https://github.com/scp-fs2open/fs2open.github.com/pull/6948/commits/af833f059cc0cfc925792e019f6c2b754c6d53c1

Index: code/sound/ffmpeg/FFmpegWaveFile.cpp
--- code/sound/ffmpeg/FFmpegWaveFile.cpp.orig
+++ code/sound/ffmpeg/FFmpegWaveFile.cpp
@@ -151,9 +151,10 @@ FFmpegWaveFile::~FFmpegWaveFile()
 	av_frame_free(&m_decodeFrame);
 
 	if (m_audioCodecCtx) {
-		avcodec_close(m_audioCodecCtx);
 #if LIBAVCODEC_VERSION_INT > AV_VERSION_INT(57, 24, 255)
 		avcodec_free_context(&m_audioCodecCtx);
+#else
+		avcodec_close(m_audioCodecCtx);
 #endif
 		m_audioCodecCtx = nullptr;
 	}
