decoder/ffmpeg: require FFmpeg 4.0 or later

src/lib/ffmpeg/IOContext.hxx

@@ -59,13 +59,8 @@ public:
 	}
 
 	size_t Read(void *buffer, size_t size) {
-#if LIBAVFORMAT_VERSION_INT >= AV_VERSION_INT(57, 81, 100)
 		int result = avio_read_partial(io_context,
 					       (unsigned char *)buffer, size);
-#else
-		int result = avio_read(io_context,
-				       (unsigned char *)buffer, size);
-#endif
 		if (result < 0)
 			throw MakeFfmpegError(result, "avio_read() failed");
 

src/lib/ffmpeg/Init.cxx

@@ -8,16 +8,11 @@
 #include "LogCallback.hxx"
 
 extern "C" {
-#include <libavformat/avformat.h>
+#include <libavutil/log.h>
 }
 
 void
 FfmpegInit()
 {
 	av_log_set_callback(FfmpegLogCallback);
-
-#if LIBAVFORMAT_VERSION_INT < AV_VERSION_INT(58, 9, 100)
-	/* deprecated as of FFmpeg 4.0 */
-	av_register_all();
-#endif
 }

src/lib/ffmpeg/meson.build

@@ -1,6 +1,6 @@
-libavformat_dep = dependency('libavformat', version: '>= 57.40', required: get_option('ffmpeg'))
-libavcodec_dep = dependency('libavcodec', version: '>= 57.48', required: get_option('ffmpeg'))
-libavutil_dep = dependency('libavutil', version: '>= 55.27', required: get_option('ffmpeg'))
+libavformat_dep = dependency('libavformat', version: '>= 58.12', required: get_option('ffmpeg'))
+libavcodec_dep = dependency('libavcodec', version: '>= 58.18', required: get_option('ffmpeg'))
+libavutil_dep = dependency('libavutil', version: '>= 56.14', required: get_option('ffmpeg'))
 conf.set('HAVE_LIBAVUTIL', libavutil_dep.found())
 
 enable_ffmpeg = libavformat_dep.found() and libavcodec_dep.found() and libavutil_dep.found()