[vlc-devel] [PATCHv2 2/9] aout: add the vlc_audio_meter API
Thomas Guillem
thomas at gllm.fr
Mon Aug 24 10:21:49 CEST 2020
On Fri, Aug 21, 2020, at 20:56, Rémi Denis-Courmont wrote:
> Le mercredi 19 août 2020, 22:25:56 EEST Thomas Guillem a écrit :
> > This API will be used by the aout, and could be used by any visualisation
> > module needing audio measurements.
> >
> > This API allows to create "audio meter" filters plugins. This new type of
> > filter is measuring audio blocks without modifying them and send the
> > measurement via audio filters callbacks. These events are then propagated to
> > vlc_audio_meter events.
> > ---
> > include/vlc_aout.h | 148 +++++++++++++++++++++++++
> > include/vlc_filter.h | 18 ++++
> > src/Makefile.am | 1 +
> > src/audio_output/meter.c | 225 +++++++++++++++++++++++++++++++++++++++
> > src/libvlccore.sym | 7 ++
> > 5 files changed, 399 insertions(+)
> > create mode 100644 src/audio_output/meter.c
> >
> > diff --git a/include/vlc_aout.h b/include/vlc_aout.h
> > index 5baa460f6de..1c35bba16eb 100644
> > --- a/include/vlc_aout.h
> > +++ b/include/vlc_aout.h
> > @@ -24,6 +24,7 @@
> > #define VLC_AOUT_H 1
> >
> > #include <assert.h>
> > +#include <vlc_list.h>
> >
> > /**
> > * \defgroup audio_output Audio output
> > @@ -537,4 +538,151 @@ static inline int aout_TimeGet(audio_output_t *aout,
> > vlc_tick_t *delay)
> >
> > /** @} */
> >
> > +/**
> > + * @defgroup audio_output__meter Audio meter API
> > + */
> > +
> > +/**
> > + * Audio loudness measurement
> > + */
> > +struct vlc_audio_loudness
> > +{
> > + /** Momentary loudness (last 400 ms), in LUFS */
> > + double loudness_momentary;
> > + /** Short term loudness (last 3seconds), in LUFS */
> > + double loudness_shortterm;
> > + /** Integrated loudness (global), in LUFS */
> > + double loudness_integrated;
> > + /** Loudness range, in LU */
> > + double loudness_range;
> > + /** True Peak, in dBTP */
> > + double truepeak;
> > +};
> > +
> > +/**
> > + * Audio meter plugin opaque structure
> > + *
> > + * This opaque structure is returned by vlc_audio_meter_AddPlugin().
> > + */
> > +typedef struct vlc_audio_meter_plugin vlc_audio_meter_plugin;
> > +
> > +/**
> > + * Audio meter events
> > + *
> > + * Triggered from vlc_audio_meter_Process() and vlc_audio_meter_Flush().
> > + * Can be registered with vlc_audio_meter_AddPlugin().
> > + */
> > +struct vlc_audio_meter_events
> > +{
> > + /**
> > + * Called when new loudness measurements are available
> > + *
> > + * @param date absolute date (likely in the future) of this measurement
> > + * @param loudness pointer to the loudness measurement
> > + * @param opaque pointer set by vlc_audio_meter_AddPlugin().
