[gnome-shell] screencast: Always copy buffers in pipewiresrc

[Marge Bot <marge-bot src gnome org>]

commit d32c03488fcf6cdb0ca2e99b0ed6ade078460deb
Author: Sebastian Keller <skeller gnome org>
Date:   Sun Aug 21 16:00:40 2022 +0200

    screencast: Always copy buffers in pipewiresrc
    
    Pipewire 0.3.52 via commit a1f33a99 introduced a change that affects how
    long pipewiresrc holds onto the pw_buffers it dequeued. Before that
    change the pw_buffer was held until the end of the videoconvert element
    at the beginning of the pipeline. After that change the pw_buffer was
    held onto until the filesink at the end of the pipeline. This was
    starving MetaScreenCastStreamSrc of pw_buffers to record new frames
    into, resulting in the majority of frames being missed, especially in
    situations in which the encoder was taking longer.
    
    Pipewire 0.3.57 via commit 1ea1d525 will allow queuing the pw_buffer
    early again via the `always-copy` option. This however is only a
    workaround until a proper solution is found in either pipewire or
    gstreamer that does not depend on copying the buffer contents and
    instead queues the pw_buffer again after videoconvert as prior to
    a1f33a99.
    
    Since it is not clear yet when a proper solution will arrive, this makes
    use of `always-copy` as a workaround for now and should be reverted once
    it is no longer needed.
    
    Related: https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/5585
    Related: https://gitlab.freedesktop.org/pipewire/pipewire/-/issues/2461
    Related: https://gitlab.freedesktop.org/gstreamer/gstreamer/-/issues/283
    Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2436>

 js/dbusServices/screencast/screencastService.js | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/js/dbusServices/screencast/screencastService.js b/js/dbusServices/screencast/screencastService.js
index 75ffba7c21..5ff5aff529 100644
--- a/js/dbusServices/screencast/screencastService.js
+++ b/js/dbusServices/screencast/screencastService.js
@@ -230,9 +230,12 @@ var Recorder = class {
 
     _ensurePipeline(nodeId) {
         const framerate = this._framerate;
+        const needsCopy =
+            Gst.Registry.get().check_feature_version('pipewiresrc', 0, 3, 57);
 
         let fullPipeline = `
             pipewiresrc path=${nodeId}
+                        always-copy=${needsCopy}
                         do-timestamp=true
                         keepalive-time=1000
                         resend-last=true !