x11/freerdp sndio backend

Hi,

please find attached a sndio backend for FreeRDP which implements

- Audio Output Virtual Channel
(= sound on remote desktop is redirected to local sndiod) and

- Audio Input Redirection Virtual Channel
(= local microphone is redirected to remote desktop).

This allows me to use MS Teams on a remote desktop via FreeRDP. The audio
quality is very good in my test setup; sometimes Windows chimes crackle a bit;
the same behavior is observed with a recent FreeRDP on a Linux machine
(with a pulseaudio/alsa backend).

The backend is based on the oss backend with inspiration from alsa und
pulseaudio. Neither of those three work on OpenBSD. At the moment I do not
plan to submit this upstream as the implementation uses a slightly outdated
API. I am willing to do this once (whether?) our FreeRDP ports gets updated
(which is blocked to due missing timer_create()) as I cannot test
against newer versions easily at the moment.

If a developer thinks this is a useful contribution (and gives an OK) we can
add it to our FreeRDP port locally for the moment.

I attached a .tar.gz to make it easier to review as I did not dare to
cvs add a new "files" directory (as CVS won't forget?). The following diff
shows everything besides the "files" directory.

You need to add /sound:sys:sndio /microphone:sys:sndio to activate the
new features. (x11/remmina cannot handle it; I did not investigate in
depth as we have an outdated version in ports). E.g.:

xfreerdp /d:yourdomain /u:yourusername /v:yourservername.com /sound:sys:sndio /microphone:sys:sndio

OK?

Best regards,
Ingo

Index: Makefile
===================================================================
RCS file: /cvs/ports/x11/freerdp/Makefile,v
retrieving revision 1.39
diff -u -p -r1.39 Makefile
--- Makefile 4 Nov 2019 10:30:20 -0000 1.39
+++ Makefile 10 Sep 2020 14:17:31 -0000
@@ -6,7 +6,7 @@ BROKEN-hppa = undefined reference to __
COMMENT = client for Microsoft RDP (remote desktop protocol)
DISTNAME = freerdp-2.0.0-rc1
PKGNAME = freerdp-2.0.0rc1
-REVISION = 4
+REVISION = 5
CATEGORIES = x11 net

# XXX This version has known security issues.
@@ -26,7 +26,7 @@ MASTER_SITES = https://pub.freerdp.com/
PERMIT_PACKAGE = Yes

WANTLIB += X11 Xcursor Xext Xfixes Xi Xinerama Xrender Xv avcodec
-WANTLIB += avutil c crypto cups execinfo m pthread ssl xkbfile
+WANTLIB += avutil c crypto cups execinfo m pthread sndio ssl xkbfile

# thread-local storage
COMPILER = base-clang ports-gcc
@@ -50,9 +50,15 @@ CONFIGURE_ARGS += -DBUILD_TESTING=ON \
-DWITH_OPENSLES=OFF \
-DWITH_PCSC=ON \
-DWITH_LIBSYSTEMD=OFF \
- -DWITH_OSS=OFF
+ -DWITH_OSS=OFF \
+ -DWITH_SNDIO=ON

pre-configure:
+ mkdir ${WRKSRC}/channels/{audin,rdpsnd}/client/sndio
+ cp ${FILESDIR}/audin/{CMakeLists.txt,audin_sndio.c} \
+ ${WRKSRC}/channels/audin/client/sndio
+ cp ${FILESDIR}/rdpsnd/{CMakeLists.txt,rdpsnd_sndio.c} \
+ ${WRKSRC}/channels/rdpsnd/client/sndio
${SUBST_CMD} ${WRKSRC}/winpr/libwinpr/CMakeLists.txt
${SUBST_CMD} ${WRKSRC}/CMakeLists.txt

Index: patches/patch-channels_audin_client_CMakeLists_txt
===================================================================
RCS file: patches/patch-channels_audin_client_CMakeLists_txt
diff -N patches/patch-channels_audin_client_CMakeLists_txt
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ patches/patch-channels_audin_client_CMakeLists_txt 10 Sep 2020 14:17:31 -0000
@@ -0,0 +1,13 @@
+$OpenBSD$
+
+Index: channels/audin/client/CMakeLists.txt
+--- channels/audin/client/CMakeLists.txt.orig
++++ channels/audin/client/CMakeLists.txt
+@@ -56,3 +56,7 @@ endif()
+ if(WITH_MACAUDIO)
+ add_channel_client_subsystem(${MODULE_PREFIX} ${CHANNEL_NAME} "mac" "")
+ endif()
++
++if(WITH_SNDIO)
++ add_channel_client_subsystem(${MODULE_PREFIX} ${CHANNEL_NAME} "sndio" "")
++endif()
Index: patches/patch-channels_audin_client_audin_main_c
===================================================================
RCS file: patches/patch-channels_audin_client_audin_main_c
diff -N patches/patch-channels_audin_client_audin_main_c
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ patches/patch-channels_audin_client_audin_main_c 10 Sep 2020 14:17:31 -0000
@@ -0,0 +1,27 @@
+$OpenBSD$
+
+Index: channels/audin/client/audin_main.c
+--- channels/audin/client/audin_main.c.orig
++++ channels/audin/client/audin_main.c
+@@ -670,8 +670,11 @@ static UINT audin_load_device_plugin(IWTSPlugin* pPlug
+ AUDIN_PLUGIN* audin = (AUDIN_PLUGIN*)pPlugin;
+ UINT error;
+
++ /*
++ * Causes invalid memory access. Ignore as we do not have arguments.
+ if (!audin_process_addin_args(audin, args))
+ return CHANNEL_RC_INITIALIZATION_ERROR;
++ */
+
+ entry = (PFREERDP_AUDIN_DEVICE_ENTRY) freerdp_load_channel_addin_entry("audin", (LPSTR) name, NULL,
+ 0);
+@@ -863,6 +866,9 @@ UINT DVCPluginEntry(IDRDYNVC_ENTRY_POINTS* pEntryPoint
+