X-Git-Url: https://git.distorted.org.uk/~mdw/disorder/blobdiff_plain/7bdf42d0ac1f501bbb32e1ea3f502f7355865cb5..561d077df8d0494aeeaf3f30d847f489336cbfd6:/clients/playrtp.c

diff --git a/clients/playrtp.c b/clients/playrtp.c
index 90199c4..7eed9eb 100644
--- a/clients/playrtp.c
+++ b/clients/playrtp.c
@@ -1,6 +1,6 @@
 /*
  * This file is part of DisOrder.
- * Copyright (C) 2007, 2008 Richard Kettlewell
+ * Copyright (C) 2007-2009 Richard Kettlewell
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -324,6 +324,9 @@ static void *queue_thread(void attribute((unused)) *arg) {
     pthread_cond_broadcast(&cond);
     pthread_mutex_unlock(&lock);
   }
+#if HAVE_STUPID_GCC44
+  return NULL;
+#endif
 }
 
 /** @brief Background thread collecting samples
@@ -566,7 +569,40 @@ static size_t playrtp_callback(void *buffer,
   }
   /* Advance timestamp */
   next_timestamp += samples;
-  /* If we're getting behind then try to drop just silent packets */
+  /* If we're getting behind then try to drop just silent packets
+   *
+   * In theory this shouldn't be necessary.  The server is supposed to send
+   * packets at the right rate and compares the number of samples sent with the
+   * time in order to ensure this.
+   *
+   * However, various things could throw this off:
+   *
+   * - the server's clock could advance at the wrong rate.  This would cause it
+   *   to mis-estimate the right number of samples to have sent and
+   *   inappropriately throttle or speed up.
+   *
+   * - playback could happen at the wrong rate.  If the playback host's sound
+   *   card has a slightly incorrect clock then eventually it will get out
+   *   of step.
+   *
+   * So if we play back slightly slower than the server sends for either of
+   * these reasons then eventually our buffer, and the socket's buffer, will
+   * fill, and the kernel will start dropping packets.  The result is audible
+   * and not very nice.
+   *
+   * Therefore if we're getting behind, we pre-emptively drop silent packets,
+   * since a change in the duration of a silence is less noticeable than a
+   * dropped packet from the middle of continuous music.
+   *
+   * (If things go wrong the other way then eventually we run out of packets to
+   * play and are forced to play silence.  This doesn't seem to happen in
+   * practice but if it does then in the same way we can artificially extend
+   * silent packets to compensate.)
+   *
+   * Dropped packets are always logged; use 'disorder-playrtp --monitor' to
+   * track how close to target buffer occupancy we are on a once-a-minute
+   * basis.
+   */
   if(nsamples > minbuffer && silent) {
     info("dropping %zu samples (%"PRIu32" > %"PRIu32")",
          samples, nsamples, minbuffer);
@@ -726,9 +762,6 @@ int main(int argc, char **argv) {
       struct sockaddr_in *in = (struct sockaddr_in *)res->ai_addr;
       
       memset(&in->sin_addr, 0, sizeof (struct in_addr));
-      if(bind(rtpfd, res->ai_addr, res->ai_addrlen) < 0)
-        fatal(errno, "error binding socket to 0.0.0.0 port %d",
-              ntohs(in->sin_port));
       break;
     }
     case AF_INET6: {
@@ -825,7 +858,7 @@ int main(int argc, char **argv) {
 	  || (nsamples > 0
 	      && contains(pheap_first(&packets), next_timestamp))) {
       if(monitor) {
-        time_t now = time(0);
+        time_t now = xtime(0);
 
         if(now >= lastlog + 60) {
           int offset = nsamples - minbuffer;