> > + */
> > + void (*on_loudness)(vlc_tick_t date, const struct vlc_audio_loudness
> > *loudness, void *data); +};
> > +
> > +/**
> > + * Audio meter structure
> > + *
> > + * Initialise with vlc_audio_meter_Init()
> > + *
> > + * @warning variables of this struct should not be used directly
> > + */
> > +struct vlc_audio_meter
> > +{
> > + vlc_mutex_t lock;
> > + vlc_object_t *parent;
> > + const audio_sample_format_t *fmt;
> > +
> > + struct vlc_list plugins;
> > +};
> > +
> > +/**
> > + * Initialize the audio meter structure
> > + *
> > + * @param meter allocated audio meter structure
> > + * @param parent object that will be used to create audio filters
> > + */
> > +VLC_API void
> > +vlc_audio_meter_Init(struct vlc_audio_meter *meter, vlc_object_t *parent);
> > +#define vlc_audio_meter_Init(a,b) vlc_audio_meter_Init(a, VLC_OBJECT(b))
> > +
> > +/**
> > + * Free allocated resource from the audio meter structure
> > + *
> > + * @param meter allocated audio meter structure
> > + */
> > +VLC_API void
> > +vlc_audio_meter_Destroy(struct vlc_audio_meter *meter);
> > +
> > +/**
> > + * Set or reset the audio format
> > + *
> > + * This will reload all plugins added with vlc_audio_meter_AddPlugin()
> > + *
> > + * @param meter audio meter structure
> > + * @param fmt NULL to unload all plugins or a valid pointer to an audio
> > format, + * must stay valid during the lifetime of the audio meter (until
> > + * vlc_audio_meter_Reset() or vlc_audio_meter_Destroy() are called)
> > + *
> > + * @return VLC_SUCCESS on success, VLC_EGENERIC if a plugin failed to load
> > + */
> > +VLC_API int
> > +vlc_audio_meter_Reset(struct vlc_audio_meter *meter, const
> > audio_sample_format_t *fmt); +
> > +/**
> > + * Add an "audio meter" plugin
> > + *
> > + * The module to be loaded if meter->fmt is valid, otherwise, the module
> > + * will be loaded from a next call to vlc_audio_meter_Reset()
> > + *
> > + * @param meter audio meter structure
> > + * @param chain name of the module, can contain specific module options
> > using + * the following chain convention:"name{option1=a,option2=b}"
> > + * @param cbs pointer to a vlc_audio_meter_events structure, the
> > + * structure must stay valid during the lifetime of the plugin
> > + * @param cbs_data opaque pointer used by the callbacks
> > + * @return a valid audio meter plugin, or NULL in case of error
> > + */
> > +VLC_API vlc_audio_meter_plugin *
> > +vlc_audio_meter_AddPlugin(struct vlc_audio_meter *meter, const char *chain,
> > + const struct vlc_audio_meter_events *cbs, void
> > *cbs_data);
>
> You can do that, but usually VLC code defines an owner structure that contains
> both cbs and data. Is there a problem with that pattern because I'm not sure
> that there is a reason to add yet another pattern here.
I will change the API to match VLC pattern.
>
> > +
> > +/**
> > + * Remove an "audio meter" plugin
> > + *
> > + * @param meter audio meter structure
> > + * @param plugin plugin returned by vlc_audio_meter_AddPlugin()
> > + */
> > +VLC_API void
> > +vlc_audio_meter_RemovePlugin(struct vlc_audio_meter *meter,
> > vlc_audio_meter_plugin *plugin); +
> > +/**
> > + * Process an audio block
> > + *
> > + * vlc_audio_meter_events callbacks can be triggered from this function.
> > + *
> > + * @param meter audio meter structure
> > + * @param block pointer to a block, this block won't be released of
> > modified + * from this function
> > + * @param date absolute date (likely in the future) when this block should
> > be rendered + */
> > +VLC_API void
> > +vlc_audio_meter_Process(struct vlc_audio_meter *meter, block_t *block,
> > vlc_tick_t date); +
> > +/**
> > + * Flush all "audio meter" plugins
> > + *
> > + * vlc_audio_meter_events callbacks can be triggered from this function.
> > + *
> > + * @param meter audio meter structure
> > + */
> > +VLC_API void
> > +vlc_audio_meter_Flush(struct vlc_audio_meter *meter);
> > +
> > +/** @} */
> > +
> > #endif /* VLC_AOUT_H */
>
> --
> Rémi Denis-Courmont
>
>
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