Thu Apr 28 2011 17:13:33

Asterisk developer's documentation


format_vox.c

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00001 /*
00002  * Asterisk -- An open source telephony toolkit.
00003  *
00004  * Copyright (C) 1999 - 2005, 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, ADPCM vox file format.
00022  * \arg File name extensions: vox
00023  * 
00024  * \ingroup formats
00025  */
00026  
00027 #include "asterisk.h"
00028 
00029 ASTERISK_FILE_VERSION(__FILE__, "$Revision: 233694 $")
00030 
00031 #include "asterisk/mod_format.h"
00032 #include "asterisk/module.h"
00033 #include "asterisk/endian.h"
00034 
00035 #define BUF_SIZE  80    /* 80 bytes, 160 samples */
00036 #define VOX_SAMPLES  160
00037 
00038 static struct ast_frame *vox_read(struct ast_filestream *s, int *whennext)
00039 {
00040    int res;
00041 
00042    /* Send a frame from the file to the appropriate channel */
00043    s->fr.frametype = AST_FRAME_VOICE;
00044    s->fr.subclass = AST_FORMAT_ADPCM;
00045    s->fr.mallocd = 0;
00046    AST_FRAME_SET_BUFFER(&s->fr, s->buf, AST_FRIENDLY_OFFSET, BUF_SIZE);
00047    if ((res = fread(s->fr.data.ptr, 1, s->fr.datalen, s->f)) < 1) {
00048       if (res)
00049          ast_log(LOG_WARNING, "Short read (%d) (%s)!\n", res, strerror(errno));
00050       return NULL;
00051    }
00052    *whennext = s->fr.samples = res * 2;
00053    s->fr.datalen = res;
00054    return &s->fr;
00055 }
00056 
00057 static int vox_write(struct ast_filestream *s, struct ast_frame *f)
00058 {
00059    int res;
00060    if (f->frametype != AST_FRAME_VOICE) {
00061       ast_log(LOG_WARNING, "Asked to write non-voice frame!\n");
00062       return -1;
00063    }
00064    if (f->subclass != AST_FORMAT_ADPCM) {
00065       ast_log(LOG_WARNING, "Asked to write non-ADPCM frame (%d)!\n", f->subclass);
00066       return -1;
00067    }
00068    if ((res = fwrite(f->data.ptr, 1, f->datalen, s->f)) != f->datalen) {
00069          ast_log(LOG_WARNING, "Bad write (%d/%d): %s\n", res, f->datalen, strerror(errno));
00070          return -1;
00071    }
00072    return 0;
00073 }
00074 
00075 static int vox_seek(struct ast_filestream *fs, off_t sample_offset, int whence)
00076 {
00077      off_t offset=0,min,cur,max,distance;
00078    
00079      min = 0;
00080      cur = ftello(fs->f);
00081      fseeko(fs->f, 0, SEEK_END);
00082     max = ftello(fs->f);
00083     
00084      /* have to fudge to frame here, so not fully to sample */
00085      distance = sample_offset/2;
00086      if(whence == SEEK_SET)
00087      offset = distance;
00088      else if(whence == SEEK_CUR || whence == SEEK_FORCECUR)
00089      offset = distance + cur;
00090      else if(whence == SEEK_END)
00091      offset = max - distance;
00092      if (whence != SEEK_FORCECUR) {
00093      offset = (offset > max)?max:offset;
00094      offset = (offset < min)?min:offset;
00095      }
00096      return fseeko(fs->f, offset, SEEK_SET);
00097 }
00098 
00099 static int vox_trunc(struct ast_filestream *fs)
00100 {
00101      return ftruncate(fileno(fs->f), ftello(fs->f));
00102 }
00103 
00104 static off_t vox_tell(struct ast_filestream *fs)
00105 {
00106      off_t offset;
00107      offset = ftello(fs->f) << 1;
00108      return offset; 
00109 }
00110 
00111 static const struct ast_format vox_f = {
00112    .name = "vox",
00113    .exts = "vox",
00114    .format = AST_FORMAT_ADPCM,
00115    .write = vox_write,
00116    .seek = vox_seek,
00117    .trunc = vox_trunc,
00118    .tell = vox_tell,
00119    .read = vox_read,
00120    .buf_size = BUF_SIZE + AST_FRIENDLY_OFFSET,
00121 };
00122 
00123 static int load_module(void)
00124 {
00125    if (ast_format_register(&vox_f))
00126       return AST_MODULE_LOAD_FAILURE;
00127    return AST_MODULE_LOAD_SUCCESS;
00128 }
00129 
00130 static int unload_module(void)
00131 {
00132    return ast_format_unregister(vox_f.name);
00133 }  
00134 
00135 AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_LOAD_ORDER, "Dialogic VOX (ADPCM) File Format",
00136    .load = load_module,
00137    .unload = unload_module,
00138    .load_pri = 10,
00139 );