Author: michael Date: Fri Nov 3 22:13:50 2006 New Revision: 20647 Modified: trunk/DOCS/tech/nut.txt Log: 2nd try for a keyframe definition based on richs comment Modified: trunk/DOCS/tech/nut.txt ============================================================================== --- trunk/DOCS/tech/nut.txt (original) +++ trunk/DOCS/tech/nut.txt Fri Nov 3 22:13:50 2006 @@ -42,11 +42,15 @@ SHOULD it is recommended to be done that way, but not strictly required keyframe - a frame which can be decoded correctly on its own (=without using - information from any other frames) - if no such frames exist in a codec (for example due to use of overlapped - transforms like the MDCT in an audio codec) then a keyframe shall be any - frame from which onward all frames can be decoded correctly + The nth frame is a keyframe if and only if frames n, n+1, ... in + presentation order (that are all frames with a pts >= frame[n].pts) can + be decoded successfully without reference to frames prior n in storeage + order (that are all frames with a dts < frame[n].dts) + if no such frames exist (for example due to use of overlapped transforms + like the MDCT in an audio codec) then the definition shall be extended + by droping n out of the set of frames which must be decodable, if this + is still insufficient then n+1 shall be droped, and so on until there is + a keyframe (FIXME maybe move somewhere else?)