From 29ca1c1a789ad26fe5b768a3d3daa258ba1112bc Mon Sep 17 00:00:00 2001
From: jopejoe1 <jopejoe1@missing.ninja>
Date: Tue, 4 Feb 2025 21:24:03 +0100
Subject: [PATCH 1/2] lcevcdec: fix to make it work when avx is not supported

---
 pkgs/by-name/lc/lcevcdec/package.nix | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/pkgs/by-name/lc/lcevcdec/package.nix b/pkgs/by-name/lc/lcevcdec/package.nix
index 201d76afd5bc..e27c62ca9358 100644
--- a/pkgs/by-name/lc/lcevcdec/package.nix
+++ b/pkgs/by-name/lc/lcevcdec/package.nix
@@ -42,16 +42,26 @@ stdenv.mkDerivation (finalAttrs: {
     })
   ];
 
-  postPatch = ''
-    substituteInPlace cmake/tools/version_files.py \
-      --replace-fail "args.git_version" '"${finalAttrs.version}"' \
-      --replace-fail "args.git_hash" '"${finalAttrs.src.rev}"' \
-      --replace-fail "args.git_date" '"1970-01-01"'
-  '';
+  postPatch =
+    ''
+      substituteInPlace cmake/tools/version_files.py \
+        --replace-fail "args.git_version" '"${finalAttrs.version}"' \
+        --replace-fail "args.git_hash" '"${finalAttrs.src.rev}"' \
+        --replace-fail "args.git_date" '"1970-01-01"'
+
+    ''
+    + lib.optionalString (!stdenv.hostPlatform.avxSupport) ''
+      substituteInPlace cmake/modules/Compiler/GNU.cmake \
+        --replace-fail "-mavx" ""
+
+       substituteInPlace src/core/decoder/src/common/simd.c \
+        --replace-fail "((_xgetbv(kControlRegister) & kOSXSaveMask) == kOSXSaveMask)" "false"
+    '';
 
   env = {
     includedir = "${placeholder "dev"}/include";
     libdir = "${placeholder "out"}/lib";
+    NIX_CFLAGS_COMPILE = "-Wno-error=unused-variable";
   };
 
   pkgconfigItems = [
@@ -95,6 +105,9 @@ stdenv.mkDerivation (finalAttrs: {
     (lib.cmakeFeature "VN_SDK_FFMPEG_LIBS_PACKAGE" "")
     (lib.cmakeBool "VN_SDK_UNIT_TESTS" false)
     (lib.cmakeBool "VN_SDK_SAMPLE_SOURCE" false)
+    (lib.cmakeBool "VN_CORE_AVX2" stdenv.hostPlatform.avx2Support)
+    # Requires avx for checking on runtime
+    (lib.cmakeBool "VN_CORE_SSE" stdenv.hostPlatform.avxSupport)
   ];
 
   passthru = {

From 2959d7514d037433996c2bceab52c7cda67dd8d3 Mon Sep 17 00:00:00 2001
From: jopejoe1 <jopejoe1@missing.ninja>
Date: Tue, 4 Feb 2025 21:26:21 +0100
Subject: [PATCH 2/2] ffmpeg-full: renable lcevcdec support

---
 pkgs/development/libraries/ffmpeg/generic.nix | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pkgs/development/libraries/ffmpeg/generic.nix b/pkgs/development/libraries/ffmpeg/generic.nix
index 650db88130ad..c0bc22ffeec0 100644
--- a/pkgs/development/libraries/ffmpeg/generic.nix
+++ b/pkgs/development/libraries/ffmpeg/generic.nix
@@ -90,7 +90,7 @@
   withKvazaar ? withFullDeps, # HEVC encoding
   withLadspa ? withFullDeps, # LADSPA audio filtering
   withLc3 ? withFullDeps && lib.versionAtLeast version "7.1", # LC3 de/encoding
-  withLcevcdec ? false && lib.versionAtLeast version "7.1", # LCEVC decoding # FIXME currently makes ffmpeg crash in any operation on non-AVX CPUs
+  withLcevcdec ? withFullDeps && lib.versionAtLeast version "7.1", # LCEVC decoding
   withLcms2 ? withFullDeps, # ICC profile support via lcms2
   withLzma ? withHeadlessDeps, # xz-utils
   withMetal ? false, # Unfree and requires manual downloading of files