Encoder Comparison NVENC x264 Quicksync QSV VP9 and AV1



x265 is the natural sequal to x264. The H.265 format is also known as HEVC and was designed to bring about 25% to 50% less data for the same quality video as H.264 aka AVC. Conversely, given a fixed bitrate, HEVC will almost always give more quality than an AVC version would. HEVC was first demonstrated in 2012, around a decade after AVC’s release.

Recent versions of QuickSync and NVENC are capable of encoding HEVC, albeit with limitations. The x265 encoder is licensed under GPL v2 and is the software encoder of choice for most enthusiasts.

In case you are wondering why it’s 2019 and HEVC isn’t the standard most used, there are 2 main reasons. First, it’s significantly more complicated than AVC and requires much more processing power. Second, it includes far more patents than AVC ever did. There are several different groups and individual companies who license out the patents for HEVC. None of them cover the entire chain of use and many use different pricing schemes. As a result, many mainstream video providers have refused to adopt HEVC due to its expense and legal difficulties.

x265 Slower was tested and it encoded at half the speed of Slow. However Slower preset is excluded from this graph since it often scores lower than the Slow preset anyway.


x265 VMAF Scores on 2560x1440 60 fps
x265 VMAF Scores on 2560×1440 60 fps

Things to note for x265:

  • Slow preset performs very similarly to Turing HEVC/H.265 NVENC of the same bitrate.
  • Many presets beat both Pascal and Maxwell HEVC NVENC at 4Mbps and 6Mbps, but at 8Mbps the advantage fades. Therefore x265 is better when bandwidth is tight, instead of when bandwidth is abundant.
  • No H.264 AVC encoder tested beats any of x265’s results across all bandwidths tested here.
  • None of the x265 presets/settings tested beat any VP9 or AV1 tests at any bandwidth.

Conclusions for x265

The complicated patenting for H.265 HEVC overall has discouraged enough vendors for it to remain relatively unused for over 5 years since its release. As such, to the best of my knowledge, live streaming to Twitch and YouTube is not possible with HEVC. However, YouTube will accept uploads in H.265 formats, but convert them to other formats before viewers can access the video.

For offline encoding, such as archiving old videos, x265 certainly has its place. If speed is all you’re concerned with, and hard drive space is plentiful, then NVENC HEVC is the optimal solution. Turing RTX 2080TI, 2080, 2070 and 2060 will all compete well with x265 at high bitrates. Even Pascal and Maxwell HEVC NVENC competes reasonably well with x265. However if you are concerned about saving some more space, x265 Slow is the way to go. Even Medium, to VeryFast will still beat Pascal and Maxwell.

Beware though, x265 takes considerably longer to encode than x264 or any NVENC or QuickSync varieties! It’s beyond most people’s CPU power to encode real-time, even if Twitch and YouTube accepted it. On my stock i7-8086k at 100% CPU usage, x265 Slow averaged around 8 fps on the test video. With this CPU or faster, you could technically live-stream a smaller resolution if it’s free from other tasks. A 9900k, threadripper or 9980XE X-series can do 720p or maybe 1080p at 30 fps.



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