Re: [Qemu-devel] [PATCH] PNG screendump alternative

[Rafael da Veiga Cabral]

On 03/19/2012 06:10 PM, Anthony Liguori wrote:
> On 03/17/2012 05:45 PM, Rafael wrote:
> > Hi,
> >
> > I  had already started to work on supporting PNG dump output on
> > screendump when got to know there was another effort to do the same
> > (see Add PNG screendump thread from Daniel P. Berrange). Anyway, I'd
> > like to share my implementation which is a little bit different. It
> > does not use any resource/lib besides libpng and qemu itself and is
> > based on qemu-kvm 0.15.1 ppm_save code.
> >
> > I'm using that for a personal project developed at Mandriva which uses
> > QMP directly to communicate with qemu VMs rather than using the
> > libvirt although its usage is considered for the future. There is
> > something more to show but it is just QMP related and soon I'll have
> > it done to share.
> >
> > Comments and suggestions are appreciated.
>
> I think the added value of this is minimal compared to the alternative 
> implementation (just run convert on the PPM).
>
> Can you talk a bit more about your use-case any why post-processing 
> the PPM isn't a reasonable alternative?

It's because my use-case requires a screenshoot on each second or less. 
It's a functional testing tool based on what is happening on the vm 
screen. The testing stuff  is based on basic image processing of the 
screens. Therefore as screen are grabbed all time the less CPU and Disk 
I/O are required the better,  for example, by changing from PPM to PNG 
at least 2.2 Megas of disk writing are saved on each second. Think about 
a session of 15 minutes or more  (15 * 60 * 2.2).  I've also thought 
that by saving directly from the screen buffer to png should save some 
CPU cycles rather than saving to PPM first and converting it to PNG on 
the qemu runtime.


> Regards,
>
> Anthony Liguori
>
> > Cheers
> > Rafael Cabral

Thanks Anthony
Rafael Cabral