asterisk/main/fixedjitterbuf.c

354 lines
8.7 KiB
C

/*
* Copyright (C) 2005, Attractel OOD
*
* Contributors:
* Slav Klenov <slav@securax.org>
*
* See http://www.asterisk.org for more information about
* the Asterisk project. Please do not directly contact
* any of the maintainers of this project for assistance;
* the project provides a web site, mailing lists and IRC
* channels for your use.
*
* This program is free software, distributed under the terms of
* the GNU General Public License Version 2. See the LICENSE file
* at the top of the source tree.
*
* A license has been granted to Digium (via disclaimer) for the use of
* this code.
*/
/*! \file
*
* \brief Jitterbuffering algorithm.
*
* \author Slav Klenov <slav@securax.org>
*/
/*** MODULEINFO
<support_level>core</support_level>
***/
#include "asterisk.h"
#include <assert.h>
#include "asterisk/utils.h"
#include "fixedjitterbuf.h"
#undef FIXED_JB_DEBUG
#ifdef FIXED_JB_DEBUG
#define ASSERT(a)
#else
#define ASSERT(a) ast_assert(a)
#endif
/*! \brief private fixed_jb structure */
struct fixed_jb
{
struct fixed_jb_frame *frames;
struct fixed_jb_frame *tail;
struct fixed_jb_conf conf;
long rxcore;
long delay;
long next_delivery;
int force_resynch;
};
static struct fixed_jb_frame *alloc_jb_frame(struct fixed_jb *jb);
static void release_jb_frame(struct fixed_jb *jb, struct fixed_jb_frame *frame);
static void get_jb_head(struct fixed_jb *jb, struct fixed_jb_frame *frame);
static int resynch_jb(struct fixed_jb *jb, void *data, long ms, long ts, long now);
static inline struct fixed_jb_frame *alloc_jb_frame(struct fixed_jb *jb)
{
return ast_calloc(1, sizeof(*jb));
}
static inline void release_jb_frame(struct fixed_jb *jb, struct fixed_jb_frame *frame)
{
ast_free(frame);
}
static void get_jb_head(struct fixed_jb *jb, struct fixed_jb_frame *frame)
{
struct fixed_jb_frame *fr;
/* unlink the frame */
fr = jb->frames;
jb->frames = fr->next;
if (jb->frames) {
jb->frames->prev = NULL;
} else {
/* the jb is empty - update tail */
jb->tail = NULL;
}
/* update next */
jb->next_delivery = fr->delivery + fr->ms;
/* copy the destination */
memcpy(frame, fr, sizeof(struct fixed_jb_frame));
/* and release the frame */
release_jb_frame(jb, fr);
}
struct fixed_jb *fixed_jb_new(struct fixed_jb_conf *conf)
{
struct fixed_jb *jb;
if (!(jb = ast_calloc(1, sizeof(*jb))))
return NULL;
/* First copy our config */
memcpy(&jb->conf, conf, sizeof(struct fixed_jb_conf));
/* we don't need the passed config anymore - continue working with the saved one */
conf = &jb->conf;
/* validate the configuration */
if (conf->jbsize < 1)
conf->jbsize = FIXED_JB_SIZE_DEFAULT;
if (conf->resync_threshold < 1)
conf->resync_threshold = FIXED_JB_RESYNCH_THRESHOLD_DEFAULT;
/* Set the constant delay to the jitterbuf */
jb->delay = conf->jbsize;
return jb;
}
void fixed_jb_destroy(struct fixed_jb *jb)
{
/* jitterbuf MUST be empty before it can be destroyed */
ASSERT(jb->frames == NULL);
ast_free(jb);
}
static int resynch_jb(struct fixed_jb *jb, void *data, long ms, long ts, long now)
{
long diff, offset;
struct fixed_jb_frame *frame;
/* If jb is empty, just reinitialize the jb */
if (!jb->frames) {
/* debug check: tail should also be NULL */
ASSERT(jb->tail == NULL);
return fixed_jb_put_first(jb, data, ms, ts, now);
}
/* Adjust all jb state just as the new frame is with delivery = the delivery of the last
frame (e.g. this one with max delivery) + the length of the last frame. */
/* Get the diff in timestamps */
diff = ts - jb->tail->ts;
/* Ideally this should be just the length of the last frame. The deviation is the desired
offset */
offset = diff - jb->tail->ms;
/* Do we really need to resynch, or this is just a frame for dropping? */
if (!jb->force_resynch && (offset < jb->conf.resync_threshold && offset > -jb->conf.resync_threshold))
return FIXED_JB_DROP;
/* Reset the force resynch flag */
jb->force_resynch = 0;
/* apply the offset to the jb state */
jb->rxcore -= offset;
frame = jb->frames;
while (frame) {
frame->ts += offset;
frame = frame->next;
}
/* now jb_put() should add the frame at a last position */
return fixed_jb_put(jb, data, ms, ts, now);
}
void fixed_jb_set_force_resynch(struct fixed_jb *jb)
{
jb->force_resynch = 1;
}
int fixed_jb_put_first(struct fixed_jb *jb, void *data, long ms, long ts, long now)
{
/* this is our first frame - set the base of the receivers time */
jb->rxcore = now - ts;
/* init next for a first time - it should be the time the first frame should be played */
jb->next_delivery = now + jb->delay;
/* put the frame */
return fixed_jb_put(jb, data, ms, ts, now);
}
int fixed_jb_put(struct fixed_jb *jb, void *data, long ms, long ts, long now)
{
struct fixed_jb_frame *frame, *next, *newframe;
long delivery;
/* debug check the validity of the input params */
ASSERT(data != NULL);
/* do not allow frames shorter than 2 ms */
ASSERT(ms >= 2);
ASSERT(ts >= 0);
ASSERT(now >= 0);
delivery = jb->rxcore + jb->delay + ts;
/* check if the new frame is not too late */
if (delivery < jb->next_delivery) {
/* should drop the frame, but let first resynch_jb() check if this is not a jump in ts, or
the force resynch flag was not set. */
return resynch_jb(jb, data, ms, ts, now);
}
/* what if the delivery time is bigger than next + delay? Seems like a frame for the future.
