diff --git a/src/video/ffmpeg.rs b/src/video/ffmpeg.rs
index 0a340d5..ddb35d5 100644
--- a/src/video/ffmpeg.rs
+++ b/src/video/ffmpeg.rs
@@ -263,7 +263,8 @@ pub async fn generate_preview_clip(input_file: &str, output_file: &str) -> Resul
 
     if duration < 1.0 {
         // Very short video (<1s): transcode the whole thing to 480p MP4
-        cmd.args(["-vf", "scale=-2:480"]);
+        // format=yuv420p ensures 10-bit sources are converted to 8-bit for h264_nvenc
+        cmd.args(["-vf", "scale=-2:480,format=yuv420p"]);
     } else {
         let segment_count = if duration < 10.0 {
             duration.floor() as u32
@@ -272,8 +273,9 @@ pub async fn generate_preview_clip(input_file: &str, output_file: &str) -> Resul
         };
         let interval = duration / segment_count as f64;
 
+        // format=yuv420p ensures 10-bit sources are converted to 8-bit for h264_nvenc
         let vf = format!(
-            "select='lt(mod(t,{:.4}),1)',setpts=N/FRAME_RATE/TB,fps=30,scale=-2:480",
+            "select='lt(mod(t,{:.4}),1)',setpts=N/FRAME_RATE/TB,fps=30,scale=-2:480,format=yuv420p",
             interval
         );
         let af = format!(