qt: Add support for ProRes 4444 XQ

And also 4444 in the muxer.

https://bugzilla.gnome.org/show_bug.cgi?id=769048

gst/isomp4/fourcc.h

@@ -245,6 +245,7 @@ G_BEGIN_DECLS
 #define FOURCC_wide     GST_MAKE_FOURCC('w','i','d','e')
 #define FOURCC_zlib     GST_MAKE_FOURCC('z','l','i','b')
 
+#define FOURCC_ap4x     GST_MAKE_FOURCC('a','p','4','x')
 #define FOURCC_ap4h     GST_MAKE_FOURCC('a','p','4','h')
 #define FOURCC_apch     GST_MAKE_FOURCC('a','p','c','h')
 #define FOURCC_apcn     GST_MAKE_FOURCC('a','p','c','n')

gst/isomp4/gstqtmux.c

@@ -4250,6 +4250,10 @@ gst_qt_mux_video_sink_set_caps (GstQTPad * qtpad, GstCaps * caps)
       entry.fourcc = FOURCC_apch;
     else if (!g_strcmp0 (variant, "proxy"))
       entry.fourcc = FOURCC_apco;
+    else if (!g_strcmp0 (variant, "4444"))
+      entry.fourcc = FOURCC_ap4h;
+    else if (!g_strcmp0 (variant, "4444xq"))
+      entry.fourcc = FOURCC_ap4x;
   }
 
   if (!entry.fourcc)

gst/isomp4/qtdemux.c

@@ -13375,6 +13375,12 @@ qtdemux_video_caps (GstQTDemux * qtdemux, QtDemuxStream * stream,
           gst_caps_new_simple ("video/x-prores", "variant", G_TYPE_STRING,
           "4444", NULL);
       break;
+    case FOURCC_ap4x:
+      _codec ("Apple ProRes 4444 XQ");
+      caps =
+          gst_caps_new_simple ("video/x-prores", "variant", G_TYPE_STRING,
+          "4444xq", NULL);
+      break;
     case FOURCC_vc_1:
     case FOURCC_ovc1:
       _codec ("VC-1");