Sat Mar 10 01:54:17 2012

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: alaw, al, alw, pcm, ulaw, ul, mu, ulw, g722, au
00023  * 
00024  * \ingroup formats
00025  */
00026 
00027 /*** MODULEINFO
00028    <support_level>core</support_level>
00029  ***/
00030  
00031 #include "asterisk.h"
00032 
00033 ASTERISK_FILE_VERSION(__FILE__, "$Revision: 328209 $")
00034 
00035 #include "asterisk/mod_format.h"
00036 #include "asterisk/module.h"
00037 #include "asterisk/endian.h"
00038 #include "asterisk/ulaw.h"
00039 #include "asterisk/alaw.h"
00040 
00041 #define BUF_SIZE 160    /* 160 bytes, and same number of samples */
00042 
00043 static char ulaw_silence[BUF_SIZE];
00044 static char alaw_silence[BUF_SIZE];
00045 
00046 /* #define REALTIME_WRITE */  /* XXX does it work at all ? */
00047 
00048 #ifdef REALTIME_WRITE
00049 struct pcm_desc {
00050    unsigned long start_time;
00051 };
00052 
00053 /* Returns time in msec since system boot. */
00054 static unsigned long get_time(void)
00055 {
00056    struct tms buf;
00057    clock_t cur;
00058 
00059    cur = times( &buf );
00060    if( cur < 0 ) {
00061       ast_log( LOG_WARNING, "Cannot get current time\n" );
00062       return 0;
00063    }
00064    return cur * 1000 / sysconf( _SC_CLK_TCK );
00065 }
00066 
00067 static int pcma_open(struct ast_filestream *s)
00068 {
00069    if (s->fmt->format == AST_FORMAT_ALAW)
00070       pd->starttime = get_time();
00071    return 0;
00072 }
00073 
00074 static int pcma_rewrite(struct ast_filestream *s, const char *comment)
00075 {
00076    return pcma_open(s);
00077 }
00078 #endif
00079 
00080 static struct ast_frame *pcm_read(struct ast_filestream *s, int *whennext)
00081 {
00082    int res;
00083    
00084    /* Send a frame from the file to the appropriate channel */
00085 
00086    s->fr.frametype = AST_FRAME_VOICE;
00087    s->fr.subclass.codec = s->fmt->format;
00088    s->fr.mallocd = 0;
00089    AST_FRAME_SET_BUFFER(&s->fr, s->buf, AST_FRIENDLY_OFFSET, BUF_SIZE);
00090    if ((res = fread(s->fr.data.ptr, 1, s->fr.datalen, s->f)) < 1) {
00091       if (res)
00092          ast_log(LOG_WARNING, "Short read (%d) (%s)!\n", res, strerror(errno));
00093       return NULL;
00094    }
00095    s->fr.datalen = res;
00096    if (s->fmt->format == AST_FORMAT_G722)
00097       *whennext = s->fr.samples = res * 2;
00098    else
00099       *whennext = s->fr.samples = res;
00100    return &s->fr;
00101 }
00102 
00103 static int pcm_seek(struct ast_filestream *fs, off_t sample_offset, int whence)
00104 {
00105    off_t cur, max, offset = 0;
00106    int ret = -1;  /* assume error */
00107 
00108    cur = ftello(fs->f);
00109    fseeko(fs->f, 0, SEEK_END);
00110    max = ftello(fs->f);
00111 
00112    switch (whence) {
00113    case SEEK_SET:
00114       offset = sample_offset;
00115       break;
00116    case SEEK_END:
00117       offset = max - sample_offset;
00118       break;
00119    case SEEK_CUR:
00120    case SEEK_FORCECUR:
00121       offset = cur + sample_offset;
00122       break;
00123    default:
00124       ast_log(LOG_WARNING, "invalid whence %d, assuming SEEK_SET\n", whence);
00125       offset = sample_offset;
00126    }
00127    if (offset < 0) {
00128       ast_log(LOG_WARNING, "negative offset %ld, resetting to 0\n", (long) offset);
00129       offset = 0;
00130    }
