[AVT] RFC 4103 - RTP Payload for Text Conversation

[Marc Petit-Huguenin <petithug at acm.org>]

I hope that this is the right place for questions on RFC 4103.

- Section 5.2, 3rd paragraph:  "The last packet before an idle
period will contain only one non-empty T140block as redundant data..."

I am not sure how to reconcile this with the first paragraph in the
same section that states that the beginning of an idle period is
when the empty T140block is sent.  Does it means that the idle
period starts with the empty T140block when no redundancy is used,
but with the last retransmitted packet when redundancy is used?

This also does not fit well with the next sentence; "Any empty
T140block sent as primary data MUST be included as redundant
T140block in subsequent packets, just as normal text."  If it was
the case, wouldn't the last redundant packet sent entirely be
composed of empty T140block?

- Section 7.1: "As a follow-on to the previous example, the example
belows shows the next RTP packet in the sequence..."

The example that follow does not seems to be correct.  The previous
packet contains an empty primary block and data in the secondary
block.  The next packet contains 3 blocks so I understand that the
third block in the previous packet was removed because it contained
an empty block that has a too old timestamp.  So the previous packet
contains (older first): {empty, data, empty}, but the next packet
contains {empty, data, data}, which does not make sense.  If I
understand correctly the protocol, it should be {data, empty, data}.
 Is my understanding correct?

- T-140 says that the byte order mark should be inserted at the
beginning of the session, which I understand as the first packet
sent (as RFC 4103 does not say anything about it).  But the byte
order mark is useless after been converted to UTF-8 so why a sender
should send it?


Thanks.

-- 
Marc Petit-Huguenin
Home: marc at petit-huguenin.org
Work: petithug at acm.org