Saturday, June 30, 2018

The Great Unknown : 720p and 480p Retro Solutions

While retro video games and consoles have been getting the digital treatment in the forms of emulators, PCs and services like the Virtual Console, buying hardware to specifically play retro games in a digital form (as opposed to a clone console) is a relatively recent phenomenon.  There has been a draw for people who want to really use their cartridges on a high quality, high definition system using a modern TV.  There has also been a market for people who want a plug-and-play box where they don't have to fiddle with emulator options.  Most modern TVs use the HDMI connector for passing digital content through to a LCD panel's display processor.  HDMI licensing issues aside (search my blog for information about those issues), most of these retro devices support a maximum resolution of 480p, 720p or 1080p.  While some of these devices support 1080p, many only support 720p or 480p. which can lead to thorny problems with lag and image resizing.  Let's take a look at the issues in this blog article.

First, here is a list of current or actually released retro-centered solutions by the maximum resolution they support :




1080p Solutions
Open Source Scan Converter (OSSC)^
Micomsoft XRGB-mini Framemeister
Atari Jaguar Kitty Box
Hi-Def NES Mod & Analogue Nt HDMI
UltraHDMI N64 Mod
Analogue Nt Mini
Analogue Super Nt
MiST & MiSTer$

720p Solutions
Hyperkin RetroN 77
Hyperkin RetroN 5
RetroUSB AVS
Hyperkin RetroN 1 HD
Gamerz Tek 8-Bit HD
Retro-bit RES Plus
Hyperkin SupaRetroN HD
Gamerz Tek 16-bit HD
OldSkool Classiq II HD before
Gamerz Tek Minigen HD
Gamerz TekG-Tek 2in1 HD
Feo Hao HD Retro Game
Retro-bit Super RetroTRIO Plus
atgames Atari Flashback 8 Gold (Includes Activision Edition)
Nintendo NES Classic Mini
Nintendo SNES Classic Mini
atgames Sega Genesis Flashback HD
Retro-bit Generations
Retro-bit Super Retro-Cade
UperGrafx^
Retro Games Ltd. The C64 Mini

480p Solutions
EON GCHD
GC Video Plug n Play 3.0
Akura DC
HD Link Cable for Dreamcast
PS2 to HDMI converter
Wii2HDMI
HD Link Cable for Original Xbox System

^ - UperGrafx uses DVI, old versions of OSSC use DVI
$ - Cores vary considerably in quality, the Atari ST and Amiga cores are excellent, most of the rest, not so much

Even though I do not consider this a comprehensive list, as you can see, the number of 720p solutions outweighs the 1080p solutions by a wide margin.  (I have not included HDMI-equipped consoles that can emulate classic games like the PS3, PS4, Switch, Wii U, Xbox 360 or Xbox One).  I am pretty sure I missed a few 720p solutions.  The 480p solutions are merely digitizers, the PS/2, Xbox and Wii HDMI solutions are essentially component to HDMI converters.  I don't even pretend to do more than just give a sampler of them.  The Dreamcast devices are VGA to HDMI converters.  The GameCube adapters are more expensive because they must decode the GameCube's proprietary digital format and fit into a unique connector.

The most troubling issue with the 720p resolution is that there is no such thing as a native 720p display.  All "720p" TVs use a native resolution of 1366x768.  A 1280x720 resolution must be upscaled or windowboxed.  720p TVs are cheap devices with few features, always assume that the resolution will be upscaled.  Upscaling induces lag.

Most quality TVs use 1080p (1920x1080) and 4K (3840x2160) resolutions.  720p does not evenly fit into 1080p but it does into 4K.  So then wouldn't 4K be the ideal solution?  Not so much.  TVs tend to add more filtering and processing to get the picture up to snuff with lower resolutions.  Often the resulting picture looks less sharp than a 1080p scaled image.  480p does not fit evenly into either 1080p or 4K.  LCD panels tend to make things fit into the native resolution regardless of what the viewer may prefer.  The premier site for testing TV latency, rtings.com, doesn't test for 480p or 720p latency and I don't know of another site that does. 

I have tried the Nt Mini and Super Nt on my 4K TV.  In 1080p mode, the pixels are very sharp and distinct.  In 720p mode, the pixels almost as sharp and the colors almost as pure as 1080p but not quite.  Scanlines in 720p looked uneven at the ideal 3x setting.

What about computer monitors?  Newegg does list a few 1280x800 monitors, but they are small and from no-name brands.  1280x1024 monitors are still sold, but if you have an image that has been scaled from 256x240 to 1024x720, you are going to see large borders.  This assumes your monitor will display that or not try to stretch it to fill the screen in a way you can't do anything about.  Those monitors aren't meant for gaming these days, so expect poor panel response times.

I have a pair of 1280x1024 native resolution LCD computer monitors.  These monitors only have DVI and VGA inputs.  They refused to display a signal from my Nt Mini unless I had set the DVI mode.  The Super Nt does not have a DVI mode setting and I do not expect any of the other devices except the XRGB-mini. OSSC and the MiST/er do.  When they received the signal in DVI mode, both monitors stretched a 1280x720 image into a 1280x1024 image.  With stretching options in the Nt Mini I was able to a nearly perfectly sharp image but there was a lot of ghosting.  Latency is unknown.

Then we come to the old standard, the high-definition CRT.  They come in two varieties, the computer monitor, typically with a VGA connector and the HDTV.  Many later VGA monitors can do 1600x1200 and virtually all of them can do 1280x1024, so they can easily display 720p and 480p.  But they have their drawbacks, namely requiring HDMI to VGA conversion, possible incompatibilities with displaying a 720p signal and graphics requiring use of the horizontal size option on the monitor's OSD.  They are also small, rarely going above 21", and their phosphors are generally more muted than you would expect from a TV.  Lag with these devices is unknown.  HD CRTs can be larger, up to 36", but they are almost always widescreen, so the 4:3 image of a retro console will not fill the screen.  They are also huge and heavy.  The Sony KD-34XBR960, which uses a 34" display weighs 194 pounds!  HDTV CRTs only do a maximum of 1080i and some may not do 720p.  Finally, HDTV CRTs act more like LCD panels and will have some latency and may upscale 240p sources to 480i, 480p or 1080i.

720p is a good capturing solution, captures are smaller, much less demanding on the capture card's host CPU and can be scaled via nearest neighbor scaling to get to 1080p or better.  There are no capture cards that can capture 1080p60 for less than $150, but almost all HDMI capture devices can capture 720p60.  It is also the ideal resolution for scanlines because you get scanlines that are neither too thick (480p) or too thin (1080p).  However, have you tried to play games through the capture window?  There is a sizeable amount of latency added to those captures unless you have a really fast system.  480p requires even fewer CPU resources and given that it is usually a 2x scale, the file sizes will be smaller than 720p but your scaling options can make it out to be 4K with no loss in quality.

Ultimately, 720p is not a good playing solution unless you can measure the latency of a 720p display and can be satisfied with its upscaling quality.  rtings.com uses a special tool to measure panel latency : https://www.rtings.com/company/input-lag-tool  Retro systems can get a reasonably accurate comparison of latency by using the 240p test suite for various consoles.  This requires an original console, a CRT and a camera, so it isn't something everyone will be able to use.  Moreover, you can hardly walk into your local Best Buy, Sears, Wal-mart or Target and expect the employees to perform strange tests with the floor display models.  The good 1080p solutions tend to start where the 720p solutions end, but they are high-quality products designed to minimize latency.

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