[Spice-devel] [spice] Enable mm_time adjustments on startup

[Francois Gouget]

On Thu, 11 Apr 2019, Victor Toso wrote:

> Hi,
> 
> On Wed, Apr 10, 2019 at 11:25:17AM +0200, Francois Gouget wrote:
> > We send mm_time adjustments to the client whenever there is no audio
> > playback. There is no audio playback on startup. Therefore
> > mm_time_enabled must be true on startup. QED.
> > 
> > Signed-off-by: Francois Gouget <fgouget at codeweavers.com>
> 
> But what are you trying to fix/improve exactly?

The goal is to reduce the video stream latency.

The reason for that is that while a minimum 400 ms latency is fine when 
playing a YouTube video [1], it's very annoying when the whole desktop 
is being streamed, either through the streaming agent or through the 
future Virgl remote access, because then it translates into a 400 ms 
lag between every mouse click, keypress and the screen update.

This patch is the first step in that without it adjusting the latency is 
impossible unless one has played some sound first.

Other steps are:
* Reducing the default latency.
* Increasing the latency when needed.
* Reducing the latency after network hiccups.
* Ensuring latency adjustments don't interfere with the video stream bit 
  rate control.


[1] Even in that case the 400 ms latency shows up as the hiccup you get 
    when Spice switches from sending frames as regular screen updates to 
    the streaming code.

-- 
Francois Gouget <fgouget at codeweavers.com>