--- qt6-webengine-6.4.2.orig/src/3rdparty/chromium/build/linux/unbundle/ffmpeg.gn
+++ qt6-webengine-6.4.2/src/3rdparty/chromium/build/linux/unbundle/ffmpeg.gn
@@ -12,6 +12,7 @@ pkg_config("system_ffmpeg") {
     "libavformat",
     "libavutil",
   ]
+  defines = [ "av_stream_get_first_dts(stream)=stream->first_dts" ]
 }
 
 buildflag_header("ffmpeg_features") {