[Spice-devel] [spice-gtk v1] display-gst: Improve h264 elements filtering

[Victor Toso]

From: Victor Toso <me at victortoso.com>

This patch fixes the avdec_h264 element not being present on
gstvideo_has_codec() which get all decoder elements from GstRegistry
and filter them on our GstCaps in order to get the ones for given
codec.

The issue is around the filtering. The current GstCaps for h264 is not
consider a subset of avdec_h264's capabilites and that will fiter this
element out of the list.

The proposed solution for that is to set `subsetonly` parameter from
gst_element_factory_list_filter() to false.

While at it, the cap "stream-format=byte-stream" is less useful now
because it isn't needed to play the stream - see 6fe88871240c53b8

In my system, our debug shows:
.. gstvideo_debug_available_decoders: From 228 video decoder elements,
- 4 can handle caps   image/jpeg: jpegdec, nvdec, avdec_mjpeg, vaapijpegdec
- 3 can handle caps  video/x-vp8: vaapidecodebin, vp8dec, avdec_vp8
- 4 can handle caps video/x-h264: vaapidecodebin, avdec_h264, nvdec, vaapih264dec
- 3 can handle caps  video/x-vp9: vaapidecodebin, vp9dec, avdec_vp9

Signed-off-by: Victor Toso <victortoso at redhat.com>
---
 src/channel-display-gst.c  | 2 +-
 src/channel-display-priv.h | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/channel-display-gst.c b/src/channel-display-gst.c
index 20d236a..1bd7df1 100644
--- a/src/channel-display-gst.c
+++ b/src/channel-display-gst.c
@@ -647,7 +647,7 @@ gboolean gstvideo_has_codec(int codec_type)
     }
 
     caps = gst_caps_from_string(gst_opts[codec_type].dec_caps);
-    codec_decoders = gst_element_factory_list_filter(all_decoders, caps, GST_PAD_SINK, TRUE);
+    codec_decoders = gst_element_factory_list_filter(all_decoders, caps, GST_PAD_SINK, FALSE);
     gst_caps_unref(caps);
 
     if (codec_decoders == NULL) {
diff --git a/src/channel-display-priv.h b/src/channel-display-priv.h
index 04cb4d1..9bfd4ac 100644
--- a/src/channel-display-priv.h
+++ b/src/channel-display-priv.h
@@ -181,7 +181,7 @@ static const struct {
      * (hardcoded in spice-server), let's add it here to avoid the warning.
      */
     { SPICE_DISPLAY_CAP_CODEC_H264, "h264",
-      "h264parse ! avdec_h264", "video/x-h264,stream-format=byte-stream" },
+      "h264parse ! avdec_h264", "video/x-h264" },
 
     /* SPICE_VIDEO_CODEC_TYPE_VP9 */
     { SPICE_DISPLAY_CAP_CODEC_VP9, "vp9",
-- 
2.13.0