# ReadPackedDoubleDelta(double, in StreamCompressionModel)

> Reads a 8-byte floating point value from the data stream. If the first bit is 0, the data did not change and baseline will be returned.

## Definition

* **Type:** Method
* **Namespace:** [Unity.Collections](/engine/6000.7/script-reference/unity/collections.md)
* **Assembly:** UnityEngine.ManagedKernelModule

## ReadPackedDoubleDelta(double, StreamCompressionModel)

```csharp
public double ReadPackedDoubleDelta(double baseline, in StreamCompressionModel model)
```

### Parameters

**** (\[double]\(https\://learn.microsoft.com/dotnet/api/system.double)): The previous 8-byte floating point value.**** (\[StreamCompressionModel]\(/engine/6000.7/script-reference/unity/collections/streamcompressionmodel)): Not currently used.

### Returns

| Type                                                           | Description                                                                                                     |
| -------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------- |
| [double](https://learn.microsoft.com/dotnet/api/system.double) | A 8-byte floating point value read from the current stream, or `baseline` if there are no changes to the value. |