Clock Generator
[Clock/Timing]

Interface for generating clock. More...

Typedefs
typedef typedefPJ_BEGIN_DECL struct pjmedia_clock	pjmedia_clock
typedef void	pjmedia_clock_callback (const pj_timestamp *ts, void *user_data)
Enumerations
enum	pjmedia_clock_options {   PJMEDIA_CLOCK_NO_ASYNC = 1,   PJMEDIA_CLOCK_NO_HIGHEST_PRIO = 2 }
Functions
pj_status_t	pjmedia_clock_create (pj_pool_t *pool, unsigned clock_rate, unsigned channel_count, unsigned samples_per_frame, unsigned options, pjmedia_clock_callback *cb, void *user_data, pjmedia_clock **p_clock)
pj_status_t	pjmedia_clock_start (pjmedia_clock *clock)
pj_status_t	pjmedia_clock_stop (pjmedia_clock *clock)
pj_bool_t	pjmedia_clock_wait (pjmedia_clock *clock, pj_bool_t wait, pj_timestamp *ts)
pj_status_t	pjmedia_clock_destroy (pjmedia_clock *clock)

---

Detailed Description

The clock generator provides the application with media timing, and it is used by the Master Port for its sound clock.

The clock generator may be configured to run asynchronously (the default behavior) or synchronously. When it is run asynchronously, it will call the application's callback every time the clock tick expires. When it is run synchronously, application must continuously polls the clock generator to synchronize the timing.

---

Typedef Documentation

typedef typedefPJ_BEGIN_DECL struct pjmedia_clock pjmedia_clock

Opaque declaration for media clock.

typedef void pjmedia_clock_callback(const pj_timestamp *ts, void *user_data)

Type of media clock callback.

Parameters:

	ts	Current timestamp, in samples.
	user_data	Application data that is passed when the clock was created.

---

Enumeration Type Documentation

enum pjmedia_clock_options

Options when creating the clock.

Enumerator:

PJMEDIA_CLOCK_NO_ASYNC	Prevents the clock from running asynchronously. In this case, application must poll the clock continuously by calling pjmedia_clock_wait() in order to synchronize timing.
PJMEDIA_CLOCK_NO_HIGHEST_PRIO	Prevent the clock from setting it's thread to highest priority.

---

Function Documentation

pj_status_t pjmedia_clock_create	(	pj_pool_t *	pool,
		unsigned	clock_rate,
		unsigned	channel_count,
		unsigned	samples_per_frame,
		unsigned	options,
		pjmedia_clock_callback *	cb,
		void *	user_data,
		pjmedia_clock **	p_clock
	)

Create media clock.

Parameters:

	pool	Pool to allocate memory.
	clock_rate	Number of samples per second.
	channel_count	Number of channel.
	samples_per_frame	Number of samples per frame. This argument along with clock_rate and channel_count, specifies the interval of each clock run (or clock ticks).
	options	Bitmask of pjmedia_clock_options.
	cb	Callback to be called for each clock tick.
	user_data	User data, which will be passed to the callback.
	p_clock	Pointer to receive the clock instance.

Returns:

PJ_SUCCESS on success, or the appropriate error code.

pj_status_t pjmedia_clock_start

(

pjmedia_clock *

clock

)

Start the clock. For clock created with asynchronous flag set to TRUE, this may start a worker thread for the clock (depending on the backend clock implementation being used).

Parameters:

clock

The media clock.

Returns:

PJ_SUCCES on success.

pj_status_t pjmedia_clock_stop

(

pjmedia_clock *

clock

)

Stop the clock.

Parameters:

clock

The media clock.

Returns:

PJ_SUCCES on success.

pj_bool_t pjmedia_clock_wait	(	pjmedia_clock *	clock,
		pj_bool_t	wait,
		pj_timestamp *	ts
	)

Poll the media clock, and execute the callback when the clock tick has elapsed. This operation is only valid if the clock is created with async flag set to FALSE.

Parameters:

	clock	The media clock.
	wait	If non-zero, then the function will block until a clock tick elapsed and callback has been called.
	ts	Optional argument to receive the current timestamp.

Returns:

Non-zero if clock tick has elapsed, or FALSE if the function returns before a clock tick has elapsed.

pj_status_t pjmedia_clock_destroy

(

pjmedia_clock *

clock

)

Destroy the clock.

Parameters:

clock

The media clock.

Returns:

PJ_SUCCES on success.