While we were testing our latest batch of 2014 TVs, which includes several new Ultra HD sets, we found out something interesting: Despite having built-in HEVC decoders, not all TVs can play Netflix 4K videos.

Among the TVs that we've tested so far, models from LG Electronics, Samsung, and Sony have been able to play 4K videos from Netflix—basically, the second season of "House of Cards" and "Breaking Bad," plus a few movies. But a TV from another major brand—Panasonic's TC-58AX800U—was not able to play the Netflix 4K streams.

Up to this point, we assumed that all TVs with built-in HEVC decoders—needed to "unlock" the 4K videos that used the codec—would be able to play Netflix 4K streams. HEVC, also called H.265, is a new, more efficient video compression scheme that's being used to send 4K videos, which take up a lot more space, through existing broadband networks at speeds as low as 15 to 16Mbps.

But what we learned is that Netflix has its own certification program that TV manufacturers must pass in order for their TVs to be able to receive Netflix 4K videos. According to Netflix, beyond a TV having an HEVC decoder, its certification program examines things such as picture quality (whether the 4K streams from a particular model look good enough) and whether the TV (and the HEVC chipset it uses) can support a wider gamut of colors. Some manufacturers may start selling TVs before the sets have passed the certification process. Once they do, the software can be updated to deliver 4K Netflix streams if the set passes, but if it's the chipset that is the problem, they may never be able to play Netflix 4K streams.