From e79f30604f4fe77cba65dc6094384f033cca1328 Mon Sep 17 00:00:00 2001
From: Gregor Richards <hg-yff@gregor.im>
Date: Sat, 17 Dec 2016 20:10:51 -0500
Subject: [PATCH] Better stall timing

We now stall not until we've reached parity (which makes no sense since
we expect latency), but only until we're not likely to stall again.
---
 network/netplay/netplay_frontend.c | 39 ++++++++++++++++++++----------
 network/netplay/netplay_io.c       | 18 +++-----------
 2 files changed, 30 insertions(+), 27 deletions(-)

diff --git a/network/netplay/netplay_frontend.c b/network/netplay/netplay_frontend.c
index 8f5c0300cc..c5571b0493 100644
--- a/network/netplay/netplay_frontend.c
+++ b/network/netplay/netplay_frontend.c
@@ -152,6 +152,26 @@ static bool get_self_input_state(netplay_t *netplay)
    return true;
 }
 
+static uint32_t netplay_max_ahead(netplay_t *netplay)
+{
+   uint32_t max_ahead;
+
+   /* Figure out how many frames we're allowed to be ahead: Ideally we need to be
+    * able to run our entire stall worth of frames in one real frame. In
+    * practice, we'll allow a couple jitter frames.  (FIXME: hard coded
+    * as three 60FPS frames) */
+   if (netplay_data->frame_run_time_avg)
+      max_ahead = 50000 / netplay_data->frame_run_time_avg;
+   else
+      max_ahead = NETPLAY_MAX_STALL_FRAMES;
+   if (max_ahead > NETPLAY_MAX_STALL_FRAMES)
+      max_ahead = NETPLAY_MAX_STALL_FRAMES;
+   if (max_ahead < 2)
+      max_ahead = 2;
+
+   return max_ahead;
+}
+
 /**
  * netplay_poll:
  * @netplay              : pointer to netplay object
@@ -198,8 +218,11 @@ static bool netplay_poll(void)
    switch (netplay_data->stall)
    {
       case NETPLAY_STALL_RUNNING_FAST:
+      {
+         uint32_t max_ahead = netplay_max_ahead(netplay_data);
          netplay_update_unread_ptr(netplay_data);
-         if (netplay_data->unread_frame_count >= netplay_data->self_frame_count)
+         if (netplay_data->unread_frame_count + max_ahead - 2
+               > netplay_data->self_frame_count)
          {
             netplay_data->stall = NETPLAY_STALL_NONE;
             for (i = 0; i < netplay_data->connections_size; i++)
@@ -210,6 +233,7 @@ static bool netplay_poll(void)
             }
          }
          break;
+      }
 
       case NETPLAY_STALL_NO_CONNECTION:
          /* We certainly haven't fixed this */
@@ -217,18 +241,7 @@ static bool netplay_poll(void)
 
       default: /* not stalling */
       {
-         retro_time_t max_ahead;
-
-         /* Figure out how many frames we're allowed to be ahead: Ideally we need to be
-          * able to run our entire stall worth of frames in one real frame. In
-          * practice, we'll allow a couple jitter frames.  (FIXME: hard coded
-          * as three 60FPS frame) */
-         if (netplay_data->frame_run_time_avg)
-            max_ahead = 50000 / netplay_data->frame_run_time_avg;
-         else
-            max_ahead = NETPLAY_MAX_STALL_FRAMES;
-         if (max_ahead > NETPLAY_MAX_STALL_FRAMES)
-            max_ahead = NETPLAY_MAX_STALL_FRAMES;
+         uint32_t max_ahead = netplay_max_ahead(netplay_data);
 
          /* Are we too far ahead? */
          netplay_update_unread_ptr(netplay_data);
diff --git a/network/netplay/netplay_io.c b/network/netplay/netplay_io.c
index e710992866..76f2f3b56a 100644
--- a/network/netplay/netplay_io.c
+++ b/network/netplay/netplay_io.c
@@ -479,9 +479,8 @@ static bool netplay_get_cmd(netplay_t *netplay,
             dframe = &netplay->buffer[netplay->read_ptr[player]];
             if (!netplay_delta_frame_ready(netplay, dframe, netplay->read_frame_count[player]))
             {
-               /* FIXME: Catastrophe! */
-               RARCH_ERR("Netplay input from %u without a ready delta frame!\n", player);
-               return netplay_cmd_nak(netplay, connection);
+               /* Hopefully we'll be ready after another round of input */
+               goto shrt;
             }
             memcpy(dframe->real_input_state[player], buffer + 2,
                WORDS_PER_INPUT*sizeof(uint32_t));
@@ -1078,8 +1077,8 @@ static bool netplay_get_cmd(netplay_t *netplay,
 
             if (!netplay_delta_frame_ready(netplay, &netplay->buffer[netplay->read_ptr[connection->player]], frame))
             {
-               RARCH_ERR("CMD_LOAD_SAVESTATE with unready delta frame.\n");
-               return netplay_cmd_nak(netplay, connection);
+               /* Hopefully it will be after another round of input */
+               goto shrt;
             }
 
             RECV(&isize, sizeof(isize))
@@ -1236,15 +1235,6 @@ int netplay_poll_net_input(netplay_t *netplay, bool block)
 
       netplay->timeout_cnt++;
 
-      /* Make sure we're actually ready for data */
-      if (netplay->self_mode >= NETPLAY_CONNECTION_CONNECTED)
-      {
-         netplay_update_unread_ptr(netplay);
-         if (!netplay_delta_frame_ready(netplay,
-               &netplay->buffer[netplay->unread_ptr], netplay->unread_frame_count))
-            break;
-      }
-
       /* Read input from each connection */
       for (i = 0; i < netplay->connections_size; i++)
       {