sitegen/src/file-viewer/ffmpeg.ts

// Utilities for spawning ffmpeg and consuming its output as a `Progress`
// A headless parser is available with `Parse`

export type Line =
  | { kind: "ignore" }
  | { kind: "log"; level: "info" | "warn" | "error"; message: string }
  | {
    kind: "progress";
    frame: number;
    totalFrames: number;
    speed: string | null;
    fps: number | null;
    rest: Record<string, string>;
  };

export const defaultExtraOptions = [
  "-hide_banner",
  "-stats",
];

export interface SpawnOptions {
  args: string[];
  title: string;
  ffmpeg?: string;
  progress?: Progress;
  cwd: string;
}

export async function spawn(options: SpawnOptions) {
  const { ffmpeg = "ffmpeg", args, title, cwd } = options;
  const proc = child_process.spawn(ffmpeg, [...defaultExtraOptions, ...args], {
    stdio: ["ignore", "inherit", "pipe"],
    env: { ...process.env, SVT_LOG: "2" },
    cwd,
  });
  const parser = new Parse();
  const bar = options.progress ?? new Progress({ text: title });
  let running = true;
  const splitter = readline.createInterface({ input: proc.stderr });
  splitter.on("line", (line) => {
    const result = parser.onLine(line);
    if (result.kind === "ignore") {
      return;
    } else if (result.kind === "log") {
      console[result.level](result.message);
    } else if (result.kind === "progress") {
      if (!running) return;
      const { frame, totalFrames, fps, speed } = result;
      bar.value = frame;
      bar.total = totalFrames;
      const extras = [
        `${fps} fps`,
        speed,
        parser.hlsFile,
      ].filter(Boolean).join(", ");
      bar.text = `${title} ${frame}/${totalFrames} ${
        extras.length > 0 ? `(${extras})` : ""
      }`;
    } else result satisfies never;
  });
  const [code, signal] = await events.once(proc, "close");
  running = false;
  if (code !== 0) {
    const fmt = code ? `code ${code}` : `signal ${signal}`;
    const e: any = new Error(`ffmpeg failed with ${fmt}`);
    e.args = [ffmpeg, ...args].join(" ");
    e.code = code;
    e.signal = signal;
    bar.error(e.message);
    return e;
  }
  bar.success(title);
}

export class Parse {
  parsingStart = true;
  inIndentedIgnore: null | "out" | "inp" | "other" = null;
  durationTime = 0;
  targetFps: number | null = null;

  hlsFile: string | null = null;
  durationFrames = 0;

  onLine(line: string): Line {
    line = line.trimEnd();
    if (/^frame=/.test(line)) {
      if (this.parsingStart) {
        this.parsingStart = false;
        this.durationFrames = Math.ceil(
          (this.targetFps ?? 25) * this.durationTime,
        );
      }
      const parts = Object.fromEntries(
        [...line.matchAll(/\b([a-z0-9]+)=\s*([^ ]+)(?= |$)/ig)].map((
          [, k, v],
        ) => [k, v]),
      );
      const { frame, fps, speed, ...rest } = parts;
      return {
        kind: "progress",
        frame: Number(frame),
        totalFrames: this.durationFrames,
        fps: Number(fps),
        speed,
        rest,
      };
    }

    if (this.parsingStart) {
      if (this.inIndentedIgnore) {
        if (line.startsWith(" ") || line.startsWith("\t")) {
          line = line.trimStart();
          if (this.inIndentedIgnore === "inp") {
            const match = line.match(/^Duration: (\d+):(\d+):(\d+\.\d+)/);
            if (match) {
              const [h, m, s] = match.slice(1).map((x) => Number(x));
              this.durationTime = Math.max(
                this.durationTime,
                h * 60 * 60 + m * 60 + s,
              );
            }
            if (!this.targetFps) {
              const match = line.match(/^Stream.*, (\d+) fps/);
              if (match) this.targetFps = Number(match[1]);
            }
          }
          return { kind: "ignore" };
        }
        this.inIndentedIgnore = null;
      }
      if (line === "Press [q] to stop, [?] for help") {
        return { kind: "ignore" };
      }
      if (line === "Stream mapping:") {
        this.inIndentedIgnore = "other";
        return { kind: "ignore" };
      }
      if (line.startsWith("Output #") || line.startsWith("Input #")) {
        this.inIndentedIgnore = line.slice(0, 3).toLowerCase() as "inp" | "out";
        return { kind: "ignore" };
      }
    }

    const hlsMatch = line.match(/^\[hls @ .*Opening '(.+)' for writing/);
    if (hlsMatch) {
      if (!hlsMatch[1].endsWith(".tmp")) {
        this.hlsFile = path.basename(hlsMatch[1]);
      }
      return { kind: "ignore" };
    }

    let level: Extract<Line, { kind: "log" }>["level"] = "info";
    if (line.toLowerCase().includes("err")) level = "error";
    else if (line.toLowerCase().includes("warn")) level = "warn";

    return { kind: "log", level, message: line };
  }
}

import * as child_process from "node:child_process";
import * as readline from "node:readline";
import * as process from "node:process";
import events from "node:events";
import * as path from "node:path";
import { Progress } from "@paperclover/console/Progress";