Add new API to libvlc for persistent equalizer settings.

New methods are provided to:

 - get the available equalizer presets;
 - get the available frequency bands (useful for creating a UI);
 - create a new default equalizer, or create a new equalizer from a preset;
 - release a previously created equalizer;
 - get/set preamp and individual frequency amplification values;
 - apply equalizer settings to a media player.

Equalizer settings are persistent, can be made whether media is currently playing or not, and will automatically be applied to subsequently played media.
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

NEWS

@@ -113,6 +113,7 @@ libVLC:
    to replace the deprecated libvlc_audio_output_device_count, libvlc_audio_output_device_longname
    and libvlc_audio_output_device_id
  * new libvlc_log_subscribe and libvlc_log_unsubscribe function to register logging callbacks
+ * new audio equalizer API
 
 Removed modules:
  * portaudio audio output: use the native audio output instead

include/vlc/libvlc_media_player.h

@@ -120,6 +120,13 @@ typedef enum libvlc_navigate_mode_t
     libvlc_navigate_right
 } libvlc_navigate_mode_t;
 
+/**
+ * Opaque equalizer handle.
+ *
+ * Equalizer settings can be applied to a media player.
+ */
+typedef struct libvlc_equalizer_t libvlc_equalizer_t;
+
 /**
  * Create an empty Media Player object
  *
@@ -1626,6 +1633,166 @@ LIBVLC_API int64_t libvlc_audio_get_delay( libvlc_media_player_t *p_mi );
  */
 LIBVLC_API int libvlc_audio_set_delay( libvlc_media_player_t *p_mi, int64_t i_delay );
 
