Why reciver can't get the information of caller wanted a video call?

Why the reciver can't get the information of video call
about the
caller want a video call?
I debug found the reciver's format always audio format,eg.
 A caller,B reciver
 A call B   Audio code=4 + Video=8000 the wanted format is
8004
 but the B got the format  only is 4( ies->format=4
),why?the reciver
can't detect caller
want a video call?

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