Wed Oct 28 15:47:54 2009

Asterisk developer's documentation


format_pcm.c

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00001 /*
00002  * Asterisk -- An open source telephony toolkit.
00003  *
00004  * Copyright (C) 1999 - 2006, Digium, Inc.
00005  *
00006  * Mark Spencer <markster@digium.com>
00007  *
00008  * See http://www.asterisk.org for more information about
00009  * the Asterisk project. Please do not directly contact
00010  * any of the maintainers of this project for assistance;
00011  * the project provides a web site, mailing lists and IRC
00012  * channels for your use.
00013  *
00014  * This program is free software, distributed under the terms of
00015  * the GNU General Public License Version 2. See the LICENSE file
00016  * at the top of the source tree.
00017  */
00018 
00019 /*! \file
00020  *
00021  * \brief Flat, binary, ulaw PCM file format.
00022  * \arg File name extension: pcm, ulaw, ul, mu
00023  * 
00024  * \ingroup formats
00025  */
00026  
00027 #include <unistd.h>
00028 #include <netinet/in.h>
00029 #include <arpa/inet.h>
00030 #include <stdlib.h>
00031 #include <sys/time.h>
00032 #include <stdio.h>
00033 #include <errno.h>
00034 #include <string.h>
00035 
00036 #include "asterisk.h"
00037 
00038 ASTERISK_FILE_VERSION(__FILE__, "$Revision: 7819 $")
00039 
00040 #include "asterisk/lock.h"
00041 #include "asterisk/channel.h"
00042 #include "asterisk/file.h"
00043 #include "asterisk/logger.h"
00044 #include "asterisk/sched.h"
00045 #include "asterisk/module.h"
00046 #include "asterisk/endian.h"
00047 #include "asterisk/ulaw.h"
00048 
00049 #define BUF_SIZE 160    /* 160 samples */
00050 
00051 struct ast_filestream {
00052    void *reserved[AST_RESERVED_POINTERS];
00053    /* This is what a filestream means to us */
00054    FILE *f; /* Descriptor */
00055    struct ast_channel *owner;
00056    struct ast_frame fr;          /* Frame information */
00057    char waste[AST_FRIENDLY_OFFSET]; /* Buffer for sending frames, etc */
00058    char empty;                   /* Empty character */
00059    unsigned char buf[BUF_SIZE];           /* Output Buffer */
00060    struct timeval last;
00061 };
00062 
00063 
00064 AST_MUTEX_DEFINE_STATIC(pcm_lock);
00065 static int glistcnt = 0;
00066 
00067 static char *name = "pcm";
00068 static char *desc = "Raw uLaw 8khz Audio support (PCM)";
00069 static char *exts = "pcm|ulaw|ul|mu";
00070 
00071 static char ulaw_silence[BUF_SIZE];
00072 
00073 static struct ast_filestream *pcm_open(FILE *f)
00074 {
00075    /* We don't have any header to read or anything really, but
00076       if we did, it would go here.  We also might want to check
00077       and be sure it's a valid file.  */
00078    struct ast_filestream *tmp;
00079    if ((tmp = malloc(sizeof(struct ast_filestream)))) {
00080       memset(tmp, 0, sizeof(struct ast_filestream));
00081       if (ast_mutex_lock(&pcm_lock)) {
00082          ast_log(LOG_WARNING, "Unable to lock pcm list\n");
00083          free(tmp);
00084          return NULL;
00085       }
00086       tmp->f = f;
00087       tmp->fr.data = tmp->buf;
00088       tmp->fr.frametype = AST_FRAME_VOICE;
00089       tmp->fr.subclass = AST_FORMAT_ULAW;
00090       /* datalen will vary for each frame */
00091       tmp->fr.src = name;
00092       tmp->fr.mallocd = 0;
00093       glistcnt++;
00094       ast_mutex_unlock(&pcm_lock);
00095       ast_update_use_count();
00096    }
00097    return tmp;
00098 }
00099 
00100 static struct ast_filestream *pcm_rewrite(FILE *f, const char *comment)
00101 {
00102    /* We don't have any header to read or anything really, but
00103       if we did, it would go here.  We also might want to check
00104       and be sure it's a valid file.  */
00105    struct ast_filestream *tmp;
00106    if ((tmp = malloc(sizeof(struct ast_filestream)))) {
00107       memset(tmp, 0, sizeof(struct ast_filestream));
00108       if (ast_mutex_lock(&pcm_lock)) {
00109          ast_log(LOG_WARNING, "Unable to lock pcm list\n");
00110          free(tmp);
00111          return NULL;
00112       }
00113       tmp->f = f;
00114       glistcnt++;
00115       ast_mutex_unlock(&pcm_lock);
00116       ast_update_use_count();
00117    } else
00118       ast_log(LOG_WARNING, "Out of memory\n");
00119    return tmp;
00120 }
00121 
00122 static void pcm_close(struct ast_filestream *s)
00123 {
