fix(remotion): address PR #592 review feedback

lib/services/ffmpeg-compress.ts

@@ -0,0 +1,392 @@
+/**
+ * FFmpeg post-render compression for video pipeline.
+ *
+ * Downloads the rendered video from Remotion Lambda's S3 output,
+ * compresses it with FFmpeg, and returns the compressed buffer.
+ *
+ * Uses two-pass encoding for optimal quality/size ratio.
+ */
+
+import { execFileSync, execSync } from "child_process";
+import { writeFileSync, readFileSync, unlinkSync, mkdtempSync, rmSync } from "fs";
+import { join } from "path";
+import { tmpdir } from "os";
+
+// ---------------------------------------------------------------------------
+// Types
+// ---------------------------------------------------------------------------
+
+export interface CompressOptions {
+  /** Target bitrate for video (default: "2M" for 2 Mbps) */
+  videoBitrate?: string;
+  /** Audio bitrate (default: "128k") */
+  audioBitrate?: string;
+  /** CRF value for quality (default: 23, lower = better quality) */
+  crf?: number;
+  /** Preset (default: "medium", options: ultrafast … veryslow) */
+  preset?: string;
+  /** Max width — will scale down if larger, maintaining aspect ratio */
+  maxWidth?: number;
+  /** Max height — will scale down if larger, maintaining aspect ratio */
+  maxHeight?: number;
+}
+
+export interface CompressResult {
+  /** Compressed video as Buffer */
+  buffer: Buffer;
+  /** Original size in bytes */
+  originalSize: number;
+  /** Compressed size in bytes */
+  compressedSize: number;
+  /** Compression ratio (e.g., 0.6 means 60% of original) */
+  ratio: number;
+  /** Duration of compression in ms */
+  durationMs: number;
+}
+
+export interface VideoMetadata {
+  /** Duration in seconds */
+  duration: number;
+  /** Width in pixels */
+  width: number;
+  /** Height in pixels */
+  height: number;
+  /** Video codec (e.g. "h264") */
+  videoCodec: string;
+  /** Audio codec (e.g. "aac") */
+  audioCodec: string;
+  /** Overall bitrate in bits/s */
+  bitrate: number;
+  /** File size in bytes */
+  fileSize: number;
+}
+
+// ---------------------------------------------------------------------------
+// Helpers
+// ---------------------------------------------------------------------------
+
+const LOG_PREFIX = "[FFMPEG]";
+
+function log(...args: unknown[]) {
+  console.log(LOG_PREFIX, ...args);
+}
+
+function warn(...args: unknown[]) {
+  console.warn(LOG_PREFIX, ...args);
+}
+
+function isFfmpegAvailable(): boolean {
+  try {
+    execSync("ffmpeg -version", { stdio: "ignore" });
+    return true;
+  } catch {
+    return false;
+  }
+}
+
+function isFfprobeAvailable(): boolean {
+  try {
+    execSync("ffprobe -version", { stdio: "ignore" });
+    return true;
+  } catch {
+    return false;
+  }
+}
+
+/**
+ * Download a URL to a Buffer. Works in Node 18+ (global fetch).
+ */
+async function downloadUrl(url: string): Promise<Buffer> {
+  log("Downloading video from URL …");
+  const res = await fetch(url);
+  if (!res.ok) {
+    throw new Error(`${LOG_PREFIX} Failed to download video: ${res.status} ${res.statusText}`);
+  }
+  const arrayBuffer = await res.arrayBuffer();
+  return Buffer.from(arrayBuffer);
+}
+
+/**
+ * Create a temp directory and return helpers for managing temp files.
