OSSC (DIY video digitizer & scandoubler)

[Guspaz]

Only because adaptive sync needs to be supported by the source device. Somebody could make a little dongle that sits between the source and display that converts the sync of non-standard framerates at the source and outputs adaptive sync on the other end.

[marqs]

If I plug the Model 3 in to my PC Crt "raw", the status shows 58hz, 24khz input although obviously I don't get a picture due to the medium res. I should imagine CRTs are more tolerant of unusual refresh rates than LCDs, but the proof will be in the puddimg I suppose.

It's probably more about 24kHz being too low hfreq for CRT than 58Hz being too low refresh rate. OSSC can linedouble 384p which results to 48kHz/58Hz which most LCD PC monitors can handle (and CRTs should too if used with a VGA converter).

Is this something display port 1.3 can handle better since it can do adaptive sync? Ever since upgrading to gsync monitor i can't look back.

Adaptive sync is only relevant if the source supports it. Personally I'm not that excited about gsync/adaptive sync, even as a PC gamer. It's only good with high-persistence displays which are not a good thing for motion to begin with - I'd rather take a 100+Hz monitor which has a strobing/rolling scan. That said, there's some chance that a monitor with gsync/adaptive support is more tolerant to input refresh rates (also with standard sources) without trying to convert everything to 60Hz internally.

[BazookaBen]

That said, there's some chance that a monitor with gsync/adaptive support is more tolerant to input refresh rates (also with standard sources) without trying to convert everything to 60Hz internally.

This is what I'm interested to see. I'm not aware of anyone that has tested this, though. Especially over VGA.

I still use CRT's with my PC, so I can't test it myself. I'm not really interested in an adaptive sync display until the tech is present on a 4k OLED display.

[Xyga]

I'm not that excited about gsync/adaptive sync, even as a PC gamer. It's only good with high-persistence displays which are not a good thing for motion to begin with - I'd rather take a 100+Hz monitor which has a strobing/rolling scan.

The thing is it's those G-Sync equipped monitors that also feature ULMB (the PG279Q does it at 120Hz) and they're all quite expensive. ^^

[ZellSF]

I uh... somehow missed this was going to have multiple inputs, I thought it was strictly SCART in, imagine my surprise

So question, can this act as a component to dvi transcoder for 480i? Leaving the deinterlacing to the TV?

Or is straight transcoding to 480i over DVI going into HDMI territory?

[BuckoA51]

It's only good with high-persistence displays which are not a good thing for motion to begin with

Drifting somewhat off topic but I thought the main point of gsync/adaptive sync was to remove the need to tear a frame (no vsync) or drop framerate down to the next refresh rate multiple (vysnc) whenever the GPU couldn't keep up with the refresh of the monitor....

surely that's awesome no matter what your display? Or am I missing something here?

[Xyga]

That's awesome but I think he was just saying he's more interested in active blur reduction.
Now if two could work together...

[marqs]

I uh... somehow missed this was going to have multiple inputs, I thought it was strictly SCART in, imagine my surprise

So question, can this act as a component to dvi transcoder for 480i? Leaving the deinterlacing to the TV?

Or is straight transcoding to 480i over DVI going into HDMI territory?

Bare digitization (without linedouble) and YPbPr->RGB conversion for 480i is possible - I can add an option for that in a future firmware. Not sure though whether all HDMI displays support 480i input.

Drifting somewhat off topic but I thought the main point of gsync/adaptive sync was to remove the need to tear a frame (no vsync) or drop framerate down to the next refresh rate multiple (vysnc) whenever the GPU couldn't keep up with the refresh of the monitor....

surely that's awesome no matter what your display? Or am I missing something here?

True, but the display elements must be kept fully illuminated (versus a short bright burst like with a scanning CRT beam) until next frame with adaptive sync, or otherwise framerate will directly control brightness. This is harmful to motion clarity due to the way how our eyes interpret it. Recently there has been a lot of discussion about this in the context of VR because bad motion reproduction literally makes you sick there. That's why all the major upcoming VR systems utilize low-persistence displays, which also operate at >100Hz to avoid flicker caused by strobing.

[TechyTom]

Really looking forward to this project! I was always hesitant to jump ship to a framemeister and this sounds like exactly what I've been looking for, keep up the great work marqs!

[cleeg]

I'm not being impatient, but I'd like to ask roughly when we can expect a confirmation of preorder forms? I have money ready to throw at you marqs!

Cheers.

[marqs]

I'm not being impatient, but I'd like to ask roughly when we can expect a confirmation of preorder forms? I have money ready to throw at you marqs!

Cheers.

I've sent confirmations to first DIY-kit reservers since a few kits are ready to be shipped later this week. I was expecting to get first batch of pre-assembled boards before March but Chinese New Year may add some delay to the process as the boards are assembled there. I'll send confirmation mail to respective people on the list when I can give a more accurate availability estimate of their reserved board.

