Some useful acronyms:

PTS: Presentation time stamp; used to order frames for display. Wikipedia
DTS: Decoding time stamp; used to order frames for decoding
VBV: Video Buffering Verifier; used to prevent underflow/overflow of MPEG bit stream
PCR: Program Clock reference, base timme for PTS values. Wikipedia

FLV files have a CompositionTime field in the VideoData segment; this is PTS - DTS.

PTS and DTS should be 90Khz values. CTS is in units of milliseconds, so compositionTime = (PTS - DTS) / 90.0.

Reference