Netflix is currently in the process of re-encoding its entire 4K range: Previously, titles were set to fixed bitrate levels – 8, 10, 12 or 16 Mbps. According to Netflix, this is an outdated model, because it makes more sense to create dynamic bitrates and optimizations depending on the title. In addition, they now rely on heavily optimized encoding techniques. Therefore, you are currently optimizing your 4K portfolio.
The streaming provider wants to set lower bitrates and still offer higher image quality overall. This saves the customer traffic and increases the quality at the same time. In the case of 4K animation films, for example, you can sometimes get as low as 1.8 Mbps because they can be encoded very efficiently. If you’d like to see a few examples.
In extreme scenarios, even higher bit rates are allowed – up to 17.2 Mbps. According to Netflix, this is only necessary in very few cases – such as nature documentaries or concerts, where there is very colorful and rapidly changing lighting with hard contrasts. As a rule, you can now achieve better image quality with lower bit rates thanks to more modern encoding and updated algorithms than before with higher bit rates.
If you compare your old method with the new one, you can achieve an identical image quality on average with a 50% lower bit rate. In plain language, 4K image quality could be achieved at 8 Mbps, which is equal to earlier streams at 16 Mbps.
According to Netflix, the reduced bit rates would also bring advantages for mobile devices: For example, it would make it possible to conserve the data volume and still heave HDR streams onto smartphones. As a result, higher resolutions can now also be achieved more often on the go, since the requirements are lower.
Rebuffering will also become a much smaller problem. And it is easier to achieve the constant quality that does not have to be downshifted on the go if the LTE connection temporarily deteriorates. However, Netflix warns that although they have started re-coding their 4K content, it will take several months before the work can be completely completed.
You have to judge with your own eyes whether this is really such a win-win situation. In a direct comparison, Ultra HD Blu-rays offer significantly higher bit rates and, ideally, a more detailed and better-compressed image. How much the differences are noticeable depends, among other things, on the playback device selected, the distance between the seats and the content.