Allow unsupported warning to be returned when identifying container b…

…rands

src/PIL/AvifImagePlugin.py

@@ -24,24 +24,26 @@
 def _accept(prefix: bytes) -> bool | str:
     if prefix[4:8] != b"ftyp":
         return False
-    coding_brands = (b"avif", b"avis")
-    container_brands = (b"mif1", b"msf1")
     major_brand = prefix[8:12]
-    if major_brand in coding_brands:
-        if not SUPPORTED:
-            return (
-                "image file could not be identified because AVIF "
-                "support not installed"
-            )
-        return True
-    if major_brand in container_brands:
+    if major_brand in (
+        # coding brands
+        b"avif",
+        b"avis",
         # We accept files with AVIF container brands; we can't yet know if
         # the ftyp box has the correct compatible brands, but if it doesn't
         # then the plugin will raise a SyntaxError which Pillow will catch
         # before moving on to the next plugin that accepts the file.
         #
         # Also, because this file might not actually be an AVIF file, we
         # don't raise an error if AVIF support isn't properly compiled.
+        b"mif1",
+        b"msf1",
+    ):
+        if not SUPPORTED:
+            return (
+                "image file could not be identified because AVIF "
+                "support not installed"
+            )
         return True
     return False
 
@@ -104,10 +106,8 @@ def load(self) -> Image.core.PixelAccess | None:
             data, timescale, tsp_in_ts, dur_in_ts = self._decoder.get_frame(
                 self.__frame
             )
-            timestamp = round(1000 * (tsp_in_ts / timescale))
-            duration = round(1000 * (dur_in_ts / timescale))
-            self.info["timestamp"] = timestamp
-            self.info["duration"] = duration
+            self.info["timestamp"] = round(1000 * (tsp_in_ts / timescale))
+            self.info["duration"] = round(1000 * (dur_in_ts / timescale))
             self.__loaded = self.__frame
 
             # Set tile