+ */
+function makeTempDir() {
+  const dir = mkdtempSync(join(tmpdir(), "ffmpeg-compress-"));
+  const inputPath = join(dir, "input.mp4");
+  const outputPath = join(dir, "output.mp4");
+  const passLogPrefix = join(dir, "ffmpeg2pass");
+
+  function cleanup() {
+    for (const f of [inputPath, outputPath]) {
+      try {
+        unlinkSync(f);
+      } catch {
+        /* ignore */
+      }
+    }
+    // Two-pass log files
+    for (const suffix of ["", "-0.log", "-0.log.mbtree"]) {
+      try {
+        unlinkSync(passLogPrefix + suffix);
+      } catch {
+        /* ignore */
+      }
+    }
+    try {
+      // Remove the temp directory itself
+      rmSync(dir, { recursive: true, force: true });
+    } catch {
+      /* ignore */
+    }
+  }
+
+  return { dir, inputPath, outputPath, passLogPrefix, cleanup };
+}
+
+// ---------------------------------------------------------------------------
+// Build FFmpeg arguments
+// ---------------------------------------------------------------------------
+
+function buildScaleFilter(opts: CompressOptions): string | null {
+  if (!opts.maxWidth && !opts.maxHeight) return null;
+
+  const w = opts.maxWidth ? `'min(${opts.maxWidth},iw)'` : "-2";
+  const h = opts.maxHeight ? `'min(${opts.maxHeight},ih)'` : "-2";
+
+  // Ensure dimensions are divisible by 2 for H.264
+  return `scale=${w}:${h}:force_original_aspect_ratio=decrease,pad=ceil(iw/2)*2:ceil(ih/2)*2`;
+}
+
+function buildFfmpegArgs(
+  inputPath: string,
+  outputPath: string,
+  opts: CompressOptions,
+  pass: 1 | 2 | "crf",
+  passLogPrefix?: string,
+): string[] {
+  const args: string[] = ["-y", "-i", inputPath];
+
+  // Video codec
+  args.push("-c:v", "libx264");
+
+  // Preset
+  args.push("-preset", opts.preset || "medium");
+
+  // Scale filter
+  const scaleFilter = buildScaleFilter(opts);
+  if (scaleFilter) {
+    args.push("-vf", scaleFilter);
+  }
+
+  if (pass === "crf") {
+    // Single-pass CRF mode
+    args.push("-crf", String(opts.crf ?? 23));
+    // Audio
+    args.push("-c:a", "aac", "-b:a", opts.audioBitrate || "128k");
+    // Faststart for web playback
+    args.push("-movflags", "+faststart");
+    args.push(outputPath);
+  } else if (pass === 1) {
+    // Two-pass: first pass
+    args.push("-b:v", opts.videoBitrate || "2M");
+    args.push("-pass", "1");
+    args.push("-passlogfile", passLogPrefix!);
+    args.push("-an"); // No audio in first pass
+    args.push("-f", "null");
+    args.push(process.platform === "win32" ? "NUL" : "/dev/null");
+  } else {
+    // Two-pass: second pass
+    args.push("-b:v", opts.videoBitrate || "2M");
+    args.push("-pass", "2");
+    args.push("-passlogfile", passLogPrefix!);
+    args.push("-c:a", "aac", "-b:a", opts.audioBitrate || "128k");
+    args.push("-movflags", "+faststart");
+    args.push(outputPath);
+  }
+
+  return args;
+}
+
+// ---------------------------------------------------------------------------
+// Main: compressVideo
+// ---------------------------------------------------------------------------
+
+/**
+ * Compress a video using FFmpeg.
+ *
+ * @param input - A video URL (string) or a Buffer containing the video data.
+ * @param options - Compression options.
+ * @returns CompressResult with the compressed buffer and stats.
+ */
+export async function compressVideo(
+  input: string | Buffer,
+  options: CompressOptions = {},
+): Promise<CompressResult> {
+  const startTime = Date.now();
+
+  // 1. Resolve input to a Buffer
+  let inputBuffer: Buffer;
+  if (typeof input === "string") {
+    inputBuffer = await downloadUrl(input);
+  } else {
+    inputBuffer = input;
+  }
+
+  const originalSize = inputBuffer.length;
+  log(`Original video size: ${(originalSize / 1024 / 1024).toFixed(2)} MB`);
+
+  // 2. Check FFmpeg availability
+  if (!isFfmpegAvailable()) {
+    warn("FFmpeg is not available — returning original video uncompressed.");
+    return {
+      buffer: inputBuffer,
+      originalSize,
+      compressedSize: originalSize,
+      ratio: 1,
+      durationMs: Date.now() - startTime,
+    };
+  }
+
+  // 3. Write input to temp file
+  const { inputPath, outputPath, passLogPrefix, cleanup } = makeTempDir();
+
+  try {
+    writeFileSync(inputPath, inputBuffer);
