[Mp4-tech] About the definition of num_ref_frames

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Hi all,
I am confused about that the parameter in JM is different with 
the definition of H.264 recommendation.
In recommendation document JVT-G050(It seems to be a old version), I check some definitions in 7.4 as below:
[=============
num_ref_frames specifies the maximum total number of short-term and long-term reference frames, complementary reference field pairs, and non-paired reference fields used by the decoding process for inter prediction of any picture in the sequence. num_ref_frames also determines the size of the sliding window operation as specified in subclause 8.2.5.3. The value of num_ref_frames shall be in the range of 0 to 16, inclusive.
max_long_term_frame_idx_plus1 minus 1 specifies the maximum value of long-term frame index allowed for long-term reference pictures (until receipt of another value of max_long_term_frame_idx_plus1). The value of max_long_term_frame_idx_plus1 shall be in the range of 0 to num_ref_frames, inclusive.
=============]
Here the text "The value of num_ref_frames shall be in the range of 0 to 16, inclusive"
is obey the parameter in JM.
However, I download the latest recommendation document from ITU web-site
the definitions change as below:
[=============
num_ref_frames specifies the maximum number of short-term and long-term reference frames, complementary reference field pairs, and non-paired reference fields that may be used by the decoding process for inter prediction of any picture in the sequence. num_ref_frames also determines the size of the sliding window operation as specified in subclause 8.2.5.3. The value of num_ref_frames shall be in the range of 0 to MaxDpbSize (as specified in subclause A.3.1), inclusive.
=============]
It defines the maximum value of num_ref_frame is 0 to MaxDpbSize instead of 0 to 16.
For example , if we use the profile with the level value equal to 5, and the picure format is CIF,
we might have a huge amount DPB size to store many reference frames in CIF format. 
At this situation, We can store more than '16' reference frames(including short-term and long-term) in the DPB.
So, the questions are:
Qn 1>
Why does JM restrict the parameter 'NumberReferenceFrames' in the range 1-16 ?
("NumberReferenceFrames =  5  # Number of previous frames used for inter motion search (1-16)")
Can we set the parameter "NumberReferenceFrames" more than '16' for reference if the DPB size is enough ?(In JM)
Qn 2>
Can the long-term reference picture stay in the DPB as long as the encoder wants it to ?
(Will the parameter'NumberReferenceFrames' restrict the logh-term reference index ?)
Qn 3>
Could anyone tell me that the meaning of the parameter in JM 'PList0Reference'  ?
Best regards,
H.B.
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