RTC: Use transformed mid, not the mid of track.
RTC: Use transformed mid, not the mid of track.

ossrs/srs,winlinvip/srs,winlinvip/srs,winlinvip/srs,winlinvip/srs,ossrs/srs,winlinvip/srs,winlinvip/simple-rtmp-server,ossrs/srs,winlinvip/srs,ossrs/srs,ossrs/srs,ossrs/srs