VGA to HDMI converter

[shmupsrocks]

Any recommendations for a VGA to HDMI converter with great picture quality?

[ldeveraux]

The ossc

[headlesshobbs]

I'd imagine you're talking about just a normal converter adapter and not something that costs $200 just to get the job done without compromising quality. Unfortunately there isn't a lot of options on the table aside from simple ones you'd see in the Walmart isle like those from Berkin (avoid those).

If there are any there are any good ones like the number of $20 HDMI to VGA adapters out there on the market, I'd like to know of some as well. Don't expect any to properly support the dreamcast for VESA 480p though. I attempted that and the results were quite disappointing.

[maxtherabbit]

Extron RGB-HDMI 300A

[fernan1234]

Extron RGB-HDMI 300A

This is a good one, though in my experience it can introduce frame stuttering, and also crushes some fine color detail/gradation.

[orange808]

If you absolutely want a no lag converter that simply handles RGBHV and outputs HDMI with embedded audio, the DVC RGB-HD A works well and it allows EDID programming using the Extron software. The EDID management is very helpful with finicky displays that refuse to accept audio with other converters. It even knew to properly sample the Dreamcast output. Converts DOS signals properly as well--if your display can handle the signal. (It's not a video scaler/processor)
https://www.extron.com/product/dvcrgbhda

It's a nice little machine, but it's hard to find and it's probably going to be expensive for you. The OSSC is a better value.

[kitty666cats]

The Monoprice one (has a LKVin the model number, Lenkeng rebrand I suppose) that is black with rounded sides is good!



^ Ones that look like this are also pretty decent



^ https://www.amazon.com/Ableconn-VGA2HDM ... B00WAIX5S4

THIS one I have not heard of anyone trying, but it sounds quite interesting to me:

"The Ableconn VGA2HDMIB VGA to HDMI adapter converts analog VGA video and 3.5mm jack audio to digital HDMI signals with resolution up to 1080p/60Hz. It's built with Silicon Image Sil8784 and TI PCM1808 chipset to ensure high quality signals and compatibility with most of HDMI input displays such as projectors, HDTV, home theater systems, etc."

The datasheet for that Sil8784 they mention is what has me so interested - https://www.latticesemi.com/-/media/Lat ... t_id=51619 (WARNING: PDF)

Excerpt:

1. General Description
The Lattice Semiconductor SiI8784 device is a high
quality, multi-format analog video decoder and
processor with an integrated dual-mode High
Definition Multimedia Interface (HDMI®)/Mobil
High-definition Link (MHL®) transmitter. A
microcontroller is integrated to reduce the system Bill
Of Materials (BOM) cost.
The SiI8784 device supports worldwide PAL, NTSC and
SECAM standards, YPbPr video signals up to 1080p @
60 Hz resolution, and RGB graphics signals from VGA
to UXGA resolutions. It also supports the SCART
interface with Fast Blanking and the D-Terminal.
This device contains a Time Base Correction (TBC)
module, a de-interlacer with a post-processor engine,
and a VBI decoder. For content protected analog
videos, HDCP will automatically be enabled on the
HDMI or MHL output.
1.1. Features
1.1.1. Analog Video Front-end
 Four 10-bit Analog to Digital Convertors (ADC)
sampling up to 170 MHz
 Flexible input multiplexers to support composite,
component, VGA, SCART with Fast Blanking and
D-Terminal interfaces
 Supports cable plug-in detection and active video
signal detection
1.1.2. Multi-format Video Decoder
 Automatic format detection
 Supports NTSC, PAL, and SECAM standards of
composite input with adaptive comb filter
 Supports 240p, 480i/p, 576i/p, 720p, 1080i/p
component video
 Supports RGB graphics from VGA to UXGA
 Supports Macrovision Type I, II, III copy protection
detection
 Supports multi-standard VBI decoding: Teletext,
WSS, VPS, CC, CGMS, and V-CHIP
1.1.3. Video Processing
 Time Base Correction
 De-interlacer with Edge Smoothing
 Automatic Phase/Position Detection
1.1.4. HDMI/MHL Transmitter
 Selectable HDMI/MHL Dual-mode
 Compliant with HDMI 1.4b and MHL 2.1
specifications
 HDMI output up to 1080p @ 60 Hz or
UXGA @ 60 Hz resolution
 MHL output up to 1080p @ 60 Hz resolution
 HDCP 1.4
 Audio insertion with I2
S/ SPDIF input
 VBI data forwarding over HDMI/MHL

...

