From 2f620dfdeb330685e4aa94a47b1a87507df664d5 Mon Sep 17 00:00:00 2001
From: Mike Brady <mikebrady@eircom.net>
Date: Tue, 23 Dec 2014 13:16:38 +0000
Subject: [PATCH] Modify latency calculation -- default 88,200 and only use
 99,400 for iTunes V 10 or later

---
 rtsp.c      | 47 +++++++++++++++++++++++++++++++----------------
 shairport.c |  4 ++--
 2 files changed, 33 insertions(+), 18 deletions(-)

diff --git a/rtsp.c b/rtsp.c
index 04bb5a47..71e78008 100644
--- a/rtsp.c
+++ b/rtsp.c
@@ -447,24 +447,39 @@ static void handle_setup(rtsp_conn_info *conn,
       // debug(1,"Active Remote is %u.",active_remote);
     }
     
-    if (config.userSuppliedLatency==0) {
-      char * ua = msg_get_header(req,"User-Agent");
-      if (!ua) {
-        debug(1,"No User-Agent string found in the SETUP message and no user-supplied latency. Using AirPlay latency of %d frames.",config.AirPlayLatency);
-        return;
-      }
-      if (strstr(ua,"iTunes")==ua) {
-        //debug(1,"User-Agent is iTunes; selecting the iTunes latency of %d frames.",config.iTunesLatency);
-        config.latency=config.iTunesLatency;
-      } else if (strstr(ua,"AirPlay")==ua) {
-        //debug(1,"User-Agent is AirPlay; selecting the AirPlay latency of %d frames.",config.AirPlayLatency);
-        config.latency=config.AirPlayLatency;
-      }
-    } else {
-      //debug(1,"Selecting the latency of %d frames supplied with the -L option.",config.userSuppliedLatency);
+    // select latency
+    // if iTunes V10 or later is detected, use the iTunes latency setting
+    // if AirPlay is detected, use the AirPlay latency setting
+    // for everything else, use the general latency setting, if given, or
+    // else use the default latency setting
+    
+    if (config.userSuppliedLatency)
       config.latency=config.userSuppliedLatency;
+    
+    char * ua = msg_get_header(req,"User-Agent");
+//    if (ua==0) {
+//      debug(1,"No User-Agent string found in the SETUP message. Using latency of %d frames.",config.latency);
+//    } else {  
+    if (ua) {  
+      if (strstr(ua,"iTunes")==ua) {
+        int iTunesVersion=0;
+        // now check it's version 10 or later
+        char *pp = strchr(ua,'/') + 1;
+        if (pp)
+          iTunesVersion=atoi(pp);
+        // else
+        //  debug(1,"iTunes Version Number not found.");
+        if (iTunesVersion>=10) {        
+          // debug(1,"User-Agent is iTunes 10 or better, (actual version is %d); selecting the iTunes latency of %d frames.",iTunesVersion,config.iTunesLatency);
+          config.latency=config.iTunesLatency;
+        }
+      } else if (strstr(ua,"AirPlay")==ua) {
+        // debug(1,"User-Agent is AirPlay; selecting the AirPlay latency of %d frames.",config.AirPlayLatency);
+        config.latency=config.AirPlayLatency;
+      } // else {
+        // debug(1,"Unrecognised User-Agent. Using latency of %d frames.",config.latency);
+      // }
     }
-
     char *hdr = msg_get_header(req, "Transport");
     if (!hdr)
         return;
diff --git a/shairport.c b/shairport.c
index d3248fe5..d29b81f4 100644
--- a/shairport.c
+++ b/shairport.c
@@ -335,9 +335,9 @@ int main(int argc, char **argv) {
 
     // set defaults
     config.statistics_requested - 0; // don't print stats in the log
-    config.latency = 99400; // iTunes
+    config.latency = 88200; // AirPlay
     config.userSuppliedLatency = 0; // zero means none supplied
-    config.iTunesLatency = 99400; // this seems to work pretty well for iTunes -- two left-ear headphones, one from the iMac jack, one from an NSLU2 running a cheap "3D Sound" USB Soundcard
+    config.iTunesLatency = 99400; // this seems to work pretty well for iTunes from Version 10 (?) upwards-- two left-ear headphones, one from the iMac jack, one from an NSLU2 running a cheap "3D Sound" USB Soundcard
     config.AirPlayLatency = 88200; // this seems to work pretty well for AirPlay -- Syncs sound and vision on AppleTV, but also used for iPhone/iPod/iPad sources
     config.resyncthreshold = 441*5; // this number of frames is 50 ms
     config.timeout = 120; // this number of seconds to wait for [more] audio before switching to idle.