get_caps_from_media

Mapping of caps from SDP fields:

a=rtpmap:(payload) (encoding_name)/(clock_rate)[/(encoding_params)]

a=framesize:(payload) (width)-(height)

a=fmtp:(payload) (param)[=(value)];...

Note that the extmap, ssrc and rid attributes are set only by attributes_to_caps.

Parameters:

this	a Media
pt	a payload type

Returns:

a Caps, or null if an error happened