avformat/dashdec: add min_buffer_time process logic

if there have min_buffer_time in playlist, use the min_buffer_time
value for realtime.
Signed-off-by: Steven Liu <lq@onvideo.cn>

libavformat/dashdec.c

@@ -1343,7 +1343,11 @@ static int64_t calc_cur_seg_no(AVFormatContext *s, struct representation *pls)
             if (pls->presentation_timeoffset) {
                 num = pls->presentation_timeoffset * pls->fragment_timescale / pls->fragment_duration;
             } else if (c->publish_time > 0 && !c->availability_start_time) {
+                if (c->min_buffer_time) {
+                    num = pls->first_seq_no + (((c->publish_time + pls->fragment_duration) - c->suggested_presentation_delay) * pls->fragment_timescale) / pls->fragment_duration - c->min_buffer_time;
+                } else {
                 num = pls->first_seq_no + (((c->publish_time - c->time_shift_buffer_depth + pls->fragment_duration) - c->suggested_presentation_delay) * pls->fragment_timescale) / pls->fragment_duration;
+                }
             } else {
                 num = pls->first_seq_no + (((get_current_time_in_sec() - c->availability_start_time) - c->suggested_presentation_delay) * pls->fragment_timescale) / pls->fragment_duration;
             }