LibVLC audio controls

原文 http://www.videolan.org/developers/vlc/doc/doxygen/html/group__libvlc__audio.html

LibVLC audio controls

LibVLC media player

Collaboration diagram for LibVLC audio controls:

Typedefs
typedef enum  libvlc_audio_output_device_types_t	libvlc_audio_output_device_types_t
	Audio device types.
typedef enum  libvlc_audio_output_channel_t	libvlc_audio_output_channel_t
	Audio channels.

Enumerations
enum	libvlc_audio_output_device_types_t {    libvlc_AudioOutputDevice_Error = -1, libvlc_AudioOutputDevice_Mono = 1, libvlc_AudioOutputDevice_Stereo = 2, libvlc_AudioOutputDevice_2F2R = 4,    libvlc_AudioOutputDevice_3F2R = 5, libvlc_AudioOutputDevice_5_1 = 6, libvlc_AudioOutputDevice_6_1 = 7, libvlc_AudioOutputDevice_7_1 = 8,    libvlc_AudioOutputDevice_SPDIF = 10  }
	Audio device types. More...
enum	libvlc_audio_output_channel_t {    libvlc_AudioChannel_Error = -1, libvlc_AudioChannel_Stereo = 1, libvlc_AudioChannel_RStereo = 2, libvlc_AudioChannel_Left = 3,    libvlc_AudioChannel_Right = 4, libvlc_AudioChannel_Dolbys = 5  }
	Audio channels. More...

