The use and distribution of 3G-SDI within a broadcast environment has enormous logistical advantages, but along with these advantages come some real challenges for both engineers and manufacturers who may be familiar with more conventional SD 270MB or HD 1.5GB SDI systems. 3G-SDI is attractive to broadcasters looking to move from 720p or 1080i based systems to full 1080p 50 or 59.94 for live production. It’s also used as part of quad 1080p as part of a UHD system.
One advantage is the ability to send numerous different video broadcast, production and digital cinema formats down the same single wire, but the impact of this on engineers who have to understand all of the complexities of the SMPTE 424M, 425A (3G-A) and 425B (3G-B) when connecting and routing signals is not insignificant. Manufacturers too have the challenge of designing broadcast equipment to test all of the possible format combinations of HD-SDI, Dual Link HD, 2K, 3D stereoscopic 2K; colour spaces of YCrCb, RGB and XYZ; sampling methods such as 4:2:2, 4:4:4; specific data mappings for each format; not to mention the added complexity of Alpha channels.
The challenges of 3G-SDI use also have an impact on signal distribution, signal routing, switching, editing and grading. Two significant areas to take into account when using 3G-SDI are signal quality, which if out of specification will have a dramatic impact on the integrity of the data, and the ability of broadcast equipment to transparently process the numerous video formats combinations that may appear on the end of the cable.