Figure 3.7. Transmitter Video Data Processing Path Embedded Sync Decoder
The input processor can create DE, HSYNC, and VSYNC signals using the start of active video (SAV) and end of active
video (EAV) codes within the ITU-R BT.656-format video stream.
3.4.2.1. Data Enable Generator
The transmitter includes logic to construct a DE signal from the incoming HSYNC, VSYNC, and clock. Registers are
programmed to enable the DE signal to define the size of the active display region.
3.4.2.2. Combiner
The clock, data, and sync information is combined into a complete set of signals required for TMDS encoding. From
here, the signals are manipulated by the register-selected video processing blocks.
3.4.2.3. 422 to 444 Up-sampler
Chrominance up-sampling and down-sampling increase or decrease the number of chrominance samples in each line of
video. Up-sampling doubles the number of chrominance samples in each line, converting 4:2:2 sampled video to 4:4:4
sampled video.
3.4.2.4. 444 to 422 Decimation
Decimation reduces the number of chrominance samples in each line by half, converting 4:4:4 sampled video to 4:2:2
video.
3.4.2.5. Color Space Converters (CSC)
Two color space converters (CSCs) (YCbCr to RGB and RGB to YCbCr) are available to interface to the many video
formats supplied by A/V processors and to provide full DVI backward compatibility. The CSC can be adjusted to perform
standard-definition conversions (ITU.601) or high-definition conversions (ITU.709) by setting the appropriate registers.
RGB to YCbCr
The RGBYCbCr color space converter can convert from video data RGB to standard definition or to high definition
YCbCr formats. The HDMI AVI packet defines the color space of the incoming video.

[fernan1234]

That does sound interesting. But putting this together:

The SiI8784 device supports worldwide PAL, NTSC and
SECAM standards, YPbPr video signals up to 1080p @
60 Hz resolution, and RGB graphics signals from VGA
to UXGA resolutions.

 Automatic format detection
 Supports NTSC, PAL, and SECAM standards of
composite input with adaptive comb filter
 Supports 240p, 480i/p, 576i/p, 720p, 1080i/p
component video
 Supports RGB graphics from VGA to UXGA

It makes me worry that it may be like some old video processors that accepted SD/15khz signals but only via component inputs. Sounds like a device with a SCART input and this chip would be fine, but this adapter here only has a "VGA"/DE-15 connector. It would be perfect if it could also work with the 15khz RGBS sources most prevalent in our SD RGB gaming or video setups. Maybe it does, in spite of what the above may suggest.

[kitty666cats]

That does sound interesting. But putting this together:

The SiI8784 device supports worldwide PAL, NTSC and
SECAM standards, YPbPr video signals up to 1080p @
60 Hz resolution, and RGB graphics signals from VGA
to UXGA resolutions.

 Automatic format detection
 Supports NTSC, PAL, and SECAM standards of
composite input with adaptive comb filter
 Supports 240p, 480i/p, 576i/p, 720p, 1080i/p
component video
 Supports RGB graphics from VGA to UXGA

It makes me worry that it may be like some old video processors that accepted SD/15khz signals but only via component inputs. Sounds like a device with a SCART input and this chip would be fine, but this adapter here only has a "VGA"/DE-15 connector. It would be perfect if it could also work with the 15khz RGBS sources most prevalent in our SD RGB gaming or video setups. Maybe it does, in spite of what the above may suggest.

Yeah, tempted to pick one up and try SCART via a SCART2DVI (similar to the Sync Strike).

[shmupsrocks]

I use an OSSC in my JAMMA rig but this is actually for video so lag is not a concern. Will an OSSC outperform an Extron for video picture quality?

[orange808]

I use an OSSC in my JAMMA rig but this is actually for video so lag is not a concern. Will an OSSC outperform an Extron for video picture quality?

Should be about the same if you set up the OSSC for low pass filtering. Send the RGB lines into the OSSC on the AV2 RCA plugs and use the AV3 HD15/DE15 plug for sync.

The OSSC adds plenty of options to tweak the picture that the Extron doesn't have (the Extron leaves color and porch adjustment to the source and display). The Extron has an EDID editor that the OSSC doesn't have.

You may need a separate audio embedder (as well) to get more than 2 channel audio--if the source machine supports it. The Extron only handles two channel unbalanced stereo.

Overall, they both have great image quality. The OSSC is still the better buy (if you don't need the integrated EDID editor).

If you don't mind me asking, what are the details of the RGBHV source machine?

[shmupsrocks]

Send the RGB lines into the OSSC on the AV2 RCA plugs and use the AV3 HD15/DE15 plug for sync.

Why do this instead of sending everything over HD15?

I thought component could do 1080i max but I'm looking to do 1080p.

I won't be sending audio over HDMI.

Source material is a Faroudja scaler fed by a VCR:

viewtopic.php?f=6&t=67567

[orange808]

Send the RGB lines into the OSSC on the AV2 RCA plugs and use the AV3 HD15/DE15 plug for sync.

