[FFmpeg-devel] [PATCH v2] libavfilter: add PipeWire-based grab

[Quack Doc]

> The patch already supports passing a file descriptor and a PipeWire node ID
> directly via the "fd" and "node" options. The portal is only used if these
> values are not provided by the user.
>
> The original motivation for adding these options was to allow communication
> with the portal to be handled outside of FFmpeg, but I imagine they could also
> be used on e.g. Weston to bypass the portal entirely.

I see, I tried to pull the patch and test it. How does invocation with
node work? I'm a bit confused with the invocation. For testing I tried
using "gamescope --headless -- glxgears" to generate a raw pipewire
stream. (cameras will automatically create one with pipewire) used
"pw-dump | jq '.[] | select(.info.props["node.name"] == "gamescope") |
.id'" to get the node id and tried to use it but it still seemed to
trigger the portal. If you have a camera installed I use the below
command to dump all of the video sources, gamescope and cameras
included

pw-dump | jq '.[] | select(.info.props["media.class"] ==
"Video/Source") | .info.props."node.name" + " | " +
.info.props."node.description" + " | " + (.id|tostring)'

does the current patch have a hard requirement on file descriptors to
not use xdg?

I did also test xdg capture on cosmic, it seems to only sporadically
work, usually spitting out the below error. I can spam it to keep
retrying it until it works

[Parsed_hwmap_0 @ 0x79fabc003600] Mapping requires a hardware context
(a device, or frames on input).
[Parsed_hwmap_0 @ 0x79fabc003600] Failed to configure output pad on
Parsed_hwmap_0
[vf#0:0 @ 0x55cf4daff480] Error reinitializing filters!
[vf#0:0 @ 0x55cf4daff480] Task finished with error code: -22 (Invalid argument)
[vf#0:0 @ 0x55cf4daff480] Terminating thread with return code -22
(Invalid argument)
[vost#0:0/h264_vaapi @ 0x55cf4db38080] Could not open encoder before EOF
[vost#0:0/h264_vaapi @ 0x55cf4db38080] Task finished with error code:
-22 (Invalid argument)
[vost#0:0/h264_vaapi @ 0x55cf4db38080] Terminating thread with return
code -22 (Invalid argument)
[out#0/mp4 @ 0x55cf4db37800] Nothing was written into output file,
because at least one of its streams received no packets.


On Fri, Aug 2, 2024 at 3:41 PM François-Simon Fauteux-Chapleau
<francois-simon.fauteux-chapleau at savoirfairelinux.com> wrote:
>
> ----- On Aug 2, 2024, at 12:11 PM, Quack Doc quackdoctech at gmail.com wrote:
> > Pipewire video capture is more generic. Some compositors like weston
> > support pipewire as a backend without portals. Gamescope also creates a
> > pipewire output without need for portals, it would be *really* nice to
> > support gamescope capture with this. Pipewire also gives access to video
> > devices directly as well without needing portals, which allows
> > ergonomically letting multiple apps accsess v4l2 devices for instance like
> > firefox and say discord. So being able to support the file descriptor
> > directly, or using target-object much like the pipewiresrc gstreamer would
> > be greatly appreciated.
>
> The patch already supports passing a file descriptor and a PipeWire node ID
> directly via the "fd" and "node" options. The portal is only used if these
> values are not provided by the user.
>
> The original motivation for adding these options was to allow communication
> with the portal to be handled outside of FFmpeg, but I imagine they could also
> be used on e.g. Weston to bypass the portal entirely.
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