LKV7600 Video converter yPbPr to VGA review: input lag, upscaling and deinterlacing issues

The Goal: video console to monitor connectivity

This device takes YPbPr (component) video and converts it to VGA. It is not just simple signal digitizer; but also provides upscaling and deinterlacing. As such it introduces some amount of lag into the process, which is the primary focus of this review. 

It doesn't have a model number printed anywhere on it, but the packaging and internals appear to be identical to the popular Lenkeng LKV7600. I'm guessing it's a clone but probably performs very similarly.  

How it performs

It supports 480i/p, 720p, and 1080p inputs, and maybe more but those were the one's I tested. As an upscaler it supports a wide range of target resolutions, but notably missing is 1080p. The closest was 1680x1050, but that's likely to introduce aliasing on your display. You could do lower resolutions and let the TV/monitor do some additional upscaling, but the device doesn't do a great job at 640x480 output, looking quite blurry, with significant lost detail. It fairs better at higher output resolutions, which include 1440x900 and even 1920x1200, all of which have minimal aliasing or jaggies if your display can handle them. A very strange oversight that 1080p is missing.

So, what about lag? I measured as usual with the piLagTesterPRO, converting the HDMI output of the pi0 to yPrPb using a zero lag converter. Unfortunately, the results are not pretty. it adds between 16 and 32ms of lag to the output. You might think the range was due to it treating interlaced and progressive content differently, but unfortunately the lag introduced is the same for both.  The variability is due to the device not synchronizing the input vsync and output vsync. The long and short of this is that lag slowly increases on every frame until it reaches 32ms and then it jumps back down to 16 with a visible motion glitch. This is ugly, and hard to adapt to, meaning that even though the average lag is 24ms it feels like more, probably even more than 32ms. If you want the full technical details read the link above of the shorter version below in gray:

The device buffers the input, and always outputs at nearly 60hz. It's fairly easy to see why this would cause drift if the input was only 59.94hz (aka NTSC): the start of the input and output frames slowly drift out of sync with each other by about 1ms per second; and several times a minute it has a motion glitch when the device shows the same input frame twice to make up for the difference. Unfortunately, the same behavior happens with 60hz input signals, the drift is just much slower, with the glitches happening every few minutes. 

While this is disappointing, honestly only action games really suffer. I played a number of more sedate games including some zelda-alikes and never noticed. But a fighting game or a FPS will definitely feel a bit off. 

What's inside

While it's not a slam dunk, I'm pretty sure this is the same as the LKV7600; the outside exactly matches the  Lenkeng LKV7600, see for instance http://retrogaming.hazard-city.de/

I was hoping to find confirmation on the PCB inside, so I took it apart. As you can see it has very few markings inside. Even the chips are bare, except for the lower one which is marked 7600 - presumably this chip is why Lenkeng chose the model number LKV7600. 

I suspect this device is also closely related to another well-know product, the GBS 8200/8220. The on-screen menus are very similar, and the board layout is quite similar, including a spot where you could hook in to apply the Gbs-control firmware. No idea if it would be compatible with this, though. The GBS-control firmware supposedly increases the quality of the output significantly, so it would be interesting to see if they managed to work around the drift issue so that you always got the minimum of 16ms. 

If you are interested in that, given the GBS 8220 is just $20 +s&h it probably makes sense to get the real deal instead of trying to mod one of these.

WickedHD Video Converter YPbPr to HDMI review: input lag, upscaling and deinterlacing issues

The Goal: zero lag

This device takes YPbPr (component) video and converts it to HDMI. It is a simple signal digitizer,

with no deinterlacing or upscaling applied; it passes the resolution and refresh rate given to it directly to your TV or monitor leaving the display to do whatever upscaling or deinterlacing required. The upside of this approach is that it adds very little lag (I measured at most 0.5ms of extra lag using the PiLagTesterPRO). Think of it as an ultra-budget alternative to the OSSC, especially if your display does a good job of upscaling and/or deinterlacing. Many computer monitors in particular use BOB deinterlacing, so a device like this might be a good way to get YPbPr into your computer monitor, displaying your retro consoles with very low lag, nearly as fast as those long-out-of-production CRTs.

How it performs

It supports 480i/p, 720p, and 1080p inputs, passing them along more or less unmodified. The only consistent issue is that the color space output over HDMI is very dark on my PC monitor (aka black crush). On my TV, however, it looks right, so I suspect it's an issue of using the "video" color space.  Since I intended to use it for my computer, that kind of ruins it for me. 

There's a 2nd problem as well: There's something about the original Xbox video output that cause the signal to intermittently drop out when displayed via this device. It doesn't happen at all during the first 10 or so minutes that it's being used but eventually the screen will briefly go blank. With time the frequency of this starts to go up significantly; once it has been on 20 minutes it happens every couple minutes, making the device useless.