Functions
LIBVLC_API libvlc_audio_output_t *	libvlc_audio_output_list_get (libvlc_instance_t *p_instance)
	Gets the list of available audio output modules.
LIBVLC_API void	libvlc_audio_output_list_release (libvlc_audio_output_t *p_list)
	Frees the list of available audio output modules.
LIBVLC_API int	libvlc_audio_output_set (libvlc_media_player_t *p_mi, const char *psz_name)
	Selects an audio output module.
LIBVLC_DEPRECATED LIBVLC_API int	libvlc_audio_output_device_count (libvlc_instance_t *, const char *)
	Backward compatibility stub.
LIBVLC_DEPRECATED LIBVLC_API char *	libvlc_audio_output_device_longname (libvlc_instance_t *, const char *, int)
	Backward compatibility stub.
LIBVLC_DEPRECATED LIBVLC_API char *	libvlc_audio_output_device_id (libvlc_instance_t *, const char *, int)
	Backward compatibility stub.
LIBVLC_API  libvlc_audio_output_device_t *	libvlc_audio_output_device_enum (libvlc_media_player_t *mp)
	Gets a list of potential audio output devices,.
LIBVLC_API  libvlc_audio_output_device_t *	libvlc_audio_output_device_list_get (libvlc_instance_t *p_instance, const char *aout)
	Gets a list of audio output devices for a given audio output module,.
LIBVLC_API void	libvlc_audio_output_device_list_release (libvlc_audio_output_device_t *p_list)
	Frees a list of available audio output devices.
LIBVLC_API void	libvlc_audio_output_device_set (libvlc_media_player_t *mp, const char *module, const char *device_id)
	Configures an explicit audio output device.
LIBVLC_DEPRECATED LIBVLC_API int	libvlc_audio_output_get_device_type (libvlc_media_player_t *p_mi)
	Stub for backward compatibility.
LIBVLC_DEPRECATED LIBVLC_API void	libvlc_audio_output_set_device_type (libvlc_media_player_t *, int)
	Stub for backward compatibility.
LIBVLC_API void	libvlc_audio_toggle_mute (libvlc_media_player_t *p_mi)
	Toggle mute status.
LIBVLC_API int	libvlc_audio_get_mute (libvlc_media_player_t *p_mi)
	Get current mute status.
LIBVLC_API void	libvlc_audio_set_mute (libvlc_media_player_t *p_mi, int status)
	Set mute status.
LIBVLC_API int	libvlc_audio_get_volume (libvlc_media_player_t *p_mi)
	Get current software audio volume.
LIBVLC_API int	libvlc_audio_set_volume (libvlc_media_player_t *p_mi, int i_volume)
	Set current software audio volume.
LIBVLC_API int	libvlc_audio_get_track_count (libvlc_media_player_t *p_mi)
	Get number of available audio tracks.
LIBVLC_API  libvlc_track_description_t *	libvlc_audio_get_track_description (libvlc_media_player_t *p_mi)
	Get the description of available audio tracks.
LIBVLC_API int	libvlc_audio_get_track (libvlc_media_player_t *p_mi)
	Get current audio track.
LIBVLC_API int	libvlc_audio_set_track (libvlc_media_player_t *p_mi, int i_track)
	Set current audio track.
LIBVLC_API int	libvlc_audio_get_channel (libvlc_media_player_t *p_mi)
	Get current audio channel.
LIBVLC_API int	libvlc_audio_set_channel (libvlc_media_player_t *p_mi, int channel)
	Set current audio channel.
LIBVLC_API int64_t	libvlc_audio_get_delay (libvlc_media_player_t *p_mi)
	Get current audio delay.
LIBVLC_API int	libvlc_audio_set_delay (libvlc_media_player_t *p_mi, int64_t i_delay)
	Set current audio delay.
LIBVLC_API unsigned	libvlc_audio_equalizer_get_preset_count (void)
	Get the number of equalizer presets.
LIBVLC_API const char *	libvlc_audio_equalizer_get_preset_name (unsigned u_index)
	Get the name of a particular equalizer preset.
LIBVLC_API unsigned	libvlc_audio_equalizer_get_band_count (void)
	Get the number of distinct frequency bands for an equalizer.
LIBVLC_API float	libvlc_audio_equalizer_get_band_frequency (unsigned u_index)
	Get a particular equalizer band frequency.
LIBVLC_API libvlc_equalizer_t *	libvlc_audio_equalizer_new (void)
	Create a new default equalizer, with all frequency values zeroed.
LIBVLC_API libvlc_equalizer_t *	libvlc_audio_equalizer_new_from_preset (unsigned u_index)
	Create a new equalizer, with initial frequency values copied from an existing preset.
LIBVLC_API void	libvlc_audio_equalizer_release (libvlc_equalizer_t *p_equalizer)
	Release a previously created equalizer instance.
LIBVLC_API int	libvlc_audio_equalizer_set_preamp (libvlc_equalizer_t *p_equalizer, float f_preamp)
	Set a new pre-amplification value for an equalizer.
LIBVLC_API float	libvlc_audio_equalizer_get_preamp (libvlc_equalizer_t *p_equalizer)
	Get the current pre-amplification value from an equalizer.
LIBVLC_API int	libvlc_audio_equalizer_set_amp_at_index (libvlc_equalizer_t *p_equalizer, float f_amp, unsigned u_band)
	Set a new amplification value for a particular equalizer frequency band.
LIBVLC_API float	libvlc_audio_equalizer_get_amp_at_index (libvlc_equalizer_t *p_equalizer, unsigned u_band)
	Get the amplification value for a particular equalizer frequency band.
LIBVLC_API int	libvlc_media_player_set_equalizer (libvlc_media_player_t *p_mi, libvlc_equalizer_t *p_equalizer)
	Apply new equalizer settings to a media player.

Detailed Description

Typedef Documentation

typedef enum libvlc_audio_output_channel_t libvlc_audio_output_channel_t

Audio channels.

typedef enum libvlc_audio_output_device_types_t libvlc_audio_output_device_types_t

Audio device types.

Enumeration Type Documentation

enum libvlc_audio_output_channel_t

Audio channels.

Enumerator:

libvlc_AudioChannel_Error
libvlc_AudioChannel_Stereo
libvlc_AudioChannel_RStereo
libvlc_AudioChannel_Left
libvlc_AudioChannel_Right
libvlc_AudioChannel_Dolbys

enum libvlc_audio_output_device_types_t

Audio device types.

Enumerator:

libvlc_AudioOutputDevice_Error
libvlc_AudioOutputDevice_Mono
libvlc_AudioOutputDevice_Stereo
libvlc_AudioOutputDevice_2F2R
libvlc_AudioOutputDevice_3F2R
libvlc_AudioOutputDevice_5_1
libvlc_AudioOutputDevice_6_1
libvlc_AudioOutputDevice_7_1
libvlc_AudioOutputDevice_SPDIF

Function Documentation

LIBVLC_API float libvlc_audio_equalizer_get_amp_at_index	(	libvlc_equalizer_t *	p_equalizer,
		unsigned	u_band
	)

Get the amplification value for a particular equalizer frequency band.

