Make avdevice library optional again (#1246)

* 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.

* Add USE_AVDEVICE option

This option is ON by default and will disable linking to
avdevice when set to OFF.

If the option is ON, but avdevice is not found, then the
build will fail as per #1115

Author: dimula73

CMakeLists.txt

@@ -20,6 +20,7 @@ option(CLANG_FORMAT "Enable Clang Format" ON)
 option(BUILD_TESTS_WITH_QT6 "Build test against Qt 6" ON)
 
 option(MOD_AVFORMAT "Enable avformat module" ON)
+option(USE_AVDEVICE "Integrate FFmpeg libavdevice for capture" ON)
 option(MOD_DECKLINK "Enable DeckLink module" ON)
 option(MOD_FREI0R "Enable Frei0r module" ON)
 option(MOD_GDK "Enable GDK module" ON)
@@ -227,14 +228,19 @@ if(MOD_GDK OR MOD_GTK)
 endif()
 
 if(MOD_AVFORMAT)
+  set(OPTIONAL_FFMPEG_COMPONENTS)
+  if(USE_AVDEVICE)
+    list(APPEND OPTIONAL_FFMPEG_COMPONENTS AVDEVICE)
+  endif()
+
   find_package(FFmpeg REQUIRED COMPONENTS
     AVFORMAT
     SWSCALE
     AVUTIL
     AVCODEC
     AVFILTER
-    AVDEVICE
     SWRESAMPLE
+    ${OPTIONAL_FFMPEG_COMPONENTS}
   )
 
   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(USE_AVDEVICE AND 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")) {