I suspected that it was overheating (the device does get warm) so I strapped a heatsink to the case (no improvement) and also tried taking the cover off (also no improvement).  More likely, it's an issue with the 1st Gen Xbox video output being out of spec, because I have another radically different looking adapter, the ozsc-3, that has this issue.

What's inside

Since I had the cover off I decided to snap some photos so I could identify the chipset and board revision.

The HDMI output comes from the MacroSilicon MS9282N-AVA (also marked N8SKQ 1350).  The spec sheet suggests it does the conversion work too.

There's also a STC microcontroller, an 11L16XE/35I-LGFP44G which has flash memory built in. It seems to have the same instruction set as the ozsc-3 that I tested that also had xbox issues, suggesting that they might run similar firmware, though this device can handle 480i so perhaps this is the better version.

It would be very interesting to see if you could hack this to make it work better. The signal digitization is excellent, with low noise and the right amount of crispness and softness. If it were not for the black crush/color space issue and xbox incompatibility it would be a pretty nice converter. 

All this is so close to being an excellent solution to my needs that I got a 2nd one just to make sure I wasn't suffering from a faulty unit, but it performed identically. 

 How to recognize it in the stores 

These kinds of devices get packaged in all kinds of generic boxes so it's going to be hard to tell what you are getting from the box alone. So pay attention to the device itself . One thing that is somewhat unique is the two status lights in the back (one for power, one for signal). The board itself is marked HY-202-B2-VO VGA&YPBPR to HDMI. There's no VGA port on the board but it looks like there's a spot for it.

The manual also is upfront with how this device works, stating "This converter box is without scaler function and the output resolution is the same s the input one."(typo's theirs). 

ozsc-3 YPbPr to HDMI converter review: input lag, upscaling and deinterlacing issues

The Goal

This device takes YPbPr (component) video and converts it to HDMI. It is a simple signal digitizer, with no deinterlacing or upscaling applied; it passes the resolution and refresh rate given to it directly to your TV or monitor leaving the display to do whatever upscaling or deinterlacing required. The upside of this approach is that it adds very little lag (I measured at most 0.3ms of extra lag using the PiLagTesterPRO). Think of it as an ultra-budget alternative to the OSSC, especially if your display does a good job of upscaling and/or deinterlacing. Many computer monitors in particular use BOB deinterlacing, so a device like this might be a good way to get YPbPr into your computer monitor, displaying your retro consoles with very low lag, nearly as fast as those long-out-of-production CRTs.

How it performs

Unfortunately, this particular device has some significant limitations that means I can't really recommend it for retro gaming. 

First, it doesn't support 480i inputs. Thus consoles like the PS2 are not going to work well with it. 1080i is supported, so it's just bad luck that they didn't include 480i, I guess.

So it's not a good choice for the PS2. What about the original Xbox, which supported 480p for almost every game released? Unfortunately, there's something about the Xbox video output that cause the signal to intermittently drop out when displayed via this device. It doesn't happen at all during the first 10 or so minutes that it's being used but eventually the screen will briefly go blank. With time the frequency of this starts to go up significantly; once it has been on 20 minutes it happens every couple minutes, making the device useless.

I suspected that it was overheating (the device does get warm) so I strapped a heatsink to the case (no improvement) and also tried taking the cover off (also no improvement).

What's inside

Since I had the cover off I decided to snap some photos so I could identify the chipset and board revision. 

The HDMI output is done by a chip for which I can find no documentation: it's the 8786-EX (also marked HP5981.03 1830). 

There's also a nuvoTon microcontroller, which combines eight 400khz ADCs, a 16mhz CPU, and built in flash ROM too. I'd guess the 8786-EX does all the heavy lifting, and it does look like the YPbPr traces go to that chip, but the 8 high speed ADCs in the micro controller seem like overkill unless they somehow process the input signal as well.

It would be very interesting to see if you could hack this to make it work better. The signal digitization is excellent, with low noise and the right amount of crispness and softness. If it could work with 480i or the xbox's 480p it would be a pretty nice converter. It also outputs in the proper color space for a computer monitor, with no black crush.

All this is so close to being an excellent solution to my needs that I was tempted to buy some other similar looking ones to see if a later revision worked better but sadly they did not. I'll post reviews and teardowns of them separately.

 How to recognize it in the stores 

These kinds of devices get packaged in all kinds of generic boxes so it's going to be hard to tell what you are getting from the box alone. So pay attention to the device itself and some of it's odd features. First, the inputs are not RCA jacks but RCA plugs. So you'll need a gender changer to get your console to plug into it. It uses a USB plug for power (although it can also get power over HDMI). And while the version I purchased has a built in (but very short) HDMI cord, if you disassemble the case you'll find that the cord just plugs into the PC board. 

On the board itself is the model number: OZSC-3 and the product name sometimes used to advertise it: YPBPR+RL TO HDMI. After the product name is the number 1.8 which might seem like a version number but on the board itself it also reports YPBPR2HDMI REV1 which is clearly a version number. But notice the text is in a different font, so who knows which one is valid.