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}]`,
+  ];
+}

lib/ffmpeg/encode.ts

@@ -0,0 +1,286 @@
+import { spawn } from "child_process";
+import fs from "fs/promises";
+import path from "path";
+import ffmpegStatic from "ffmpeg-static";
+import { getVideoAttributionText } from "../branding";
+import { getResolution } from "../constants";
+import {
+  isCuratedFontKey,
+  sanitizeFontfileForFilter,
+} from "../fonts";
+import { resolveCuratedFontPath } from "../fonts-server";
+import {
+  buildArtTrackFilterComplex,
+  type LayoutSettings,
+} from "../layout";
+import {
+  WATERMARK_WIDTH_FRACTION,
+  watermarkFontSizeForWidth,
+} from "../preview-typography";
+import { getWatermarkPath } from "../storage";
+import {
+  buildDrawtextFilter,
+  normalizeWatermarkSettings,
+  overlayXy,
+  sanitizeDrawtext,
+  type WatermarkSettings,
+} from "../watermark";
+import { buildBrandWatermarkOverlayFilters } from "./brand-watermark";
+
+function getFfmpegPath(): string {
+  if (process.env.FFMPEG_PATH) return process.env.FFMPEG_PATH;
+  if (ffmpegStatic) return ffmpegStatic;
+  return "ffmpeg";
+}
+
+export { getFfmpegPath };
+
+async function fileExists(p: string): Promise<boolean> {
+  try {
+    await fs.access(p);
+    return true;
+  } catch {
+    return false;
+  }
+}
+
+/** Verify PNG magic bytes (prevents MIME spoof → FFmpeg surprises). */
+export async function assertPngFile(filePath: string): Promise<void> {
+  const fh = await fs.open(filePath, "r");
+  try {
+    const buf = Buffer.alloc(8);
+    await fh.read(buf, 0, 8, 0);
+    const sig = Buffer.from([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a]);
+    if (!buf.equals(sig)) {
+      throw new Error("Logo must be a valid PNG file");
+    }
+  } finally {
+    await fh.close();
+  }
+}
+
+async function resolveFontfileEscaped(
+  settings: WatermarkSettings,
+): Promise<string | null> {
+  const key = settings.fontKey ?? "system";
+  if (key === "system") return null;
+
+  if (key === "custom") {
+    if (!settings.fontPath) return null;
+    if (!(await fileExists(settings.fontPath))) {
+      throw new Error("Custom watermark font file not found");
+    }
+    return sanitizeFontfileForFilter(path.resolve(settings.fontPath));
+  }
+
+  if (isCuratedFontKey(key)) {
+    const fontPath = resolveCuratedFontPath(key);
+    if (!(await fileExists(fontPath))) {
+      console.warn(`[ffmpeg] curated font missing: ${key} at ${fontPath}; using system font`);
+      return null;
+    }
+    return sanitizeFontfileForFilter(fontPath);
+  }
+
+  return null;
+}
+
+function classicScaleFilter(width: number, height: number): string {
+  return `scale=${width}:${height}:force_original_aspect_ratio=decrease,pad=${width}:${height}:(ow-iw)/2:(oh-ih)/2:black`;
+}
+
+/**
+ * Art-track filter that ends at `outLabel` instead of hardcoded [laid].
+ */
+function artTrackFilterEndingAt(
+  opts: Parameters<typeof buildArtTrackFilterComplex>[0],
+  outLabel: string,
+): string {
+  return buildArtTrackFilterComplex(opts).replace(/\[laid\]$/, `[${outLabel}]`);
+}
+
+export async function encodeVideo(options: {
+  imagePath: string;
+  audioPath: string;
+  outputPath: string;
+  resolution: string;
+  includeWatermark: boolean;
+  watermark?: Partial<WatermarkSettings> | null;
+  layout?: LayoutSettings | null;
+  /** On-video song title (art-track layouts). */
+  songTitle?: string;
+  artist?: string | null;
+}): Promise<void> {
+  const res = getResolution(options.resolution);
+  if (!res) throw new Error(`Invalid resolution: ${options.resolution}`);
+
+  await fs.mkdir(path.dirname(options.outputPath), { recursive: true });
+
+  const settings = normalizeWatermarkSettings(options.watermark, options.includeWatermark);
+  const layout = options.layout?.template ? options.layout : null;
+  const watermarkWidth = Math.max(1, Math.round(res.width * WATERMARK_WIDTH_FRACTION));
+  const fontSize = watermarkFontSizeForWidth(res.width);
+  const fontfile = await resolveFontfileEscaped(settings);
+
+  const args = ["-y", "-loop", "1", "-r", "1", "-i", options.imagePath, "-i", options.audioPath];
+
+  let nextInput = 2;
+  let logoInputIndex: number | null = null;
+  let defaultWmInputIndex: number | null = null;
+
+  const needsLogo = settings.mode === "logo" && Boolean(settings.logoPath);
+  const defaultPath = getWatermarkPath();
+  const useDefaultPng =
+    settings.mode === "default" && (await fileExists(defaultPath));
+
