On 13 Apr 2005, at 12:40, Magnus Westerlund wrote:
Colin Perkins wrote:
Packet 0: Type 1: SIDX=1
Packet 1: Type 5: SIDX=2
Type 1: SIDX=2
Packet 2: Type 1: SIDX=2
Packet 3: Type 5: SIDX=2 (Repetition)
Type 1: SIDX=2
With the proposed timestamp model, the timestamp of the
TYPE 5 unit
in packet 3 should have a TS equal to the TS of packet 1, rather
than the TS of packet 3 to indicate that it is useful from the TS
time of packet 1.
Why? If you give the type 5 unit sent in packet 3 the timestamp of
packet 3, then the behaviour is unchanged from the
previous, except
that the timing model is used to decode the data.
The reason is that otherwise, you would not care to
depacketize packet
3 until after you have tried to consume packet 2 and
failing that due
to lack of sample description, and moved on.
Yes, of course. That's exactly the behaviour that was defined
in the earlier versions of the draft, which made the Type 5
units available for use as soon as they arrived.
Right now, for TYPE 5 units applies:
o In general, TYPE 5 units MUST receive their timestamp from
the first non-TYPE 5 unit following them in the payload.
o However, if:
Rey & Matsui [Page 31]
Internet Draft Payload Format for 3GPP Timed Text March 29, 2005
o the payload only contains (one or several) TYPE 5
units or,
o if one or several TYPE 5 units follow a sample of
unknown duration (see Section 4.1.2, SDUR
definition),
then (all) TYPE 5 units MUST use the RTP timestamp.
Is this what you refer as too much complexity?