00131    if (whence == SEEK_FORCECUR && offset > max) { /* extend the file */
00132       size_t left = offset - max;
00133       const char *src = (fs->fmt->format == AST_FORMAT_ALAW) ? alaw_silence : ulaw_silence;
00134 
00135       while (left) {
00136          size_t written = fwrite(src, 1, (left > BUF_SIZE) ? BUF_SIZE : left, fs->f);
00137          if (written == -1)
00138             break;   /* error */
00139          left -= written;
00140       }
00141       ret = 0; /* successful */
00142    } else {
00143       if (offset > max) {
00144          ast_log(LOG_WARNING, "offset too large %ld, truncating to %ld\n", (long) offset, (long) max);
00145          offset = max;
00146       }
00147       ret = fseeko(fs->f, offset, SEEK_SET);
00148    }
00149    return ret;
00150 }
00151 
00152 static int pcm_trunc(struct ast_filestream *fs)
00153 {
00154    return ftruncate(fileno(fs->f), ftello(fs->f));
00155 }
00156 
00157 static off_t pcm_tell(struct ast_filestream *fs)
00158 {
00159    return ftello(fs->f);
00160 }
00161 
00162 static int pcm_write(struct ast_filestream *fs, struct ast_frame *f)
00163 {
00164    int res;
00165 
00166    if (f->frametype != AST_FRAME_VOICE) {
00167       ast_log(LOG_WARNING, "Asked to write non-voice frame!\n");
00168       return -1;
00169    }
00170    if (f->subclass.codec != fs->fmt->format) {
00171       ast_log(LOG_WARNING, "Asked to write incompatible format frame (%s)!\n", ast_getformatname(f->subclass.codec));
00172       return -1;
00173    }
00174 
00175 #ifdef REALTIME_WRITE
00176    if (s->fmt->format == AST_FORMAT_ALAW) {
00177       struct pcm_desc *pd = (struct pcm_desc *)fs->_private;
00178       struct stat stat_buf;
00179       unsigned long cur_time = get_time();
00180       unsigned long fpos = ( cur_time - pd->start_time ) * 8;  /* 8 bytes per msec */
00181       /* Check if we have written to this position yet. If we have, then increment pos by one frame
00182       *  for some degree of protection against receiving packets in the same clock tick.
00183       */
00184       
00185       fstat(fileno(fs->f), &stat_buf );
00186       if (stat_buf.st_size > fpos )
00187          fpos += f->datalen;  /* Incrementing with the size of this current frame */
00188 
00189       if (stat_buf.st_size < fpos) {
00190          /* fill the gap with 0x55 rather than 0. */
00191          char buf[1024];
00192          unsigned long cur, to_write;
00193 
00194          cur = stat_buf.st_size;
00195          if (fseek(fs->f, cur, SEEK_SET) < 0) {
00196             ast_log( LOG_WARNING, "Cannot seek in file: %s\n", strerror(errno) );
00197             return -1;
00198          }
00199          memset(buf, 0x55, 512);
00200          while (cur < fpos) {
00201             to_write = fpos - cur;
00202             if (to_write > sizeof(buf))
00203                to_write = sizeof(buf);
00204             fwrite(buf, 1, to_write, fs->f);
00205             cur += to_write;
00206          }
00207       }
00208 
00209       if (fseek(s->f, fpos, SEEK_SET) < 0) {
00210          ast_log( LOG_WARNING, "Cannot seek in file: %s\n", strerror(errno) );
00211          return -1;
00212       }
00213    }
00214 #endif   /* REALTIME_WRITE */
00215    
00216    if ((res = fwrite(f->data.ptr, 1, f->datalen, fs->f)) != f->datalen) {
00217       ast_log(LOG_WARNING, "Bad write (%d/%d): %s\n", res, f->datalen, strerror(errno));
