kVTCompressionPropertyKey_SourceFrameCount
The number of source frames, if known.
Declaration
let kVTCompressionPropertyKey_SourceFrameCount: CFStringDiscussion
This property allows a client to give the video encoder advance guidance as to how many frames will be encoded. If nonzero, this value should be the exact number of times that the client calls VTCompressionSessionEncodeFrame(_:imageBuffer:presentationTimeStamp:duration:frameProperties:sourceFrameRefcon:infoFlagsOut:) in each pass.
The default is 0, which indicates that the number of source frames is unknown.