jitterbuf.h

Go to the documentation of this file.

/*
 * jitterbuf: an application-independent jitterbuffer
 *
 * Copyrights:
 * Copyright (C) 2004-2005, Horizon Wimba, Inc.
 *
 * Contributors:
 * Steve Kann <stevek@stevek.com>
 *
 * 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