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

[Snir Sheriber]

Hi,


On 4/17/19 7:27 AM, Francois Gouget wrote:
> 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

Are you working on something like that (remote virgl)?

>   
> 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.


Notice that currently there's small hacky patch on client to ignore 
latency when it's full
screen streaming and there is no audio playback.

(d047b2fb7f5d492d6c49f589ba5ff862c6b115da)


> Other steps are:
> * Reducing the default latency.


What will be the default? what will happen to late video frames?


> * Increasing the latency when needed.


IIRC this latency is also considered when we match the video frames to
the audio playback, such adjustments wouldn't affect the video-audio
synchronization / stream flow?

what about playing both audio and video as fast as possible when it's 
streaming
case, have you considered it? (i was looking at this issue before and 
thought this
not too bad option :p)


Thanks, Snir.

> * 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.
>