build: ffmpeg 6.0 support (#3812)

It seems to work fine with the new 6.0 with no code modifications, other
than our cmake build misidentifying the version.

INSTALL.md

@@ -44,7 +44,7 @@ NEW or CHANGED MINIMUM dependencies since the last major release are **bold**.
        ACES support and much better recognition of camera metadata; if
        building with C++17 or higher, LibRaw >= 0.20 is necessary)
  * If you want support for a wide variety of video formats:
-     * ffmpeg >= 3.0 (tested through 5.1)
+     * ffmpeg >= 3.0 (tested through 6.0)
  * If you want support for jpeg 2000 images:
      * OpenJpeg >= 2.0 (tested through 2.5; we recommend 2.4 or higher
        for multithreading support)

src/cmake/modules/FindFFmpeg.cmake

@@ -68,12 +68,14 @@ if (FFMPEG_INCLUDES)
   string (REGEX MATCHALL "[0-9]+[.0-9]+" LIBAVCODEC_VERSION_MAJOR "${TMP}")
   file(STRINGS "${FFMPEG_INCLUDES}/libavcodec/version.h" TMP
        REGEX "^#define LIBAVCODEC_VERSION_MINOR .*$")
-  string (REGEX MATCHALL "[0-9]+[.0-9]+" LIBAVCODEC_VERSION_MINOR "${TMP}")
+  string (REGEX MATCHALL "[0-9]+[.]?[0-9]*" LIBAVCODEC_VERSION_MINOR "${TMP}")
   file(STRINGS "${FFMPEG_INCLUDES}/libavcodec/version.h" TMP
        REGEX "^#define LIBAVCODEC_VERSION_MICRO .*$")
   string (REGEX MATCHALL "[0-9]+[.0-9]+" LIBAVCODEC_VERSION_MICRO "${TMP}")
   set (LIBAVCODEC_VERSION "${LIBAVCODEC_VERSION_MAJOR}.${LIBAVCODEC_VERSION_MINOR}.${LIBAVCODEC_VERSION_MICRO}")
-  if (LIBAVCODEC_VERSION VERSION_GREATER_EQUAL 59.37.100)
+  if (LIBAVCODEC_VERSION VERSION_GREATER_EQUAL 60.3.100)
+      set (FFMPEG_VERSION 6.0)
+  elseif (LIBAVCODEC_VERSION VERSION_GREATER_EQUAL 59.37.100)
       set (FFMPEG_VERSION 5.1)
   elseif (LIBAVCODEC_VERSION VERSION_GREATER_EQUAL 59.18.100)
       set (FFMPEG_VERSION 5.0)