Saturday, 1 November 2014

Achieving 4K UHD DATV- very draft


Achieving 4K UHD DATV- very draft

Perhaps a little early, but 4K DATV may be more achievable than I first thought. It would be a bit of a technological coup if amateur radio can do 4K before regular free-to-air broadcast TV. 4K video cameras and monitors are already relatively inexpensive. 4K TV capture/switchers are available and not too expensive. The missing link are modulators, transmitters and receivers, but may be possible using inexpensive SDR TRX; they can already do DVB-T/S.

As far as I am aware, broadcast TV is still struggling with Full HD digital TV in some countries, notably the USA with a very large number of small TV stations and the not insignificant cost of having to replace virtually everything, other than their antenna. I suspect the same across some of Europe and Asia. For both terrestrial and satellite, while they may have digital TV, most of it is SD (standard definition) or HD (high definition 720p), rather than wide-screen Full HD (1080i; wish it was 1080p).

While I raise the possibility of 4K DATV, the other technology for the future that I raise, networked, internet-linked DATV is probably a greater personal objective. However, others may be interested in low-cost 4K. I can see a real need for 4K in CCTV, where definition matters; it is not just technology bling.

4K DATV is a good use of the numerous UHF bands/spectrum that amateur radio has, but only makes limited use of. In many countries there is pressure to take amateur radio spectrum and use it for other purposes. Use it or loose it?
I will start with the easy bits and progress toward the more difficult aspects.

4K UHD TV Standards: 2160p

Fortunately there is a 4K UHDTV standard, 2160p, (3840 x2160)  http://en.wikipedia.org/wiki/Ultra-high-definition_television, http://en.wikipedia.org/wiki/2160p. It is similar but not the same as the video standard used in cinemas with digital projectors.
It is interesting that it is progressive, 2160p, not interlaced, 2160i. While those who developed digital TV standards a couple of decades ago, 1080i would have been virtually unachievable, but like so many computer standards, it has been surpassed. Further, I suspect that the step will be straight to 2160p TV, with 1080p languishing. 1080p is needed for recording, but not likely to be used live. It is difficult to buy a 1080p to 1080i converter, well, relatively expensive at $600+ per camera; my current dilemma.

4K UHD Displays/TVs

4K PC 28” displays are common and fairly cheap, about $600. I have a Samsung one, but don’t use it as a PC monitor. They use older-style TN LED screens that are good straight on, but are poor for angle viewing. Sitting 500mm from the PC monitor, the sides are blurry.  Tried it for a month, great for reading PDF magazines, but tiring otherwise. I went back to my 28” 2K IPS LED monitor. Still much better than Full HD 1080p!

I use a Panasonic plasma for the little bit of TV I watch, and have a Full HD projector, that gets even less use. Both get around the side-view problem of LCD.

Apple has announced a 5K monitor since I started writing this post. 4K IPS LCD panels are available, but still a bit expensive.

4K UHD cameras

There are a range of 4K UHD cameras on the market, starting with the Hero action cameras, about $450, a number of consumer 4K DSLR, the cheapest currently  Panasonic Lumix DMC-GH4, about $1500 body only, BlackMagic Studio Camera 4K, about $3000 body only. The costs are likely to drop quickly, as it did for the 1080p cameras.
One caveat with 4K UHD cameras is that while they can record at 4K, I am not sure what they stream live. It may be 2160p, but it wouldn’t surprise me if it is still 1080p, with the exception of the BM Studio Camera 4K, it has no record function and will stream live 4K. The GH4 streams 4K too. To be investigated further.  All the same, the cheaper cameras can record at 4K. An amateur 4K system is likely to start with recorded media then move to live.

4K Production switcher

Perhaps not essential, but likely kit even for a Full HD DATV station, the BM ATEM Production Studio 4K, about $1700, allows the use of multiple HDMI and SDI cameras and other devices (recorded media, PC) https://www.blackmagicdesign.com/products/atem/techspecs/W-APS-04.

HDMI devices negotiate connection standards that can be problematic when connecting devices in ways other than what the manufacturer intended. The switchers handle those problems well.
HDMI is not the preferred interface for 4K, the switcher can output UHD SDI, potentially making the interface with the modulator much simpler.

4K Compression standards

There is a 4K compression standard: H-265: http://en.wikipedia.org/wiki/High_Efficiency_Video_Coding. Not a simple subject, but amazing technology.

Compression is a key to usable 4K, to reduce the storage space and data rate but keep the quality; a contradiction. There has been considerable progress in compression, the move from MPEG-2 to H-264 for Full HD being a recent example.

4K Transmitter/amplifier

Compressed 4K UHD will fit in a standard 6, 7 or 8 MHz ATV channel. I think DATV in some countries are restricted to 2 MHz, but that may only be for lower UHF bands such as 70cm. The bandwidth and modulation parameters determine the necessary data rate, which clearly will be higher than for Full HD. In Australia we can use 7 Mhz on 70cm up, at the same standards as free-to-air broadcast TV.

DVB-T at 7 MHz bandwidth has the capacity to handle 4K UHD, but always needs a very linear amplifier. I am not sure what data rates are possible with DVB-S.
As such any good DVB-T transmitter/amplifier should be able to handle 4k; to a point the content is not relevant, although modulation parameters can make greater demands on the TX linearity.

4K modulator/encoder

Ok, now we are into the curly stuff. Current 4K modulators are expensive broadcast devices ($10000+).
However, Nuand BladeRF SDR TRX, a FPGA-based device, may be able to be programed for 4K UHD, linked by USB3 with a PC, networked to the BM ATEM TV Studio for digital and audio inputs. As noted in my last post, the BladeRF has been used for DATV DVB-T: http://yo3iiu.ro/blog/?p=1191, http://www.irrational.net/2014/03/02/digital-atv/. They may be interested in the challenge of 4K UHD DATV with GNU radio. Developing the modulation/encoding It is beyond me.

4K UHD CCTV with dedicated chips per HiDes/ITE DVB-T devices??

optical-astronomy: reducing interference: noise cancelling

…. To be continued ….

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