get fmp4mux with av1

fmp4mux-with-av1.diff

diff --git mux/fmp4/Cargo.toml mux/fmp4/Cargo.toml
index 73e1f01b..090dc3a7 100644
--- mux/fmp4/Cargo.toml
+++ mux/fmp4/Cargo.toml
@@ -3,7 +3,7 @@ name = "gst-plugin-fmp4"
 version = "0.12.0-alpha.1"
 authors = ["Sebastian Dröge <sebastian@centricular.com>"]
 license = "MPL-2.0"
-description = "GStreamer Fragmented MP4 Plugin"
+description = "GStreamer Fragmented MP4 Plugin (Supports AV1)"
 repository = "https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs"
 edition = "2021"
 rust-version = "1.70"
diff --git mux/fmp4/src/fmp4mux/boxes.rs mux/fmp4/src/fmp4mux/boxes.rs
index 9d84158e..23fb7cbd 100644
--- mux/fmp4/src/fmp4mux/boxes.rs
+++ mux/fmp4/src/fmp4mux/boxes.rs
@@ -157,6 +157,11 @@ fn cmaf_brands_from_caps(caps: &gst::CapsRef, compatible_brands: &mut Vec<&'stat
                 }
             }
         }
+        "video/x-av1" => {
+            // https://aomediacodec.github.io/av1-isobmff/#cmaf
+            compatible_brands.push(b"cmfc");
+            compatible_brands.push(b"cmf2");
+        }
         "audio/mpeg" => {
             compatible_brands.push(b"caac");
         }
diff --git mux/fmp4/src/fmp4mux/imp.rs mux/fmp4/src/fmp4mux/imp.rs
index 3a090d6d..1454a2cc 100644
--- mux/fmp4/src/fmp4mux/imp.rs
+++ mux/fmp4/src/fmp4mux/imp.rs
@@ -3539,6 +3539,10 @@ impl ElementImpl for CMAFMux {
                         .field("width", gst::IntRange::new(1, u16::MAX as i32))
                         .field("height", gst::IntRange::new(1, u16::MAX as i32))
                         .build(),
+                    gst::Structure::builder("video/x-av1")
+                        .field("stream-format", "obu-stream")
+                        .field("alignment", "tu")
+                        .build(),
                     gst::Structure::builder("video/x-h265")
                         .field("stream-format", gst::List::new(["hvc1", "hev1"]))
                         .field("alignment", "au")