[Spice-devel] Information about video detection

[Matilde Yanez]

Hi,
thanks for answers.

2013/7/2 Yonit Halperin <yhalperi at redhat.com>

> Hi,
>
> On 07/01/2013 04:27 AM, Matilde Yanez wrote:
>
>> Hello,
>>
>> I need some information about video detection, on VM.
>> When I am on web pages, or documents, with images the VM seems to detect
>> video and start the mjpeg_encoder process.
>> Thus, the display is slows down.
>>
>>  What vm are you using? We encountered such behaviour with gnome-shell,
> due to high frequency updates of regions over the primary surface.


On CentOs and Windows VMs, indeed with high frequency updates of regions it
considers that is video. Such as large Excel documents or web page with
many images. Adding log I can see that spice server starts stream, and does
the same treatment as video.


>  With argument streaming-video=off, the CPU consomation goes up.
>>
> This is unexpected. On which guest scenarios?


When I play a movie, with default "streaming-video" arguments, on windows
VM, I am around 60% of CPU consomation of VM's qemu process ("top"
command), and with "streaming-video=off" I am around 120%.
Due to all images that are send to refresh client display?


>

 Increasing the value of "RED_STREAM_FRAMES_START_**CONDITION", does not
>> launch the video detection on these documents and keep fluidity on
>> videos and documents
>>
>> How can i make difference between real video, and documents with images?
>>
> I'm afraid there is no simple answer for this
> (1) Why does the driver send frequent updates? Does the rectangles that
> are being updated really change? Can it be prevented on the driver side?
> (2) If the area that is being refreshed doesn't change much, we can apply
> a quick comparison of sampled regions of 2 successive "frames", and if most
> of the pixels stay the same, we won't consider those "frames" as part of a
> video stream. (for such scenarios we would also like to improve and employ
> the GLZ encoding, or change our caching mechanism, to be applied on slices
> of bitmaps)


I think I will investigate on the 2nd point.

>

   On what part of the spice-server code can i make changes?
>>
> Code that is related to video streams is located in red_worker.c, in
> routines with "stream|upgrade" in their names.
>
>>
>> Thanks,
>> Matilde.
>>
>>  Regards,
> Yonit.


Matilde.

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