Many thanks for this insight Mike! Best,
András On Fri, Aug 7, 2020 at 5:26 PM Mike Jumper <[email protected]> wrote: > On Fri, Aug 7, 2020, 06:30 Andras Sali <[email protected]> wrote: > > > Hi Nick, > > > > Yes, thanks, I am aware that guacd already can use WebP if it's > available. > > However if I see correctly, it is only used for **lossy compression** - > the > > lossless flag is set to 0 ( > > > > > https://github.com/apache/guacamole-server/blob/master/src/common/surface.c#L1794 > > ). > > > > WebP also supports lossless compression using a separate algorithm ( > > > > > https://developers.google.com/speed/webp/docs/webp_lossless_bitstream_specification > > ), > > which would be a direct alternative for PNG updates. In the benchmark I > > linked in my previous email, lossless webP encoding can be faster and > more > > efficient for many types of images than PNG (question if this is also the > > case for screen updates). > > > > So I understand that guacd already intelligently switches between PNG / > > WebP Lossy depending on different metrics, however my question is > regarding > > using WebP Lossless instead of PNG. In this case the switching would be > > between WebP Lossless and / WebP Lossy depending on the metrics. > > > > Has this already been tried and discarded for some reason? > > > > Yes, waaayyy back when WebP support was first finding its way into > Guacamole, prior to the project moving to the ASF. There were mixed results > in our own testing, showing that WebP would often compress worse and slower > than PNG, resulting in increased latency and bandwidth usage. > > There was also a mysterious issue where libwebp would effectively ignore > the lossless quality setting and produce lossy images. By now, this may no > longer be a problem, however I suspect the negative performance > characteristics relative to PNG will still be there. > > If you would like to give it a try, by all means see whether things do > improve, however the answer to your question is "yes, lossless WebP was > investigated and ultimately rejected due to poor performance > characteristics compared to PNG." > > - Mike >
