Initial OSS scaffold from Songs2VID (pre-strip)

lib/ffmpeg/brand-watermark.ts

@@ -0,0 +1,20 @@
+/**
+ * Modular FFmpeg filter fragments for the Songs2VID brand watermark overlay.
+ * Always bottom-right with padding; scales to a fraction of frame width.
+ */
+export function buildBrandWatermarkOverlayFilters(options: {
+  baseLabel: string;
+  watermarkInputIndex: number;
+  watermarkWidthPx: number;
+  offsetX?: number;
+  offsetY?: number;
+  outLabel?: string;
+}): string[] {
+  const ox = options.offsetX ?? 20;
+  const oy = options.offsetY ?? 20;
+  const out = options.outLabel ?? "vout";
+  return [
+    `[${options.watermarkInputIndex}:v]scale=${options.watermarkWidthPx}:-1[wm]`,
+    `[${options.baseLabel}][wm]overlay=W-w-${ox}:H-h-${oy}[${out}]`,
+  ];
+}