Grand Challenge on
Open-Source HEVC Encoding

Organized and sponsored by

Comcast NBCUniversal

Challenge Description

The amount of available premium UltraHD content is growing fast, with hundreds of movies produced or remastered, and a growing number of popular events and linear channels produced in UltraHD. For example, the final game of the World Cup 2018 was produced in UltraHD and had resulted in about 10 million concurrent streams.

High-quality and efficient compression of this content is a challenge for the industry due to the high bitrates required for its transmission. HEVC is the codec of choice for UltraHD content, and the open-source x265 project is currently the most widely used HEVC encoder. The goal of this challenge is to produce algorithmic improvements to HEVC encoding, and make them available to the open-source community.

Code, Software and Entry Requirements

x265 v3.2


Note: A cloud instance for SSIMPLUS will be soon provided free of charge to the challenge participants.

The entry requirements are:

  • Making the proposed algorithmic improvement available as a patch that should apply on top of the v3.2 tag. The patch must be licensed as GPLv2. Patch acceptance and merge into x265 are not required.
  • Independence of the proposed improvement from special purpose hardware or proprietary software. Dependence on open source software such as OpenCV or TensorFlow is permitted.
  • Compliance with Main/Main10 profile and level of 5.1 or lower.

Evaluation Criteria

Each entry will be judged according to the following criteria:

  • Evaluations will focus on 4K content; both HDR and non-HDR sequences will be used.
  • For PSNR and SSIM-based evaluations, we will measure Bjontegaard metrics with bitrates of 10, 12, 14, 16 Mbps for 24p content, and 18, 20, 22, 24 Mbps for 60p content with realistic VBV settings. For perceptual evaluations, we will use the SSIMPlus quality metric.
  • Content used for evaluation will be a number of cinematic and sports content similar to and
  • Run-time computational complexity of the proposed algorithm, assuming Intel Sky Lake-generation or newer Xeon CPU for assessing the potential of assembly optimization of the proposed technique. Assembly optimization is not expected.

Important Dates

  • Submission: Mar. 27, 2020
  • Acceptance notification: Apr. 22
  • Camera-ready submission: May 1
  • Entry presentations: During the MMSys week

Submission Guidelines

Submissions should provide enough details for the implemented software patch. A technical paper along with the patch code, prepared according to the guidelines provided for the Open Dataset and Software Track, is required by the submission deadline indicated above.

The authors will be notified after a review process and the authors of the accepted papers need to prepare a camera-ready version, so that their papers can be published by ACM Digital Library.

Winners are to be chosen by a committee appointed by the challenge organizers and results will be final. If contributions of sufficient quality are not received, then some or all of the awards may not be granted. The challenge is open to any individual, commercial or academic institution.


The winner will be awarded 5,000 USD and the runner-up will be awarded 2,500 USD.


If you have any questions, please contact the organizers (2020-x265-challenge AT