[Spice-devel] [PATCH spice 1/3] dcc_compress_image: Handle NULL drawable

[Frediano Ziglio]

> 
> On Thu, Jan 14, 2016 at 10:27:02AM -0500, Frediano Ziglio wrote:
> > Had a small discussion with Pavel.
> > We agree that original code is quite complicated and is hard to understand
> > the final compression format used.
> > 
> > So we would like to have some public discussion about the topic.
> > 
> > I personally agree we should have a single code deciding the compression
> > to use.
> 
> I definitely agree here. For one, having different compression being
> used depending on whether the qxl driver is used or not is unexpected
> (eg if you set image compression to glz, lz will still be used during
> initial bootup, and then will 'switch' to glz later on. I haven't looked
> at the code, so there might be good reasons for that).
> 
> > 
> > This is the list of actual compressions:
> > - AUTO_GLZ;
> > - AUTO_LZ;
> > - QUIC;
> > - GLZ;
> > - LZ;
> > - LZ4.
> > A client can also decide to disable compression.
> > 
> > The AUTO_XXX looks like they should use QUIC as a fallback if XXX is not
> > possible or if an image with high graduality is detected.
> 
> (side question, do we have numbers on compression ratio and cpu usage
> for quic/lz/glz/lz4?)
> 

Brief and raw of a Windows replay capture

        Images  MB before   MB after  Ratio     CPU time
LZ4     193     24.21       2.43      10.04%    0.04
QUIC    204     23.11       1.66       7.18%    0.44
GLZ     190     20.05       1.2        5.99%    0.14
LZ      202     20.42       2.04       9.99%    0.15

So why use Quic ?

Frediano