12G cabling - test results and a video presentation

I presented a recent Tech Breakfast at Jigsaw24, Golden Square. Here I detail the tests we've done across four cable types and how they perform at twelve gigabits/sec (as per SMPTE 2082-1).

We've recently taken on Leader as a manufacturer of test sets and they excel in several areas - namely UHD/4K/HDR and 12G physical layer measurements. 

 all the specs for SMPTE 2082-1

I got through all the details in the video (below and on YouTube) but you can snag my results here - if you go into the 12G folder you can see the screen grabs for all the eye patterns - the filename number related to the test line in the PDF.  The Powerpoint presentation is in there too; but if you watch the video I cut all the slides full-screen as appropriate.

 The cable types are;

SD05 - Belden 1855; otherwise known as "Image 360"
SD10 - Belden 1694
SD50 - Belden 1505; otherwise known as "Image 1000"
SD73 - Belden 7731 - about the most ungainly cable you can crimp a BNC onto!

HDR for Television; HLG, DolbyPQ etc - a primer

I have been such a poor blogger! It's been a month-and-a-half since I set finger-to-keyboard but I have been busy at work and home. Here is a presentation I gave at the Soho Screening Rooms for one of Root6's Tech Breakfasts.


You can download the notes from root6.com.

BM UHD/4k converters - some gotchas

https://www.blackmagicdesign.com/products/miniconverters/techspecs/W-CONM-17

I've used a few of these guys recently - Blackmagic's quad HD/SDi input to HDMI 2.0 output for taking the UHD / 4k (either tile or 2SI standard) and making something that will display on a 4k domestic TV.

They seem to work quite well, but here are a few things that I had to get around;

1. Firmware - I had two identical ones and I initially tested both with Quad-SDi out of Avids at UHD (3840x2160 at 25 & 30P) - all good. But when I started a 4k project (4096x2160 at 24P) only one worked - the other showed nothing on it's HDMI output. Eventually discovered only one of them had current (v.7 as of May 2016) firmware!
2. Power cycle if colour space wrong - both have periodically decided they are going to mistranslate Y, Cb, Cr -> R, G, B - power cycling fixing it; hopefully the next firmware update will stop this?
3. Four signals are always interpreted as UHD; if the Avid is running an HD project the four SDi feeds out of the back are all identical and the converter has no way of knowing it's not quad-link. The Tektronix 8200-series and the Canon VP3010 monitor both have to be told (and I set presets for just this) but the BM converter needs to see three or fewer signals to realise it's only a 1920x1080 raster. In the case of this job setting up two macros on the video router (one to route all four, one to send a non-used input to i/p's B, C, & D of the BM).
4. Glad I'm rocking a MacBook Pro! I would not have been able to update the firmware otherwise as I've yet to move on from Windows 7 - and the workshop PC is still 32-bit Windows 7!

Free Tektronix UHD/4k info posters

Get 'em here & here!

4k and UHD cabling and signal standards

I've had to dig into signal transport for 4k/UHD over the last week or so. Essentially I have a test-signal generator (SRI Visualizer TG100) running at a maximum raster of 4096x2160 at a maximum of 25 progressive frames/sec (and only 4:2:2 colour sampling; Y, Cr, Cb) with a 6G single-link output (so really 4 x 1.5G links) and HDMI 1.4 (so the same raster as the SDi). The monitors are the 24" and 30" Canon IPS 4k native monitors.

The Canon monitors will take quad-link HD/SDi and (in the case of the 24") HDMI. So, feeding the SRI single-link into a Blackmagic 4k multiplex (to produce quad-link) and then into the Canon produces four quads in the wrong colour-space!

 For an insight into what the multiplex is doing it's worth looking at the two standards for quad-link SDi. Put aside if it's 4 x 1.5G or 4 x 3G (that allows an increase to 50 or 60P OR 4:4:4 colour). But, in this case we're de-mux'ing a 6G to 4 x 1.5G signals. 

The original 4k-over-four-BNCs standard

The more recent standard; each link looks like an HD version

Clearly the converter is producing 2SI but the Canon expects SD quad-link. In fact the guys at Canon tell me they have a firmware update early in 2016 to address this. The other error is that the Canon has mistaken the 4:2:2 video as RGB - but it has at least got the raster correct.

