Find FFMPEG using pkg-config

This is the standard method of finding it on Unix systems, so make sure
we use it. Still keep a fallback, though, for other systems, e.g.
Windows.

CMakeLists.txt

@@ -179,18 +179,11 @@ if(ENABLE_H264)
     set(H264_LIBS "WIN")  # may be LIBAV in the future
     set(H264_LIBRARIES ole32 mfplat mfuuid wmcodecdspuuid)
   else()
-    check_include_files(libavcodec/avcodec.h HAVE_AVCODEC_H)
-    check_include_files(libavutil/avutil.h HAVE_AVUTIL_H)
-    check_include_files(libswscale/swscale.h HAVE_SWSCALE_H)
-    if (HAVE_AVCODEC_H AND HAVE_AVUTIL_H AND HAVE_SWSCALE_H)
-      find_path(AVCODEC_INCLUDE_DIR libavcodec/avcodec.h)
-      find_library(AVCODEC_LIBRARY avcodec)
-      find_path(AVUTIL_INCLUDE_DIR libavutil/avutil.h)
-      find_library(AVUTIL_LIBRARY avutil)
-      find_path(SWSCALE_INCLUDE_DIR libswscale/swscale.h)
-      find_library(SWSCALE_LIBRARY swscale)
+    find_package(Ffmpeg)
+    if (AVCODEC_FOUND AND AVUTIL_FOUND AND SWSCALE_FOUND)
       set(H264_INCLUDE_DIRS ${AVCODEC_INCLUDE_DIRS} ${AVUTIL_INCLUDE_DIRS} ${SWSCALE_INCLUDE_DIRS})
-      set(H264_LIBRARIES ${AVCODEC_LIBRARY} ${AVUTIL_LIBRARY} ${SWSCALE_LIBRARY})
+      set(H264_LIBRARIES ${AVCODEC_LIBRARIES} ${AVUTIL_LIBRARIES} ${SWSCALE_LIBRARIES})
+      set(H264_LIBRARY_DIRS ${AVCODEC_LIBRARY_DIRS} ${AVUTIL_LIBRARY_DIRS} ${SWSCALE_LIBRARY_DIRS})
       add_definitions("-D__STDC_CONSTANT_MACROS")
       add_definitions("-DHAVE_H264")
       set(H264_LIBS "LIBAV")

cmake/Modules/FindFfmpeg.cmake

@@ -0,0 +1,17 @@
+find_package(PkgConfig)
+
+if (PKG_CONFIG_FOUND)
+	pkg_check_modules(AVCODEC libavcodec)
+	pkg_check_modules(AVUTIL libavutil)
+	pkg_check_modules(SWSCALE libswscale)
+else()
+	find_path(AVCODEC_INCLUDE_DIRS NAMES avcodec.h PATH_SUFFIXES libavcodec)
+	find_library(AVCODEC_LIBRARIES NAMES avcodec)
+	find_package_handle_standard_args(AVCODEC DEFAULT_MSG AVCODEC_LIBRARIES AVCODEC_INCLUDE_DIRS)
+	find_path(AVUTIL_INCLUDE_DIRS NAMES avutil.h PATH_SUFFIXES libavutil)
+	find_library(AVUTIL_LIBRARIES NAMES avutil)
+	find_package_handle_standard_args(AVUTIL DEFAULT_MSG AVUTIL_LIBRARIES AVUTIL_INCLUDE_DIRS)
+	find_path(SWSCALE_INCLUDE_DIRS NAMES swscale.h PATH_SUFFIXES libswscale)
+	find_library(SWSCALE_LIBRARIES NAMES swscale)
+	find_package_handle_standard_args(SWSCALE DEFAULT_MSG SWSCALE_LIBRARIES SWSCALE_INCLUDE_DIRS)
+endif()

common/rfb/CMakeLists.txt

@@ -76,6 +76,7 @@ if(ENABLE_H264 AND NOT H264_LIBS STREQUAL "NONE")
     target_sources(rfb PRIVATE H264WinDecoderContext.cxx)
   endif()
   target_link_libraries(rfb ${H264_LIBRARIES})
+  target_link_directories(rfb PUBLIC ${H264_LIBRARY_DIRS})
 endif()
 
 if(UNIX)