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Concurrency

Remotion Lambda is a highly concurrent distributed video rendering system. That means that the video rendering work is split up across many Lambda functions. How many Lambda functions exactly can be defined by you, or you let Remotions defaults decide.

Setting the concurrency​

You can set the concurrency via the framesPerLambda option (or --frames-per-lambda via CLI).

The concurrency is defined as frameCount / framesPerLambda. That means that the higher you set framesPerLambda, the lower the concurrency gets.

note

Example: You render a video that has a durationInFrames of 300 with a framePerLambda setting of 15. The concurrency is 300 / 15 = 20.

Default values​

By default, Remotion chooses a value between 20 and ∞ for framesPerLambda. The longer the video, the higher the concurrency. As a baseline, no matter how short the video, always at least 20 frames are rendered per Lambda.

The following chart shows how the framesPerLambda and the implied concurrency is chosen based on the frame count:

The code for determining the framesPerLambda parameter is:

tsx
import { interpolate } from "remotion";
 
export const bestFramesPerLambdaParam = (frameCount: number) => {
  // Between 0 and 10 minutes (at 30fps), interpolate the concurrency from 75 to 150
  const concurrency = interpolate(frameCount, [0, 18000], [75, 150], {
    extrapolateRight: "clamp",
  });
 
  // At least have 20 as a `framesPerLambda` value
  const framesPerLambda = Math.max(frameCount / concurrency, 20);
 
  // Evenly distribute: For 21 frames over 2 lambda functions, distribute as 11 + 10 ==> framesPerLambda = 11
  const lambdasNeeded = Math.ceil(frameCount / framesPerLambda);
 
  return Math.ceil(frameCount / lambdasNeeded);
};
tsx
import { interpolate } from "remotion";
 
export const bestFramesPerLambdaParam = (frameCount: number) => {
  // Between 0 and 10 minutes (at 30fps), interpolate the concurrency from 75 to 150
  const concurrency = interpolate(frameCount, [0, 18000], [75, 150], {
    extrapolateRight: "clamp",
  });
 
  // At least have 20 as a `framesPerLambda` value
  const framesPerLambda = Math.max(frameCount / concurrency, 20);
 
  // Evenly distribute: For 21 frames over 2 lambda functions, distribute as 11 + 10 ==> framesPerLambda = 11
  const lambdasNeeded = Math.ceil(frameCount / framesPerLambda);
 
  return Math.ceil(frameCount / lambdasNeeded);
};

Concurrency limits​

Ensure that you only set parameter within these limits to ensure the renders don't throw any errors:

  • Minimum framesPerLambda: 4
  • Maximum concurrency: 200

The Remotion Lambda defaults will never go outside these bounds.