---
title: kVTCompressionPropertyKey_MoreFramesBeforeStart
framework: videotoolbox
role: symbol
role_heading: Global Variable
path: videotoolbox/kvtcompressionpropertykey_moreframesbeforestart
---

# kVTCompressionPropertyKey_MoreFramesBeforeStart

A Boolean value that indicates whether and how a compression session concatenates frames with other compressed frames to form a longer series.

## Declaration

```swift
let kVTCompressionPropertyKey_MoreFramesBeforeStart: CFString
```

## Discussion

Discussion This value is true if frames compressed in a separate session will be concatenated before the beginning of the current session. The value is false if the current session is a stand-alone session, or if this session will encode the first segment of a multi-segment compression. The default value is false. This information enables video encoders to ensure that compressed segments can be concatenated smoothly – for example, avoiding data rate spikes where segments are joined.

## See Also

### Rate Control

- [kVTCompressionPropertyKey_AverageBitRate](videotoolbox/kvtcompressionpropertykey_averagebitrate.md)
- [kVTCompressionPropertyKey_ConstantBitRate](videotoolbox/kvtcompressionpropertykey_constantbitrate.md)
- [kVTCompressionPropertyKey_DataRateLimits](videotoolbox/kvtcompressionpropertykey_dataratelimits.md)
- [kVTCompressionPropertyKey_EstimatedAverageBytesPerFrame](videotoolbox/kvtcompressionpropertykey_estimatedaveragebytesperframe.md)
- [kVTCompressionPropertyKey_MoreFramesAfterEnd](videotoolbox/kvtcompressionpropertykey_moreframesafterend.md)
- [kVTCompressionPropertyKey_Quality](videotoolbox/kvtcompressionpropertykey_quality.md)
- [kVTCompressionPropertyKey_TargetQualityForAlpha](videotoolbox/kvtcompressionpropertykey_targetqualityforalpha.md)
- [kVTCompressionPropertyKey_VariableBitRate](videotoolbox/kvtcompressionpropertykey_variablebitrate.md)
- [kVTCompressionPropertyKey_VBVBufferDuration](videotoolbox/kvtcompressionpropertykey_vbvbufferduration.md)
- [kVTCompressionPropertyKey_VBVInitialDelayPercentage](videotoolbox/kvtcompressionpropertykey_vbvinitialdelaypercentage.md)
- [kVTCompressionPropertyKey_VBVMaxBitRate](videotoolbox/kvtcompressionpropertykey_vbvmaxbitrate.md)