make_setup_request

static int 
make_setup_request (AVFormatContext *s, const char *host, int port,
                    int lower_transport, const char *real_challenge)

{

if (rt->transport == RTSP_TRANSPORT_RDT) trans_pref = "x-pn-tng"; else trans_pref = "RTP/AVP";

如果是使用RDT协议传输数据，那么TRANSPORT命令采用x-pn-tng的传输协议，如果采用RTP，那么TRANSPORT命令采用RTP/XXX的传输协议， XXX表示rtp profile的简称。

for(j = RTSP_RTP_PORT_MIN, i = 0; i < rt->nb_rtsp_streams; ++i) { char transport[2048]; rtsp_st = rt->rtsp_streams[i]; /* RTP/UDP */ if (lower_transport == RTSP_LOWER_TRANSPORT_UDP) { char buf[256]; /* first try in specified port range */ if (RTSP_RTP_PORT_MIN != 0) { while(j <= RTSP_RTP_PORT_MAX) { snprintf(buf, sizeof(buf), "rtp://%s?localport=%d", host, j); j += 2; /* we will use two port by rtp stream (rtp and rtcp) */ if (url_open(&rtsp_st->rtp_handle, buf, URL_RDWR) == 0) { goto rtp_opened; } } }

上述代码循环为每个rtsp_streams构建一个SETUP命令，rtsp协议里面定义SETUP的格式：

C->S: SETUP rtsp://example.com/foo/bar/baz.rm RTSP/1.0CSeq: 302Transport: RTP/AVP;unicast;client_port=4588-4589S->C: RTSP/1.0 200 OKCSeq: 302Date: 23 Jan 1997 15:35:06 GMTSession: 47112344Transport: RTP/AVP;unicast;client_port=4588-4589;server_port=6256-6257

在transport header中定义传输的参数。

接下来打开rtp media stream,参考rtsp_open_transport_ctx函数

       

}