[Live-devel] Frames from the future - or maybe not

[Ross Finlayson]

First, you should use the term “presentation time”, not “timestamp”.  (The word “timestamp” typically refers to the RTP timestamp, which LIVE555 programmers never need to concern themselves with.)

Yes, it is perfectly normal for video frames’ presentation times to be non-monotonic - i.e., not always increasing.  The reason for this is that frames are sent in ‘decoding order’ - i.e., in the order that they are to be fed into a decoder, not the order in which they are displayed on a screen (i.e., the presentation time).  Because of ‘B frames’ (a MPEG term; they might be called something different in H.26*), some video frames depend upon a frame that will be displayed later; therefore the later frame will actually be sent first.

“Nothing to see here.  Move along” :-)


Ross Finlayson
Live Networks, Inc.
http://www.live555.com/