GstBaseSink.havePreroll

• GstReserved
• canActivatePull
• canActivatePush
• clockId
• element
• eos
• flushing
• haveNewsegment
• havePreroll
• maxLateness
• needPreroll
• offset
• padMode
• playingAsync
• prerollCond
• prerollLock
• priv
• running
• segment
• sinkpad
• sync