jitterbuf.h

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/*
 * jitterbuf: an application-independent jitterbuffer
 *
 * Copyrights:
 * Copyright (C) 2004-2005, Horizon Wimba, Inc.
 *
 * Contributors:
 * Steve Kann <[email protected]>
 *
 * This program is free software, distributed under the terms of
 * the GNU Lesser (Library) General Public License
 *
 * Copyright on this file is disclaimed to Digium for inclusion in Asterisk
 */

/*! \file
 * \brief
 * jitterbuf: an application-independent jitterbuffer
 * \ref jitterbuf.c
 */


#ifndef _JITTERBUF_H_
#define _JITTERBUF_H_

#ifdef __cplusplus
extern "C" {
#endif

/*! \name configuration constants */
/*@{ */
 /*! Number of historical timestamps to use in calculating jitter and drift */
#define JB_HISTORY_SZ 500
 /*! what percentage of timestamps should we drop from the history when we examine it;
 * this might eventually be something made configurable */
#define JB_HISTORY_DROPPCT 3
 /*! the maximum droppct we can handle (say it was configurable). */
#define JB_HISTORY_DROPPCT_MAX 4
 /*! the size of the buffer we use to keep the top and botton timestamps for dropping */
#define JB_HISTORY_MAXBUF_SZ JB_HISTORY_SZ * JB_HISTORY_DROPPCT_MAX / 100
 /*! amount of additional jitterbuffer adjustment */
#define JB_TARGET_EXTRA 40
 /*! ms between growing and shrinking; may not be honored if jitterbuffer runs out of space */
#define JB_ADJUST_DELAY 40
/*@} */

enum jb_return_code {
 /* return codes */
 JB_OK, /* 0 */
 JB_EMPTY, /* 1 */
 JB_NOFRAME, /* 2 */
 JB_INTERP, /* 3 */
 JB_DROP, /* 4 */
 JB_SCHED /* 5 */
};

enum jb_frame_type {
 /* frame types */
 JB_TYPE_CONTROL, /*!< 0 */
 JB_TYPE_VOICE, /*!< 1 */
 JB_TYPE_VIDEO, /*!< 2 - reserved */
 JB_TYPE_SILENCE /*!< 3 */
};

typedef struct jb_conf {
 /* settings */
 long max_jitterbuf; /*!< defines a hard clamp to use in setting the jitter buffer delay */
 long resync_threshold; /*!< the jb will resync when delay increases to (2 * jitter) + this param */
 long max_contig_interp; /*!< the max interp frames to return in a row */
 long target_extra ; /*!< amount of additional jitterbuffer adjustment, overrides JB_TARGET_EXTRA */
} jb_conf;

typedef struct jb_info {
 jb_conf conf;

 /* statistics */
 long frames_in; /*!< number of frames input to the jitterbuffer.*/
 long frames_out; /*!< number of frames output from the jitterbuffer.*/
 long frames_late; /*!< number of frames which were too late, and dropped.*/
 long frames_lost; /*!< number of missing frames.*/
 long frames_dropped; /*!< number of frames dropped (shrinkage) */
 long frames_ooo; /*!< number of frames received out-of-order */
 long frames_cur; /*!< number of frames presently in jb, awaiting delivery.*/
 long jitter; /*!< jitter measured within current history interval*/
 long min; /*!< minimum lateness within current history interval */
 long current; /*!< the present jitterbuffer adjustment */
 long target; /*!< the target jitterbuffer adjustment */
 long losspct; /*!< recent lost frame percentage (* 1000) */
 long next_voice_ts; /*!< the ts of the next frame to be read from the jb - in receiver's time */
 long last_voice_ms; /*!< the duration of the last voice frame */
 long silence_begin_ts; /*!< the time of the last CNG frame, when in silence */
 long last_adjustment; /*!< the time of the last adjustment */
 long last_delay; /*!< the last now added to history */
 long cnt_delay_discont; /*!< the count of discontinuous delays */
 long resync_offset; /*!< the amount to offset ts to support resyncs */
 long cnt_contig_interp; /*!< the number of contiguous interp frames returned */
} jb_info;

typedef struct jb_frame {
 void *data; /* the frame data */
 long ts; /* the relative delivery time expected */
 long ms; /* the time covered by this frame, in sec/8000 */
 enum jb_frame_type type; /* the type of frame */
 struct jb_frame *next, *prev;
} jb_frame;

typedef struct jitterbuf {
 jb_info info;

 /* history */
 long history[JB_HISTORY_SZ]; /*!< history */
 int hist_ptr; /*!< points to index in history for next entry */
 long hist_maxbuf[JB_HISTORY_MAXBUF_SZ]; /*!< a sorted buffer of the max delays (highest first) */
 long hist_minbuf[JB_HISTORY_MAXBUF_SZ]; /*!< a sorted buffer of the min delays (lowest first) */
 int hist_maxbuf_valid; /*!< are the "maxbuf"/minbuf valid? */
 unsigned int dropem:1; /*!< flag to indicate dropping frames (overload) */

 jb_frame *frames; /*!< queued frames */
 jb_frame *free; /*!< free frames (avoid malloc?) */
} jitterbuf;


/*! \brief new jitterbuf */
jitterbuf * jb_new(void);

/*! \brief destroy jitterbuf */
void jb_destroy(jitterbuf *jb);

/*! \brief reset jitterbuf
 * \note The jitterbuffer should be empty before you call this, otherwise
 * you will leak queued frames, and some internal structures */
void jb_reset(jitterbuf *jb);

/*!\brief queue a frame
 *
 * data=frame data, timings (in ms): ms=length of frame (for voice), ts=ts (sender's time)
 * now=now (in receiver's time) return value is one of
 * JB_OK: Frame added. Last call to jb_next() still valid
 * JB_DROP: Drop this frame immediately
 * JB_SCHED: Frame added. Call jb_next() to get a new time for the next frame
 */
enum jb_return_code jb_put(jitterbuf *jb, void *data, const enum jb_frame_type type, long ms, long ts, long now);

/*! \brief get a frame for time now (receiver's time) return value is one of
 * JB_OK: You've got frame!
 * JB_DROP: Here's an audio frame you should just drop. Ask me again for this time..
 * JB_NOFRAME: There's no frame scheduled for this time.
 * JB_INTERP: Please interpolate an interpl-length frame for this time (either we need to grow, or there was a lost frame)
 * JB_EMPTY: The jb is empty.
 */
enum jb_return_code jb_get(jitterbuf *jb, jb_frame *frame, long now, long interpl);

/*! \brief unconditionally get frames from jitterbuf until empty */
enum jb_return_code jb_getall(jitterbuf *jb, jb_frame *frameout);

/*! \brief when is the next frame due out, in receiver's time (0=EMPTY)
 * This value may change as frames are added (esp non-audio frames) */
long jb_next(jitterbuf *jb);

/*! \brief get jitterbuf info: only "statistics" may be valid */
enum jb_return_code jb_getinfo(jitterbuf *jb, jb_info *stats);

/*! \brief set jitterbuf conf */
enum jb_return_code jb_setconf(jitterbuf *jb, jb_conf *conf);

typedef void __attribute__((format(printf, 1, 2))) (*jb_output_function_t)(const char *fmt, ...);
void jb_setoutput(jb_output_function_t err, jb_output_function_t warn, jb_output_function_t dbg);

/*! \brief Checks if the given time stamp is late */
int jb_is_late(jitterbuf *jb, long ts);

#ifdef __cplusplus
}
#endif


#endif