<!--
{
  "availability" : [
    "iOS: 18.0.0 -",
    "iPadOS: 18.0.0 -",
    "macCatalyst: 18.0.0 -",
    "macOS: 15.0.0 -",
    "tvOS: 18.0.0 -",
    "visionOS: 2.0.0 -"
  ],
  "documentType" : "symbol",
  "framework" : "VideoToolbox",
  "identifier" : "/documentation/VideoToolbox/kVTDecompressionPropertyKey_AllowBitstreamToChangeFrameDimensions",
  "metadataVersion" : "0.1.0",
  "role" : "Global Variable",
  "symbol" : {
    "kind" : "Global Variable",
    "modules" : [
      "Video Toolbox"
    ],
    "preciseIdentifier" : "c:@kVTDecompressionPropertyKey_AllowBitstreamToChangeFrameDimensions"
  },
  "title" : "kVTDecompressionPropertyKey_AllowBitstreamToChangeFrameDimensions"
}
-->

# kVTDecompressionPropertyKey_AllowBitstreamToChangeFrameDimensions

A Boolean value that indicates whether a decoder is allowed to output buffers matching reduced frame dimensions in the bitstream rather than
under-filling them.

```
let kVTDecompressionPropertyKey_AllowBitstreamToChangeFrameDimensions: CFString
```

## Discussion

This is an optional property only supported by video decoders for bitstream formats that have a provision
for specifying output dimensions per-frame, such as AV1.

If a decoder doesn’t support this property or if the property value is set to `kCFBooleanFalse`, all decoded
frames have the same dimensions as specified in the format description. In this case, if the bitstream
changes the frame dimensions, the output buffer is padded to the dimensions specified in the format
description.

When this property is set to `kCFBooleanTrue`, the decoder sets the dimensions of each output buffer to
match the dimensions specified in the bitstream for that frame.

In all cases, output buffer dimensions will never exceed the dimensions specified in the format description.

In apps linked to SDK versions before this property was added, the AV1 decoder will behave as if this property
is set to `kCFBooleanFalse`. Otherwise, value of this property defaults to `kCFBooleanTrue` where supported.

---

Copyright &copy; 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)