cmake: Restore DECAF_FFMPEG option.

BUILDING.md

@@ -74,6 +74,7 @@ Currently decaf-emu can build on MacOS using Xcode 11 although MoltenVK is missi
 
 ## CMake
 Options interesting to users:
+- DECAF_FFMPEG - Build with ffmpeg which is used for decoding h264 videos
 - DECAF_QT - Build with Qt frontend.
 - DECAF_VULKAN - Build with Vulkan backend.
 

CMakeLists.txt

@@ -18,6 +18,7 @@ else()
     set(DECAF_PCH_DEFAULT ON)
 endif()
 
+option(DECAF_FFMPEG          "Build with ffmpeg support"                    ON)
 option(DECAF_VULKAN          "Build with Vulkan rendering support"          ON)
 option(DECAF_QT              "Build with Qt support"                        ON)
 
@@ -82,7 +83,6 @@ find_package(Threads REQUIRED)
 if(VCPKG_TARGET_TRIPLET)
     find_package(c-ares CONFIG REQUIRED)
     find_package(CURL CONFIG REQUIRED)
-    find_package(FFMPEG REQUIRED)
     find_package(OpenSSL REQUIRED)
     find_package(SDL2 CONFIG REQUIRED)
     find_package(unofficial-libuv CONFIG REQUIRED)
@@ -90,7 +90,6 @@ if(VCPKG_TARGET_TRIPLET)
 
     set(CARES_LIBRARY c-ares::cares)
     set(CURL_LIBRARY CURL::libcurl)
-    set(FFMPEG_LIBRARY FFMPEG::AVCODEC FFMPEG::AVFILTER FFMPEG::AVUTIL FFMPEG::SWSCALE)
     set(LIBUV_LIBRARY unofficial::libuv::libuv)
     set(OPENSSL_LIBRARY OpenSSL::SSL)
     set(SDL2_LIBRARY SDL2::SDL2)
@@ -99,7 +98,6 @@ if(VCPKG_TARGET_TRIPLET)
 else()
     find_package(CARES REQUIRED)
     find_package(CURL REQUIRED)
-    find_package(FFMPEG REQUIRED)
     find_package(LibUV REQUIRED)
     find_package(OpenSSL REQUIRED)
     find_package(SDL2 REQUIRED)
@@ -107,7 +105,6 @@ else()
 
     set(CARES_LIBRARY CARES::CARES)
     set(CURL_LIBRARY CURL::libcurl)
-    set(FFMPEG_LIBRARY FFMPEG::AVCODEC FFMPEG::AVFILTER FFMPEG::AVUTIL FFMPEG::SWSCALE)
     set(LIBUV_LIBRARY LibUV::LibUV)
     set(OPENSSL_LIBRARY OpenSSL::SSL)
     set(SDL2_LIBRARY SDL2::SDL2)
@@ -115,8 +112,13 @@ else()
     set(ZLIB_LIBRARY ZLIB::ZLIB)
 endif()
 
-# TODO: Remove these definitions as they are no longer optional
-add_definitions(-DDECAF_FFMPEG)
+if(DECAF_FFMPEG)
+    find_package(FFMPEG REQUIRED)
+    set(FFMPEG_LIBRARY FFMPEG::AVCODEC FFMPEG::AVFILTER FFMPEG::AVUTIL FFMPEG::SWSCALE)
+    add_definitions(-DDECAF_FFMPEG)
+endif()
+
+# TODO: Remove this definitions as it is no longer optional
 add_definitions(-DDECAF_SDL)
 
 if(DECAF_VULKAN)