*/
#define BUFFER_SECONDS 5
-/** @brief Frame batch size
+/** @brief Minimum number of frames to try to play at once
*
- * This controls how many frames are written in one go.
+ * The main loop will only attempt to play any audio when this many
+ * frames are available (or the current track has reached the end).
+ * The actual number of frames it attempts to play will often be
+ * larger than this (up to three times).
*
* For ALSA we request a buffer of three times this size and set the low
* watermark to this amount. The goal is then to keep between 1 and 3 times
* this many frames in play.
*
- * For all backends we attempt to play up to three times this many frames per
+ * For other we attempt to play up to three times this many frames per
* shot. In practice we will often only send much less than this.
*/
#define FRAMES 4096
*
* Called to activate the output device.
*
- * After this function succeeds, @ref ready should be non-0. As well as
- * opening the audio device, this function is responsible for reconfiguring
- * if it necessary to cope with different samples formats (for backends that
- * don't demand a single fixed sample format for the lifetime of the server).
+ * On input @ref device_state may be anything. If it is @ref
+ * device_open then the device is already open but might be using
+ * the wrong sample format. The device should be reconfigured to
+ * use the right sample format.
+ *
+ * If it is @ref device_error then a retry is underway and an
+ * attempt to recover or re-open the device (with the right sample
+ * format) should be made.
+ *
+ * If it is @ref device_closed then the device should be opened with
+ * the right sample format.
+ *
+ * If the @ref FIXED_FORMAT flag is not set then @ref device_format
+ * must be set on success.
+ *
+ * Some devices are effectively always open and have no error state,
+ * in which case this callback can be NULL. In this case @ref
+ * FIXED_FORMAT must be set. Note that @ref device_state still
+ * switches between @ref device_open and @ref device_closd in this
+ * case.
*/
- int (*activate)(void);
+ void (*activate)(void);
/** @brief Play sound
* @param frames Number of frames to play
* @return Number of frames actually played
+ *
+ * If an error occurs (and it is not immediately recovered) this
+ * should set @ref device_state to @ref device_error.
*/
size_t (*play)(size_t frames);
/** @brief Deactivation
*
- * Called to deactivate the sound device. This is the inverse of
- * @c activate above.
+ * Called to deactivate the sound device. This is the inverse of @c
+ * activate above.
+ *
+ * For sound devices that are open all the time and have no error
+ * state, this callback can be NULL. Note that @ref device_state
+ * still switches between @ref device_open and @ref device_closd in
+ * this case.
*/
void (*deactivate)(void);
/** @brief Called before poll()
*
- * Called before the call to poll(). Should call addfd() to update the FD
- * array and stash the slot number somewhere safe.
+ * Called before the call to poll(). Should call addfd() to update
+ * the FD array and stash the slot number somewhere safe. This will
+ * only be called if @ref device_state = @ref device_open.
*/
void (*beforepoll)(void);
/** @brief Called after poll()
- * @return 0 if we could play, non-0 if not
+ * @return 1 if output device ready for play, 0 otherwise
*
- * Called after the call to poll(). Should arrange to play some audio if the
- * output device is ready.
+ * Called after the call to poll(). This will only be called if
+ * @ref device_state = @ref device_open.
*
- * The return value should be 0 if the device was ready to play, or nonzero
- * if it was not.
+ * The return value should be 1 if the device was ready to play, or
+ * 0 if it was not.
*/
- int (*afterpoll)(void);
+ int (*ready)(void);
};
-/** @brief Linked list of all prepared tracks */
-extern struct track *tracks;
+/** @brief Possible device states */
+enum device_states {
+ /** @brief The device is closed */
+ device_closed,
+
+ /** @brief The device is open and ready to receive sound
+ *
+ * The current device sample format is potentially part of this state.
+ */
+ device_open,
+
+ /** @brief An error has occurred on the device
+ *
+ * This state is used to ensure that a small interval is left
+ * between retrying the device. If errors just set @ref
+ * device_closed then the main loop would busy-wait on broken output
+ * devices.
+ *
+ * The current device sample format is potentially part of this state.
+ */
+ device_error
+};
-/** @brief Playing track, or NULL */
+extern enum device_states device_state;
+extern ao_sample_format device_format;
+extern struct track *tracks;
extern struct track *playing;
#endif /* SPEAKER_H */
~mdw / disorder / blobdiff