[Asbrandt]

This is only loosely related to the project here but since you seem to have a very strong understanding of the digitizer and sync stages, I'm curious if an idea is within your knowledge to comment on.

I have a very nice VGA monitor that I like to use when I can, but it's a low persistence phosphor monitor, which does not play nicely with signals under about 70hz and flickers enough to give me a headache after about an hour's use, and I have not had any luck trying to find a 'normal' phosphor monitor locally, only other low persistence models.
I'm curious if a device that, in addition to the usual Line Doubler features, is capable of "Frame Doubling" (for example, taking a 60hz input and creating a 120hz output) would be within the realm of possibility.

By my admittedly minimal understanding, I theorize it can be done without any "effective" latency by buffering the input frame, when the input frame reaches half way start the double-speed output, resulting in the final output pixel occurring immediately after the final input pixel.
But this requires 2 framebuffers of the highest resolution and color depth supported (1024/1366x768 is likely the maximum even for a high end monitor) and a mastery of RAM write/read timings I wouldn't know if is actually possible and perhaps most troubling, a VGA DAC that can actually support a high enough pixel rate.

If you have any thoughts, I'd like to hear them.

[Fudoh]

of course you can do that. Has been done in the home theater area forever. Nobody ever wanted to drive a CRT projector at just 60Hz. You can do that today with most better video processors. Marqs' current unit is missing the memory for the neccessary full frame buffer.

I've done this on Sony FW 900, see here:

[Guspaz]

Your approach would require a scanline buffer that can hold one and a half frames (it could be a ring buffer), and would result in half a frame of input lag (~8ms). 120Hz CRTs are pretty rare, and I doubt Marq's unit has enough onboard memory.

[Asbrandt]

of course you can do that. Has been done in the home theater area forever. Nobody ever wanted to drive a CRT projector at just 60Hz. You can do that today with most better video processors. Marqs' current unit is missing the memory for the neccessary full frame buffer.

Neat that it exists, although since its a home theater thing theres no guarantee any device that does it does it -fast-.
As for the unit not having the memory, I wasn't really asking for him to adapt his project to do it, just his thoughts on it since he's working with the necessary ADC hardware and FPGA and might have insight.

Your approach would require a scanline buffer that can hold one and a half frames (it could be a ring buffer), and would result in half a frame of input lag (~8ms). 120Hz CRTs are pretty rare, and I doubt Marq's unit has enough onboard memory.

Strictly speaking, 120hz output would -start- with half a frame of lag, but it would -finish- on time if you can actually do the RAM access optimization. If you can cut it down to a framebuffer and a half, all the better, although I'm not sure that would affect too much.
As for 120Hz CRTs being rare, as mentioned I'm struggling to find anything that -isn't- a high speed model, around here people seem to have already sent anything less off to the landfill.
As for the unit not having the memory, see above about looking for this thoughts rather than for it to become a project.

[Fudoh]

Neat that it exists, although since its a home theater thing theres no guarantee any device that does it does it -fast-.

some do, yes. Lumagen's unit can genlock the output at high refresh rates, so you end up with about half a frame of lag. DVDOs are slower at it, since they don't allow framelock for 120Hz outputs (no idea why - technically it was certainly possible).

As for the unit not having the memory, I wasn't really asking for him to adapt his project to do it, just his thoughts on it since he's working with the necessary ADC hardware and FPGA and might have insight.

there is other neat stuff you can do with more memory and a frame buffer (think of image rotation or support for other output resolutions than linedoubling/tripling), so it certainly makes sense to look into this for future generation of the unit.

[Asbrandt]

there is other neat stuff you can do with more memory and a frame buffer (think of image rotation or support for other output resolutions than linedoubling/tripling), so it certainly makes sense to look into this for future generation of the unit.

To image rotate would force a full input frame of latency wouldn't it? Because you need the first pixel of every input line for the first output line.

The main thing I'd like to know is if it's even possible to push the write/read timings so that input and output can happen simultaneously at that speed, so that the latency essentially zeroes out at the completion of the output.

[Guspaz]

I'm not sure what the read/write timings have to do with anything, if you're genlocked to the input sync, it's pretty straight forward.

[Asbrandt]

I'm not sure what the read/write timings have to do with anything, if you're genlocked to the input sync, it's pretty straight forward.

Wouldn't managing simultaneous reads / writes to the same buffer at higher input resolutions take some doing, or am I really underestimating the speed of RAM available even to hobby projects?

[Yohanov]

Does someone have a particular hdmi to vga transcoder to recommend ? I want to buy one in anticipation for using this board with a pc crt.

[cleeg]

I'm not being impatient, but I'd like to ask roughly when we can expect a confirmation of preorder forms? I have money ready to throw at you marqs!

Cheers.

