[Spice-devel] Few questions regarding Gstreamer

[Victor Toso]

Hi Armin,

Thanks for your questions.

On Wed, Aug 02, 2017 at 06:56:07PM +0430, Armin Ranjbar wrote:
> Hello List,
>
> Thanks for the effort on Spice :)
>
> given recent changes by Victor, i'm not sure how can i verify that i'm
> actually using Gstreamer to encode or decode the stream:

Things to consider:
- GStreamer is not default option for encoding
- You have to enable stream encoding [0] as it is disabled by default
- mjpeg is the default encoding/decoding video-codec

[0] if you use libvirt, you can add streaming mode with:
virsh edit $domain
  <graphics type='spice' autoport='yes'>
    <streaming mode='all'/>
  </graphics>

> 1> how can i make sure that server is using gstreamer to encode the stream?
> setting GST_DEBUG and SPICE_DEBUG i can't see anything gstreamer specific
> in servers logs.

There are pending work to better configuration in the host for that. The
easiest way is to use spicy and chose a video codec which is not mjpeg
(h264, vp8, vp9); Go to options > preferred video codec type > h264

This will send a message to the spice server to use h264 instead of
mjpeg and only gstreamer can encode it.

> 2> how can i make sure same thing happens on client side? again with debug
> options, i can see that spicy is streaming using channel-display.c:1840 not
> channel-display-gst.c.

You can also use mjpeg decoders in GStremear (it actually works well)
but you will need to build spice-gtk with --disable-builtin-mjpeg, so
every new stream will use gstreamer.

Note that we don't stream all the content all the time. Video streams
start/stop based on detection of regions that have high frequency of
updates, you can check [1] for a better understanding.

[1] https://youtu.be/C5ox_M-k63w

>
> 3> afaik video encoding and compression selection is for now specific to
> spicy, how can i set these options using remote-viewer?

The video-codec message is part of spice-protocol and implemented in
spice-gtk. We have an API in spice-gtk which spicy uses but none other
client does at the moment.

The goal is to automatically detect which video codecs we can hw decode
in the client and send this to spice-server. That is not implemented
yet.

> note that i'm building both spice and spice-gtk from latest git commit,
>
> ---
> Armin ranjbar

Let me know if you have any issues or suggestions!

Cheers,
    toso
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