HDR Encoding Example

const { VideoEncoder, VideoFrame } = require('node-webcodecs');
const fs = require('fs');

async function encodeHDR10Video() {
  console.log('Encoding 4K HDR10 video...');

  const chunks = [];

  const encoder = new VideoEncoder({
    output: (chunk, metadata) => {
      const buffer = Buffer.alloc(chunk.byteLength);
      chunk.copyTo(buffer);
      chunks.push(buffer);

      if (metadata?.decoderConfig) {
        console.log('HDR Config:', metadata.decoderConfig.codec);
      }
    },
    error: (err) => {
      console.error('Error:', err);
      throw err;
    }
  });

  // HDR10 configuration
  encoder.configure({
    codec: 'hevc_videotoolbox',  // HEVC for HDR
    width: 3840,
    height: 2160,
    bitrate: 25_000_000,
    framerate: 30,
    hardwareAcceleration: 'prefer-hardware',

    // HDR10 color space (BT.2020 + PQ)
    colorSpace: {
      primaries: 'bt2020',
      transfer: 'pq',
      matrix: 'bt2020-ncl',
      fullRange: false
    }
  });

  // Encode 60 frames (2 seconds)
  for (let i = 0; i < 60; i++) {
    const data = createHDRFrame(3840, 2160, i);

    const frame = new VideoFrame(data, {
      format: 'RGBA',
      codedWidth: 3840,
      codedHeight: 2160,
      timestamp: i * 33333,
      colorSpace: {
        primaries: 'bt2020',
        transfer: 'pq',
        matrix: 'bt2020-ncl'
      }
    });

    encoder.encode(frame, { keyFrame: i % 30 === 0 });
    frame.close();

    if ((i + 1) % 10 === 0) {
      console.log(`  Progress: ${i + 1}/60 frames`);
    }
  }

  await encoder.flush();
  encoder.close();

  const output = Buffer.concat(chunks);
  fs.writeFileSync('hdr10_output.hevc', output);

  console.log(`✓ Encoded ${output.length} bytes`);
  console.log('Verify: ffprobe -show_streams hdr10_output.hevc');
}

function createHDRFrame(width, height, frameNum) {
  const data = new Uint8Array(width * height * 4);

  for (let y = 0; y < height; y++) {
    for (let x = 0; x < width; x++) {
      const idx = (y * width + x) * 4;

      // HDR gradient
      const brightness = ((x / width) + (frameNum / 60)) % 1.0;
      const value = Math.floor(brightness * 255);

      data[idx] = value;
      data[idx + 1] = Math.floor(value * 0.8);
      data[idx + 2] = Math.floor(value * 0.6);
      data[idx + 3] = 255;
    }
  }

  return data;
}

encodeHDR10Video().catch(console.error);