360_player/lib/probe.js

import { spawn } from 'node:child_process';
import fs from 'node:fs/promises';
import path from 'node:path';

/** Run ffprobe and return a compact description of the file. */
export function ffprobe(file) {
  return new Promise((resolve, reject) => {
    const args = [
      '-v', 'error',
      '-show_entries',
      'stream=index,codec_type,codec_name,width,height,r_frame_rate,bit_rate,channels,duration:stream_side_data_list:stream_tags=rotate:format=duration,size,bit_rate',
      '-of', 'json',
      file,
    ];
    const p = spawn('ffprobe', args, { windowsHide: true });
    let out = '', err = '';
    p.stdout.on('data', d => (out += d));
    p.stderr.on('data', d => (err += d));
    p.on('error', reject);
    p.on('close', code => {
      if (code !== 0) return reject(new Error(err.trim() || `ffprobe exited ${code}`));
      try { resolve(summarize(JSON.parse(out))); }
      catch (e) { reject(e); }
    });
  });
}

function parseFps(r) {
  if (!r) return null;
  const [a, b] = r.split('/').map(Number);
  return b ? +(a / b).toFixed(3) : a;
}

function summarize(j) {
  const v = (j.streams || []).find(s => s.codec_type === 'video');
  const a = (j.streams || []).find(s => s.codec_type === 'audio');
  const fmt = j.format || {};
  const info = {
    duration: +(fmt.duration || v?.duration || 0),
    size: +(fmt.size || 0),
    bitrate: +(fmt.bit_rate || 0),
    video: v ? {
      codec: v.codec_name,
      width: v.width,
      height: v.height,
      fps: parseFps(v.r_frame_rate),
      bitrate: +(v.bit_rate || 0),
    } : null,
    audio: a ? { codec: a.codec_name, channels: a.channels } : null,
    projection: 'flat',
    projectionSource: 'none',
    stereo: 'mono',
  };
  const sph = (v?.side_data_list || []).find(s => s.side_data_type === 'Spherical Mapping');
  if (sph) {
    info.projection = sph.projection === 'equirectangular' ? 'equirectangular' : (sph.projection || 'unknown');
    info.projectionSource = 'metadata';
    info.sphericalYaw = sph.yaw || 0;
    info.sphericalPitch = sph.pitch || 0;
    info.sphericalRoll = sph.roll || 0;
  } else if (v && v.width >= 2048 && Math.abs(v.width / v.height - 2) < 0.02) {
    // No metadata, but a 2:1 frame at this size is almost certainly an equirect panorama.
    info.projection = 'equirectangular';
    info.projectionSource = 'aspect-guess';
  }
  const st = (v?.side_data_list || []).find(s => s.side_data_type === 'Stereo 3D');
  if (st && st.type && st.type !== '2D') info.stereo = st.type;
  return info;
}

/** Small persistent cache keyed on path + size + mtime so we don't re-probe on restart. */
export class ProbeCache {
  constructor(file) {
    this.file = file;
    this.map = new Map();
    this.loaded = false;
    this.saving = null;
  }
  async load() {
    try {
      const j = JSON.parse(await fs.readFile(this.file, 'utf8'));
      for (const [k, v] of Object.entries(j)) this.map.set(k, v);
    } catch { /* first run */ }
    this.loaded = true;
  }
  async get(file, stat) {
    if (!this.loaded) await this.load();
    const key = `${file}|${stat.size}|${Math.floor(stat.mtimeMs)}`;
    if (this.map.has(key)) return this.map.get(key);
    const info = await ffprobe(file);
    this.map.set(key, info);
    this.save();
    return info;
  }
  save() {
    // Debounce writes; a stale cache file only costs a re-probe.
    if (this.saving) return;
    this.saving = setTimeout(async () => {
      this.saving = null;
      try {
        await fs.mkdir(path.dirname(this.file), { recursive: true });
        await fs.writeFile(this.file, JSON.stringify(Object.fromEntries(this.map), null, 1));
      } catch (e) { console.warn('probe cache save failed:', e.message); }
    }, 500);
  }
}