From https://gitlab.kitware.com/ben.boeckel/vtk/-/commit/bad8f3e9d0aad03e8f2aff9524cb3c5f2d10ccaf
From: Ben Boeckel <ben.boeckel@kitware.com>
Date: Fri, 28 Jan 2022 10:44:28 -0500
Subject: [PATCH] IO/FFMPEG: support FFmpeg 5.0 API changes

Fixes: #18445
--- /dev/null
+++ b/Documentation/release/dev/ffmpeg-5.0.md
@@ -0,0 +1,3 @@
+## FFmpeg 5.0 support
+
+FFmpeg 5.0 API changes are now supported.
--- a/IO/FFMPEG/CMakeLists.txt
+++ b/IO/FFMPEG/CMakeLists.txt
@@ -6,7 +6,9 @@ vtk_module_find_package(
     avformat
     avcodec
     avutil
-    swscale)
+    swscale
+  OPTIONAL_COMPONENTS
+    swresample)
 
 set(classes
   vtkFFMPEGWriter)
@@ -21,6 +23,17 @@ if (NOT FFMPEG_VERSION VERSION_LESS "3.1")
     vtkFFMPEGVideoSource)
 endif ()
 
+set(ffmpeg_libraries)
+if (NOT FFMPEG_VERSION VERSION_LESS "5.0")
+  if (NOT FFMPEG_swresample_FOUND)
+    message(FATAL_ERROR
+      "FFMPEG 5.0 requires the `swresample` library.")
+  endif ()
+
+  list(APPEND ffmpeg_libraries
+    FFMPEG::swresample)
+endif ()
+
 vtk_module_add_module(VTK::IOFFMPEG
   CLASSES ${classes})
 vtk_module_link(VTK::IOFFMPEG
@@ -28,4 +41,5 @@ vtk_module_link(VTK::IOFFMPEG
     FFMPEG::avformat
     FFMPEG::avcodec
     FFMPEG::avutil
-    FFMPEG::swscale)
+    FFMPEG::swscale
+    ${ffmpeg_libraries})
--- a/IO/FFMPEG/vtkFFMPEGVideoSource.cxx
+++ b/IO/FFMPEG/vtkFFMPEGVideoSource.cxx
@@ -205,7 +205,7 @@ void vtkFFMPEGVideoSource::Initialize()
 
   this->Internal->VideoStream = fcontext->streams[this->Internal->VideoStreamIndex];
 
-  AVCodec* dec = avcodec_find_decoder(this->Internal->VideoStream->codecpar->codec_id);
+  const AVCodec* dec = avcodec_find_decoder(this->Internal->VideoStream->codecpar->codec_id);
   if (!dec)
   {
     vtkErrorMacro("Failed to find codec for video");
@@ -271,7 +271,7 @@ void vtkFFMPEGVideoSource::Initialize()
   {
     this->Internal->AudioStream = fcontext->streams[this->Internal->AudioStreamIndex];
 
-    AVCodec* adec = avcodec_find_decoder(this->Internal->AudioStream->codecpar->codec_id);
+    const AVCodec* adec = avcodec_find_decoder(this->Internal->AudioStream->codecpar->codec_id);
     if (!adec)
     {
       vtkErrorMacro("Failed to find codec for audio");
--- a/IO/FFMPEG/vtkFFMPEGWriter.cxx
+++ b/IO/FFMPEG/vtkFFMPEGWriter.cxx
@@ -21,10 +21,17 @@
 
 extern "C"
 {
+#include <libavcodec/avcodec.h>
 #include <libavformat/avformat.h>
 #include <libswscale/swscale.h>
 }
 
+#if LIBAVFORMAT_VERSION_MAJOR < 59
+#define vtk_ff_const59
+#else
+#define vtk_ff_const59 const
+#endif
+
 #if defined(LIBAVFORMAT_VERSION_MAJOR) && LIBAVFORMAT_VERSION_MAJOR >= 57
 extern "C"
 {
@@ -51,7 +58,7 @@ private:
 
   AVFormatContext* avFormatContext;
 
-  AVOutputFormat* avOutputFormat;
+  vtk_ff_const59 AVOutputFormat* avOutputFormat;
 
   AVStream* avStream;
 
@@ -115,15 +122,9 @@ int vtkFFMPEGWriterInternal::Start()
     return 0;
   }
 
-  if (this->Writer->GetCompression())
-  {
-    // choose a codec that is easily playable on windows
-    this->avOutputFormat->video_codec = AV_CODEC_ID_MJPEG;
-  }
-  else
-  {
-    this->avOutputFormat->video_codec = AV_CODEC_ID_RAWVIDEO;
-  }
+  enum AVCodecID video_codec = this->Writer->GetCompression()
+    ? AV_CODEC_ID_MJPEG // choose a codec that is easily playable on windows
+    : AV_CODEC_ID_RAWVIDEO;
 
   // create the format context that wraps all of the media output structures
   if (avformat_alloc_output_context2(
@@ -133,8 +134,8 @@ int vtkFFMPEGWriterInternal::Start()
     return 0;
   }
 
-  AVCodec* codec;
-  if (!(codec = avcodec_find_encoder(this->avOutputFormat->video_codec)))
+  vtk_ff_const59 AVCodec* codec;
+  if (!(codec = avcodec_find_encoder(video_codec)))
   {
     vtkGenericWarningMacro(<< "Failed to get video codec.");
     return 0;
@@ -155,7 +156,7 @@ int vtkFFMPEGWriterInternal::Start()
     return 0;
   }
 
-  this->avStream->codecpar->codec_id = static_cast<AVCodecID>(this->avOutputFormat->video_codec);
+  this->avStream->codecpar->codec_id = video_codec;
   this->avStream->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
   this->avStream->codecpar->width = this->Dim[0];
   this->avStream->codecpar->height = this->Dim[1];
-- 
2.35.1