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# requestedTimeToleranceBefore

A maximum length of time before the requested time to allow image generation to occur.

```
var requestedTimeToleranceBefore: CMTime { get set }
```

## Discussion

The default value is <doc://com.apple.documentation/documentation/CoreMedia/CMTime/positiveInfinity>. Set the values of [`requestedTimeToleranceBefore`](/documentation/AVFoundation/AVAssetImageGenerator/requestedTimeToleranceBefore) and [`requestedTimeToleranceAfter`](/documentation/AVFoundation/AVAssetImageGenerator/requestedTimeToleranceAfter) to <doc://com.apple.documentation/documentation/CoreMedia/CMTime/zero> to request frame-accurate image generation; this may incur additional decoding delay.

---

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