[winswitch] xpra 0.6.1 -- feedback

Antoine Martin antoine at nagafix.co.uk
Mon Sep 17 14:21:07 BST 2012

On 09/17/2012 07:33 PM, Dmitry Smirnov wrote:
> On Mon, 17 Sep 2012 18:24:27 Antoine Martin wrote:
>> No, sorry, x264 is the way forward, I'd rather fix the remaining latency
>> and quality issues than use a slow and outdated encoding.
> No worries but please-please keep PNG encoding for high-speed connections. :)
PNG, rgb24, jpeg (and mmap!) are not deprecated and I have no intention
of removing them.

> Just thinking: how about choosing the encoding dynamically on attaching? 
winswitch does this a little bit better because it knows what command is
being run, so it can pre-select x264 or vpx for video apps, etc..

> Something like when attaching, if bandwidth is high, choose PNG from very 
> beginning but if connection is slow choose x264? I think it could be measured 
> as number of KiB per sec for first 2-10 seconds after attaching....
> I would try PNG first (because it's for highest quality) and see how fast we 
> can pull the data. After few seconds xpra may decide to change encoding if 
> data is coming too slow. 
> Obviously we will need to calibrate but that's not difficult.
> Also in configuration file instead of "encoding = png" we could put something 
> like "encoding = png,x264,jpg" to specify list of allowed encodings in the 
> order of preference.
Could do... but:

> Important thing would be to choose encoding only in the beginning but then 
> allow user to switch while adjusting chosen encoding parameters dynamically as 
> it is now.
This was originally planned, but x264 does all that and better: at high
quality it is indistinguishable from lossless encodings (png or rgb24),
at lower quality settings it is an order of magnitude more efficient
than jpeg (and still with much better quality)
All that's needed is to properly tune the quality based on bandwidth
availability. Sounds simple, but it isn't.
Bandwidth availability varies widely, and so does our "framerate" -
which isn't necessarily a full-frame rate (from 0fps when idle to up to
200 updates per second). Then there are latency issues, etc..

>> Downloaded and installed iceweasel, cannot reproduce...
> Interesting... I was trying it too and now I took away
>    https://www.xpra.org/trac/changeset/1543
> and found that it has no effect whatsoever. I couldn't crash new sessions and 
> one of the old ones which was not affected anyway.
> I still can crash one session where I initially fount the problem. 
> I'll find out how to reproduce and will let you know.
I'll try to make a 1x1 window and see if it happens again.


> Cheers,
> Dmitry.
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