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# kVTCompressionPropertyKey_H264EntropyMode

The entropy encoding mode for H.264 compression.

```
let kVTCompressionPropertyKey_H264EntropyMode: CFString
```

## Discussion

If supported by an H.264 encoder, this property controls whether the encoder should use Context-based Adaptive Variable Length Coding (CAVLC) or Context-based Adaptive Binary Arithmetic Coding (CABAC). CABAC generally gives better compression at the expense of higher computational overhead. The default value is encoder-specific and may change depending on other encoder settings.

> Note:
> Changing the default entropy mode may result in a configuration that is not compatible with a requested Profile and Level.  Results in this case are undefined, and could include encode errors or a noncompliant output stream.

## Topics

### Entropy Modes

[`kVTH264EntropyMode_CAVLC`](/documentation/VideoToolbox/kVTH264EntropyMode_CAVLC)

[`kVTH264EntropyMode_CABAC`](/documentation/VideoToolbox/kVTH264EntropyMode_CABAC)


---

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