+/**
+ * Get the number of equalizer presets.
+ *
+ * \return number of presets
+ * \version LibVLC 2.1.0 or later
+ */
+LIBVLC_API unsigned libvlc_audio_equalizer_get_preset_count( void );
+
+/**
+ * Get the name of a particular equalizer preset.
+ *
+ * This name can be used, for example, to prepare a preset label or menu in a user
+ * interface.
+ *
+ * \param u_index index of the preset, counting from zero
+ * \return preset name, or NULL if there is no such preset
+ * \version LibVLC 2.1.0 or later
+ */
+LIBVLC_API const char *libvlc_audio_equalizer_get_preset_name( unsigned u_index );
+
+/**
+ * Get the number of distinct frequency bands for an equalizer.
+ *
+ * \return number of frequency bands
+ * \version LibVLC 2.1.0 or later
+ */
+LIBVLC_API unsigned libvlc_audio_equalizer_get_band_count( void );
+
+/**
+ * Get a particular equalizer band frequency.
+ *
+ * This value can be used, for example, to create a label for an equalizer band control
+ * in a user interface.
+ *
+ * \param u_index index of the band, counting from zero
+ * \return equalizer band frequency (Hz), or -1 if there is no such band
+ * \version LibVLC 2.1.0 or later
+ */
+LIBVLC_API float libvlc_audio_equalizer_get_band_frequency( unsigned u_index );
+
+/**
+ * Create a new default equalizer, with all frequency values zeroed.
+ *
+ * The new equalizer can subsequently be applied to a media player by invoking
+ * libvlc_media_player_set_equalizer().
+ *
+ * The returned handle should be freed via libvlc_audio_equalizer_release() when
+ * it is no longer needed.
+ *
+ * \return opaque equalizer handle, or NULL on error
+ * \version LibVLC 2.1.0 or later
+ */
+LIBVLC_API libvlc_equalizer_t *libvlc_audio_equalizer_new( void );
+
+/**
+ * Create a new equalizer, with initial frequency values copied from an existing
+ * preset.
+ *
+ * The new equalizer can subsequently be applied to a media player by invoking
+ * libvlc_media_player_set_equalizer().
+ *
+ * The returned handle should be freed via libvlc_audio_equalizer_release() when
+ * it is no longer needed.
+ *
+ * \param u_index index of the preset, counting from zero
+ * \return opaque equalizer handle, or NULL on error
+ * \version LibVLC 2.1.0 or later
+ */
+LIBVLC_API libvlc_equalizer_t *libvlc_audio_equalizer_new_from_preset( unsigned u_index );
+
+/**
+ * Release a previously created equalizer instance.
+ *
+ * The equalizer was previously created by using libvlc_audio_equalizer_new() or
+ * libvlc_audio_equalizer_new_from_preset().
+ *
+ * It is safe to invoke this method with a NULL p_equalizer parameter for no effect.
+ *
+ * \param p_equalizer opaque equalizer handle, or NULL
+ * \version LibVLC 2.1.0 or later
+ */
+LIBVLC_API void libvlc_audio_equalizer_release( libvlc_equalizer_t *p_equalizer );
+
+/**
+ * Set a new pre-amplification value for an equalizer.
+ *
+ * The new equalizer settings are subsequently applied to a media player by invoking
+ * libvlc_media_player_set_equalizer().
+ *
+ * \param p_equalizer opaque equalizer handle
+ * \param f_preamp preamp value (-20.0 to 20.0 Hz)
+ * \return zero on success, -1 on error
+ * \version LibVLC 2.1.0 or later
+ */
+LIBVLC_API int libvlc_audio_equalizer_set_preamp( libvlc_equalizer_t *p_equalizer, float f_preamp );
+
+/**
+ * Get the current pre-amplification value from an equalizer.
+ *
+ * \param p_equalizer opaque equalizer handle
+ * \return preamp value (Hz)
+ * \version LibVLC 2.1.0 or later
+ */
+LIBVLC_API float libvlc_audio_equalizer_get_preamp( libvlc_equalizer_t *p_equalizer );
+
+/**
+ * Set a new amplification value for a particular equalizer frequency band.
+ *
+ * The new equalizer settings are subsequently applied to a media player by invoking
+ * libvlc_media_player_set_equalizer().
+ *
+ * \param p_equalizer opaque equalizer handle
+ * \param f_amp amplification value (-20.0 to 20.0 Hz)
+ * \param u_band index, counting from zero, of the frequency band to set
+ * \return zero on success, -1 on error
+ * \version LibVLC 2.1.0 or later
+ */
+LIBVLC_API int libvlc_audio_equalizer_set_amp_at_index( libvlc_equalizer_t *p_equalizer, float f_amp, unsigned u_band );
+
+/**
+ * Get the amplification value for a particular equalizer frequency band.
+ *
+ * \param p_equalizer opaque equalizer handle
+ * \param u_band index, counting from zero, of the frequency band to get
+ * \return amplification value (Hz); zero if there is no such frequency band
+ * \version LibVLC 2.1.0 or later
+ */
+LIBVLC_API float libvlc_audio_equalizer_get_amp_at_index( libvlc_equalizer_t *p_equalizer, unsigned u_band );
+
+/**
+ * Apply new equalizer settings to a media player.
+ *
+ * The equalizer is first created by invoking libvlc_audio_equalizer_new() or
+ * libvlc_audio_equalizer_new_from_preset().
+ *
+ * It is possible to apply new equalizer settings to a media player whether the media
+ * player is currently playing media or not.
+ *
+ * Invoking this method will immediately apply the new equalizer settings to the audio
+ * output of the currently playing media if there is any.
+ *
+ * If there is no currently playing media, the new equalizer settings will be applied
+ * later if and when new media is played.
+ *
+ * Equalizer settings will automatically be applied to subsequently played media.
+ *
+ * To disable the equalizer for a media player invoke this method passing NULL for the
+ * p_equalizer parameter.
+ *
+ * The media player does not keep a reference to the supplied equalizer so it is safe
+ * for an application to release the equalizer reference any time after this method
+ * returns.
+ *
+ * \param p_mi opaque media player handle
+ * \param p_equalizer opaque equalizer handle, or NULL to disable the equalizer for this media player
+ * \return zero on success, -1 on error
+ * \version LibVLC 2.1.0 or later
+ */
+LIBVLC_API int libvlc_media_player_set_equalizer( libvlc_media_player_t *p_mi, libvlc_equalizer_t *p_equalizer );
+
 /** @} audio */
 
