audio.h

   1 #ifndef _AUDIO_H
   2 #define _AUDIO_H
   3
   4 #include <libconfig.h>
   5 #include <stdint.h>
   6
   7 typedef struct {
   8   double current_volume_dB;
   9   int32_t minimum_volume_dB;
  10   int32_t maximum_volume_dB;
  11 } audio_parameters;
  12
  13 typedef struct {
  14   void (*help)(void);
  15   char *name;
  16
  17   // start of program
  18   int (*init)(int argc, char **argv);
  19   // at end of program
  20   void (*deinit)(void);
  21
  22   void (*start)(int sample_rate, int sample_format);
  23
  24   // block of samples
  25   int (*play)(void *buf, int samples);
  26   void (*stop)(void);
  27
  28   // may be null if no implemented
  29   int (*is_running)(void); // if implemented, will return 0 if everything is okay, non-zero otherwise
  30
  31   // may be null if not implemented
  32   void (*flush)(void);
  33
  34   // returns the delay before the next frame to be sent to the device would actually be audible.
  35   // almost certainly wrong if the buffer is empty, so put silent buffers into it to make it busy.
  36   // will change dynamically, so keep watching it. Implemented in ALSA only.
  37   // returns a negative error code if there's a problem
  38   int (*delay)(long *the_delay); // snd_pcm_sframes_t is a signed long
  39   int (*rate_info)(uint64_t *elapsed_time,
  40                    uint64_t *frames_played); // use this to get the true rate of the DAC
  41
  42   // may be NULL, in which case soft volume is applied
  43   void (*volume)(double vol);
  44
  45   // may be NULL, in which case soft volume parameters are used
  46   void (*parameters)(audio_parameters *info);
  47
  48   // may be NULL, in which case software muting is used.
  49   void (*mute)(int do_mute);
  50
  51 } audio_output;
  52
  53 audio_output *audio_get_output(char *name);
  54 void audio_ls_outputs(void);
  55 void parse_general_audio_options(void);
  56
  57 #endif //_AUDIO_H