00124    if (ast_mutex_lock(&pcm_lock)) {
00125       ast_log(LOG_WARNING, "Unable to lock pcm list\n");
00126       return;
00127    }
00128    glistcnt--;
00129    ast_mutex_unlock(&pcm_lock);
00130    ast_update_use_count();
00131    fclose(s->f);
00132    free(s);
00133    s = NULL;
00134 }
00135 
00136 static struct ast_frame *pcm_read(struct ast_filestream *s, int *whennext)
00137 {
00138    int res;
00139    int delay;
00140    /* Send a frame from the file to the appropriate channel */
00141 
00142    s->fr.frametype = AST_FRAME_VOICE;
00143    s->fr.subclass = AST_FORMAT_ULAW;
00144    s->fr.offset = AST_FRIENDLY_OFFSET;
00145    s->fr.mallocd = 0;
00146    s->fr.data = s->buf;
00147    if ((res = fread(s->buf, 1, BUF_SIZE, s->f)) < 1) {
00148       if (res)
00149          ast_log(LOG_WARNING, "Short read (%d) (%s)!\n", res, strerror(errno));
00150       return NULL;
00151    }
00152    s->fr.samples = res;
00153    s->fr.datalen = res;
00154    delay = s->fr.samples;
00155    *whennext = delay;
00156    return &s->fr;
00157 }
00158 
00159 static int pcm_write(struct ast_filestream *fs, struct ast_frame *f)
00160 {
00161    int res;
00162    if (f->frametype != AST_FRAME_VOICE) {
00163       ast_log(LOG_WARNING, "Asked to write non-voice frame!\n");
00164       return -1;
00165    }
00166    if (f->subclass != AST_FORMAT_ULAW) {
00167       ast_log(LOG_WARNING, "Asked to write non-ulaw frame (%d)!\n", f->subclass);
00168       return -1;
00169    }
00170    if ((res = fwrite(f->data, 1, f->datalen, fs->f)) != f->datalen) {
00171          ast_log(LOG_WARNING, "Bad write (%d/%d): %s\n", res, f->datalen, strerror(errno));
00172          return -1;
00173    }
00174    return 0;
00175 }
00176 
00177 static int pcm_seek(struct ast_filestream *fs, long sample_offset, int whence)
00178 {
00179    long cur, max, offset = 0;
00180 
00181    cur = ftell(fs->f);
00182    fseek(fs->f, 0, SEEK_END);
00183    max = ftell(fs->f);
00184 
00185    switch (whence) {
00186    case SEEK_SET:
00187       offset = sample_offset;
00188       break;
00189    case SEEK_END:
00190       offset = max - sample_offset;
00191       break;
00192    case SEEK_CUR:
00193    case SEEK_FORCECUR:
00194       offset = cur + sample_offset;
00195       break;
00196    }
00197 
00198    switch (whence) {
00199    case SEEK_FORCECUR:
00200       if (offset > max) {
00201          size_t left = offset - max;
00202          size_t res;
00203 
00204          while (left) {
00205             res = fwrite(ulaw_silence, sizeof(ulaw_silence[0]),
00206                     (left > BUF_SIZE) ? BUF_SIZE : left, fs->f);
00207             if (res == -1)
00208                return res;
00209             left -= res * sizeof(ulaw_silence[0]);
00210          }
00211          return offset;
00212       }
00213       /* fall through */
00214    default:
00215       offset = (offset > max) ? max : offset;
00216       offset = (offset < 0) ? 0 : offset;
00217       return fseek(fs->f, offset, SEEK_SET);
00218    }
00219 }
00220 
00221 static int pcm_trunc(struct ast_filestream *fs)
00222 {
00223    return ftruncate(fileno(fs->f), ftell(fs->f));
00224 }
00225 
00226 static long pcm_tell(struct ast_filestream *fs)
00227 {
00228    off_t offset;
00229    offset = ftell(fs->f);
00230    return offset;
00231 }
00232 
00233 static char *pcm_getcomment(struct ast_filestream *s)
00234 {
00235    return NULL;
00236 }
00237 
00238 int load_module()
00239 {
00240    int index;
00241 
00242    for (index = 0; index < (sizeof(ulaw_silence) / sizeof(ulaw_silence[0])); index++)
00243       ulaw_silence[index] = AST_LIN2MU(0);
00244 
00245    return ast_format_register(name, exts, AST_FORMAT_ULAW,
00246                pcm_open,
00247                pcm_rewrite,
00248                pcm_write,
00249                pcm_seek,
00250                pcm_trunc,
00251                pcm_tell,
00252                pcm_read,
00253                pcm_close,
00254                pcm_getcomment);
00255 }
00256 
00257 int unload_module()
00258 {
00259    return ast_format_unregister(name);
00260 }  
00261 
00262 int usecount()
00263 {
00264    return glistcnt;
00265 }
00266 
00267 char *description()
00268 {
00269    return desc;
00270 }
00271 
00272 
00273 char *key()
00274 {
00275    return ASTERISK_GPL_KEY;
00276 }

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