HEVC Plugin for hls.js

$ npm install @hevcjs/hlsjs-plugin hls.js

import Hls from 'hls.js';
import { attachHevcSupport } from '@hevcjs/hlsjs-plugin';

const video = document.querySelector('video');

// Must run BEFORE `new Hls()` — hls.js filters levels against
// MediaSource.isTypeSupported at manifest parse time.
await attachHevcSupport({
  workerUrl: '/transcode-worker.js',
  wasmUrl: '/hevc-decode.js',
});

const hls = new Hls({
  ...(typeof MediaSource !== 'undefined' ? { preferManagedMediaSource: false } : {}),
});
hls.attachMedia(video);
hls.loadSource('https://example.com/stream/playlist.m3u8');

<script type="module">
  import { attachHevcSupport } from 'https://esm.sh/@hevcjs/hlsjs-plugin@0';

  const video = document.querySelector('video');

  await attachHevcSupport({
    workerUrl:     'https://unpkg.com/@hevcjs/core@1/dist/transcode-worker.js',
    wasmUrl:       'https://unpkg.com/@hevcjs/core@1/dist/wasm/hevc-decode.js',
    wasmBinaryUrl: 'https://unpkg.com/@hevcjs/core@1/dist/wasm/hevc-decode.wasm',
  });

  const hls = new Hls({
    ...(typeof MediaSource !== 'undefined' ? { preferManagedMediaSource: false } : {}),
  });
  hls.attachMedia(video);
  hls.loadSource('https://example.com/stream/playlist.m3u8');
</script>

attachHevcSupport(config?)

Probes native HEVC support (by actually creating an HEVC SourceBuffer, not just isTypeSupported), checks WebCodecs H.264 encoding, then installs the MSE intercept. Returns a Promise resolving to a cleanup() function that reverses all patches. No player instance is needed — but it must run before new Hls().

const cleanup = await attachHevcSupport({
  workerUrl:     '/transcode-worker.js',   // Web Worker URL
  wasmUrl:       '/hevc-decode.js',         // WASM glue location
  wasmBinaryUrl: '/hevc-decode.wasm',       // WASM binary location
});

// Then create the player
const hls = new Hls({
  ...(typeof MediaSource !== 'undefined' ? { preferManagedMediaSource: false } : {}),
});

// Remove all patches when done
cleanup();

Options

Compute-aware ABR — handle.attachComputeAware(hls)

On by default. The handle returned by attachHevcSupport exposes attachComputeAware(hls): it observes per-segment transcode speedX and caps hls.autoLevelCapping when the device can't transcode the current level in real time — hls.js's own ABR keeps choosing freely below that ceiling. Pass adaptiveCompute: false at attach time to opt out, or an object to tune the decider. subscribeSegmentStat stays re-exported for custom telemetry.

import { subscribeSegmentStat } from '@hevcjs/hlsjs-plugin';

const handle = await attachHevcSupport({ workerUrl: './transcode-worker.js' });

const hls = new Hls({
  ...(typeof MediaSource !== 'undefined' ? { preferManagedMediaSource: false } : {}),
});
handle.attachComputeAware(hls);  // caps hls.autoLevelCapping under compute pressure