1 files changed, 351 insertions, 0 deletions
diff --git a/main/fixedjitterbuf.c b/main/fixedjitterbuf.c
new file mode 100644
index 000000000..1d7a5cc30
--- /dev/null
+++ b/main/fixedjitterbuf.c
@@ -0,0 +1,351 @@
+/*
+ * 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>
+ */
+
+#include "asterisk.h"
+
+ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <assert.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "asterisk/utils.h"
+#include "fixedjitterbuf.h"
+
+#undef FIXED_JB_DEBUG
+
+#ifdef FIXED_JB_DEBUG
+#define ASSERT(a)
+#else
+#define ASSERT(a) 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(struct fixed_jb_frame));
+}
+
+static inline void release_jb_frame(struct fixed_jb *jb, struct fixed_jb_frame *frame)
+{
+	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 dont 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);
+	
+	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;
+}