PJSIP Video User's Guide 日本語訳 ref: http://qiita.com/hiroeorz@github/items/f0c6e1eebc1238fcaa31

file0.c

pjsua_acc_config cfg;

pjsua_acc_config_default(&cfg);
cfg.vid_in_auto_show = PJ_TRUE;

file1.c

int vid_idx;
pjsua_vid_win_id wid;

vid_idx = pjsua_call_get_vid_stream_idx(call_id);

if (vid_idx >= 0) {
    pjsua_call_info ci;

    pjsua_call_get_info(call_id, &ci);
    wid = ci.media[vid_idx].stream.vid.win_in;
}