Why do this instead of sending everything over HD15?

I thought component could do 1080i max but I'm looking to do 1080p.

I won't be sending audio over HDMI.

AV3 doesn't have low pass filtering and you may get noisy output (depending on the source). For best results, I'd go ahead and use AV2 if you're buying a separate OSSC.

[shmupsrocks]

Source material info edited in above.

I actually like AV3 better than SCART on my arcade OSSC and if that's due to the low pass filter I might like AV3 better than AV2.

Am I right that AV2 is 1080i max?

[maxtherabbit]

No, 1080p

[kitty666cats]

Any particular special settings you need to punch in if feeding RGB into AV2 and sync into AV3? I have heard you mention that unsung method before, but never heard the down-n-dirty of setup/image or video of results. Curious! Getting another OSSC pretty soon (sold mine once I got GBSControl set up, but now I am Keen on having BOTH for some wonky experiments lol)

[almnk]

Internals of the Gefen VGA to DVI converter, main IC is MSTAR MST6250LA-LF-165:
https://drive.google.com/file/d/11T1UKp ... sp=sharing

[Guspaz]

The OSSC is a bad VGA to HDMI converter at anything but low resolutions. The VGA signal has everything the ADC device needs to do automatic per-pixel sampling by automatically determining the phase using the DDC information (that has the detailed timings), and that's how LCD monitors figure out the exact sampling/phase to use. The OSSC doesn't do that, and so the image quality falls apart at higher resolutions. Either that or the OSSC just doesn't sample at high enough resolution, not sure. Either way the results are very poor. Which isn't really the OSSC's fault, that's not what it's designed for, and at lower VGA resolutions it look great.

[maxtherabbit]

The OSSC is a bad VGA to HDMI converter at anything but low resolutions.

Absolutely false. It works great up to 1600x1200p60.

If you said "anything but low *refresh rate* for higher resolutions" I could see your argument.

[fernan1234]

The good thing is that virtually any source that outputs high resolution, and even more so at high refresh rates, has digital output and therefore has no need for an ADC.

The OSSC really is the best ADC on the market, perhaps in absolute terms.

[Guspaz]

The OSSC is a bad VGA to HDMI converter at anything but low resolutions.

Absolutely false. It works great up to 1600x1200p60.

If you said "anything but low *refresh rate* for higher resolutions" I could see your argument.

No, it doesn't. I've tried it. It produces what looks like subsampled output at higher resolutions. It works great for 480p, it performed quite poorly at higher resolutions, and yes, 75Hz is straight out. And as I pointed out, it doesn't support automatic image adjustment based on the DCC data. Perhaps my issues could have been resolved by manually tweaking the timings and phase, but that just illustrates that the OSSC is not the right tool for the job when VGA-to-HDMI adapters should be doing that automatically.

The good thing is that virtually any source that outputs high resolution, and even more so at high refresh rates, has digital output and therefore has no need for an ADC.

The OSSC really is the best ADC on the market, perhaps in absolute terms.

The output is a Mac Mini G4 running OS 9. It has a DVI-I port, which means that HDMI and VGA output are both natively supported. The problem is that the set of output resolutions supported is very different for VGA and DVI/HDMI, and the resolution list is hardcoded into the driver and can't be changed, even if the actual hardware supports other resolutions/timings.

I'm using it primarily over HDMI, but was trying out VGA to see if any of the VGA resolutions might be a better fit for my 1440p monitor. Unfortunately, I ran into two problems:

1) The OSSC works perfectly for low VGA resolutions and OK for medium resolutions, but does not properly sample higher resolutions, and does not support at all the highest resolutions (won't sync).

2) The OSSC can't double anything above 480p. So it won't double 800x600 to 1600x1200, for example.

Between the limitations at higher resolutions and the inability to double medium resolutions, it's basically only useful for getting sharper 480p output out of the mac mini as compared to my LCD display's very soft/blurry internal scaler.

[fernan1234]

2) The OSSC can't double anything above 480p. So it won't double 800x600 to 1600x1200, for example.

What are your results like when you simply pass through these resolutions rather than expect to double them? I've had fantastic results with the output of a GBS-C (1280x960) going into the OSSC's AV3, which it passes through as is and looks perfect on a monitor that displays it without scaling, but if the monitor does scale them I imagine that the result would then depend on how well it does the scaling.

[Guspaz]

The passthrough was the problem, it was either subsampling or the sampling was misaligned, and vertical details like text and vertical lines were like, spread over multiple samples pixels. To be clear, this is with a computer desktop, where there's a bunch of black text on white backgrounds without antialiasing, so it's just about the least forgiving environment. I'll try to remember to take some screenshots after work when I have time to set it up with the OSSC again. IIRC the problem was also present with the LCD monitor set to just scan, though the image is too small for that to be practical for actual use.