Parameters

p_equalizer	valid equalizer handle, must not be NULL
u_band	index, counting from zero, of the frequency band to get

Returns

amplification value (Hz); NaN if there is no such frequency band

Version

LibVLC 2.2.0 or later

LIBVLC_API unsigned libvlc_audio_equalizer_get_band_count

(

void

)

Get the number of distinct frequency bands for an equalizer.

Returns

number of frequency bands

Version

LibVLC 2.2.0 or later

LIBVLC_API float libvlc_audio_equalizer_get_band_frequency

(

unsigned

u_index

)

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.

Parameters

u_index

index of the band, counting from zero

Returns

equalizer band frequency (Hz), or -1 if there is no such band

Version

LibVLC 2.2.0 or later

LIBVLC_API float libvlc_audio_equalizer_get_preamp

(

libvlc_equalizer_t *

p_equalizer

)

Get the current pre-amplification value from an equalizer.

Parameters

p_equalizer

valid equalizer handle, must not be NULL

Returns

preamp value (Hz)

Version

LibVLC 2.2.0 or later

LIBVLC_API unsigned libvlc_audio_equalizer_get_preset_count

(

void

)

Get the number of equalizer presets.

Returns

number of presets

Version

LibVLC 2.2.0 or later

LIBVLC_API const char* libvlc_audio_equalizer_get_preset_name

(

unsigned

u_index

)

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.

Parameters

u_index

index of the preset, counting from zero

Returns

preset name, or NULL if there is no such preset

Version

LibVLC 2.2.0 or later

LIBVLC_API libvlc_equalizer_t* libvlc_audio_equalizer_new

(

void

)

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.

Returns

opaque equalizer handle, or NULL on error

Version

LibVLC 2.2.0 or later

LIBVLC_API libvlc_equalizer_t* libvlc_audio_equalizer_new_from_preset

(

unsigned

u_index

)

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.

Parameters

u_index

index of the preset, counting from zero

Returns

opaque equalizer handle, or NULL on error

Version

LibVLC 2.2.0 or later

LIBVLC_API void libvlc_audio_equalizer_release

(

libvlc_equalizer_t *

p_equalizer

)

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.

Parameters

p_equalizer

opaque equalizer handle, or NULL

Version

LibVLC 2.2.0 or later

LIBVLC_API int libvlc_audio_equalizer_set_amp_at_index	(	libvlc_equalizer_t *	p_equalizer,
		float	f_amp,
		unsigned	u_band
	)

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().

The supplied amplification value will be clamped to the -20.0 to +20.0 range.

Parameters

p_equalizer	valid equalizer handle, must not be NULL
f_amp	amplification value (-20.0 to 20.0 Hz)
u_band	index, counting from zero, of the frequency band to set

Returns

zero on success, -1 on error

Version

LibVLC 2.2.0 or later

LIBVLC_API int libvlc_audio_equalizer_set_preamp	(	libvlc_equalizer_t *	p_equalizer,
		float	f_preamp
	)

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().

The supplied amplification value will be clamped to the -20.0 to +20.0 range.

Parameters

p_equalizer	valid equalizer handle, must not be NULL
f_preamp	preamp value (-20.0 to 20.0 Hz)

Returns

zero on success, -1 on error

Version

LibVLC 2.2.0 or later

LIBVLC_API int libvlc_audio_get_channel

(

libvlc_media_player_t *

p_mi

)

Get current audio channel.

Parameters

p_mi	media player

Returns

the audio channel

See Also

libvlc_audio_output_channel_t

LIBVLC_API int64_t libvlc_audio_get_delay

(

libvlc_media_player_t *

p_mi

)

Get current audio delay.

Parameters

p_mi	media player

Returns

the audio delay (microseconds)

Version

LibVLC 1.1.1 or later

LIBVLC_API int libvlc_audio_get_mute

(

libvlc_media_player_t *

p_mi

)

Get current mute status.

Parameters

p_mi	media player

Returns

the mute status (boolean) if defined, -1 if undefined/unapplicable

LIBVLC_API int libvlc_audio_get_track

(

libvlc_media_player_t *

p_mi

)

Get current audio track.

Parameters

p_mi	media player

Returns

the audio track ID or -1 if no active input.