 /** @} media_player */

lib/audio.c

@@ -449,3 +449,152 @@ int libvlc_audio_set_delay( libvlc_media_player_t *p_mi, int64_t i_delay )
     }
     return ret;
 }
+
+/*****************************************************************************
+ * libvlc_audio_equalizer_get_preset_count : Get the number of equalizer presets
+ *****************************************************************************/
+unsigned libvlc_audio_equalizer_get_preset_count( void )
+{
+    return NB_PRESETS;
+}
+
+/*****************************************************************************
+ * libvlc_audio_equalizer_get_preset_name : Get the name for a preset
+ *****************************************************************************/
+const char *libvlc_audio_equalizer_get_preset_name( unsigned u_index )
+{
+    if ( u_index >= NB_PRESETS )
+        return NULL;
+
+    return preset_list_text[ u_index ];
+}
+
+/*****************************************************************************
+ * libvlc_audio_equalizer_get_band_count : Get the number of equalizer frequency bands
+ *****************************************************************************/
+unsigned libvlc_audio_equalizer_get_band_count( void )
+{
+    return EQZ_BANDS_MAX;
+}
+
+/*****************************************************************************
+ * libvlc_audio_equalizer_get_band_frequency : Get the frequency for a band
+ *****************************************************************************/
+float libvlc_audio_equalizer_get_band_frequency( unsigned u_index )
+{
+    if ( u_index >= EQZ_BANDS_MAX )
+        return -1.f;
+
+    return f_vlc_frequency_table_10b[ u_index ];
+}
+
+/*****************************************************************************
+ * libvlc_audio_equalizer_new : Create a new audio equalizer with zeroed values
+ *****************************************************************************/
+libvlc_equalizer_t *libvlc_audio_equalizer_new( void )
+{
+    libvlc_equalizer_t *p_equalizer;
+
+    p_equalizer = malloc( sizeof( *p_equalizer ) );
+    if ( unlikely( p_equalizer == NULL ) )
+        return NULL;
+
+    p_equalizer->f_preamp = 0.f;
+
+    for ( unsigned i = 0; i < EQZ_BANDS_MAX; i++ )
+        p_equalizer->f_amp[ i ] = 0.f;
+
+    return p_equalizer;
+}
+
+/*****************************************************************************
+ * libvlc_audio_equalizer_new_from_preset : Create a new audio equalizer based on a preset
+ *****************************************************************************/
+libvlc_equalizer_t *libvlc_audio_equalizer_new_from_preset( unsigned u_index )
+{
+    libvlc_equalizer_t *p_equalizer;
+
+    if ( u_index >= NB_PRESETS )
+        return NULL;
+
+    p_equalizer = malloc( sizeof( *p_equalizer ) );
+    if ( unlikely( p_equalizer == NULL ) )
+        return NULL;
+
+    p_equalizer->f_preamp = eqz_preset_10b[ u_index ].f_preamp;
+
+    for ( unsigned i = 0; i < EQZ_BANDS_MAX; i++ )
+        p_equalizer->f_amp[ i ] = eqz_preset_10b[ u_index ].f_amp[ i ];
+
+    return p_equalizer;
+}
+
+/*****************************************************************************
+ * libvlc_audio_equalizer_release : Release a previously created equalizer
+ *****************************************************************************/
+void libvlc_audio_equalizer_release( libvlc_equalizer_t *p_equalizer )
+{
+    free( p_equalizer );
+}
+
+/*****************************************************************************
+ * libvlc_audio_equalizer_set_preamp : Set the preamp value for an equalizer
+ *****************************************************************************/
+int libvlc_audio_equalizer_set_preamp( libvlc_equalizer_t *p_equalizer, float f_preamp )
+{
+    if ( !p_equalizer )
+        return -1;
+
+    if ( f_preamp < -20.0f )
+        f_preamp = -20.0f;
+    else if ( f_preamp > 20.0f )
+        f_preamp = 20.0f;
+
+    p_equalizer->f_preamp = f_preamp;
+    return 0;
+}
+
+/*****************************************************************************
+ * libvlc_audio_equalizer_get_preamp : Get the preamp value for an equalizer
+ *****************************************************************************/
+float libvlc_audio_equalizer_get_preamp( libvlc_equalizer_t *p_equalizer )
+{
+    if ( !p_equalizer )
+        return 0.f;
+
+    return p_equalizer->f_preamp;
+}
+
+/*****************************************************************************
+ * libvlc_audio_equalizer_set_amp_at_index : Set the amplification value for an equalizer band
+ *****************************************************************************/
+int libvlc_audio_equalizer_set_amp_at_index( libvlc_equalizer_t *p_equalizer, float f_amp, unsigned u_band )
+{
+    if ( !p_equalizer )
+        return -1;
+
+    if ( u_band >= EQZ_BANDS_MAX )
+        return -1;
+
+    if ( f_amp < -20.0f )
+        f_amp = -20.0f;
+    else if ( f_amp > 20.0f )
+        f_amp = 20.0f;
+
+    p_equalizer->f_amp[ u_band ] = f_amp;
+    return 0;
+}
+
+/*****************************************************************************
+ * libvlc_audio_equalizer_get_amp_at_index : Get the amplification value for an equalizer band
+ *****************************************************************************/
+float libvlc_audio_equalizer_get_amp_at_index( libvlc_equalizer_t *p_equalizer, unsigned u_band )
+{
+    if ( !p_equalizer )
+        return 0.f;
+
+    if ( u_band >= EQZ_BANDS_MAX )
+        return 0.f;
+
+    return p_equalizer->f_amp[ u_band ];
+}

