Re: [AVT] Retransmission draft

Jose,

--> "Jose Rey" <rey@panasonic.de> writes:
> thanks for your feedback. Let me try to clarify: the statement says there
> are other alternatives to solve the problems the retransmission
> addresses. However, this doesn't mean that these other solutions are
> better or worse. It is a matter of trade-off between, e.g., client/server
> complexity, buffer space and bit rate available.  And these depend on
> your scenario (!). Typically, FEC and packet interleaving schemes offer
> less protection for the same available bitrate, as pro-active schemes
> send redundant packets in advance. You also need to XOR-encode and
> -decode packets.  FEC and packet interleaving have a fixed repetition
> scheme, which means that packets are repeated a fixed number of times
> (whether they are lost or not!) whereas retransmission is more flexible
> here by allowing each lost packet to be retransmitted as often as
> necessary within the given timing constraints.  An advantage of
> pro-active schemes might be that they don't require a feedback channel.

Note that there's nothing in RFC 2733 that requires FEC to be sent with a
fixed repetition scheme. One could imagine a scenario where the receiver
used the RTCP feedback extensions to inform the sender of loss, and the
sender then generated FEC packets on demand to correct that loss...

Colin

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