[Mp4-tech] Complementary Field Pairs

[Jagannathan, Shyam]

Dear Experts,

 

What qualifies a pair of fields as complementary field pairs?

 

The standard says,

 

3.1                 complementary field pair: A collective term for a
complementary reference field pair or a complementary non-reference
field pair.

3.2                 complementary non-reference field pair: Two
non-reference fields that are in consecutive access units in decoding
order as two coded fields of opposite parity where the first field is
not already a paired field.

3.3                 complementary reference field pair: Two reference
fields that are in consecutive access units in decoding order as two
coded fields and share the same value of the frame_num syntax element,
where the second field in decoding order is not an IDR picture and does
not include a memory_management_control_operation syntax element equal
to 5.

 

 

Let us assume a case where 2 non-reference field pairs appear in
decoding order as below,

 

    Frame num   :      7             7          

Decoding order  :| TF - BF - BF - TF |

 

 

If the BF picture access unit in the first pair is lost in a streaming
network (say),

 

    Frame num   :      7             7          

Decoding order  :| TF - X - BF - TF |

 

 

 the decoder will see TF belonging to first pair and BF belonging to
second pair and 'pair' them together as complementary non-reference
field pair as per standard definition.

This disturbs the correct decoding and hence display sequence.

 

Is my understanding correct? 

How should a decoder behave in such cases?

Is there a sure shot way of finding complementary field pairs?

 

Thanks and Regards,

Shyam

 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: /pipermail/mp4-tech/attachments/20080206/c380122c/attachment.html