Sequence and PMAP Question

, ,
1

Imported from previous forum

2

Hi,

When decoding CME data, I stumble upon the following Sequence entry:
+++++++++++++++++++++++++++++++++++++++++++++++++++++







+++++++++++++++++++++++++++++++++++++++++++++++++++++

The question is:
1 - If the sequence is optional, then the Length field is also optional. Should I expect (11) to be set in the PMAP if the sequence is present and the Lenght is also present?

2 - If the sequence is always mandatory, why we allow presence=“optional” (thus making the length optional)?

I am very confused with this… According to the FAST 1x1 Spec, this sequence (and length) would both require 2 bits set in the global PMAP (at the template level) but I receive 00 instead, and my decoding fails.

What is the correct behaviour of sequences and PMAP? I understand how the PMAP works for each specific segment for the sequence, but I don’t understand how it works at the top-level.

3

1 - Since the length preamble of this sequence doesn’t have an operator, it won’t use any bit in the presence map.

2 - The absence of an optional sequence without a length operator
is indicated by a NULL (0x80) in the stream.

The top level presence map works as the non top level presence maps
with two differences: it is always present and the first bit is used
for the implicit template identifier copy operator.

/David

Hi,

When decoding CME data, I stumble upon the following Sequence entry:
+++++++++++++++++++++++++++++++++++++++++++++++++++++



+++++++++++++++++++++++++++++++++++++++++++++++++++++

The question is: 1 - If the sequence is optional, then the Length field
is also optional. Should I expect (11) to be set in the PMAP if the
sequence is present and the Lenght is also present?

2 - If the sequence is always mandatory, why we allow
presence=“optional” (thus making the length optional)?

I am very confused with this… According to the FAST 1x1 Spec, this
sequence (and length) would both require 2 bits set in the global PMAP
(at the template level) but I receive 00 instead, and my decoding fails.

What is the correct behaviour of sequences and PMAP? I understand how
the PMAP works for each specific segment for the sequence, but I don’t
understand how it works at the top-level.

4

Thanks, but I am still confused.

Does the Optional Sequence require a bit in the presence map?

5

No

Thanks, but I am still confused.

Does the Optional Sequence require a bit in the presence map?