[Mp4-tech] h.264 - difference between short term reference pictureand long term reference picture

[Gary Sullivan]

I guess there are two primary differences.
1) Short-term reference pictures are indexed by referring to variables
that are a function of their frame_num value.  But frame_num is a modulo
counter that wraps over periodically.  Therefore there is a limit on how
long a short-term reference picture can remain in the buffer -- it
cannot remain there after the frame_num value has wrapped all the way
around and crossed over the same value again.  In contrast, long-term
reference pictures are referenced by an index that is explicitly
assigned to them by syntax -- their long-term frame index.  So a
long-term reference picture can stay in the decoded picture buffer as
long as the encoder wants it to.
2) There is no use of temporal (picture order count) relationships when
referencing long-term reference pictures in the decoding process.
Best Regards,
Gary Sullivan
________________________________
	From: mp4-tech-bounces lists.mpegif.org
[mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of Shinjith
Unithrattil
	Sent: Thursday, February 03, 2024 8:09 PM
	To: mp4-tech lists.mpegif.org
	Subject: [Mp4-tech] h.264 - difference between short term
reference pictureand long term reference picture
	  sir,
	      I am working on h.264 decoder. I couldnt find out the
actual difference between short term reference picture and long term
reference picture. Can you kindly make it clear to me
	thank you
	regards,
	shinjith
	 <http://clients.rediff.com/signature/track_sig.asp>  
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