Add libvlc functions for custom audio output

This is not tested due to lack of use cases. Please test and report
bugs or limitations BEFORE final 1.2.0 release (or shut up).

include/vlc/libvlc_media_player.h

@@ -31,8 +31,12 @@
 #ifndef VLC_LIBVLC_MEDIA_PLAYER_H
 #define VLC_LIBVLC_MEDIA_PLAYER_H 1
 
+# include <stddef.h>
+
 # ifdef __cplusplus
 extern "C" {
+# else
+#  include <stdbool.h>
 # endif
 
 /*****************************************************************************
@@ -461,7 +465,91 @@ LIBVLC_API void libvlc_media_player_set_hwnd ( libvlc_media_player_t *p_mi, void
  */
 LIBVLC_API void *libvlc_media_player_get_hwnd ( libvlc_media_player_t *p_mi );
 
+/**
+ * Callback prototype for audio playback.
+ * \param data data pointer as passed to libvlc_audio_set_callbacks() [IN]
+ * \param samples pointer to the first audio sample to play back [IN]
+ * \param count number of audio samples to play back
+ * \param pts expected play time stamp (see libvlc_delay())
+ */
+typedef void (*libvlc_audio_play_cb)(void *data, const void *samples,
+                                     size_t count, int64_t pts);
+
+/**
+ * Callback prototype for audio volume change.
+ * \param data data pointer as passed to libvlc_audio_set_callbacks() [IN]
+ * \param volume linear volume (1. = nominal, 0. = mute)
+ * \param mute muted flag
+ */
+typedef void (*libvlc_audio_set_volume_cb)(void *data,
+                                           float volume, bool mute);
+
+/**
+ * Set callbacks and private data for decoded audio.
+ * Use libvlc_audio_set_format() or libvlc_audio_set_format_callbacks()
+ * to configure the decoded audio format.
+ *
+ * \param mp the media player
+ * \param play callback to play audio samples (must not be NULL)
+ * \param set_volume callback to set audio volume, or NULL for software volume
+ * \param opaque private pointer for the two callbacks (as first parameter)
+ * \version LibVLC 1.2.0 or later
+ */
+LIBVLC_API
+void libvlc_audio_set_callbacks( libvlc_media_player_t *mp,
+                                 libvlc_audio_play_cb play,
+                                 libvlc_audio_set_volume_cb set_volume,
+                                 void *opaque );
+
+/**
+ * Callback prototype to setup the audio playback.
+ * This is called when the media player needs to create a new audio output.
+ * \param opaque pointer to the data pointer passed to
+ *               libvlc_audio_set_callbacks() [IN/OUT]
+ * \param format 4 bytes sample format [IN/OUT]
+ * \param rate sample rate [IN/OUT]
+ * \param channels channels count [IN/OUT]
+ * \return 0 on success, anything else to skip audio playback
+ */
+typedef int (*libvlc_audio_setup_cb)(void **data, char *format, unsigned *rate,
+                                     unsigned *channels);
+
+/**
+ * Callback prototype for audio playback cleanup.
+ * This is called when the media player no longer needs an audio output.
+ * \param opaque data pointer as passed to libvlc_audio_set_callbacks() [IN]
+ */
+typedef void (*libvlc_audio_cleanup_cb)(void *data);
 
+/**
+ * Set decoded audio format. This only works in combination with
+ * libvlc_audio_set_callbacks().
+ *
+ * \param mp the media player
+ * \param setup callback to select the audio format (cannot be NULL)
+ * \param cleanup callback to release any allocated resources (or NULL)
+ * \version LibVLC 1.2.0 or later
+ */
+LIBVLC_API
+void libvlc_audio_set_format_callbacks( libvlc_media_player_t *mp,
+                                        libvlc_audio_setup_cb setup,
+                                        libvlc_audio_cleanup_cb cleanup );
+
+/**
+ * Set decoded audio format.
+ * This only works in combination with libvlc_audio_set_callbacks(),
+ * and is mutually exclusive with libvlc_audio_set_format_callbacks().
+ *
+ * \param mp the media player
+ * \param fourcc a four-characters string identifying the sample format
+ *               (e.g. "S16N" or "FL32")
+ * \param rate sample rate (expressed in Hz)
+ * \param channels channels count
+ * \version LibVLC 1.2.0 or later
+ */
+LIBVLC_API
+void libvlc_audio_set_format( libvlc_media_player_t *mp, const char *format,
+                              unsigned rate, unsigned channels );
 
 /** \bug This might go away ... to be replaced by a broader system */
 

src/control/media_player.c

@@ -458,6 +458,14 @@ libvlc_media_player_new( libvlc_instance_t *instance )
     var_Create (mp, "volume", VLC_VAR_INTEGER | VLC_VAR_DOINHERIT);
     var_Create (mp, "find-input-callback", VLC_VAR_ADDRESS);
     var_SetAddress (mp, "find-input-callback", find_input);
+    var_Create (mp, "amem-data", VLC_VAR_ADDRESS);
+    var_Create (mp, "amem-setup", VLC_VAR_ADDRESS);
+    var_Create (mp, "amem-close", VLC_VAR_ADDRESS);
+    var_Create (mp, "amem-play", VLC_VAR_ADDRESS);
+    var_Create (mp, "amem-set-volume", VLC_VAR_ADDRESS);
+    var_Create (mp, "amem-format", VLC_VAR_STRING | VLC_VAR_DOINHERIT);
+    var_Create (mp, "amem-rate", VLC_VAR_INTEGER | VLC_VAR_DOINHERIT);
+    var_Create (mp, "amem-channels", VLC_VAR_INTEGER | VLC_VAR_DOINHERIT);
 
     mp->p_md = NULL;
     mp->state = libvlc_NothingSpecial;
@@ -933,6 +941,34 @@ void *libvlc_media_player_get_hwnd( libvlc_media_player_t *p_mi )
 #endif
 }
 
+void libvlc_audio_set_callbacks( libvlc_media_player_t *mp,
+                                 libvlc_audio_play_cb play_cb,
+                                 libvlc_audio_set_volume_cb set_volume_cb,
+                                 void *opaque )
+{
+    var_SetAddress( mp, "amem-play", play_cb );
+    var_SetAddress( mp, "amem-set-volume", set_volume_cb );
+    var_SetAddress( mp, "amem-data", opaque );
+    var_SetString( mp, "aout", "amem" );
+}
+
+void libvlc_audio_set_format_callbacks( libvlc_media_player_t *mp,
+                                        libvlc_audio_setup_cb setup,
+                                        libvlc_audio_cleanup_cb cleanup )
+{
+    var_SetAddress( mp, "amem-setup", setup );
+    var_SetAddress( mp, "amem-cleanup", cleanup );
+}
+
+void libvlc_audio_set_format( libvlc_media_player_t *mp, const char *format,
+                              unsigned rate, unsigned channels )
+{
+    var_SetString( mp, "amem-format", format );
+    var_SetInteger( mp, "amem-rate", rate );
+    var_SetInteger( mp, "amem-channels", channels );
+}
+
+
 /**************************************************************************
  * Getters for stream information
  **************************************************************************/

src/libvlc.sym

@@ -25,6 +25,9 @@ libvlc_audio_set_mute
 libvlc_audio_set_track
 libvlc_audio_set_volume
 libvlc_audio_toggle_mute
+libvlc_audio_set_format
+libvlc_audio_set_format_callbacks
+libvlc_audio_set_callbacks
 libvlc_clock
 libvlc_event_attach
 libvlc_event_detach