LIBVLC_API int libvlc_audio_get_track_count

(

libvlc_media_player_t *

p_mi

)

Get number of available audio tracks.

Parameters

p_mi	media player

Returns

the number of available audio tracks (int), or -1 if unavailable

LIBVLC_API libvlc_track_description_t* libvlc_audio_get_track_description

(

libvlc_media_player_t *

p_mi

)

Get the description of available audio tracks.

Parameters

p_mi	media player

Returns

list with description of available audio tracks, or NULL

LIBVLC_API int libvlc_audio_get_volume

(

libvlc_media_player_t *

p_mi

)

Get current software audio volume.

Parameters

p_mi	media player

Returns

the software volume in percents (0 = mute, 100 = nominal / 0dB)

LIBVLC_DEPRECATED LIBVLC_API int libvlc_audio_output_device_count	(	libvlc_instance_t *	,
		const char *
	)

Backward compatibility stub.

Do not use in new code. Use libvlc_audio_output_device_list_get() instead.

Returns

always 0.

LIBVLC_API libvlc_audio_output_device_t* libvlc_audio_output_device_enum

(

libvlc_media_player_t *

mp

)

Gets a list of potential audio output devices,.

See Also

libvlc_audio_output_device_set().

Note

Not all audio outputs support enumerating devices. The audio output may be functional even if the list is empty (NULL).

The list may not be exhaustive.

Warning

Some audio output devices in the list might not actually work in some circumstances. By default, it is recommended to not specify any explicit audio device.

Parameters

mp	media player

Returns

A NULL-terminated linked list of potential audio output devices. It must be freed it with  libvlc_audio_output_device_list_release()

Version

LibVLC 2.2.0 or later.

LIBVLC_DEPRECATED LIBVLC_API char* libvlc_audio_output_device_id	(	libvlc_instance_t *	,
		const char *	,
		int
	)

Backward compatibility stub.

Do not use in new code. Use libvlc_audio_output_device_list_get() instead.

Returns

always NULL.

LIBVLC_API libvlc_audio_output_device_t* libvlc_audio_output_device_list_get	(	libvlc_instance_t *	p_instance,
		const char *	aout
	)

Gets a list of audio output devices for a given audio output module,.

See Also

libvlc_audio_output_device_set().

Note

Not all audio outputs support this. In particular, an empty (NULL) list of devices does  not imply that the specified audio output does not work.

The list might not be exhaustive.

Warning

Some audio output devices in the list might not actually work in some circumstances. By default, it is recommended to not specify any explicit audio device.

Parameters

p_instance	libvlc instance
psz_aout	audio output name (as returned by libvlc_audio_output_list_get())

Returns

A NULL-terminated linked list of potential audio output devices. It must be freed it with  libvlc_audio_output_device_list_release()

Version

LibVLC 2.1.0 or later.

LIBVLC_API void libvlc_audio_output_device_list_release

(

libvlc_audio_output_device_t *

p_list

)

Frees a list of available audio output devices.

Parameters

p_list

list with audio outputs for release

Version

LibVLC 2.1.0 or later.

LIBVLC_DEPRECATED LIBVLC_API char* libvlc_audio_output_device_longname	(	libvlc_instance_t *	,
		const char *	,
		int
	)

Backward compatibility stub.

Do not use in new code. Use libvlc_audio_output_device_list_get() instead.

Returns

always NULL.

LIBVLC_API void libvlc_audio_output_device_set	(	libvlc_media_player_t *	mp,
		const char *	module,
		const char *	device_id
	)

Configures an explicit audio output device.

If the module paramater is NULL, audio output will be moved to the device specified by the device identifier string immediately. This is the recommended usage.

A list of adequate potential device strings can be obtained with libvlc_audio_output_device_enum().

However passing NULL is supported in LibVLC version 2.2.0 and later only; in earlier versions, this function would have no effects when the module parameter was NULL.

If the module parameter is not NULL, the device parameter of the corresponding audio output, if it exists, will be set to the specified string. Note that some audio output modules do not have such a parameter (notably MMDevice and PulseAudio).

A list of adequate potential device strings can be obtained with libvlc_audio_output_device_list_get().

Note

This function does not select the specified audio output plugin.  libvlc_audio_output_set() is used for that purpose.

