fixed build problems with older ffmpeg versions

changed includes to not use ffmpeg internal headers

libobs/CMakeLists.txt

@@ -8,6 +8,10 @@ find_package(Libavutil REQUIRED)
 include_directories(${Libavutil_INCLUDE_DIR})
 add_definitions(${Libavutil_DEFINITIONS})
 
+find_package(Libavformat REQUIRED)
+include_directories(${Libavformat_INCLUDE_DIR})
+add_definitions(${Libavformat_DEFINITIONS})
+
 add_definitions(-DLIBOBS_EXPORTS)
 add_definitions(-DPTW32_STATIC_LIB)
 

libobs/media-io/audio-resampler-ffmpeg.c

@@ -18,8 +18,8 @@
 #include "../util/bmem.h"
 #include "audio-resampler.h"
 #include "audio-io.h"
-#include <libavutil/opt.h>
-#include <libavutil/channel_layout.h>
+#include <libavutil/avutil.h>
+#include <libavformat/avformat.h>
 #include <libswresample/swresample.h>
 
 struct audio_resampler {