添加ffmpeg相关cmake文件

cmake/FindAVCODEC.cmake

 find_path(AVCODEC_INCLUDE_DIR
-  NAMES libavcodec/avcodec.h)
+        NAMES libavcodec/avcodec.h
+        HINTS ${FFMPEG_PATH_ROOT}
+        PATH_SUFFIXES include)
 
 find_library(AVCODEC_LIBRARY
-  NAMES avcodec)
+        NAMES avcodec
+        HINTS ${FFMPEG_PATH_ROOT}
+        PATH_SUFFIXES bin lib)
 
 set(AVCODEC_LIBRARIES ${AVCODEC_LIBRARY})
 set(AVCODEC_INCLUDE_DIRS ${AVCODEC_INCLUDE_DIR})

cmake/FindAVFORMAT.cmake

+find_path(AVFORMAT_INCLUDE_DIR
+        NAMES libavformat/avformat.h
+        HINTS ${FFMPEG_PATH_ROOT}
+        PATH_SUFFIXES include)
+
+find_library(AVFORMAT_LIBRARY
+        NAMES avformat
+        HINTS ${FFMPEG_PATH_ROOT}
+        PATH_SUFFIXES bin lib)
+
+set(AVFORMAT_LIBRARIES ${AVFORMAT_LIBRARY})
+set(AVFORMAT_INCLUDE_DIRS ${AVFORMAT_INCLUDE_DIR})
+
+include(FindPackageHandleStandardArgs)
+
+find_package_handle_standard_args(AVFORMAT DEFAULT_MSG AVFORMAT_LIBRARY AVFORMAT_INCLUDE_DIR)

cmake/FindAVUTIL.cmake

 find_path(AVUTIL_INCLUDE_DIR
-  NAMES libavutil/avutil.h)
+        NAMES libavutil/avutil.h
+        HINTS ${FFMPEG_PATH_ROOT}
+        PATH_SUFFIXES include)
 
 find_library(AVUTIL_LIBRARY
-  NAMES avutil)
+        NAMES avutil
+        HINTS ${FFMPEG_PATH_ROOT}
+        PATH_SUFFIXES bin lib)
 
 set(AVUTIL_LIBRARIES ${AVUTIL_LIBRARY})
 set(AVUTIL_INCLUDE_DIRS ${AVUTIL_INCLUDE_DIR})

cmake/FindSWRESAMPLE.cmake

 find_path(SWRESAMPLE_INCLUDE_DIR
-  NAMES libswresample/swresample.h)
+        NAMES libswresample/swresample.h
+        HINTS ${FFMPEG_PATH_ROOT}
+        PATH_SUFFIXES include)
 
 find_library(SWRESAMPLE_LIBRARY
-  NAMES swresample)
+        NAMES swresample
+        HINTS ${FFMPEG_PATH_ROOT}
+        PATH_SUFFIXES bin lib)
 
 set(SWRESAMPLE_LIBRARIES ${SWRESAMPLE_LIBRARY})
 set(SWRESAMPLE_INCLUDE_DIRS ${SWRESAMPLE_INCLUDE_DIR})

cmake/FindSWSCALE.cmake

+find_path(SWSCALE_INCLUDE_DIR
+        NAMES libswscale/swscale.h
+        HINTS ${FFMPEG_PATH_ROOT}
+        PATH_SUFFIXES include)
+
+find_library(SWSCALE_LIBRARY
+        NAMES swscale
+        HINTS ${FFMPEG_PATH_ROOT}
+        PATH_SUFFIXES bin lib)
+
+set(SWSCALE_LIBRARIES ${SWSCALE_LIBRARY})
+set(SWSCALE_INCLUDE_DIRS ${SWSCALE_INCLUDE_DIR})
+
+include(FindPackageHandleStandardArgs)
+
+find_package_handle_standard_args(SWSCALE DEFAULT_MSG SWSCALE_LIBRARY SWSCALE_INCLUDE_DIR)