Presently,  the  highest release series of "ffmpeg" that this distro's
version of "gnash" supports is "ffmpeg4".

For "ffmpeg4":

#define LIBAVCODEC_VERSION_MAJOR  58
#define LIBAVCODEC_VERSION_MINOR  91
#define LIBAVCODEC_VERSION_MICRO 100

--- gnash-patches-git-29748750e.old/libmedia/ffmpeg/VideoDecoderFfmpegVaapi.h
+++ gnash-patches-git-29748750e/libmedia/ffmpeg/VideoDecoderFfmpegVaapi.h
@@ -29,6 +29,11 @@
 #include <libavcodec/vaapi.h>
 }
 
+#ifdef  LIBAVCODEC_VERSION_INT
+#undef  LIBAVCODEC_VERSION_INT
+#endif
+#define LIBAVCODEC_VERSION_INT AV_VERSION_INT(58,91,100)
+
 #if LIBAVCODEC_VERSION_INT >= AV_VERSION_INT(55,18,102)
 #define CODECID AVCodecID
 #else
--- gnash-patches-git-29748750e.old/libmedia/ffmpeg/ffmpegHeaders.h
+++ gnash-patches-git-29748750e/libmedia/ffmpeg/ffmpegHeaders.h
@@ -64,7 +64,6 @@
 }
 #endif
 
-
 #ifdef HAVE_SWSCALE_H
 extern "C" {
 #include <swscale.h>
@@ -85,6 +84,15 @@
 #define HAVE_SWSCALE_H 1
 #endif
 
+extern "C" {
+#include <libavutil/imgutils.h>
+}
+
+#ifdef  LIBAVCODEC_VERSION_INT
+#undef  LIBAVCODEC_VERSION_INT
+#endif
+#define LIBAVCODEC_VERSION_INT AV_VERSION_INT(58,91,100)
+
 #if LIBAVCODEC_VERSION_INT < AV_VERSION_INT(52,94,1)
 #define AV_SAMPLE_FMT_NONE SAMPLE_FMT_NONE
 #define AV_SAMPLE_FMT_U8   SAMPLE_FMT_U8
--- gnash-patches-git-29748750e.old/macros/ffmpeg.m4
+++ gnash-patches-git-29748750e/macros/ffmpeg.m4
@@ -241,9 +241,9 @@
   
       AC_MSG_CHECKING([ffmpeg version])
 
-      ffmpeg_major_version=`$EGREP "define LIBAVCODEC_VERSION_MAJOR " ${versionmajorfile} 2>&1 | sed -e "s%[[^0-9]]%%g"`
-      ffmpeg_minor_version=`$EGREP "define LIBAVCODEC_VERSION_MINOR " ${versionfile} 2>&1 | sed -e "s%[[^0-9]]%%g"`
-      ffmpeg_micro_version=`$EGREP "define LIBAVCODEC_VERSION_MICRO " ${versionfile} 2>&1 | sed -e "s%[[^0-9]]%%g"`
+      ffmpeg_major_version=58
+      ffmpeg_minor_version=91
+      ffmpeg_micro_version=100
 
       if test x"${ffmpeg_major_version}" != x ; then
 
--- gnash-patches-git-29748750e.old/macros/pango.m4
+++ gnash-patches-git-29748750e/macros/pango.m4
@@ -52,6 +52,7 @@
   if test x$cross_compiling = xno; then
     if test x"$PKG_CONFIG" != x; then
       $PKG_CONFIG --exists $pango_pkg && gnash_pango_version=`$PKG_CONFIG --modversion $pango_pkg | cut -d "." -f 1 | awk '{print $'0'".0"}'`
+      gnash_pango_version=0.91
     fi
   fi
 
@@ -86,10 +87,10 @@
   AC_ARG_WITH(pango_lib, AS_HELP_STRING([--with-pango-lib], [directory where pango library is]), with_pango_lib=${withval})
   AC_CACHE_VAL(ac_cv_path_pango_lib,[
     if test x"${with_pango_lib}" != x ; then
-      if test -f ${with_pango_lib}/libpangox-${gnash_pango_version}.a -o -f ${with_pango_lib}/libpangox-${gnash_pango_version}.${shlibext} -o -f ${with_pango_lib}/libpangox-${gnash_pango_version}.${shlibext}.a; then
+      if test -f ${with_pango_lib}/libpangox-1.0.${shlibext}; then
 	ac_cv_path_pango_lib=-L`(cd ${with_pango_lib}; pwd)`
       else
-	AC_MSG_ERROR([${with_pango_lib} directory doesn't contain libpango.])
+	AC_MSG_ERROR([missing ${with_pango_lib}/libpangox-1.o.${shlibext}])
       fi
     fi
   ])