lib/libvlc.sym

@@ -3,6 +3,17 @@ libvlc_clearerr
 libvlc_printerr
 libvlc_vprinterr
 libvlc_add_intf
+libvlc_audio_equalizer_get_amp_at_index
+libvlc_audio_equalizer_get_band_count
+libvlc_audio_equalizer_get_band_frequency
+libvlc_audio_equalizer_get_preamp
+libvlc_audio_equalizer_get_preset_count
+libvlc_audio_equalizer_get_preset_name
+libvlc_audio_equalizer_new
+libvlc_audio_equalizer_new_from_preset
+libvlc_audio_equalizer_release
+libvlc_audio_equalizer_set_amp_at_index
+libvlc_audio_equalizer_set_preamp
 libvlc_audio_output_device_count
 libvlc_audio_output_device_id
 libvlc_audio_output_device_list_get
@@ -150,6 +161,7 @@ libvlc_media_player_release
 libvlc_media_player_retain
 libvlc_media_player_set_agl
 libvlc_media_player_set_chapter
+libvlc_media_player_set_equalizer
 libvlc_media_player_set_hwnd
 libvlc_media_player_set_media
 libvlc_media_player_set_nsobject

lib/media_player.c

@@ -34,6 +34,7 @@
 #include <vlc_input.h>
 #include <vlc_vout.h>
 #include <vlc_keys.h>
+#include <vlc_aout_intf.h>
 
 #include "libvlc_internal.h"
 #include "media_internal.h" // libvlc_media_set_state()
@@ -482,6 +483,9 @@ libvlc_media_player_new( libvlc_instance_t *instance )
     var_Create (mp, "amem-rate", VLC_VAR_INTEGER | VLC_VAR_DOINHERIT);
     var_Create (mp, "amem-channels", VLC_VAR_INTEGER | VLC_VAR_DOINHERIT);
 
+    var_Create (mp, "equalizer-preamp", VLC_VAR_FLOAT);
+    var_Create (mp, "equalizer-bands", VLC_VAR_STRING);
+
     mp->p_md = NULL;
     mp->state = libvlc_NothingSpecial;
     mp->p_libvlc_instance = instance;
@@ -746,6 +750,10 @@ int libvlc_media_player_play( libvlc_media_player_t *p_mi )
     }
     p_mi->input.p_thread = p_input_thread;
     unlock_input(p_mi);
+
+    if( strlen( var_GetString( p_mi, "equalizer-bands" ) ) > 0 )
+        aout_EnableFilter( p_mi, "equalizer", true );
+
     return 0;
 }
 
@@ -1409,3 +1417,33 @@ void libvlc_media_player_next_frame( libvlc_media_player_t *p_mi )
         vlc_object_release( p_input_thread );
     }
 }
+
+int libvlc_media_player_set_equalizer( libvlc_media_player_t *p_mi, libvlc_equalizer_t *p_equalizer )
+{
+    if ( !p_equalizer )
+    {
+        aout_EnableFilter( p_mi, "equalizer", false );
+        var_SetString( p_mi, "equalizer-bands", NULL );
+        return 0;
+    }
+
+    var_SetFloat( p_mi, "equalizer-preamp", p_equalizer->f_preamp );
+
+    char *psz_bands = NULL;
+    for ( int i = 0; i < EQZ_BANDS_MAX; i++ )
+    {
+        char *psz;
+        if ( asprintf( &psz, "%s %.07f", psz_bands ? psz_bands : "", p_equalizer->f_amp[i] ) == -1 )
+        {
+            free( psz_bands );
+            return -1;
+        }
+        free( psz_bands );
+        psz_bands = psz;
+    }
+    var_SetString( p_mi, "equalizer-bands", psz_bands );
+    free( psz_bands );
+
+    aout_EnableFilter( p_mi, "equalizer", true );
+    return 0;
+}

