fix: allow synthetic grid frames through UVC guard

Cargo.lock

@@ -1658,7 +1658,7 @@ checksum = "09edd9e8b54e49e587e4f6295a7d29c3ea94d469cb40ab8ca70b288248a81db2"
 
 [[package]]
 name = "lesavka_client"
-version = "0.25.1"
+version = "0.25.2"
 dependencies = [
  "anyhow",
  "async-stream",
@@ -1692,7 +1692,7 @@ dependencies = [
 
 [[package]]
 name = "lesavka_common"
-version = "0.25.1"
+version = "0.25.2"
 dependencies = [
  "anyhow",
  "base64",
@@ -1704,7 +1704,7 @@ dependencies = [
 
 [[package]]
 name = "lesavka_server"
-version = "0.25.1"
+version = "0.25.2"
 dependencies = [
  "anyhow",
  "base64",

client/Cargo.toml

@@ -4,7 +4,7 @@ path                    = "src/main.rs"
 
 [package]
 name                    = "lesavka_client"
-version                 = "0.25.1"
+version                 = "0.25.2"
 edition                 = "2024"
 
 [dependencies]

common/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name                    = "lesavka_common"
-version                 = "0.25.1"
+version                 = "0.25.2"
 edition                 = "2024"
 build                   = "build.rs"
 

server/Cargo.toml

@@ -16,7 +16,7 @@ bench                   = false
 
 [package]
 name                    = "lesavka_server"
-version                 = "0.25.1"
+version                 = "0.25.2"
 edition                 = "2024"
 autobins                = false
 

server/src/video_sinks/hevc_mjpeg_guard/mjpeg_visual_guard.rs

@@ -339,6 +339,9 @@ fn seam_reason(frame: &SampledFrame) -> Option<MjpegVisualArtifactReason> {
     let mut best_luma: Option<(usize, usize, u16)> = None;
     let mut best_partial: Option<(usize, usize, usize, u16)> = None;
     let mut best_chroma: Option<(usize, usize, u16)> = None;
+    let mut luma_candidate_rows = Vec::new();
+    let mut partial_candidate_rows = Vec::new();
+    let mut chroma_candidate_rows = Vec::new();
 
     for row in row_bounds(frame).skip(1) {
         let prev_start = (row - 1) * frame.width;
@@ -385,6 +388,7 @@ fn seam_reason(frame: &SampledFrame) -> Option<MjpegVisualArtifactReason> {
         let chroma_avg = (chroma_total / frame.width.max(1) as u32) as u16;
 
         if luma_coverage >= luma_coverage_threshold && luma_avg >= luma_threshold as u16 {
+            luma_candidate_rows.push(row);
             match best_luma {
                 Some((_, best_coverage, best_avg))
                     if best_coverage > luma_coverage
@@ -397,6 +401,7 @@ fn seam_reason(frame: &SampledFrame) -> Option<MjpegVisualArtifactReason> {
             && partial_luma_run_pct >= partial_run_threshold
             && partial_luma_avg >= partial_luma_threshold as u16
         {
+            partial_candidate_rows.push(row);
             match best_partial {
                 Some((_, best_coverage, best_run, best_avg))
                     if best_coverage > partial_luma_coverage
@@ -415,6 +420,7 @@ fn seam_reason(frame: &SampledFrame) -> Option<MjpegVisualArtifactReason> {
             }
         }
         if chroma_coverage >= chroma_coverage_threshold && chroma_avg >= chroma_threshold as u16 {
+            chroma_candidate_rows.push(row);
             match best_chroma {
                 Some((_, best_coverage, best_avg))
                     if best_coverage > chroma_coverage
@@ -425,6 +431,9 @@ fn seam_reason(frame: &SampledFrame) -> Option<MjpegVisualArtifactReason> {
     }
 
     if let Some((row, coverage, delta)) = best_chroma {
+        if regular_texture_seam_rows(frame, &chroma_candidate_rows) {
+            return None;
+        }
         return Some(MjpegVisualArtifactReason::ChromaTileSeam {
             row_pct: pct(row, frame.height),
             coverage_pct: coverage.min(100) as u8,
@@ -432,6 +441,9 @@ fn seam_reason(frame: &SampledFrame) -> Option<MjpegVisualArtifactReason> {
         });
     }
     if let Some((row, coverage, run_pct, delta)) = best_partial {
+        if regular_texture_seam_rows(frame, &partial_candidate_rows) {
+            return None;
+        }
         return Some(MjpegVisualArtifactReason::PartialTileSeam {
             row_pct: pct(row, frame.height),
             coverage_pct: coverage.min(100) as u8,
@@ -439,6 +451,9 @@ fn seam_reason(frame: &SampledFrame) -> Option<MjpegVisualArtifactReason> {
             delta,
         });
     }
+    if regular_texture_seam_rows(frame, &luma_candidate_rows) {
+        return None;
+    }
     best_luma.map(|(row, coverage, delta)| MjpegVisualArtifactReason::HorizontalTileSeam {
         row_pct: pct(row, frame.height),
         coverage_pct: coverage.min(100) as u8,
@@ -446,6 +461,52 @@ fn seam_reason(frame: &SampledFrame) -> Option<MjpegVisualArtifactReason> {
     })
 }
 
