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MicrosoftEdge

Over the last few years nosotros've seen several next-generation media codecs vie to supplant H.264 as the encoder of choice for both discs and streaming content. HEVC, or H.265, may accept already won the Ultra Hard disk Blu-ray race, only the battle for streaming content is just beginning. Netflix's exhaustive study, "A Large-Scale Video Codec Comparison of x264, x265 and Libvpx for Applied VOD applications," isn't available in paper form yet, but was discussed during a lengthy presentation at the August 31 SPIE Applications of Digital Image Processing conference.

Co-ordinate to StreamingMedia.com, Netflix's test involved comparing the bodily codecs in question rather than their various specifications — this was a existent-globe test meant to measure bandwidth savings using implementations of the specifications, not the specifications themselves. The comparison used x264, x265, and the libvpx codec, Google's implementation of its royalty-free VP9 standard.

The survey measured bandwidth and quality across both real-globe and animated content in more 5,000 clips of video taken from 500 sources. Each clip ran 12 seconds and included a variety of motion levels and was measured at 360p, 720p, and 1080p. The source fabric itself included both 1080p and 4K video. Further details on the encode options and targets is available from StreamingMedia and the whole commodity is worth a read. (If you lot're interested, the relevant section of the video starts effectually the 60-infinitesimal mark.)

Netflix published multiple benchmark results, but the company stated it felt its Video Multimethod Assessment Fusion (VMAF) criterion best corresponded to what stop users would meet. "We believe that VMAF results volition have the best correlation to user perception of quality," Netflix told StreamingMedia. "Nosotros utilize this metric, and sanity-check confronting other metrics (PSNR, SSIM, VIF, etc.) internally." Netflix has published all-encompassing information almost its VMAF test in a blog post; code is bachelor via GitHub.

Netflix'due south findings mostly support the argument that x265 is far more than bandwidth efficient than x264, though its superiority against VP9 does vary depending on the exact tests and criteria. How well these settings map to real-world constraints likewise depends on what you're doing — Netflix used extremely detailed and high-quality options for x264 and x265, and this may not reverberate the way about people encode video.

In my own encoding, I tend to favor settings that requite decent results in a reasonable menstruum of time, as opposed to fine-tuning each and every setting for maximum quality. Trying to rail exact configuration differences when testing batch encoding is likewise a pain and dissimilar settings are improve or worse for capturing different kinds of content. There'south a definite fine art to proper video encodes, and squeezing the best performance out of a given codec may result in different employ cases then those contemplated by Netflix, which streams vast amounts of data mean solar day and night.

Ane other trouble is browser support. Currently, HEVC is only available in Microsoft'south Edge, and 1080p Netflix streaming only works inside that browser. Given that HEVC support isn't widely available (and there are royalty fees attached), it's not however clear which codecs will win out. Netflix hasn't decided, apparently, whether the twenty% bandwidth savings over VP9 are worth paying the high price of the royalties the HEVC standard requires. Its benchmarking endeavor, while huge, is still the opening salvo in a long-term evaluation process.