lib/media_player_internal.h

@@ -34,6 +34,8 @@
 #include <vlc/libvlc_media.h>
 #include <vlc_input.h>
 
+#include "../modules/audio_filter/equalizer_presets.h"
+
 struct libvlc_media_player_t
 {
     VLC_COMMON_MEMBERS
@@ -62,4 +64,13 @@ libvlc_track_description_t * libvlc_get_track_description(
         libvlc_media_player_t *p_mi,
         const char *psz_variable );
 
+/**
+ * Internal equalizer structure.
+ */
+struct libvlc_equalizer_t
+{
+    float f_preamp;
+    float f_amp[EQZ_BANDS_MAX];
+};
+
 #endif

modules/audio_filter/equalizer.c

@@ -232,17 +232,6 @@ typedef struct
 
 } eqz_config_t;
 
-/* The frequency tables */
-static const float f_vlc_frequency_table_10b[EQZ_BANDS_MAX] =
-{
-    60, 170, 310, 600, 1000, 3000, 6000, 12000, 14000, 16000,
-};
-
-static const float f_iso_frequency_table_10b[EQZ_BANDS_MAX] =
-{
-    31.25, 62.5, 125, 250, 500, 1000, 2000, 4000, 8000, 16000,
-};
-
 /* Equalizer coefficient calculation function based on equ-xmms */
 static void EqzCoeffs( int i_rate, float f_octave_percent,
                        bool b_use_vlc_freqs,

modules/audio_filter/equalizer_presets.h

@@ -21,6 +21,9 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  *****************************************************************************/
 
+#ifndef _EQUALIZER_PRESETS_H
+#define _EQUALIZER_PRESETS_H 1
+
 /*****************************************************************************
  * Equalizer presets
  *****************************************************************************/
@@ -30,6 +33,17 @@
 
 #define EQZ_BANDS_MAX 10
 
+/* The frequency tables */
+static const float f_vlc_frequency_table_10b[EQZ_BANDS_MAX] =
+{
+    60, 170, 310, 600, 1000, 3000, 6000, 12000, 14000, 16000,
+};
+
+static const float f_iso_frequency_table_10b[EQZ_BANDS_MAX] =
+{
+    31.25, 62.5, 125, 250, 500, 1000, 2000, 4000, 8000, 16000,
+};
+
 #define NB_PRESETS 18
 static const char *const preset_list[NB_PRESETS] = {
     "flat", "classical", "club", "dance", "fullbass", "fullbasstreble",
@@ -132,3 +146,5 @@ static const eqz_preset_t eqz_preset_10b[NB_PRESETS] =
         { 8, 5.6, -1.11022e-15, -5.6, -4.8, -1.11022e-15, 8, 9.6, 9.6, 8.8 }
     },
 };
+
+#endif

src/audio_output/common.c

@@ -177,6 +177,15 @@ audio_output_t *aout_New( vlc_object_t * p_parent )
                             &val, &text);
         }
 
+    if (var_Type (p_parent, "equalizer-bands"))
+    {
+        var_Create (aout, "equalizer-preamp", VLC_VAR_FLOAT | VLC_VAR_DOINHERIT);
+        var_Create (aout, "equalizer-bands", VLC_VAR_STRING | VLC_VAR_DOINHERIT);
+
+        var_AddCallback (p_parent, "equalizer-preamp", var_Copy, aout);
+        var_AddCallback (p_parent, "equalizer-bands", var_Copy, aout);
+    }
+
     return aout;
 }
 
@@ -190,6 +199,13 @@ void aout_Destroy (audio_output_t *aout)
     var_DelCallback (aout, "mute", var_Copy, aout->p_parent);
     var_SetFloat (aout, "volume", -1.f);
     var_DelCallback (aout, "volume", var_Copy, aout->p_parent);
+
+    if (var_Type (aout->p_parent, "equalizer-bands"))
+    {
+        var_DelCallback (aout->p_parent, "equalizer-preamp", var_Copy, aout);
+        var_DelCallback (aout->p_parent, "equalizer-bands", var_Copy, aout);
+    }
+
     vlc_object_release (aout);
 }