So, what to do? Well, by throwing in another converter and taking the HDMI out of the SRI means the BM mux will get an older SD quad-link input;

This produced what we need; clearly HDMI has not concept of mutliplexed pixels and so we're now fully in SD quad-link;

tugging BNC no.4 shows the monitor is now in quad mode

The monitor gets it all right

The other thing that you have to pay attention to in "True 4k" displays (for the film snobs!) is that feeding 3840x2160 signal into a 4096x2160 monitor and letting the monitor scale-up to fill the line risks killing your resolution;

The aliasing should only the present in the top-most block, the other alias frequencies you can see here are due to my iPhone's camera!

Some very strange aliasing when a 3840-pixel line is mapped to 4096 pixels

As ever with display devices, pixel-pixel (native resolution) is always preferred

UHD-TV test material; how I'm going to demo monitors

After all the monkeying around with the Canon monitors last week I decided I need a decent variety of clips to show off UHD displays to the best of their ability. For some reason customers are not satisfied with just seeing test signals?!

So - although I have the TG-100 for uncompressed 4k test signals (the Visualiser really shows all you need to know!) and I can show:

• Resolution
• Colour Space
• Temporal performance
• Dynamic Range

So, I went looking for some well shot UHD footage at the TV 4k raster of 3840x2160 (I know, all you DCI-snobs, "true" (sic) 4k is 4096x2160). The Harmonics site has some nice short uncompressed YUV-planar format videos; http://www.harmonicinc.com/resources/videos/4k-video-clip-center#4k-clip-center - But don't expect your laptop to be able to play these guys! At 12GBits^-1 they are monsters and so for ease of use you may want to compress them down to a more manageable 500MBits^-1 (or so) using GLYUVPlay which can be found at Henryk Richter's site. In video coding research, standalone implementation and testing of video codecs often involves the use of raw YUV streams. Since these streams can be parsed and generated by very simple means, raw YUV files are very common in video codec standardization and development. 

I have made the H.264 variants and you can find them on my Google Drive folder.

Canon's 4k Native IPS television monitors

I had an excellent half day with Canon's UK imaging display guys to look at their DP-V series 4k native displays. To my shame I had assumed that they would be like the HP Dreamcolor or Eizo ColorEdge series monitors which are advertised as being suitable for film and TV work but as I've often said; "..an SDi BNC and a preset called Rec.709 does not a broadcast monitor make"!

In the case of those two manufacturers they assume that taking their print-prep graphics display and making it SDi capable is all that's needed; forget proper RGB linearity and a controlled white-point. In the case of the HP they still advertise it at 250Cd/m² for white (four times what it should be - you can't grade with that) and every time I've had an Eizo to play with I've found the same. Even employing a LUT to tame something like that is a bad idea as having to take 250Cd/m² down to a more sensible 80Cd/m² means you've lost two stops (12dBs, two significant bits) of dynamic range; not what anyone wants.

So - native 4k displays using LED-backlit IPS-LCD and not OLED. Every display technology suffers issues and although I think the poor inherent RGB tracking of OLEDs is entirely addressable in a LUT (which is why I love the Boland BVB25 for colour-accurate TV work) OLEDs are noisy once you get very close to black thus limiting their dynamic range (fine for 10-bit TV work; but for 16-bit HDR film imagery, not so much - yet!). Canon has consequently chosen IPS-style LCDs (with a level-modulated LED backlight). The LED backlight is the same technology as that used in the Dolby PRM-4220 grading monitor which is how they achieve the high dynamic range with a possibility of >1000Cd/m² for specular highlights in HDR 16-bit video. I got to see the originators of this technology, Brightside, back in 2005. 

So, proof of the pudding etc - I profiled the 24" edit suite variant and it was very close to the Rec.709 spec (the fact that I left LightSpace set for a 2.2 gamma whilst the monitor has a true BT.1886 gamma for HD rasters may be to blame). With 4k source material the results look great.

 I started at 2k to see how it did

 At 4k I can only manage 25 FPS at best!

Zooming in on the frequency grating shows aliasing, but only on the camera pics, I couldn't photograph it with my 10Mpix camera without catching aliases in the camera's OTF.

Getting closer gets a bit better, but to the eye the resolution is astounding

 

The Sarnoff ladies at true-4K

 

I profiled the display at 17-points so 5,000 measurements take around two hours with the Klein

 

Looks pretty good for greyscale performance, and I suspect if I set LightSpace's gamma correctly it would be better

The coloured dots are rec.709 and the big cube is the gamut of the display; it covers the colour space nicely.