Render

hyperframes render comp.html --out video.mp4

The default encode is hash-stable H.264 at the composition's declared size and frame rate. Everything below is how to deviate from the default with intent.

What you'll learn

• The right codec/quality knobs for delivery, archival, alpha, and HDR
• What "hash-stable" means at the sha256 level
• When to reach for --manifest and --workers

Codec presets

Four encodes, four tabs. The first is what you almost always want; the rest are for specific delivery targets.

# Web delivery, social, almost everything
hyperframes render comp.html \
  --out video.mp4 \
  --codec h264 --crf 18 --pixfmt yuv420p

CRF vs bitrate

CRF is the right default for video that humans will watch. Lower number means higher quality; 18 is visually lossless for most content; 23 is a sane "web" setting.

Use --bitrate only when you have a hard delivery target (CDN budget, broadcast spec, ABR rung). Mixing --crf and --bitrate is an error — the renderer will reject the command rather than silently pick one.

Hash-stable output

Common flags

Parallel workers

--workers N splits the frame range across N processes. Encoding is the bottleneck on most machines — go up to your physical core count and stop there. Anything beyond that mostly heats your laptop.

Caching

The renderer caches the Chromium boot artifact and the runtime bundle. On a warm start, render time is dominated by capture and encode, not boot. Set HF_CACHE_DIR to point caching at a writable, persistent path on CI runners that wipe /tmp between jobs.

Frame manifest

--manifest manifest.json writes a per-frame record — timestamps, fixture values, source asset hashes. Useful for signed-content workflows, downstream upload, and "did this frame change?" diffs.

Next

• CI & batch — N workers, one composition, M variants
• render reference — every flag, every default