H.265 benchmarked: Does the next-generation video codec live up to expectations? |

Digital modulator from

10.06.2019 10:59:36 - The next-generation High Efficiency Video codec (HEVC), H.265, has hit a major public milestone thanks to the work of the developer MultiCoreWare.

( - The next-generation High Efficiency Video codec (HEVC), H.265, has hit a major public milestone thanks to the work of the developer MultiCoreWare. MCW is launching a new commercial open-source venture around x265, and the source code for its x265 encoder is now available. Right now, the project is very much in early days ó pre-alpha level code ó but the


x265 encoder is already impressively parallelized and supports all of the major instruction sets including AVX/AVX2 and FMA3/FMA4.

The benefits of H.265

H.264 has been a huge success. Itís a flexible codec standard thatís used by streaming services, satellite providers, and for Blu-ray discs. Itís scaled remarkably well since it was first proposed and is capable of handling 3D, 48-60 fps encodes, and even 4K. The Blu-ray disc standard doesnít currently include provisions for some of these technologies, but the H.264 codec itself is capable of handling them.

The problem with H.264, however, is that while it can handle these types of encodes, it canít do so while simultaneously keeping file sizes low. A new standard is necessary to push file/stream sizes back down while driving next-generation adoption, and thatís where H.265 comes in. Itís designed to utilize substantially less bandwidth thanks to advanced encoding techniques and a more sophisticated encode/decode model.

Unlike H.264, which can extend to cover 4K television but wasnít designed with the feature in mind, H.265 was built to match the capabilities of future screens and includes support for 10-bit color and high frame rates. This is early days ó support and capability of the current alpha are limited to 8-bit color and YUV output, but we still wanted to take the alpha technology out for a spin. Armed with a freshly compiled version and some test clips, we set out to see what we could build.

First up ó file sizes. What weíre comparing here is actually the size of the elementary video stream. Note that these are video streams only ó audio isnít encoded in either instance. Encode sizes were defined by the quantizer setting, with lower q-values equaling a higher quality (and larger file size). The base encoded file is 500 frames of a 1.5GB, YUV 4:2:0 file at 50 fps. The elementary stream file size is used for comparison here because it represents whatís transmitted to the decoder to create the final output. Weíre working with elementary streams because, at this stage of the project (pre-alpha), the decoded video file always comes back at 1.5GB, regardless of the stream quality used to create it.

This gives a good basic idea of what sorts of benefits H.265 can offer compared to H.264. While itís not hitting 50% bandwidth savings in most cases, itís close ó quantizer 24 is 57% the size, q=30 is 59%, and q=40 is just 47%. Granted, at a quantizer of 40, the final output is wretched ó but itís wretched at less than half the bandwidth.

Performance & image quality

The next area we wanted to consider was performance. H.265 is known for taking more horsepower to encode and decode than H.264, though the team developing the standard continues to emphasize the role of parallel computing in speeding the encode/decode process. Itís implied that OpenCL support will materialize sooner, rather than later, which means initiatives like AMDís HSAcould get a boost from x265 support early in 2014.

Right now, weíre limited to CPU support, but Multi-CoreWare spokesperson Tom Vaughan emphasized that the team has already been working on strong multithreading. We decided to test the alpha decoder using Sandy Bridge-E, Ivy Bridge, and Haswell. We experimented with different levels of parallelization but settled on options that stuck to the number of physical cores in a system (6, 4, and 4). Hyper-Threading was enabled, but setting for 12/8-thread parallelization actually increased encode time slightly.

The parallelization performance looks good ó Sandy Bridge-E, with six cores, is somewhat ahead of Ivy Bridge with four. Similarly, Ivy Bridge is beaten out by Haswell, thanks to the new coreís AVX2 support and better performance characteristics. Compared to x264, even on the Ėveryslow preset, x265 encodes take noticeably longer ó our Ivy Bridge 3770K encoded the same file in H.264 in 129 seconds as compared to 247 seconds for H.265. Keep in mind, however, that this is very, very early software.

Of more interest is the quality question ó how does the H.265 output compare to the uncompressed original? We chose a basketball clip because, at 50 fps, itís full of the sort of fast motion that often gives encoders fits. H.265ís smaller sizes wonít be worth much if the final output isnít as good.

To that end, hereís the original uncompressed YUV output, the H.265 encode at q=24, and the H.264 output at q=24. Click on each image to enlarge it.

The variance here is minimal. The hardwood floor underneath the the leaping player is slightly less blurry in the H.264 variant, but the H.265 image quality is phenomenal considering itís half the size. What about lower qualities? Hereís H.265 and H.264 at q=30; H.265 is first.

At q=30 (file sizes of 6.39MB and 10.87MB), the H.265 video stream is arguably better than the H.264 encode stream. Weíre not trying to claim this is an absolute ó as always, encode settings matter a great deal and are sensitive to tweaking. But after waiting more than a year for H.265 to break cover, itís clear that the new standard is going to offer what its proponents have claimed.

Encode/decode support, meanwhile, is already going to be possible on a vast range of products. Modern CPUs are more than capable of decoding H.265 in software, OpenCLsupport is coming in future iterations, and hardware GPU support, while not formally guaranteed by AMD, Intel, or Nvidia for next-generation products, is a mid-term certainty. All three companies have previously leapt to include advanced video pipelines in their products ó as the H.265 presentation notes, video is something thatís become ubiquitous across every type of device.

Long-term, H.265 will likely succeed H.264ís position as the premier solution for advanced video, though that may depend on whether or not battery consumption while decoding can match H.264ís levels in the long term. Thatís something weíll only be able to evaluate once hardware is available, but for now weíre optimistic. H.265ís explicitly parallel model should map well against multi-core devices of the future.

Established in 2000, the main products are modulators both in analog and digital ones, amplifier and combiner. We are the very first one in manufacturing the headend system in China. Our 16 in 1 and 24 in 1 now are the most popular products all over the world.

For more, please access to

Company: Dingshengwei Electronics Co., Ltd

Company Address: Building A, the first industry park of Guanlong, Xili Town, Nanshan, Shenzhen, Guangdong, China

Tel : +86 0755 26909863

Fax : +86 0755 26984949

Phone: +86 13410066011

Skype: soukaken


Press Information:
Dingshengwei Electronics Co., Ltd

Contact Person:

Phone: 13410066011
eMail: eMail

Web: http://


Disclaimer: If you have any questions regarding information in this article please contact the author. Please do not contact We are not able to assist you. disclaims content contained in this article. is not authorized to give any information about content and not responsible for content posted by third party.
refer this article
Print This Article
Terms Of Use Privacy About Contact Us