diff --git a/README.md b/README.md
index 802fc671..bfd61851 100644
--- a/README.md
+++ b/README.md
@@ -67,9 +67,11 @@ See [here](https://github.com/mikebrady/shairport-sync/blob/development/INSTALL.
 
 The following procedures will build and install the `shairport-sync` application into your system.
 
-**Remove Old Versions Of Shairport Sync**
+**Remove Old Versions of Shairport Sync and its Startup Scripts**
 
-You should check to see if `shairport-sync` is already installed – you can use the command `$ which shairport-sync` to find where it is located, if installed. If it is installed you should delete it – you may need superuser privileges. After deleting, check again in case further copies are installed elsewhere. You should also remove the file `/etc/systemd/system/shairport-sync.service` if it exists.
+You should check to see if `shairport-sync` is already installed – you can use the command `$ which shairport-sync` to find where it is located, if installed. If it is installed you should delete it – you may need superuser privileges. After deleting, check again in case further copies are installed elsewhere. 
+
+You should also remove the initialisation script files `/etc/systemd/system/shairport-sync.service` and `/etc/init.d/shairport-sync` if they exist – new ones will be installed in necessary.
 
 **FreeBSD**
 
diff --git a/RELEASENOTES.md b/RELEASENOTES.md
index 63aeb9ce..bbc81907 100644
--- a/RELEASENOTES.md
+++ b/RELEASENOTES.md
@@ -1,3 +1,10 @@
+Version 3.3d4
+====
+* Sometimes `libsoxr` is built to rely on `libavutil`. With the present changes to `configure.ac`, if `libavutil` is present, link to it when linking to `libsoxr`, but if it's not present, don't link to it when linking to `libsoxr`.
+* Add `pgk_config` support to `libsoxr` selection.
+
+Thanks to [Jörg Krause](https://github.com/joerg-krause) for identifying these issues and proposing fixes.
+
 Version 3.3d3
 ====
 * Modify the code that synchronises the Shairport Sync system's clock with the source clock to try to take account of the sources's nominal rate, which (oddly, e.g. iTunes on a Mac) might not be exactly 44,100 fps. There may be a 32-bit unsigned overflow error here somewhere!
diff --git a/configure.ac b/configure.ac
index 40df449f..9ebc70d3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -176,7 +176,20 @@ AC_ARG_WITH(ssl, [ choose --with-ssl=openssl, --with-ssl=mbedtls or --with-ssl=p
 # Look for soxr flag
 AC_ARG_WITH(soxr, [  --with-soxr = choose libsoxr for high-quality interpolation], [
   AC_MSG_RESULT(>>Including support for soxr-based interpolation)
-  AC_CHECK_LIB([soxr],[soxr_create], , AC_MSG_ERROR(soxr support requested but libsoxr not found!))], )
+  if  test "x${with_pkg_config}" = xyes ; then
+    PKG_CHECK_MODULES(
+        [SOXR], [soxr],
+        [LIBS="${SOXR_LIBS} ${LIBS}"])
+  else
+    AC_CHECK_LIB([avutil],[av_get_cpu_flags])
+    if  test "x${ac_cv_lib_avutil_av_get_cpu_flags}" = xyes ; then
+      # soxr may link against libavutil, depending on the architecture, but for the sake of simplicity link with it if it is found
+      AC_CHECK_LIB([soxr],[soxr_create], , AC_MSG_ERROR(soxr support requested but libsoxr not found!), [-lavutil])
+    else
+      AC_CHECK_LIB([soxr],[soxr_create], , AC_MSG_ERROR(soxr support requested but libsoxr not found!))
+    fi
+  fi
+], )
 
 # Look for metadata flag -- set flag for conditional compilation
 AC_ARG_WITH(metadata, [  --with-metadata = include support for a metadata feed], [