I have a proposal on the tigervnc-devel list for basically capping the Zlib level at no more than 7, which is the highest useful level for the type of data we're dealing with. So basically Compression Levels 7 and 8 in TigerVNC would be virtually the same as CL 6, and CL 9 would use the same Zlib levels but would implement a higher palette threshold so as to favor indexed encoding as much as possible-- rarely beneficial, but at least it would do something different than CL 6. Currently, the only thing that CL 9 does relative to CL 6 is waste CPU time.
It is unclear whether LZ4 would help much for the type of data we would feed into it. I would like to do that research, though. I have it listed as a "hot project" on the VirtualGL web site, meaning I am looking for someone to sponsor me financially to do the work. I also have tentative sponsorship secured to investigate how H.264 compares to Tight encoding-- it will likely prove to be a much better low-bandwidth solution, at least for apps that generate high numbers of unique colors. Referring to http://code.google.com/p/lz4/, at least for what they were testing, LZ4 required nearly 3 times as much CPU time on the compressor end to achieve the same compression ratio as even Zlib level 1 (which is used by TigerVNC's Compression Level 1.) In the default mode, LZ4 compressed 6 or 7 times faster than Zlib level 1, but it also compressed 25% worse. Anyhow, further study needs to be done with it. I have the low-level tools necessary to evaluate what types of app workloads it might benefit, if any. On 1/30/14 8:11 PM, devsk wrote: > Will using a compression sceheme like LZ4 help? You can go higher levels of > compression for less CPU usage. > > -devsk > ------------------------------------------------------------------------------ WatchGuard Dimension instantly turns raw network data into actionable security intelligence. It gives you real-time visual feedback on key security issues and trends. Skip the complicated setup - simply import a virtual appliance and go from zero to informed in seconds. http://pubads.g.doubleclick.net/gampad/clk?id=123612991&iu=/4140/ostg.clktrk _______________________________________________ Tigervnc-users mailing list Tigervnc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/tigervnc-users