00218       return -1;
00219    }
00220    return 0;
00221 }
00222 
00223 /* SUN .au support routines */
00224 
00225 #define AU_HEADER_SIZE     24
00226 #define AU_HEADER(var)     uint32_t var[6]
00227 
00228 #define AU_HDR_MAGIC_OFF   0
00229 #define AU_HDR_HDR_SIZE_OFF   1
00230 #define AU_HDR_DATA_SIZE_OFF  2
00231 #define AU_HDR_ENCODING_OFF   3
00232 #define AU_HDR_SAMPLE_RATE_OFF   4
00233 #define AU_HDR_CHANNELS_OFF   5
00234 
00235 #define AU_ENC_8BIT_ULAW   1
00236 
00237 #define AU_MAGIC 0x2e736e64
00238 #if __BYTE_ORDER == __BIG_ENDIAN
00239 #define htoll(b) (b)
00240 #define htols(b) (b)
00241 #define ltohl(b) (b)
00242 #define ltohs(b) (b)
00243 #else
00244 #if __BYTE_ORDER == __LITTLE_ENDIAN
00245 #define htoll(b)  \
00246           (((((b)      ) & 0xFF) << 24) | \
00247           ((((b) >>  8) & 0xFF) << 16) | \
00248          ((((b) >> 16) & 0xFF) <<  8) | \
00249          ((((b) >> 24) & 0xFF)      ))
00250 #define htols(b) \
00251           (((((b)      ) & 0xFF) << 8) | \
00252          ((((b) >> 8) & 0xFF)      ))
00253 #define ltohl(b) htoll(b)
00254 #define ltohs(b) htols(b)
00255 #else
00256 #error "Endianess not defined"
00257 #endif
00258 #endif
00259 
00260 static int check_header(FILE *f)
00261 {
00262    AU_HEADER(header);
00263    uint32_t magic;
00264    uint32_t hdr_size;
00265    uint32_t data_size;
00266    uint32_t encoding;
00267    uint32_t sample_rate;
00268    uint32_t channels;
00269 
00270    if (fread(header, 1, AU_HEADER_SIZE, f) != AU_HEADER_SIZE) {
00271       ast_log(LOG_WARNING, "Read failed (header)\n");
00272       return -1;
00273    }
00274    magic = ltohl(header[AU_HDR_MAGIC_OFF]);
00275    if (magic != (uint32_t) AU_MAGIC) {
00276       ast_log(LOG_WARNING, "Bad magic: 0x%x\n", magic);
00277    }
00278    hdr_size = ltohl(header[AU_HDR_HDR_SIZE_OFF]);
00279    if (hdr_size < AU_HEADER_SIZE) {
00280       hdr_size = AU_HEADER_SIZE;
00281    }
00282 /* data_size = ltohl(header[AU_HDR_DATA_SIZE_OFF]); */
00283    encoding = ltohl(header[AU_HDR_ENCODING_OFF]);
00284    if (encoding != AU_ENC_8BIT_ULAW) {
00285       ast_log(LOG_WARNING, "Unexpected format: %d. Only 8bit ULAW allowed (%d)\n", encoding, AU_ENC_8BIT_ULAW);
00286       return -1;
00287    }
00288    sample_rate = ltohl(header[AU_HDR_SAMPLE_RATE_OFF]);
00289    if (sample_rate != DEFAULT_SAMPLE_RATE) {
00290       ast_log(LOG_WARNING, "Sample rate can only be 8000 not %d\n", sample_rate);
00291       return -1;
00292    }
00293    channels = ltohl(header[AU_HDR_CHANNELS_OFF]);
00294    if (channels != 1) {
00295       ast_log(LOG_WARNING, "Not in mono: channels=%d\n", channels);
00296       return -1;
00297    }
00298    /* Skip to data */
00299    fseek(f, 0, SEEK_END);
00300    data_size = ftell(f) - hdr_size;
00301    if (fseek(f, hdr_size, SEEK_SET) == -1 ) {
00302       ast_log(LOG_WARNING, "Failed to skip to data: %d\n", hdr_size);
00303       return -1;
00304    }
00305    return data_size;
00306 }
00307 
00308 static int update_header(FILE *f)
00309 {
00310    off_t cur, end;
00311    uint32_t datalen;
00312    int bytes;
00313 
00314    cur = ftell(f);
00315    fseek(f, 0, SEEK_END);
00316    end = ftell(f);
00317    /* data starts 24 bytes in */
00318    bytes = end - AU_HEADER_SIZE;
00319    datalen = htoll(bytes);
00320 
00321    if (cur < 0) {
