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Performance Recipes: Concurrency, GPU, Prefetch & Encoding

type: synthesisconfidence: highupdated: 2026-06-11sources: 8

The levers that actually move render speed (and Player smoothness), with verbatim flags and values.

Comparison

Lever How Effect Applies to
Concurrency --concurrency flag; find optimum with npx remotion benchmark Too high AND too low are both counterproductive CLI/SSR render
Image format default JPEG (quality 80); --image-format=png only for transparency; tune --jpeg-quality PNG screenshots are significantly slower than JPEG Render
GPU (--gl) enable an OpenGL backend during rendering (headless Chrome disables GPU by default) Big speedup ONLY for GPU content: WebGL (Three.js/Skia/P5/Mapbox), 2D canvas, box-shadow, text-shadow, linear-gradient/radial-gradient, filter: blur(), filter: drop-shadow(), transform Render on GPU machines; not Lambda (no GPU)
Hardware-accelerated encoding --hardware-acceleration if-possible (CLI) or hardwareAcceleration: 'if-possible' in renderMedia(); also Config.setHardwareAcceleration('if-possible') Faster encoding; macOS only (VideoToolbox); ProRes from v4.0.228, H.264/H.265 from v4.0.236; not supported on Lambda/Cloud Run Encoding step
Bitrate w/ HW accel --video-bitrate=8M HW-encoded files are much larger by default; 8M ≈ software-encoded size for H.264 Full HD; crf is incompatible with HW encoders Encoding
Codec choice avoid vp8/vp9 (WebM) unless needed WebM codecs are very slow to encode Encoding
Resolution --scale (e.g. --scale=0.5; max 16; since 4.0.328 non-integer/odd values auto-round) Lower resolution = faster; higher scale = sharper text on hi-DPI but slower Render
Video tag choice use <Video> from @remotion/media <Html5Video> and <OffthreadVideo> are "not optimized" per official docs Render + Player
OffthreadVideo flags leave transparent off; set toneMapped={false} if color accuracy is secondary PNG extraction (~40% slower) and tone mapping both cost time Render
Slow frame extraction (pre-v4) re-encode: npx remotion ffmpeg -i inputvideo.mp4 outputvideo.mp4; or prefer VP9 over VP8 / JPEG over PNG Eliminates "Using a slow method to extract the frame at 1000ms of [video]" Render (Remotion < 4.0 only)
Asset prefetch (Player) prefetch(src, {method: 'blob-url'}); free() to release; base64 for Safari audio hiccups; set contentType if server headers are wrong Media ready before playback; Player-only (no-op when rendering) Player/Studio
Slow JS / data fetching --log=verbose lists slowest frames; console.time; useMemo/useCallback; pre-compute and pass as input props; cache in localStorage Removes per-frame bottlenecks Everything
Silent video audio add muted to videos without sound Skips downloading the file for audio mixing Render

Analysis

  • Concurrency is empirical, not "more is better." The benchmark command exists precisely because the optimum depends on composition and hardware. History: Remotion once ran one browser with many tabs, which serialized rendering (issue #584 measured 67s → 43s frame time by switching to multiple browser instances; 39.7s → 22.2s on a 5900X). Modern Remotion parallelizes, but the lesson stands — measure with npx remotion benchmark.
  • Studio/Player feel fast, renders feel slow — because the GPU disappears. In Studio and Player the GPU is on; headless Chromium disables it. That's why a composition full of box-shadow, gradients, and blurs renders far slower than it previews. Options: enable --gl on a GPU machine, or replace GPU-heavy CSS with precomputed images. Note what the GPU does NOT accelerate: <Html5Video>, <OffthreadVideo>, canvas pixel manipulation, and video encoding itself.
  • Two different "hardware" levers get conflated: GPU rendering of frames (--gl, content-dependent) vs hardware-accelerated encoding (VideoToolbox on macOS only). They're independent; on Lambda you get neither.
  • Quality and speed share knobs. CRF controls quality for software encoding; --video-bitrate replaces it under hardware acceleration (mutually exclusive with --crf). --x264-preset trades speed/compression. Sharp text on hi-DPI displays needs output scaling (--scale=2), which multiplies render cost — and canvas/WebGL content won't upscale unless components support pixelDensity (<Solid>, <HtmlInCanvas> with usePixelDensity()).
  • Cloud renders pay for everything twice: GPU effects render slowly on CPU-only Lambda AND big assets cost egress. Performance work and cost work overlap heavily — see cost estimation.

Recommendations

  • Always start with npx remotion benchmark before hand-tuning --concurrency.
  • Rendering locally on a Mac with H.264/H.265/ProRes output: add --hardware-acceleration if-possible --video-bitrate=8M.
  • Composition is CSS-effect heavy (shadows/gradients/blur): either render on a GPU machine with --gl, or bake effects into images before rendering on Lambda.
  • Slow renders with embedded videos: switch to <Video> from @remotion/media (media tag picker); mute silent videos; keep transparent off.
  • Player startup jank with remote media: prefetch() assets on mount with blob-url; switch to base64 only if Safari audio stutters.
  • Diagnose before tuning: --log=verbose to find the slowest frames; if early frames are slow that's thread initialization, not your code.
  • Need 4K output of a 1080p comp: --scale=2 and accept the slowdown; don't redesign the composition.

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