spandsp 0.0.6
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00001 /* 00002 * SpanDSP - a series of DSP components for telephony 00003 * 00004 * playout.h 00005 * 00006 * Written by Steve Underwood <steveu@coppice.org> 00007 * 00008 * Copyright (C) 2005 Steve Underwood 00009 * 00010 * All rights reserved. 00011 * 00012 * This program is free software; you can redistribute it and/or modify 00013 * it under the terms of the GNU Lesser General Public License version 2.1, 00014 * as published by the Free Software Foundation. 00015 * 00016 * This program is distributed in the hope that it will be useful, 00017 * but WITHOUT ANY WARRANTY; without even the implied warranty of 00018 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 00019 * GNU Lesser General Public License for more details. 00020 * 00021 * You should have received a copy of the GNU Lesser General Public 00022 * License along with this program; if not, write to the Free Software 00023 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. 00024 */ 00025 00026 #if !defined(_SPANDSP_PLAYOUT_H_) 00027 #define _SPANDSP_PLAYOUT_H_ 00028 00029 /*! \page playout_page Play-out (jitter buffering) 00030 \section playout_page_sec_1 What does it do? 00031 The play-out module provides a static or dynamic length buffer for received frames of 00032 audio or video data. It's goal is to maximise the receiver's tolerance of jitter in the 00033 timing of the received frames. 00034 00035 Dynamic buffers are generally good for speech, since they adapt to provide the smallest delay 00036 consistent with a low rate of packets arriving too late to be used. For things like FoIP and 00037 MoIP, a static length of buffer is normally necessary. Any attempt to elastically change the 00038 buffer length would wreck a modem's data flow. 00039 */ 00040 00041 /* Return codes */ 00042 enum 00043 { 00044 PLAYOUT_OK = 0, 00045 PLAYOUT_ERROR, 00046 PLAYOUT_EMPTY, 00047 PLAYOUT_NOFRAME, 00048 PLAYOUT_FILLIN, 00049 PLAYOUT_DROP 00050 }; 00051 00052 /* Frame types */ 00053 #define PLAYOUT_TYPE_CONTROL 0 00054 #define PLAYOUT_TYPE_SILENCE 1 00055 #define PLAYOUT_TYPE_SPEECH 2 00056 00057 typedef int timestamp_t; 00058 00059 typedef struct playout_frame_s 00060 { 00061 /*! The actual frame data */ 00062 void *data; 00063 /*! The type of frame */ 00064 int type; 00065 /*! The timestamp assigned by the sending end */ 00066 timestamp_t sender_stamp; 00067 /*! The timespan covered by the data in this frame */ 00068 timestamp_t sender_len; 00069 /*! The timestamp assigned by the receiving end */ 00070 timestamp_t receiver_stamp; 00071 /*! Pointer to the next earlier frame */ 00072 struct playout_frame_s *earlier; 00073 /*! Pointer to the next later frame */ 00074 struct playout_frame_s *later; 00075 } playout_frame_t; 00076 00077 /*! 00078 Playout (jitter buffer) descriptor. This defines the working state 00079 for a single instance of playout buffering. 00080 */ 00081 typedef struct 00082 { 00083 /*! TRUE if the buffer is dynamically sized */ 00084 int dynamic; 00085 /*! The minimum length (dynamic) or fixed length (static) of the buffer */ 00086 int min_length; 00087 /*! The maximum length (dynamic) or fixed length (static) of the buffer */ 00088 int max_length; 00089 /*! The target filter threshold for adjusting dynamic buffering. */ 00090 int dropable_threshold; 00091 00092 int start; 00093 00094 /*! The queued frame list */ 00095 playout_frame_t *first_frame; 00096 playout_frame_t *last_frame; 00097 /*! The free frame pool */ 00098 playout_frame_t *free_frames; 00099 00100 /*! The total frames input to the buffer, to date. */ 00101 int frames_in; 00102 /*! The total frames output from the buffer, to date. */ 00103 int frames_out; 00104 /*! The number of frames received out of sequence. */ 00105 int frames_oos; 00106 /*! The number of frames which were discarded, due to late arrival. */ 00107 int frames_late; 00108 /*! The number of frames which were never received. */ 00109 int frames_missing; 00110 /*! The number of frames trimmed from the stream, due to buffer shrinkage. */ 00111 int frames_trimmed; 00112 00113 timestamp_t latest_expected; 00114 /*! The present jitter adjustment */ 00115 timestamp_t current; 00116 /*! The sender_stamp of the last speech frame */ 00117 timestamp_t last_speech_sender_stamp; 00118 /*! The duration of the last speech frame */ 00119 timestamp_t