My ideal setup will probably involve 1280x720 output via HDMI fed into a PixelFX Morph to do integer scaling to 2560x1440.

[Sirotaca]

No, it doesn't. I've tried it. It produces what looks like subsampled output at higher resolutions. It works great for 480p, it performed quite poorly at higher resolutions, and yes, 75Hz is straight out. And as I pointed out, it doesn't support automatic image adjustment based on the DCC data. Perhaps my issues could have been resolved by manually tweaking the timings and phase, but that just illustrates that the OSSC is not the right tool for the job when VGA-to-HDMI adapters should be doing that automatically.

Strange, because I've used my OSSC for 1600x1200 computer desktops plenty of times and I've always had fantastic results with it. If your LPF and sampling settings are correct, I'd be inclined to suspect a cabling issue. 1600x1200 is far, far more demanding on cable quality than 480p is.

[Guspaz]

That's a good point that I didn't check the LPF settings, but again, if you have to set the sampling settings at all, it's already failed as a VGA to HDMI adapter, because the video source is literally sending the full timing data over the VGA cable in the DDC data. It'd be rather inconvenient to have to manually define and swap profiles any time the resolution changes, when presumably VGA to HDMI adapters do that (and automatic phase detect) automatically. LCD monitors do, at least, when directly fed VGA.

[Sirotaca]

It'd be rather inconvenient to have to manually define and swap profiles any time the resolution changes, when presumably VGA to HDMI adapters do that (and automatic phase detect) automatically.

Normally you don't have to do that. The OSSC stores the timing settings for every input resolution in each profile, so typically you'd only need one profile corresponding to a given machine. Sure, it's not as convenient as automatic sample rate and phase adjustment, but once you set them once for a given source device, you don't usually need to change them. The one exception is that 640x400 vs. 720x400 requires manual intervention to switch the sampling mode (or just use generic sampling), but I've never had an LCD monitor that could detect that automatically either. At least the OSSC gives you the option to change it.

Also, does VGA DDC actually send any pixel timing data to the monitor? I always thought it was just to let the source device read the monitor's EDID information to determine supported modes. I've definitely needed to manually tweak phase and position on some of my LCD monitors when the automatic adjustment gets it wrong, in any case.

[Guspaz]

OK, I'll admit that I'm partially wrong, in that I appear to have misremembered some things incorrectly. My results:

- 75Hz: still no-go. Does sync at some resolutions like 480p, but with bad sampling and the viewable area is cut off/cropped.
- Resolutions above 1080p/1200p: no go
- Everything up to 1600x1200: pixel-perfect sampling with default settings, quality issues at higher resolutions are down to a low-quality VGA cable
- 1080p: Incorrectly sampled, the subsampling behaviour that I made previously mentioned, and apparently remembered applying to more resolutions

Here are three comparison shots:

640x480:

Spoiler

1600x1200:

Spoiler

1920x1080:

Spoiler

So my conclusion is, I was largely wrong, with a good quality VGA cable, the OSSC should just work with everything up to 1600x1200 at 60Hz. The inability to double 600p or 720p are still annoying limitations (which prevent me from using it for this computer, I'll need a Morph for that), 75Hz not working is also annoying (noticeably less lag on my monitor), and 1080p doesn't sample right out-of-the-box. It's possible that the latter is due to PC vs HDTV timings with the latter being the default on the OSSC.

[maxtherabbit]

1080p doesn't sample right out-of-the-box. It's possible that the latter is due to PC vs HDTV timings with the latter being the default on the OSSC.

It is. The default sampling profile on the OSSC is for DTV 1080p. It's really the video card's fault if it uses the stupid CVT or GTF timings when you select 1920x1080. Can be fixed with most video drivers by defining custom resolution conforming to DTV 1080p

[maxtherabbit]

Also, does VGA DDC actually send any pixel timing data to the monitor?

No it does not

I always thought it was just to let the source device read the monitor's EDID information to determine supported modes. I've definitely needed to manually tweak phase and position on some of my LCD monitors when the automatic adjustment gets it wrong, in any case.

Correct

[Guspaz]

1080p doesn't sample right out-of-the-box. It's possible that the latter is due to PC vs HDTV timings with the latter being the default on the OSSC.

It is. The default sampling profile on the OSSC is for DTV 1080p. It's really the video card's fault if it uses the stupid CVT or GTF timings when you select 1920x1080. Can be fixed with most video drivers by defining custom resolution conforming to DTV 1080p

As I previously mentioned, OS9 video drivers do not support custom resolutions. Nor do they even give you any information about the specific timings being used.