Google Engineer Breaks Down Steps for VP8 Optimization
Road map for VP8 codec improvements laid bare.
Google software engineer John Koleszar addressed the open source community regarding the VP8 codec and the steps needed to further optimize to codec within the WebM project.
Koleszar notes Scott LaVarnway's work in creating an x86 version of the quantizer and moved on to request a SIMD version of the ARNR temporal filtering code from the community. Koleszar also asked for newer extensions for the assembly code, as it currently only takes advantage of the SSE2 instruction set.
The last improvement Koleszar called for in the VP8 encoder was for someone to explore alternative motion search strategies, eventually hoping to decouple motion search entirely, leaving the motion field calculations to the graphics processors.
For the decoder, Koleszar highlights the work of Jeff Muizelaar, Johan Koenig, and Tim Terriberry. While he doesn't specifically ask for help on any one item as he did with the encoder, he does highlight some of the ongoing work. Terriberry is working had on the bool decoder, which is called multiple times per each bit in the input stream. Currently, the code uses a simple clamp on the innermost loops for checking and performs less frequent copies into a circular buffer. Terriberry's patch uses a more complex clamp and removes the circular buffer.
Meanwhile Muizelaar's work has combined IDCT and summation with the predicted block into a single function. Doing this reduces memory transfers and therefore reduces cache pollution. Koenig is implementing Muizellaar's work into ARM processors.
Speaking of embedded processors, Koleszar ended his post with a description of the work being done on not-desktop platforms. Fritz Koenig is working to optimize the VP8 codec for the Atom platform, quite a task considering the x86 assembly code for the codec was written for an out-of-order processor.
The Atom, of course, is in-order, so Koleszar and company are debating scheduling the code for Atom and then checking to see what performance issues arise on x86. Regardless, Koleszar notes that a lot of work lies ahead.
Finally, he spends some time on intrinsics and whether or he and his fellow programmers should use them when trying optimize the codec for multiple processors and platforms.
"If you have experience in dealing with a lot of assembly code across several similar-but-kinda-different platforms, these maintainability issues might be familiar to you. I hope you'll share your thoughts and experiences on the codec-devel mailing list," Koleszar said.
Comments
comments powered by DisqusSubscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters
Support Our Work
Linux Magazine content is made possible with support from readers like you. Please consider contributing when you’ve found an article to be beneficial.
News
-
So Long Neofetch and Thanks for the Info
Today is a day that every Linux user who enjoys bragging about their system(s) will mourn, as Neofetch has come to an end.
-
Ubuntu 24.04 Comes with a “Flaw"
If you're thinking you might want to upgrade from your current Ubuntu release to the latest, there's something you might want to consider before doing so.
-
Canonical Releases Ubuntu 24.04
After a brief pause because of the XZ vulnerability, Ubuntu 24.04 is now available for install.
-
Linux Servers Targeted by Akira Ransomware
A group of bad actors who have already extorted $42 million have their sights set on the Linux platform.
-
TUXEDO Computers Unveils Linux Laptop Featuring AMD Ryzen CPU
This latest release is the first laptop to include the new CPU from Ryzen and Linux preinstalled.
-
XZ Gets the All-Clear
The back door xz vulnerability has been officially reverted for Fedora 40 and versions 38 and 39 were never affected.
-
Canonical Collaborates with Qualcomm on New Venture
This new joint effort is geared toward bringing Ubuntu and Ubuntu Core to Qualcomm-powered devices.
-
Kodi 21.0 Open-Source Entertainment Hub Released
After a year of development, the award-winning Kodi cross-platform, media center software is now available with many new additions and improvements.
-
Linux Usage Increases in Two Key Areas
If market share is your thing, you'll be happy to know that Linux is on the rise in two areas that, if they keep climbing, could have serious meaning for Linux's future.
-
Vulnerability Discovered in xz Libraries
An urgent alert for Fedora 40 has been posted and users should pay attention.
dgdg
They use Orc, it seems to help them a lot:
http://code.entropywave.com/projects/orc/