+fn regular_texture_seam_rows(frame: &SampledFrame, rows: &[usize]) -> bool {
+    // Synthetic calibration grids create many evenly spaced hard edges; unlike a
+    // tear, they are regular across the guard window rather than isolated.
+    if rows.len() < 6 {
+        return false;
+    }
+    let mut unique_rows = rows.to_vec();
+    unique_rows.sort_unstable();
+    unique_rows.dedup();
+    if unique_rows.len() < 6 {
+        return false;
+    }
+
+    let bounds = row_bounds(frame);
+    let row_span = unique_rows
+        .last()
+        .copied()
+        .unwrap_or(0)
+        .saturating_sub(unique_rows[0]);
+    let guard_span = bounds.end.saturating_sub(bounds.start).max(1);
+    if row_span.saturating_mul(100) < guard_span.saturating_mul(30) {
+        return false;
+    }
+
+    let mut gaps: Vec<usize> = unique_rows
+        .windows(2)
+        .map(|pair| pair[1].saturating_sub(pair[0]))
+        .filter(|gap| *gap > 0)
+        .collect();
+    if gaps.len() < 5 {
+        return false;
+    }
+    gaps.sort_unstable();
+    let median_gap = gaps[gaps.len() / 2];
+    if median_gap == 0 || median_gap > frame.height.saturating_div(8).max(2) {
+        return false;
+    }
+
+    let tolerance = median_gap.saturating_div(3).max(1);
+    let consistent_gaps = gaps
+        .iter()
+        .filter(|gap| gap.abs_diff(median_gap) <= tolerance)
+        .count();
+    consistent_gaps.saturating_mul(100) >= gaps.len().saturating_mul(70)
+}
+
 fn inspect_sampled_frame_for_artifacts(frame: &SampledFrame) -> Option<MjpegVisualArtifactReason> {
     flat_block_reason(frame).or_else(|| seam_reason(frame))
 }

server/src/video_sinks/hevc_mjpeg_guard/tests.rs

@@ -206,6 +206,20 @@ fn smooth_rgb_frame(width: usize, height: usize) -> Vec<u8> {
     pixels
 }
 
+fn checker_grid_rgb_frame(width: usize, height: usize) -> Vec<u8> {
+    let mut pixels = Vec::with_capacity(width * height * 3);
+    for y in 0..height {
+        for x in 0..width {
+            let block = ((x / 16) + (y / 16)) % 2;
+            let base = if block == 0 { 42 } else { 214 };
+            pixels.push((base + (x % 17)) as u8);
+            pixels.push((base + (y % 19)) as u8);
+            pixels.push((base + ((x + y) % 13)) as u8);
+        }
+    }
+    pixels
+}
+
 #[test]
 fn pixel_guard_accepts_smooth_frames() {
     temp_env::with_vars(
@@ -220,6 +234,35 @@ fn pixel_guard_accepts_smooth_frames() {
     );
 }
 
+#[test]
+fn pixel_guard_accepts_regular_synthetic_checker_grids() {
+    temp_env::with_vars(
+        [
+            ("LESAVKA_UVC_MJPEG_PIXEL_GUARD", Some("1")),
+            ("LESAVKA_UVC_MJPEG_PIXEL_GUARD_SAMPLE_WIDTH", Some("160")),
+            (
+                "LESAVKA_UVC_MJPEG_PIXEL_GUARD_PARTIAL_SEAM_DELTA",
+                Some("28"),
+            ),
+            (
+                "LESAVKA_UVC_MJPEG_PIXEL_GUARD_PARTIAL_SEAM_COVERAGE_PCT",
+                Some("32"),
+            ),
+            (
+                "LESAVKA_UVC_MJPEG_PIXEL_GUARD_PARTIAL_SEAM_RUN_PCT",
+                Some("12"),
+            ),
+        ],
+        || {
+            let frame = checker_grid_rgb_frame(320, 180);
+            assert_eq!(
+                super::mjpeg_visual_guard::sampled_rgb_frame_for_test(320, 180, &frame),
+                None
+            );
+        },
+    );
+}
+
 #[test]
 fn pixel_guard_rejects_flat_lower_block_frames() {
     temp_env::with_vars(