ffplay: ensure that we buffer at least 1 second of content

In order to do that, we keep track of the total duration of packets in a packet
queue.
Signed-off-by: Marton Balint <cus@passwd.hu>

ffplay.c

@@ -117,6 +117,7 @@ typedef struct PacketQueue {
     MyAVPacketList *first_pkt, *last_pkt;
     int nb_packets;
     int size;
+    int64_t duration;
     int abort_request;
     int serial;
     SDL_mutex *mutex;
@@ -417,6 +418,7 @@ static int packet_queue_put_private(PacketQueue *q, AVPacket *pkt)
     q->last_pkt = pkt1;
     q->nb_packets++;
     q->size += pkt1->pkt.size + sizeof(*pkt1);
+    q->duration += pkt1->pkt.duration;
     /* XXX: should duplicate packet data in DV case */
     SDL_CondSignal(q->cond);
     return 0;
@@ -478,6 +480,7 @@ static void packet_queue_flush(PacketQueue *q)
     q->first_pkt = NULL;
     q->nb_packets = 0;
     q->size = 0;
+    q->duration = 0;
     SDL_UnlockMutex(q->mutex);
 }
 
@@ -528,6 +531,7 @@ static int packet_queue_get(PacketQueue *q, AVPacket *pkt, int block, int *seria
                 q->last_pkt = NULL;
             q->nb_packets--;
             q->size -= pkt1->pkt.size + sizeof(*pkt1);
+            q->duration -= pkt1->pkt.duration;
             *pkt = pkt1->pkt;
             if (serial)
                 *serial = pkt1->serial;
@@ -2800,7 +2804,7 @@ static int stream_has_enough_packets(AVStream *st, int stream_id, PacketQueue *q
     return stream_id < 0 ||
            queue->abort_request ||
            (st->disposition & AV_DISPOSITION_ATTACHED_PIC) ||
-           queue->nb_packets > MIN_FRAMES;
+           queue->nb_packets > MIN_FRAMES && (!queue->duration || av_q2d(st->time_base) * queue->duration > 1.0);
 }
 
 static int is_realtime(AVFormatContext *s)