[NUT-devel] [nut]: r649 - docs/nut.txt

[michael]

Author: michael
Date: Mon Mar  3 15:12:12 2008
New Revision: 649

Log:
Some additional words about seeking and keyframes spread.


Modified:
   docs/nut.txt

Modified: docs/nut.txt
==============================================================================
--- docs/nut.txt	(original)
+++ docs/nut.txt	Mon Mar  3 15:12:12 2008
@@ -1092,6 +1092,14 @@ B. forward seeking
     smallest one which has a back ptr >= the position of what was found in 1.
 2. Follow the back pointer to the corresponding syncpoint.
 
+Alternatively a demuxer can search for a shorter back ptr (which ensures that
+keyframes in all streams are closer together) before 2.
+One way to do this for backward seeking is:
+if the back ptr is longer than the demuxer wants, step back by half the ptr,
+search for another syncpoint and repeat until either the ptr is short enough
+or the search went too far.
+
+
 Seeking with an index (non-normative):
 --------------------------------------
 The demuxer only has to find the appropriate keyframe in the index and
@@ -1101,6 +1109,10 @@ Note, more complicated seeking methods e
 seeking to the optimal point in the presence of an index even if only a
 subset of all streams is active.
 
+Note2, A demuxer might wish to favor a syncpoint which has keyframes
+in all active streams shortly afterwards instead of one where they are
+distant.
+
 A muxer SHOULD place syncpoints so that that simple low complexity seeking
 works with fine granularity. That is, syncpoints should be placed prior
 to keyframes instead of non-keyframes and with high enough frequency