last_speech_sender_len; 00120 00121 int not_first; 00122 /*! The time since the target buffer length was last changed. */ 00123 timestamp_t since_last_step; 00124 /*! Filter state for tracking the packets arriving just in time */ 00125 int32_t state_just_in_time; 00126 /*! Filter state for tracking the packets arriving late */ 00127 int32_t state_late; 00128 /*! The current target length of the buffer */ 00129 int target_buffer_length; 00130 /*! The current actual length of the buffer, which may lag behind the target value */ 00131 int actual_buffer_length; 00132 } playout_state_t; 00133 00134 #if defined(__cplusplus) 00135 extern "C" 00136 { 00137 #endif 00138 00139 /*! Queue a frame 00140 \param s The play-out context. 00141 \param data The frame data. 00142 \param sender_len Length of frame (for voice) in timestamp units. 00143 \param sender_stamp Sending end's time stamp. 00144 \param receiver_stamp Local time at which packet was received, in timestamp units. 00145 \return One of 00146 PLAYOUT_OK: Frame queued OK. 00147 PLAYOUT_ERROR: Some problem occured - e.g. out of memory. */ 00148 SPAN_DECLARE(int) playout_put(playout_state_t *s, void *data, int type, timestamp_t sender_len, timestamp_t sender_stamp, timestamp_t receiver_stamp); 00149 00150 /*! Get the next frame. 00151 \param s The play-out context. 00152 \param frame The frame. 00153 \param sender_stamp The sender's timestamp. 00154 \return One of 00155 PLAYOUT_OK: Suitable frame found. 00156 PLAYOUT_DROP: A frame which should be dropped was found (e.g. it arrived too late). 00157 The caller should request the same time again when this occurs. 00158 PLAYOUT_NOFRAME: There's no frame scheduled for this time. 00159 PLAYOUT_FILLIN: Synthetic signal must be generated, as no real data is available for 00160 this time (either we need to grow, or there was a lost frame). 00161 PLAYOUT_EMPTY: The buffer is empty. 00162 */ 00163 SPAN_DECLARE(int) playout_get(playout_state_t *s, playout_frame_t *frame, timestamp_t sender_stamp); 00164 00165 /*! Unconditionally get the first buffered frame. This may be used to clear out the queue, and free 00166 all its contents, before the context is freed. 00167 \param s The play-out context. 00168 \return The frame, or NULL is the queue is empty. */ 00169 SPAN_DECLARE(playout_frame_t *) playout_get_unconditional(playout_state_t *s); 00170 00171 /*! Find the current length of the buffer. 00172 \param s The play-out context. 00173 \return The length of the buffer. */ 00174 SPAN_DECLARE(timestamp_t) playout_current_length(playout_state_t *s); 00175 00176 /*! Find the time at which the next queued frame is due to play. 00177 Note: This value may change backwards as freshly received out of order frames are 00178 added to the buffer. 00179 \param s The play-out context. 00180 \return The next timestamp. */ 00181 SPAN_DECLARE(timestamp_t) playout_next_due(playout_state_t *s); 00182 00183 /*! Reset an instance of play-out buffering. 00184 NOTE: The buffer should be empty before you call this function, otherwise 00185 you will leak queued frames, and some internal structures 00186 \param s The play-out context. 00187 \param min_length Minimum length of the buffer, in samples. 00188 \param max_length Maximum length of the buffer, in samples. If this equals min_length, static 00189 length buffering is used. */ 00190 SPAN_DECLARE(void) playout_restart(playout_state_t *s, int min_length, int max_length); 00191 00192 /*! Create a new instance of play-out buffering. 00193 \param min_length Minimum length of the buffer, in samples. 00194 \param max_length Maximum length of the buffer, in samples. If this equals min_length, static 00195 length buffering is used. 00196 \return The new context */ 00197 SPAN_DECLARE(playout_state_t *) playout_init(int min_length, int max_length); 00198 00199 /*! Release an instance of play-out buffering. 00200 \param s The play-out context to be releaased 00201 \return 0 if OK, else -1 */ 00202 SPAN_DECLARE(int) playout_release(playout_state_t *s); 00203 00204 /*! Free an instance of play-out buffering. 00205 \param s The play-out context to be destroyed 00206 \return 0 if OK, else -1 */ 00207 SPAN_DECLARE(int) playout_free(playout_state_t *s); 00208 00209 #if defined(__cplusplus) 00210 } 00211 #endif 00212 00213 #endif 00214 /*- End of file ------------------------------------------------------------*/