Converting Inputs for SDI Mixers

[JoshGuerette]

I've noticed that all the pro and many of the higher-end prosumer switchers are all SDI/HD-SDI, and that makes a lot of sense given the benefits of SDI. What I'm wondering is, not every device that might be used as an input to a switcher is SDI, such as computers, dvd players, etc.

Does one just convert the signal for all of those inputs? If so, are there racks of conversion hardware involved? I've seen the mini converters from AJA and BlackMagic, but it seems weird for me to have half my inputs running through mini converters.

[petereit]

Generally, if you're upgrading to an SDI switcher, it's because you're buying new SDI cameras. Many HD switchers have one DVI input for a computer. Some even have a VGA input.

Next, you toss your old DVD player because all the video content you need is either downloadable or ripable.

Now, the only converters you need are SDI-to-HDMI for your HDTVs and projectors. (the consumer market just needs a good smack upside the head for inventing HDMI.)

[Brad Weber]

SDI, or more commonly now one of the HD-SDI formats, works well in a production environment where the content is all original but it is not always feasible in a presentation environment. SDI to HDMI/DVI/DisplayPort conversion is simple and direct, however the inverse is not nearly as simple or direct. The biggest issue is Digital Rights Management, which is inherent in HDMI, DVI and DisplayPort but is not part of SDI and HD-SDI. Basically, converting a digital signal with content protection to a digital signal without content protection is illegal. DRM such as HDCP can be activated by the content or the device may activate it by default, thus creating a situation where HDMI, DVI, DisplayPort and similar sources or content potentially cannot be legally converted to SDI/HD-SDI. And don't forget that HDMI is not limited to video it can also include multi-channel audio, Ethernet and control, any of which may be relevant to an application and can't necessarily be converted to be part of a SDI/HD-SDI signal.

Some common challenges in the implementation of SDI/HD-SDI components in some systems are that the DVI or HDMI inputs on production switchers do not typically support HDCP. The DVI, HDMI and VGA inputs and outputs on production switchers are also typically very limited in terms of the supported resolutions and scan rates, much more limited than most video displays or projectors and computer video cards. In addition, there are situations where having files loaded in advance or even having them anywhere other than on a presenter's source device is problematic and you have to accommodate people walking in with a variety of sources and source devices.

I am working on some projects now where I can say with great certainty that integrating the presentation portion of the systems with the HD-SDI based production aspects is requiring much more than some SDI-to-HDMI converters including facing the reality that while digital video sources with DRM can be displayed and routed around the room, they cannot be fed to the production system.

So integrating SDI/HD-SDI with other digital video signals can't really be simplified down to it always being simple or so complex, you have to look at the overall system and intent.

My view is that the pro market needs a smack upside the head for letting HDMI and HDCP evolve and gain acceptance without getting involved and offering a viable alternative. It isn't like either were secrets or complete surprises, so we really have no one to blame but ourselves.

[tdangelo]

Originally Posted by JoshGuerette

Does one just convert the signal for all of those inputs? If so, are there racks of conversion hardware involved? I've seen the mini converters from AJA and BlackMagic, but it seems weird for me to have half my inputs running through mini converters.

Josh,

Yes, it is very possible to convert back and forth to other signal formats while your infrastructure is 525/60 SD SDI. Aja makes many (relatively) inexpensive converters to go to & from SD SDI and this would be quite normal. Computers would typically get downconverted, tweaked for sizing and aspect ratio and adjusted for frame rate with a computer scan converter. Folsom ViewMAX is a very popular unit for this application and has SD SDI outputs standard. The older Folsom 9700 does as well with an optional SDI card.

Just note that everytime you convert a signal, scale it, up-convert it, down-convert it, change its aspect ratio, etc., you are inducing video delay into your signal path. For certain applications like recording, webcasting, etc., this isn’t a big problem especially if you have access to a audio delay to re-sync up the audio to the delayed video. If you are however doing I-mag the delay can be a real big problem.

[JoshGuerette]

Hmm, ok thanks for the replies guys. I am planning on SDI for the cameras, which is why I'm looking at SDI for the switcher. As far as HDCP or other DRM formats, I don't think we'll run into that problem. I'm realize now that I really only need inputs for cameras (max 5 or 6 for the future) and a single computer source for graphics. At that point, a single scan converter would do the trick, and the SDI native cameras would just work.