Commit 89972c7c for libheif

commit 89972c7c2221ee22c62b5ebfd5f33a29325057b4
Author: Dirk Farin <dirk.farin@gmail.com>
Date:   Sun Dec 14 11:30:34 2025 +0100

    [BSD3] vvenc: fix encoding of monochrome input (e.g. alpha planes)

diff --git a/libheif/plugins/encoder_vvenc.cc b/libheif/plugins/encoder_vvenc.cc
index 46fe9bfc..cd1d4e2c 100644
--- a/libheif/plugins/encoder_vvenc.cc
+++ b/libheif/plugins/encoder_vvenc.cc
@@ -476,6 +476,11 @@ static heif_error vvenc_start_sequence_encoding_intern(void* encoder_raw, const
   params.m_internalBitDepth[0] = bit_depth;
   params.m_internalBitDepth[1] = bit_depth;

+  bool isGreyscale = (heif_image_get_colorspace(image) == heif_colorspace_monochrome);
+  if (isGreyscale) {
+    params.m_internChromaFormat = VVENC_CHROMA_400;
+  }
+
   if (image_sequence) {
     if (options->keyframe_distance_max) {
       params.m_IntraPeriod = options->keyframe_distance_max;