[Mp4-tech] gaps in frame num

[K.]

Hi Experts,
Thank you very much for your help, especially thanks to Gary and Glenn for taking the time to answer my questions and I have found your answers very helpful and am convinced that the "phantom frames" are not being output. However, I am still confused about some aspects of this gaps in frame num business and hope you don't mind to answer a few more questions of mine:     :)
1a) In subclause 8.2.5.2, it states that the generated frames shall be marked as "used for short term reference", if these frames are not being used and not being output, why would it be marked as "used for short term reference" for? 
1b) Does sliding window process mark these non-existing frames to "unsed for reference"?
2a) Also, if these frames are not being used any where, why would JM reference decoder taking the trouble to generate and store these frames?
2b) In JM reference decoder, the attribute "is_output" of these generated frames are set to '1' , doesn't this mean that these frames are to be output? Am I allow to set it to '0'?
2c) The bitstream "MR3_TANDBERG_B.YUV" has a picture order count type set to 2 (and has missing frames), In JM reference decoder, if picture order count type is not equal to one, the function "decode_poc" would be invoked, but I am not interested in interlaced coding yet the output of "decode_poc" are TopFieldOrderCnt and BottomFieldOrderCnt, how do I use this function for a frame coding bitstream with picture order count type set to 2? (Since these frames are not being used, can I simply ignore the decoding of POC?)
3) Are these generated frames' frame num significant (since they must be generated using equation 7-14 of the standard) ? I mean, is there somewhere in the code (after the generation of these frames) that uses these frame numbers even if they aren't to be output?
4) Are these generated frame nums being used in reference picture marking?
5) Finally, where would I be wrong if I say, "As long as these generated frames are generated using equation 7-14 and marked as 'non-existing' , the rest can be anything I want" ?
Thank you all very much,
Kathy
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