Warning

The syntax for the device parameter depends on the audio output.

Some audio output modules require further parameters (e.g. a channels map in the case of ALSA).

Parameters

mp	media player
module	If NULL, current audio output module. if non-NULL, name of audio output module (

See Also

libvlc_audio_output_t)

Parameters

device_id

device identifier string

Returns

Nothing. Errors are ignored (this is a design bug).

LIBVLC_DEPRECATED LIBVLC_API int libvlc_audio_output_get_device_type

(

libvlc_media_player_t *

p_mi

)

Stub for backward compatibility.

Returns

always -1.

LIBVLC_API libvlc_audio_output_t* libvlc_audio_output_list_get

(

libvlc_instance_t *

p_instance

)

Gets the list of available audio output modules.

Parameters

p_instance

libvlc instance

Returns

list of available audio outputs. It must be freed it with

See Also

libvlc_audio_output_list_release

libvlc_audio_output_t . In case of error, NULL is returned.

LIBVLC_API void libvlc_audio_output_list_release

(

libvlc_audio_output_t *

p_list

)

Frees the list of available audio output modules.

Parameters

p_list

list with audio outputs for release

LIBVLC_API int libvlc_audio_output_set	(	libvlc_media_player_t *	p_mi,
		const char *	psz_name
	)

Selects an audio output module.

Note

Any change will take be effect only after playback is stopped and restarted. Audio output cannot be changed while playing.

Parameters

p_mi	media player
psz_name	name of audio output, use psz_name of

See Also

libvlc_audio_output_t

Returns

0 if function succeded, -1 on error

LIBVLC_DEPRECATED LIBVLC_API void libvlc_audio_output_set_device_type	(	libvlc_media_player_t *	,
		int
	)

Stub for backward compatibility.

LIBVLC_API int libvlc_audio_set_channel	(	libvlc_media_player_t *	p_mi,
		int	channel
	)

Set current audio channel.

Parameters

p_mi	media player
channel	the audio channel,

See Also

libvlc_audio_output_channel_t

Returns

0 on success, -1 on error

LIBVLC_API int libvlc_audio_set_delay	(	libvlc_media_player_t *	p_mi,
		int64_t	i_delay
	)

Set current audio delay.

The audio delay will be reset to zero each time the media changes.

Parameters

p_mi	media player
i_delay	the audio delay (microseconds)

Returns

0 on success, -1 on error

Version

LibVLC 1.1.1 or later

LIBVLC_API void libvlc_audio_set_mute	(	libvlc_media_player_t *	p_mi,
		int	status
	)

Set mute status.

Parameters

p_mi	media player
status	If status is true then mute, otherwise unmute

Warning

This function does not always work. If there are no active audio playback stream, the mute status might not be available. If digital pass-through (S/PDIF, HDMI...) is in use, muting may be unapplicable. Also some audio output plugins do not support muting at all.

Note

To force silent playback, disable all audio tracks. This is more efficient and reliable than mute.

LIBVLC_API int libvlc_audio_set_track	(	libvlc_media_player_t *	p_mi,
		int	i_track
	)

Set current audio track.

Parameters

p_mi	media player
i_track	the track ID (i_id field from track description)

Returns

0 on success, -1 on error

LIBVLC_API int libvlc_audio_set_volume	(	libvlc_media_player_t *	p_mi,
		int	i_volume
	)

Set current software audio volume.

Parameters

p_mi	media player
i_volume	the volume in percents (0 = mute, 100 = 0dB)

Returns

0 if the volume was set, -1 if it was out of range

LIBVLC_API void libvlc_audio_toggle_mute

(

libvlc_media_player_t *

p_mi

)

Toggle mute status.

Parameters

p_mi	media player

Warning

Toggling mute atomically is not always possible: On some platforms, other processes can mute the VLC audio playback stream asynchronously. Thus, there is a small race condition where toggling will not work. See also the limitations of libvlc_audio_set_mute().

LIBVLC_API int libvlc_media_player_set_equalizer	(	libvlc_media_player_t *	p_mi,
		libvlc_equalizer_t *	p_equalizer
	)

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.

Parameters

p_mi	opaque media player handle
p_equalizer	opaque equalizer handle, or NULL to disable the equalizer for this media player

Returns

zero on success, -1 on error

Version

LibVLC 2.2.0 or later