However, allow more resync_threshold ms in advance */
if (delivery > jb->next_delivery + jb->delay + jb->conf.resync_threshold) {
/* should drop the frame, but let first resynch_jb() check if this is not a jump in ts, or
the force resynch flag was not set. */
return resynch_jb(jb, data, ms, ts, now);
}
/* find the right place in the frames list, sorted by delivery time */
frame = jb->tail;
while (frame && frame->delivery > delivery) {
frame = frame->prev;
}
/* Check if the new delivery time is not covered already by the chosen frame */
if (frame && (frame->delivery == delivery ||
delivery < frame->delivery + frame->ms ||
(frame->next && delivery + ms > frame->next->delivery)))
{
/* TODO: Should we check for resynch here? Be careful to do not allow threshold smaller than
the size of the jb */
/* should drop the frame, but let first resynch_jb() check if this is not a jump in ts, or
the force resynch flag was not set. */
return resynch_jb(jb, data, ms, ts, now);
}
/* Reset the force resynch flag */
jb->force_resynch = 0;
/* Get a new frame */
newframe = alloc_jb_frame(jb);
newframe->data = data;
newframe->ts = ts;
newframe->ms = ms;
newframe->delivery = delivery;
/* and insert it right on place */
if (frame) {
next = frame->next;
frame->next = newframe;
if (next) {
newframe->next = next;
next->prev = newframe;
} else {
/* insert after the last frame - should update tail */
jb->tail = newframe;
newframe->next = NULL;
}
newframe->prev = frame;
return FIXED_JB_OK;
} else if (!jb->frames) {
/* the frame list is empty or thats just the first frame ever */
/* tail should also be NULL is that case */
ASSERT(jb->tail == NULL);
jb->frames = jb->tail = newframe;
newframe->next = NULL;
newframe->prev = NULL;
return FIXED_JB_OK;
} else {
/* insert on a first position - should update frames head */
newframe->next = jb->frames;
newframe->prev = NULL;
jb->frames->prev = newframe;
jb->frames = newframe;
return FIXED_JB_OK;
}
}
int fixed_jb_get(struct fixed_jb *jb, struct fixed_jb_frame *frame, long now, long interpl)
{
ASSERT(now >= 0);
ASSERT(interpl >= 2);
if (now < jb->next_delivery) {
/* too early for the next frame */
return FIXED_JB_NOFRAME;
}
/* Is the jb empty? */
if (!jb->frames) {
/* should interpolate a frame */
/* update next */
jb->next_delivery += interpl;
return FIXED_JB_INTERP;
}
/* Isn't it too late for the first frame available in the jb? */
if (now > jb->frames->delivery + jb->frames->ms) {
/* yes - should drop this frame and update next to point the next frame (get_jb_head() does it) */
get_jb_head(jb, frame);
return FIXED_JB_DROP;
}
/* isn't it too early to play the first frame available? */
if (now < jb->frames->delivery) {
/* yes - should interpolate one frame */
/* update next */
jb->next_delivery += interpl;
return FIXED_JB_INTERP;
}
/* we have a frame for playing now (get_jb_head() updates next) */
get_jb_head(jb, frame);
return FIXED_JB_OK;
}
long fixed_jb_next(struct fixed_jb *jb)
{
return jb->next_delivery;
}
int fixed_jb_remove(struct fixed_jb *jb, struct fixed_jb_frame *frameout)
{
if (!jb->frames)
return FIXED_JB_NOFRAME;
get_jb_head(jb, frameout);
return FIXED_JB_OK;
}
int fixed_jb_is_late(struct fixed_jb *jb, long ts)
{
return jb->rxcore + jb->delay + ts < jb->next_delivery;
}