+  if (needsLogo && settings.logoPath) {
+    if (!(await fileExists(settings.logoPath))) {
+      throw new Error("Watermark logo file not found");
+    }
+    await assertPngFile(settings.logoPath);
+    args.push("-i", settings.logoPath);
+    logoInputIndex = nextInput++;
+  } else if (useDefaultPng) {
+    args.push("-i", defaultPath);
+    defaultWmInputIndex = nextInput++;
+  }
+
+  const applyWm =
+    settings.mode === "logo" && logoInputIndex !== null
+      ? ("logo" as const)
+      : settings.mode === "text" && settings.text?.trim()
+        ? ("text" as const)
+        : settings.mode === "default" && defaultWmInputIndex !== null
+          ? ("default-png" as const)
+          : settings.mode === "default"
+            ? ("default-text" as const)
+            : ("none" as const);
+
+  // Fast path: classic letterbox, no watermark
+  if (!layout && applyWm === "none") {
+    args.push("-vf", classicScaleFilter(res.width, res.height));
+    args.push(
+      "-c:v",
+      "libx264",
+      "-tune",
+      "stillimage",
+      "-c:a",
+      "copy",
+      "-shortest",
+      "-pix_fmt",
+      "yuv420p",
+      options.outputPath,
+    );
+    await runFfmpeg(args);
+    return;
+  }
+
+  const outDirect = applyWm === "none";
+  const baseLabel = outDirect ? "vout" : "base";
+  const filterParts: string[] = [];
+
+  if (layout) {
+    const titleEscaped = sanitizeDrawtext(options.songTitle?.trim() || "Untitled");
+    const artistRaw = options.artist?.trim();
+    const artistEscaped = artistRaw ? sanitizeDrawtext(artistRaw) : null;
+    filterParts.push(
+      artTrackFilterEndingAt(
+        {
+          width: res.width,
+          height: res.height,
+          layout,
+          titleEscaped,
+          artistEscaped,
+          fontfileEscaped: fontfile,
+        },
+        baseLabel,
+      ),
+    );
+  } else {
+    filterParts.push(`[0:v]${classicScaleFilter(res.width, res.height)}[${baseLabel}]`);
+  }
+
+  if (applyWm === "logo" && logoInputIndex !== null) {
+    const { x, y } = overlayXy(settings.position, settings.offsetX, settings.offsetY);
+    filterParts.push(
+      `[${logoInputIndex}:v]scale=${watermarkWidth}:-1[wm]`,
+      `[${baseLabel}][wm]overlay=${x}:${y}[vout]`,
+    );
+  } else if (applyWm === "text") {
+    const draw = buildDrawtextFilter({
+      text: settings.text!.trim(),
+      fontSize,
+      fontColor: "white@0.9",
+      position: settings.position,
+      offsetX: settings.offsetX,
+      offsetY: settings.offsetY,
+      fontfileEscaped: fontfile,
+    });
+    filterParts.push(`[${baseLabel}]${draw}[vout]`);
+  } else if (applyWm === "default-png" && defaultWmInputIndex !== null) {
+    filterParts.push(
+      ...buildBrandWatermarkOverlayFilters({
+        baseLabel,
+        watermarkInputIndex: defaultWmInputIndex,
+        watermarkWidthPx: watermarkWidth,
+        offsetX: settings.offsetX,
+        offsetY: settings.offsetY,
+      }),
+    );
+  } else if (applyWm === "default-text") {
+    const draw = buildDrawtextFilter({
+      text: getVideoAttributionText(),
+      fontSize,
+      fontColor: "white@0.85",
+      position: settings.position,
+      offsetX: settings.offsetX,
+      offsetY: settings.offsetY,
+      fontfileEscaped: null,
+    });
+    filterParts.push(`[${baseLabel}]${draw}[vout]`);
+  }
+
+  args.push("-filter_complex", filterParts.join(";"), "-map", "[vout]", "-map", "1:a");
+  args.push(
+    "-c:v",
+    "libx264",
+    "-tune",
+    "stillimage",
+    "-c:a",
+    "copy",
+    "-shortest",
+    "-pix_fmt",
+    "yuv420p",
+    options.outputPath,
+  );
+
+  await runFfmpeg(args);
+}
+
+function runFfmpeg(args: string[]): Promise<void> {
+  return new Promise((resolve, reject) => {
+    const proc = spawn(getFfmpegPath(), args, { stdio: ["ignore", "pipe", "pipe"] });
+    let stderr = "";
+    proc.stderr.on("data", (chunk) => {
+      stderr += chunk.toString();
+      if (stderr.length > 64_000) stderr = stderr.slice(-32_000);
+    });
+    proc.on("close", (code) => {
+      if (code === 0) resolve();
+      else reject(new Error(`FFmpeg failed (code ${code}): ${stderr.slice(-500)}`));
+    });
+    proc.on("error", (err) => {
+      reject(new Error(`FFmpeg not found or failed to start: ${err.message}`));
+    });
+  });
+}
+
+export async function cleanupFiles(paths: string[]) {
+  for (const p of paths) {
+    try {
+      await fs.unlink(p);
+    } catch {
+      // ignore missing files
+    }
+  }
+}