 PM.





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