From fefe9b605325bd04251e9ca877d9a8bd5b56295f Mon Sep 17 00:00:00 2001
From: Thomas Guillem <thomas@gllm.fr>
Date: Thu, 8 Dec 2022 11:27:30 +0100
Subject: [PATCH] lib: add libvlc_audio_set_mixmode

---
 include/vlc/libvlc_media_player.h | 46 +++++++++++++++++++++++++++++++
 lib/audio.c                       | 42 ++++++++++++++++++++++++++++
 lib/libvlc.sym                    |  2 ++
 3 files changed, 90 insertions(+)

diff --git a/include/vlc/libvlc_media_player.h b/include/vlc/libvlc_media_player.h
index 2403413eb6c1..c118f2b2c7b7 100644
--- a/include/vlc/libvlc_media_player.h
+++ b/include/vlc/libvlc_media_player.h
@@ -2229,6 +2229,17 @@ typedef enum libvlc_audio_output_stereomode_t {
     libvlc_AudioStereoMode_Mono  = 7,
 } libvlc_audio_output_stereomode_t;
 
+/**
+ * Audio mix modes
+ */
+typedef enum libvlc_audio_output_mixmode_t {
+    libvlc_AudioMixMode_Unset       = 0,
+    libvlc_AudioMixMode_Stereo      = 1,
+    libvlc_AudioMixMode_Binaural    = 2,
+    libvlc_AudioMixMode_4_0         = 3,
+    libvlc_AudioMixMode_5_1         = 4,
+    libvlc_AudioMixMode_7_1         = 5,
+} libvlc_audio_output_mixmode_t;
 
 /**
  * Gets the list of available audio output modules.
@@ -2429,6 +2440,41 @@ LIBVLC_API libvlc_audio_output_stereomode_t libvlc_audio_get_stereomode( libvlc_
 LIBVLC_API int libvlc_audio_set_stereomode( libvlc_media_player_t *p_mi,
                                             libvlc_audio_output_stereomode_t mode );
 
+/**
+ * Get current audio mix-mode.
+ *
+ * \param p_mi media player
+ * \return the audio mix-mode, \see libvlc_audio_output_mixmode_t
+ * \version LibVLC 4.0.0 or later
+ */
+LIBVLC_API libvlc_audio_output_mixmode_t libvlc_audio_get_mixmode( libvlc_media_player_t *p_mi );
+
+/**
+ * Set current audio mix-mode.
+ *
+ * By default (libvlc_AudioMixMode_Unset), the audio output will keep its
+ * original channel configuration (play stereo as stereo, or 5.1 as 5.1). Yet,
+ * the OS and Audio API might refuse a channel configuration and asks VLC to
+ * adapt (Stereo played as 5.1 or vice-versa).
+ *
+ * This function allows to force a channel configuration, it will only work if
+ * the OS and Audio API accept this configuration (otherwise, it won't have any
+ * effects). Here are some examples:
+ *  - Play multi-channels (5.1, 7.1...) as stereo (libvlc_AudioMixMode_Stereo)
+ *  - Play Stereo or 5.1 as 7.1 (libvlc_AudioMixMode_7_1)
+ *  - Play multi-channels as stereo with a binaural effect
+ *  (libvlc_AudioMixMode_Binaural). It might be selected automatically if the
+ *  OS and Audio API can detect if a headphone is plugged.
+ *
+ * \param p_mi media player
+ * \param channel the audio mix-mode, \see libvlc_audio_output_mixmode_t
+ * \return 0 on success, -1 on error
+ * \version LibVLC 4.0.0 or later
+ */
+LIBVLC_API int libvlc_audio_set_mixmode( libvlc_media_player_t *p_mi,
+                                         libvlc_audio_output_mixmode_t mode );
+
+
 /**
  * Get current audio delay.
  *
diff --git a/lib/audio.c b/lib/audio.c
index eea0142e698b..49900aa4c559 100644
--- a/lib/audio.c
+++ b/lib/audio.c
@@ -390,6 +390,48 @@ int libvlc_audio_set_stereomode( libvlc_media_player_t *mp, libvlc_audio_output_
     return ret;
 }
 
+/*****************************************************************************
+ * libvlc_audio_get_mixmode : Get the current audio mix-mode
+ *****************************************************************************/
+libvlc_audio_output_mixmode_t libvlc_audio_get_mixmode( libvlc_media_player_t *mp )
+{
+    audio_output_t *p_aout = GetAOut( mp );
+    if( !p_aout )
+        return libvlc_AudioMixMode_Unset;
+
+    int val = var_GetInteger( p_aout, "mix-mode" );
+    aout_Release(p_aout);
+    return val;
+}
+
+/*****************************************************************************
+ * libvlc_audio_set_mixmode : Set the current audio mix-mode
+ *****************************************************************************/
+int libvlc_audio_set_mixmode( libvlc_media_player_t *mp, libvlc_audio_output_mixmode_t mode )
+{
+    static_assert(libvlc_AudioMixMode_Unset == AOUT_VAR_CHAN_UNSET &&
+                  libvlc_AudioMixMode_Stereo == AOUT_MIX_MODE_STEREO &&
+                  libvlc_AudioMixMode_Binaural == AOUT_MIX_MODE_BINAURAL &&
+                  libvlc_AudioMixMode_4_0 == AOUT_MIX_MODE_4_0 &&
+                  libvlc_AudioMixMode_5_1 == AOUT_MIX_MODE_5_1 &&
+                  libvlc_AudioMixMode_7_1 == AOUT_MIX_MODE_7_1,
+                  "Mismatch with mix-mode LibVLC/VLC enums");
+
+    audio_output_t *p_aout = GetAOut( mp );
+    int ret = 0;
+
+    if( !p_aout )
+        return -1;
+
+    if( var_SetInteger( p_aout, "mix-mode", mode ) < 0 )
+    {
+        libvlc_printerr( "Audio mix-mode out of range" );
+        ret = -1;
+    }
+    aout_Release(p_aout);
+    return ret;
+}
+
 /*****************************************************************************
  * libvlc_audio_get_delay : Get the current audio delay
  *****************************************************************************/
diff --git a/lib/libvlc.sym b/lib/libvlc.sym
index 83d3157a7c0d..cfa6cd095c1f 100644
--- a/lib/libvlc.sym
+++ b/lib/libvlc.sym
@@ -19,6 +19,7 @@ libvlc_audio_output_device_set
 libvlc_audio_output_list_get
 libvlc_audio_output_list_release
 libvlc_audio_output_set
+libvlc_audio_get_mixmode
 libvlc_audio_get_stereomode
 libvlc_audio_get_delay
 libvlc_audio_get_mute
@@ -26,6 +27,7 @@ libvlc_audio_get_track
 libvlc_audio_get_track_count
 libvlc_audio_get_track_description
 libvlc_audio_get_volume
+libvlc_audio_set_mixmode
 libvlc_audio_set_stereomode
 libvlc_audio_set_delay
 libvlc_audio_set_mute