record-video/record.ts

#!/usr/bin/env -S ts-node-esm --compilerOptions='{"module": "es2022"}'

$.verbose = false;

import { $ } from "zx";
// Or
import "zx/globals";
import { spawn } from "child_process";
import { PassThrough } from "stream";

function sleep(time: number) {
  return new Promise<void>((resolve) => {
    setTimeout(() => resolve(), time);
  });
}

void (async function () {
  const source = spawn("ffmpeg", [
    "-f",
    "video4linux2",
    "-input_format",
    "nv12",
    "-thread_queue_size",
    "512",
    "-video_size",
    "3840x2160",
    "-i",
    "/dev/video2",
    "-f",
    "nut",
    "-c",
    "copy",
    "pipe:1",
  ]);
  const preview = spawn("ffplay", [
    "-f",
    "nut",
    "-use_wallclock_as_timestamps",
    "1",
    "-",
  ]);
  const convert_and_add_audio = spawn("ffmpeg", [
    "-y",
    "-vaapi_device",
    "/dev/dri/renderD128",
    "-f",
    "nut",
    "-i",
    "-",
    "-f",
    "pulse",
    "-thread_queue_size",
    "512",
    "-i",
    "alsa_input.usb-Elgato_Cam_Link_4K_0123456789000-03.analog-stereo",
    "-vf",
    "format=nv12,hwupload",
    "-c:v",
    "h264_vaapi",
    "-b:v",
    "12M",
    "-f",
    "mp4",
    "output.mp4",
  ]);
  console.log("started ffmpeg...");

  source.stderr.on("data", (data) => {
    // console.error("source", data.toString());
  });
  convert_and_add_audio.stderr.on("data", (data) => {
    // console.error("convert", data.toString());
  });
  preview.stderr.on("data", (data) => {
    // console.error("preview", data.toString());
  });

  // preview.stderr.on("data", (data) => console.error(data.toString()));

  const source_stream_for_convert = new PassThrough();
  const source_stream_for_preview = new PassThrough();
  // const source_stream_for_dump = new PassThrough();

  // source.stdout.pipe(source_stream_for_convert);
  // // source.stdout.pipe(source_stream_for_preview);
  // source.stdout.pipe(source_stream_for_dump);
  //
  source_stream_for_convert.pipe(convert_and_add_audio.stdin);
  // source_stream_for_preview.pipe(preview.stdin);

  let preview_ok = true;
  const stats = {};
  let count = 0;
  let preview_stopped = false;
  let preview_can_resume = false;
  let preview_should_stop_asap = false;
  source.stdout.on("data", (data) => {
    // this implements framedropping. we detect when a frame starts and emit it only when the stdin is drained
    count++;
    // console.log("got data!", a++);
    const beginning = data.slice(0, 4).join("");
    if (beginning == "7875228173") {
      //means the beginning of the frame (counted the most frequent start of data and that was the most frequent)
      if (preview_can_resume) {
        preview_stopped = false;
      }
      if (preview_should_stop_asap) {
        preview_should_stop_asap = false;
        preview_stopped = true;
      }
    }

    if (!preview_stopped) {
      let preview_result = preview.stdin.write(data);
      if (!preview_result && !preview_should_stop_asap) {
        preview_should_stop_asap = true;
        preview_can_resume = false;
        preview.stdin.once("drain", () => {
          preview_can_resume = true;
        });
      }
    }
    convert_and_add_audio.stdin.write(data);
  });
})();