ffplay: do not block audio thread on WIN32

The windows SDL audio driver plays the old data in the buffer in a loop if it
is not updated in time. So instead of waiting for data and blocking the the
audio thread, return silence if no data is available.

Should fix ticket #2289.

Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Marton Balint <cus@passwd.hu>

ffplay.c

@@ -2303,6 +2303,13 @@ static int audio_decode_frame(VideoState *is)
         return -1;
 
     do {
+#if defined(_WIN32)
+        while (frame_queue_nb_remaining(&is->sampq) == 0) {
+            if ((av_gettime_relative() - audio_callback_time) > 1000000LL * is->audio_hw_buf_size / is->audio_tgt.bytes_per_sec / 2)
+                return -1;
+            av_usleep (1000);
+        }
+#endif
         if (!(af = frame_queue_peek_readable(&is->sampq)))
             return -1;
         frame_queue_next(&is->sampq);