+
+    // 4. Decide encoding strategy
+    const useTwoPass = !!options.videoBitrate;
+
+    if (useTwoPass) {
+      log("Running two-pass encode …");
+
+      // Pass 1
+      const pass1Args = buildFfmpegArgs(inputPath, outputPath, options, 1, passLogPrefix);
+      log("Pass 1:", "ffmpeg", pass1Args.join(" "));
+      execFileSync("ffmpeg", pass1Args, {
+        stdio: ["ignore", "ignore", "pipe"],
+        timeout: 600_000, // 10 min
+      });
+
+      // Pass 2
+      const pass2Args = buildFfmpegArgs(inputPath, outputPath, options, 2, passLogPrefix);
+      log("Pass 2:", "ffmpeg", pass2Args.join(" "));
+      execFileSync("ffmpeg", pass2Args, {
+        stdio: ["ignore", "ignore", "pipe"],
+        timeout: 600_000,
+      });
+    } else {
+      log("Running CRF encode …");
+      const crfArgs = buildFfmpegArgs(inputPath, outputPath, options, "crf");
+      log("ffmpeg", crfArgs.join(" "));
+      execFileSync("ffmpeg", crfArgs, {
+        stdio: ["ignore", "ignore", "pipe"],
+        timeout: 600_000,
+      });
+    }
+
+    // 5. Read compressed output
+    const compressedBuffer = readFileSync(outputPath);
+    const compressedSize = compressedBuffer.length;
+    const ratio = compressedSize / originalSize;
+    const durationMs = Date.now() - startTime;
+
+    log(
+      `Compression complete: ${(compressedSize / 1024 / 1024).toFixed(2)} MB ` +
+        `(${(ratio * 100).toFixed(1)}% of original) in ${(durationMs / 1000).toFixed(1)}s`,
+    );
+
+    return {
+      buffer: compressedBuffer,
+      originalSize,
+      compressedSize,
+      ratio,
+      durationMs,
+    };
+  } catch (error) {
+    const errMsg = error instanceof Error ? error.message : String(error);
+    warn(`Compression failed: ${errMsg} — returning original video.`);
+    return {
+      buffer: inputBuffer,
+      originalSize,
+      compressedSize: originalSize,
+      ratio: 1,
+      durationMs: Date.now() - startTime,
+    };
+  } finally {
+    // 6. Clean up temp files
+    cleanup();
+  }
+}
+
+// ---------------------------------------------------------------------------
+// getVideoMetadata
+// ---------------------------------------------------------------------------
+
+/**
+ * Get video metadata using ffprobe.
+ *
+ * @param input - A file path, URL, or Buffer.
+ * @returns VideoMetadata with duration, resolution, codecs, etc.
+ */
+export async function getVideoMetadata(input: string | Buffer): Promise<VideoMetadata> {
+  if (!isFfprobeAvailable()) {
+    throw new Error(`${LOG_PREFIX} ffprobe is not available`);
+  }
+
+  let filePath: string;
+  let cleanupFn: (() => void) | null = null;
+
+  if (Buffer.isBuffer(input)) {
+    const { inputPath, cleanup } = makeTempDir();
+    writeFileSync(inputPath, input);
+    filePath = inputPath;
+    cleanupFn = cleanup;
+  } else if (input.startsWith("http://") || input.startsWith("https://")) {
+    // ffprobe can read URLs directly, but downloading is more reliable
+    const buf = await downloadUrl(input);
+    const { inputPath, cleanup } = makeTempDir();
+    writeFileSync(inputPath, buf);
+    filePath = inputPath;
+    cleanupFn = cleanup;
+  } else {
+    filePath = input;
+  }
+
+  try {
+    const probeArgs = [
+      "-v",
+      "quiet",
+      "-print_format",
+      "json",
+      "-show_format",
+      "-show_streams",
+      filePath,
+    ];
+
+    const result = execFileSync("ffprobe", probeArgs, {
+      encoding: "utf-8",
+      timeout: 30_000,
+    });
+
+    const data = JSON.parse(result);
+
+    const videoStream = data.streams?.find(
+      (s: { codec_type: string }) => s.codec_type === "video",
+    );
+    const audioStream = data.streams?.find(
+      (s: { codec_type: string }) => s.codec_type === "audio",
+    );
+    const format = data.format || {};
+
+    return {
+      duration: parseFloat(format.duration || "0"),
+      width: videoStream?.width || 0,
+      height: videoStream?.height || 0,
+      videoCodec: videoStream?.codec_name || "unknown",
+      audioCodec: audioStream?.codec_name || "unknown",
+      bitrate: parseInt(format.bit_rate || "0", 10),
+      fileSize: parseInt(format.size || "0", 10),
+    };
+  } finally {
+    if (cleanupFn) cleanupFn();
+  }
+}