With all the talk of 4K that took place at CES, some within the industry are making statements and assumptions about 4K streaming bitrates that simply aren’t accurate. Many are under the impression that 4K streaming will soon be delivered at around 10-12Mbps using HEVC and are also quoting data from Akamai incorrectly. If you look at the HEVC testing that guys like Jan Ozer and Alex Zambelli have done, and look at the data Netflix has presented around their 4K encoding (Netflix’s current bitrate for 4K is 15.6Mbps), the bitrates won’t get down to 10-12Mbps anytime soon.
The reality is that true 4K streaming can’t take place at even 12-15Mbps unless there is a 40% efficiency in encoding going from H.264 to HEVC and the content is 24/30 fps, not 60 fps. Netflix has stated they expect HEVC to provide a 20-30% encoding efficiency vs H.264, within two years. That’s a long way away from the 40% required to get bitrates down to 12-15Mbps. While 4K can in theory be compressed at 10-12Mbps, this is typically achieved by reducing the frame rate or sacrificing quality. As Encoding.com points out, to date, “most of the HEVC we’ve seen in the market is heavily noise-reduced with high frequency details blurred out to fake the 40% efficiency”. The optimal bandwidth for high quality 4K is higher than 20Mbps. UMAX in Korea, for instance, compresses its 4K p60 streams at 32Mbps (i.e. using a rate of 60 frames per second, progressive). For the full effect of sports and documentary content, this is a more realistic bit rate at today’s compression efficiency.
As state of the art HEVC improves, some benefit will be reaped in terms of target bit rate. If the 40% efficiency improvements do indeed come true for HEVC, years from now we might see 4K streaming bitrates at the 10-12Mbps level, but it would not be for a very long time. OTT streaming is completely driven by the economics of bandwidth and what it costs to deliver the content. So the video only gets delivered at the minimum bit rate required to make the video look generally acceptable. Costs drive adoption. As I have written about before, the dirty little secret about 4K streaming is that content owners can’t afford the bandwidth costs. At Frost & Sullivan, we have done a lot of work on HEVC and 4K streaming trying to set the record straight on what is and isn’t possible. See [Cutting Through The Hype Of HEVC] and [Why MSOs Should Not Consider Switching Directly from MPEG-2 to HEVC].
With Netflix already encoding 4K content at 15.6Mbps today, and with the expertise they have in encoding and the money they spend on bandwidth, they will get the bitrate lower over time. Some observers think it might go down to 10-12Mbps, but that would only be possible down the road and at 24/30 fps, not 60 fps. If you want 60 fps, it’s going to be even higher. But even if we use the 10-12Mbps number, no ISP can sustain it, at scale. So while everyone wants to talk about compression rates, and bitrates, no one is talking about what the last mile can support or how content owners are going to pay to deliver all the additional bits. The bottom line is that for the next few years at least, 4K streaming will be near impossible to deliver at scale, even at 10-12Mbps, via the cloud with guaranteed QoS.
When it comes to the percentage of consumers in the U.S. that have Internet speeds capable of getting 4K content, with a threshold of 15Mbps, many are using Akamai’s data incorrectly. Multiple media outlets have said that, “Akamai says 19% of U.S. homes now can sustain the average 15 Mbps broadband speeds necessary to stream 4K/Ultra HD video.” That is NOT what Akamai said, nor what their data shows. Akamai’s data from their State Of The Internet Report isn’t breaking down what percentage of U.S. households have 4K ready connections, but rather speaks to the percentage of unique IP addresses from the United States that connected to their platform during the third quarter that had average connection speeds over 15 Mbps. However, there’s no direct correlation between unique IP addresses and households.
So for all those repeating the 19% of U.S. households can get 4K streaming number, that is not accurate. Don’t repeat it just because you read it somewhere, check the source of the data yourself. The bottom line is that 4K and HEVC is exciting and it is the future. But vendors, content owners and the media need to have realistic expectations of what is and isn’t possible with 4K streaming and use real numbers when it comes to bitrates, costs, efficiencies and Internet speeds.