I've sent confirmations to first DIY-kit reservers since a few kits are ready to be shipped later this week. I was expecting to get first batch of pre-assembled boards before March but Chinese New Year may add some delay to the process as the boards are assembled there. I'll send confirmation mail to respective people on the list when I can give a more accurate availability estimate of their reserved board.

Smashing, thankyou very much

[werk91]

Does someone have a particular hdmi to vga transcoder to recommend ? I want to buy one in anticipation for using this board with a pc crt.

I am interested in this too. I found a cheap(ish) Extron DVI-RGB 100 that looks good for the job but something running off 5V will be even better in regards to cable management.

[marqs]

Wouldn't managing simultaneous reads / writes to the same buffer at higher input resolutions take some doing, or am I really underestimating the speed of RAM available even to hobby projects?

Dual-port on-chip memory on the Cyclone IV FPGAs I've used can run at least 130MHz according to timing analyzer, which would be sufficient for e.g. 1024x768@120Hz. Framedoubling needs more memory though as stated above, so you'd need external SRAM or DRAM. You should have no trouble finding such memory with sufficient throughput so FPGA logic and I/O speed is more likely to become the bottleneck. I can see your need for framedoubling 60Hz sources as I couldn't stand desktop CRT monitors running below ~75Hz either. Half-frame latency and possibly slightly inferior motion (as you're strobing the same content twice) are small price to pay for flicker-free result.

Does someone have a particular hdmi to vga transcoder to recommend ? I want to buy one in anticipation for using this board with a pc crt.

Please wait for some test results with DVI/HDMI->VGA converters before getting one. I haven't had a chance to test one but I'm quite confident they should work fine if they are simple and don't reject non-standard (e.g. 55Hz) input timings. Perhaps Fudoh has one to test for the review?

[Asbrandt]

Wouldn't managing simultaneous reads / writes to the same buffer at higher input resolutions take some doing, or am I really underestimating the speed of RAM available even to hobby projects?

Dual-port on-chip memory on the Cyclone IV FPGAs I've used can run at least 130MHz according to timing analyzer, which would be sufficient for e.g. 1024x768@120Hz. Framedoubling needs more memory though as stated above, so you'd need external SRAM or DRAM. You should have no trouble finding such memory with sufficient throughput so FPGA logic and I/O speed is more likely to become the bottleneck. I can see your need for framedoubling 60Hz sources as I couldn't stand desktop CRT monitors running below ~75Hz either. Half-frame latency and possibly slightly inferior motion (as you're strobing the same content twice) are small price to pay for flicker-free result.

So I was definitely assuming the bottleneck would be in the wrong place, especially since I forgot that dual-port memory is a thing that exists.
As for the half-frame of latency, it's not quite that bad since at the end of the input frame, the output frame would have caught up, to a human that's probably nearly as good as zero latency.

I did finally remember why I said 2 framebuffers of RAM instead of 1.5. If you have two fully separate buffers, you can add "weave" deinterlacing as a feature even in the framedouble mode, assuming you can write each input pixel to the right place in both buffers without affecting the output rate, but that shouldn't be an issue since only 480i would be involved, unless actual games use the higher interlaced modes of the Amiga which might complicate things.

But it's good to know that's within range of something like this. Even if 1024x768 pushes it too far, that's probably high enough resolution where using a modern monitor would be fine anyway.

[BuckoA51]

Please wait for some test results with DVI/HDMI->VGA converters before getting one. I haven't had a chance to test one but I'm quite confident they should work fine if they are simple and don't reject non-standard (e.g. 55Hz) input timings. Perhaps Fudoh has one to test for the review?

I'm buying one of the cheapest ones I can find to test with Gamecube HDMI, so I'll give it a go on the OSSC once I get my hands on one

[Das Muel]

I've been using this dirt cheap thing: http://www.amazon.co.uk/smallest-Adapte ... s=hdmi+vga

Performance has been very solid (worked fine with the Mini in a range of output modes) and I couldn't see any abnormalities when running it through the 240p test suite. I also have a slightly more expensive Startech one (still pretty cheap) http://www.amazon.co.uk/Startech-Adapte ... b_title_ce

I haven't been using that one because it doesn't have audio support, but I couldn't see any qualitative difference between the two when I compared them. Dunno how they handle unusual input timings though.

[rtw]

I've been using this dirt cheap thing: http://www.amazon.co.uk/smallest-Adapte ... s=hdmi+vga

Doesn't the OSSC require a DVI-D + Audio => HDMI combiner ?

[Das Muel]

I'm gonna break out the audio from scart before it gets to the OSSC, then run a DVI-HDMI cable in to the VGA converter.

[karma_police]

Will we be seeing a review from Fudoh soon? Hoping that maybe we also get some additional footage of the unit in action.

[Fudoh]

Will we be seeing a review from Fudoh soon?

next week