Make avdevice library optional again

It is not used by avformat when performing
playback via SDL2, the only thing it does is
initializing avdevice and not using it later.

Author: dimula73

CMakeLists.txt

@@ -229,8 +229,8 @@ if(MOD_AVFORMAT)
     AVUTIL
     AVCODEC
     AVFILTER
-    AVDEVICE
     SWRESAMPLE
+    OPTIONAL_COMPONENTS AVDEVICE
   )
 
   list(APPEND MLT_SUPPORTED_COMPONENTS avformat)

cmake/FindFFmpeg.cmake

@@ -194,7 +194,9 @@ foreach (_component ${FFmpeg_FIND_COMPONENTS})
     endif ()
     list(APPEND _FFmpeg_FOUND_LIBRARIES ${${_component}_LIBRARIES})
   endif ()
-  list(APPEND _FFmpeg_REQUIRED_VARS ${_component}_LIBRARIES ${_component}_INCLUDE_DIRS ${_component}_FOUND)
+  if (${FFMPEG_FIND_REQUIRED_${_component}})
+    list(APPEND _FFmpeg_REQUIRED_VARS ${_component}_LIBRARIES ${_component}_INCLUDE_DIRS ${_component}_FOUND)
+  endif()
 endforeach ()
 list(INSERT _FFmpeg_REQUIRED_VARS 0 _FFmpeg_FOUND_LIBRARIES)
 

src/modules/avformat/CMakeLists.txt

@@ -51,6 +51,10 @@ if(WIN32)
   endif()
 endif()
 
+if(AVDEVICE_FOUND)
+  target_compile_definitions(mltavformat PRIVATE USE_AVDEVICE)
+endif()
+
 if(CPU_MMX)
   target_compile_definitions(mltavformat PRIVATE USE_MMX)
 endif()

src/modules/avformat/factory.c

@@ -45,7 +45,9 @@ extern mlt_link link_swresample_init(mlt_profile profile, mlt_service_type, cons
 // ffmpeg Header files
 #include "mltavformat_export.h"
 #include <libavcodec/avcodec.h>
+#ifdef USE_AVDEVICE
 #include <libavdevice/avdevice.h>
+#endif
 #include <libavfilter/avfilter.h>
 #include <libavformat/avformat.h>
 #include <libavutil/opt.h>
@@ -58,7 +60,9 @@ static void avformat_init()
     // Initialise avformat if necessary
     if (avformat_initialised == 0) {
         avformat_initialised = 1;
+#ifdef USE_AVDEVICE
         avdevice_register_all();
+#endif
         avformat_network_init();
         av_log_set_level(mlt_log_get_level());
         if (getenv("MLT_AVFORMAT_PRODUCER_CACHE")) {