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Hi, I read both drafts and I would like to present my view as an
individual trying to clarify what I understand from both drafts and give my
view on some of the issues raised on the mailing list. I would like to start with an observation that RAMS is not a retransmission solution as specified in RFC 4588 "RTP retransmission is an effective packet loss recovery technique for real-time applications with relaxed delay bounds.". There is no packet loss in this case. It is using the same mechanism to convey information that will look to the RR as a retransmission stream using the RTP packet structure defined in section 4 of RFC 4588 and the SDP description from RFC 4588. Yet the RR did not know that it was missing any RTP packet with specific sequence numbers since he was not expecting them in the unicast stream until they arrived and the OSN value is not that meaningful to it. Now when talking about the preamble / PSI or information that the RR needs which may have been transmitted many packets ago I see in the two drafts two directions to convey the information1. Specified in the Begen draft is to convey the information using a new payload format that will include the needed information as a set of TLOV elements payload. 2. Specified in Xia draft that conveys the information looking like a regular MPEG2 TS retransmission packet but since it is generated by the RS it may get an OSN that is before the OSN of the first RAMS unicast stream. I cannot say which one is better. My personal analysis is that in both cases the RS will need to cache this information and will need to create the right packet structure which is the TLOV in the first case and an MPEG2 TS PSI packet in the second case. The RR will need to support this payload format in the first case while I assume that in the second case it will look like a regular MPEG2 TS stream. Other points that I see is that in the first case the packet may be smaller in size and the extensibility can allow the RS to provide additional information that was not part of the original stream (I am not sure if that was the meaning here). In the second case it looks like the RR will see an MPEG2 TS stream and will not need to support the TLOV payload format.I do not have any view about what is the right way and I was only trying to see if I understand both proposals. ThanksRoni Even as an individual |