1. Computers
  2. Display Drivers
  3. Graphics Cards
  4. Memory
  5. Motherboards
  6. Processors
  7. Software
  8. Storage
  9. Operating Systems


Facebook RSS Twitter Twitter Google Plus


Phoronix Test Suite

OpenBenchmarking.org

Avoiding Frame Jitter With GNOME's Mutter, Weston

GNOME

Published on 30 November 2012 12:29 PM EST
Written by Michael Larabel in GNOME
13 Comments

Owen Taylor has written a new blog post about avoiding jitter in composited frame display. Owen -- along with help from Kristian Høgsberg -- made improvements to the algorithm for compositor frame timing as used by GNOME's Mutter compositing window manager and also Wayland's Weston.

The basic algorithm up to this point was when receiving damage, a redraw should be scheduled immediately. If a redraw is scheduled and the system is still waiting for the previous swap to complete, a redraw should be done when the swap completes. This algorithm though doesn't work out ideally when showing content that runs at a fixed frame-rate that is less than the display's frame-rate, such as displaying video content at 24/30 FPS on a 60Hz display.

In the end the modified algorithm he came up with includes introducing a concept of "urgent" frames that can be marked by the application. Now when receiving damage, if it's part of an urgent frame, a redraw will be scheduled immediately. If it's not urgent, schedule a redraw for 2ms after the next VBlank. If a redraw is scheduled for time T and they're still waiting for the previous swap to complete at time T, redraw immediately when the swap completes. "I’m pretty happy with how this algorithm works out in testing, and it may be as good as we can get for X. The main downside I know of is that it only individually solves the two problems – handling clients that need all the rendering resources of the system and handling clients that want minimum jitter for displayed frames, it doesn’t solve the combination. The client that is rendering full-out at 24fps is also vulnerable to jitter from other clients drawing, just like the client that is choosing to run at 24fps. There are mitigation strategies – for example, not triggering a redraw when client that is obscured changes, but I don’t have a full answer. Unredirecting full-screen games definitely is a good idea."

Other possible approaches being evaluated for avoiding jitter in composited frame display include triple buffering with the compositor (though this could lead to wasted resources) or allowing applications to submit frames with their intended time frames. The later approach, however, wouldn't be good for X but could work nicely in a Wayland world.

Read the blog post at FishSoup.net.

About The Author
Michael Larabel is the principal author of Phoronix.com and founded the web-site in 2004 with a focus on enriching the Linux hardware experience and being the largest web-site devoted to Linux hardware reviews, particularly for products relevant to Linux gamers and enthusiasts but also commonly reviewing servers/workstations and embedded Linux devices. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics hardware drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated testing software. He can be followed via and or contacted via .
Latest Articles & Reviews
  1. Khronos Group Announces Vulkan, OpenCL 2.1, SPIR-V
  2. Samsung 850 EVO SSD Linux Benchmarks
  3. Kubuntu 15.04 Is Turning Out Quite Nice, Good Way To Try Out The Latest KDE
  4. 5-Way Linux Distribution Comparison On The Core i3 NUC
  5. OCZ ARC 100 Linux SSD Benchmarks
  6. Lenovo ThinkPad X1 Carbon Works Great As A Linux Ultrabook
Latest Linux News
  1. Valve Developed An Intel Linux Vulkan GPU Driver
  2. Valve Starts Listing The Steam Machines In The Steam Store
  3. Ubuntu Will Start Booting With Systemd Next Monday
  4. A Brand New Linux Network Stack Proposed: Linux XIA
  5. Niche Drivers Get Ported To Atomic Mode-Setting For Linux 4.1
  6. openSUSE Tumbleweed Continues Ascending
  7. Open-Source SPIR-V Reader & Writer Written In Java
  8. LunarGLASS Adds Experimental SPIR-V Front-End
  9. The New Open-Source Linux Test Farm Is Almost Operational
  10. Samba 4.2 Brings Transparent File Compression & Clustering Support
Most Viewed News This Week
  1. The Tremendous Features Of Fedora 22
  2. Confirmed: Vulkan Is The Next-Gen Graphics API
  3. Xfce 4.12 Released After Nearly Three Years Of Work
  4. 8cc: A Small C11 Compiler
  5. LLVM 3.6 & Clang 3.6 Deliver More Features, Complete C++14 Support
  6. Unreal Engine Made Free By Epic Games
  7. Canonical's Latest Demo Of Ubuntu Unity 8 Convergence In Action
  8. ALSA 1.0.29 Released