Group PJMEDIA_CLOCK

group PJMEDIA_CLOCK

Interface for generating clock.

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.

Typedefs

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.

Enums

enum pjmedia_clock_options

Options when creating the clock.

Values:

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.

enumerator PJMEDIA_CLOCK_NO_HIGHEST_PRIO

Prevent the clock from setting it’s thread to highest priority.

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)

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.