you could use ICE, to ensure you have connectivity.
Then, by time the ICE checks have completed you will be able to start
sending the video and expect the other end to receive it.
Paul
Richard wrote:
> Hi all,
>
> Suppose caller A wants to initiate a video call with B. He sends an
> INVITE to B and B accepts the call and then sends back 200 OK with SDP.
> According to RFC 3264, practically caller B will send the audio and
> video RTP packet to caller A immediately. Since SIP messages and RTP
> packets take different paths to the destination, the media data usually
> arrive to caller A first before the 200OK. It's okay for audio data
> because voice decoder can decode individual RTP payloads even the first
> few packets are skipped (e.g. G.711, G.729). However, it's not case in
> video. Take H.263 as an example. Usually the first encoded video frame
> is I-frame, and the next few frames are P-frames. If the first I-frame
> are skipped, caller A cannot decode the video packet properly until he
> gets next I-frames. There would cause significant delays for caller A to
> see the caller B. How to solve it? Thanks in advance.
>
> Caller A Caller B
> Invite w SDP(audio & video)
> |----------------------------------->|
> 200OK w SDP(audio & video)
> |<-----------------------------------|
> <--B start sending audio and
> video data
>
> ACK
> |----------------------------------->|
>
> Richard Wu
> ASTRI
>
>
>
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