diff --git a/conv/bidx_video.cc b/conv/bidx_video.cc
index 03e0c43..493b2b1 100644
--- a/conv/bidx_video.cc
+++ b/conv/bidx_video.cc
@@ -37,6 +37,10 @@ ValueFlag<int32_t> utime {
   parser, "10", "duration of each feature (frame)", {"utime"}, 10,
 };
 
+Flag uvfix {
+  parser, "uvfix", "fix UV values in feature", {"uvfix"},
+};
+
 Positional<std::string> dst {
   parser, "path", "destination video file path",
 };
@@ -51,8 +55,7 @@ std::vector<std::vector<int32_t>> indices;
 
 
 // util
-static std::vector<std::vector<int32_t>> ReadIndices(
-    std::istream&) noexcept;
+static std::vector<std::vector<int32_t>> ReadIndices(std::istream&) noexcept;
 
 static void Embed(int32_t t, Frame& dst, const Frame& base) {
   const auto bw  = args::get(param::bw);
@@ -76,11 +79,13 @@ static void Embed(int32_t t, Frame& dst, const Frame& base) {
       }
     }
 
-    for (int32_t y = 0; y < hbh; ++y) {
-      for (int32_t x = 0; x < hbw; ++x) {
-        const auto off = (by*hbh+y)*base.hw + (bx*hbw+x);
-        dst.U[off] = base.U[off];
-        dst.V[off] = base.V[off];
+    if (param::uvfix) {
+      for (int32_t y = 0; y < hbh; ++y) {
+        for (int32_t x = 0; x < hbw; ++x) {
+          const auto off = (by*hbh+y)*base.hw + (bx*hbw+x);
+          dst.U[off] = base.U[off];
+          dst.V[off] = base.V[off];
+        }
       }
     }
   }