Osmocom Jitter Buffer

Files
file	jibuf.h
	Osmocom Jitter Buffer helpers.
file	jibuf.c
	Osmocom Jitter Buffer helpers.

Data Structures
struct	osmo_jibuf
	A structure representing a single instance of a jitter buffer. More...
struct	osmo_jibuf_msgb_cb

Macros
#define	SAMPLES_PER_PKT   160
#define	SAMPLE_RATE   8000
#define	JIBUF_DEFAULT_MIN_DELAY_MS   60
#define	JIBUF_DEFAULT_MAX_DELAY_MS   200
#define	JIBUF_REFERENCE_TS_FREQ   60
#define	JIBUF_BUFFER_RECALC_FREQ   40
#define	JIBUF_ALLOWED_PKT_DROP   3
#define	JIBUF_ALLOWED_PKT_CONSECUTIVE_DROP   1
#define	JIBUF_BUFFER_INC_STEP   20
#define	JIBUF_BUFFER_DEC_STEP   5
#define	JIBUF_SKEW_WEIGHT   ((double)1/32)
#define	JIBUF_MSGB_CB(__msgb)   ((struct osmo_jibuf_msgb_cb *)&((__msgb)->cb[0]))

Typedefs
typedef void(*	osmo_jibuf_dequeue_cb) (struct msgb *msg, void *data)

Functions
struct osmo_jibuf *	osmo_jibuf_alloc (void *talloc_ctx)
	Allocate a new jitter buffer instance. More...
void	osmo_jibuf_delete (struct osmo_jibuf *jb)
	Destroy a previously allocated jitter buffer instance. More...
int	osmo_jibuf_enqueue (struct osmo_jibuf *jb, struct msgb *msg)
	Try to enqueue a packet into the jitter buffer. More...
bool	osmo_jibuf_empty (struct osmo_jibuf *jb)
	Check whether the jitter buffer instance has packets queued or not. More...
void	osmo_jibuf_set_min_delay (struct osmo_jibuf *jb, uint32_t min_delay)
	Set minimum buffer size for the jitter buffer. More...
void	osmo_jibuf_set_max_delay (struct osmo_jibuf *jb, uint32_t max_delay)
	Set maximum buffer size for the jitter buffer. More...
void	osmo_jibuf_enable_skew_compensation (struct osmo_jibuf *jb, bool enable)
	Toggle use of skew detection and compensation mechanism. More...
void	osmo_jibuf_set_dequeue_cb (struct osmo_jibuf *jb, osmo_jibuf_dequeue_cb dequeue_cb, void *cb_data)
	Set dequeue callback for the jitter buffer. More...
static void	ms2timeval (struct timeval *ts, uint32_t ms)
static uint32_t	timeval2ms (const struct timeval *ts)
static int	clock_gettime_timeval (clockid_t clk_id, struct timeval *tp)
static struct timeval *	msgb_scheduled_ts (const struct msgb *msg)
static void	llist_add_sorted (struct msgb *msg, struct llist_head *msg_list)
static void	enqueue_pkt (struct osmo_jibuf *jb, struct msgb *msg, bool is_syncpoint)
static bool	msg_get_marker (struct msgb *msg)
static uint16_t	msg_get_sequence (struct msgb *msg)
static uint32_t	msg_get_timestamp (struct msgb *msg)
static int32_t	samples2ms (int32_t samples)
static int	calc_pkt_rel_delay (struct osmo_jibuf *jb, struct msgb *msg)
static bool	msg_is_in_sequence (struct osmo_jibuf *jb, struct msgb *msg)
static bool	msg_is_syncpoint (struct osmo_jibuf *jb, struct msgb *msg)
static void	msg_set_as_reference (struct osmo_jibuf *jb, struct msgb *msg)
static void	dequeue_msg (struct osmo_jibuf *jb, struct msgb *msg)
static void	timer_expired (void *data)
static void	recalc_clock_skew (struct osmo_jibuf *jb, int32_t rel_delay)
static void	recalc_threshold_delay (struct osmo_jibuf *jb)

Variables
struct osmo_jibuf	__attribute__

Detailed Description

Function Documentation

osmo_jibuf_alloc()

struct osmo_jibuf * osmo_jibuf_alloc

(

void *

talloc_ctx

)

Allocate a new jitter buffer instance.

Returns

the new allocated instance

osmo_jibuf_delete()

void osmo_jibuf_delete

(

struct osmo_jibuf *

jb

)

Destroy a previously allocated jitter buffer instance.

Parameters

[in]

jb

Previously allocated (non-null) jitter buffer instance

All the queued packets are dequeued before deleting the instance.

osmo_jibuf_empty()

bool osmo_jibuf_empty

(

struct osmo_jibuf *

jb

)

Check whether the jitter buffer instance has packets queued or not.

Parameters

[in]

jb

jitter buffer instance

Returns

true if the queue is empty, false otherwise.

osmo_jibuf_enable_skew_compensation()

void osmo_jibuf_enable_skew_compensation	(	struct osmo_jibuf *	jb,
		bool	enable
	)

Toggle use of skew detection and compensation mechanism.

Parameters

[in]	jb	jitter buffer instance
[in]	enable	Whether to enable or not (default) the skew estimation and compensation mechanism

When this function is called, the estimated skew is reset.

osmo_jibuf_enqueue()

int osmo_jibuf_enqueue	(	struct osmo_jibuf *	jb,
		struct msgb *	msg
	)

Try to enqueue a packet into the jitter buffer.

Parameters

[in]	jb	jitter buffer instance
[in]	msg	msgb to enqueue, containing an RTP packet

Returns

<0 if the packet was dropped, 0 otherwise

This function calculates the delay for the enqueued packet. If the delay is bigger than the current buffer size, the function returns -1 and the caller owns the packet again and can free it if required. If the packet is enqueued, 0 is returned and the exact same packet (ownership transfer, no copy is made) will be available again through the dequeue_cb() when the queue timer for this packet expires.

osmo_jibuf_set_dequeue_cb()

void osmo_jibuf_set_dequeue_cb	(	struct osmo_jibuf *	jb,
		osmo_jibuf_dequeue_cb	dequeue_cb,
		void *	cb_data
	)

Set dequeue callback for the jitter buffer.

Parameters

[in]	jb	jitter buffer instance
[in]	dequeue_cb	function pointer to call back when the dequeue timer for a given packet expires
[in]	cb_data	data pointer to be passed to dequeue_cb together with the msgb.

osmo_jibuf_set_max_delay()

void osmo_jibuf_set_max_delay	(	struct osmo_jibuf *	jb,
		uint32_t	max_delay
	)

Set maximum buffer size for the jitter buffer.

Parameters

[in]	jb	jitter buffer instance
[in]	max_delay	Maximum buffer size, as in maximum delay in milliseconds

osmo_jibuf_set_min_delay()

void osmo_jibuf_set_min_delay	(	struct osmo_jibuf *	jb,
		uint32_t	min_delay
	)

Set minimum buffer size for the jitter buffer.

Parameters

[in]	jb	jitter buffer instance
[in]	min_delay	Minimum buffer size, as in minimum delay in milliseconds