00322       ast_log(LOG_WARNING, "Unable to find our position\n");
00323       return -1;
00324    }
00325    if (fseek(f, AU_HDR_DATA_SIZE_OFF * sizeof(uint32_t), SEEK_SET)) {
00326       ast_log(LOG_WARNING, "Unable to set our position\n");
00327       return -1;
00328    }
00329    if (fwrite(&datalen, 1, sizeof(datalen), f) != sizeof(datalen)) {
00330       ast_log(LOG_WARNING, "Unable to set write file size\n");
00331       return -1;
00332    }
00333    if (fseek(f, cur, SEEK_SET)) {
00334       ast_log(LOG_WARNING, "Unable to return to position\n");
00335       return -1;
00336    }
00337    return 0;
00338 }
00339 
00340 static int write_header(FILE *f)
00341 {
00342    AU_HEADER(header);
00343 
00344    header[AU_HDR_MAGIC_OFF] = htoll((uint32_t) AU_MAGIC);
00345    header[AU_HDR_HDR_SIZE_OFF] = htoll(AU_HEADER_SIZE);
00346    header[AU_HDR_DATA_SIZE_OFF] = 0;
00347    header[AU_HDR_ENCODING_OFF] = htoll(AU_ENC_8BIT_ULAW);
00348    header[AU_HDR_SAMPLE_RATE_OFF] = htoll(DEFAULT_SAMPLE_RATE);
00349    header[AU_HDR_CHANNELS_OFF] = htoll(1);
00350 
00351    /* Write an au header, ignoring sizes which will be filled in later */
00352    fseek(f, 0, SEEK_SET);
00353    if (fwrite(header, 1, AU_HEADER_SIZE, f) != AU_HEADER_SIZE) {
00354       ast_log(LOG_WARNING, "Unable to write header\n");
00355       return -1;
00356    }
00357    return 0;
00358 }
00359 
00360 static int au_open(struct ast_filestream *s)
00361 {
00362    if (check_header(s->f) < 0)
00363       return -1;
00364    return 0;
00365 }
00366 
00367 static int au_rewrite(struct ast_filestream *s, const char *comment)
00368 {
00369    if (write_header(s->f))
00370       return -1;
00371    return 0;
00372 }
00373 
00374 /* XXX check this, probably incorrect */
00375 static int au_seek(struct ast_filestream *fs, off_t sample_offset, int whence)
00376 {
00377    off_t min, max, cur;
00378    long offset = 0, bytes;
00379 
00380    if (fs->fmt->format == AST_FORMAT_G722)
00381       bytes = sample_offset / 2;
00382    else
00383       bytes = sample_offset;
00384 
00385    min = AU_HEADER_SIZE;
00386    cur = ftello(fs->f);
00387    fseek(fs->f, 0, SEEK_END);
00388    max = ftello(fs->f);
00389 
00390    if (whence == SEEK_SET)
00391       offset = bytes + min;
00392    else if (whence == SEEK_CUR || whence == SEEK_FORCECUR)
00393       offset = bytes + cur;
00394    else if (whence == SEEK_END)
00395       offset = max - bytes;
00396 
00397    if (whence != SEEK_FORCECUR) {
00398       offset = (offset > max) ? max : offset;
00399    }
00400 
00401    /* always protect the header space. */
00402    offset = (offset < min) ? min : offset;
00403 
00404    return fseeko(fs->f, offset, SEEK_SET);
00405 }
00406 
00407 static int au_trunc(struct ast_filestream *fs)
00408 {
00409    if (ftruncate(fileno(fs->f), ftell(fs->f)))
00410       return -1;
00411    return update_header(fs->f);
00412 }
00413 
00414 static off_t au_tell(struct ast_filestream *fs)
00415 {
00416    off_t offset = ftello(fs->f);
00417    return offset - AU_HEADER_SIZE;
00418 }
00419 
00420 static const struct ast_format alaw_f = {
00421    .name = "alaw",
00422    .exts = "alaw|al|alw",
00423    .format = AST_FORMAT_ALAW,
00424    .write = pcm_write,
00425    .seek = pcm_seek,
00426    .trunc = pcm_trunc,
00427    .tell = pcm_tell,
00428    .read = pcm_read,
00429    .buf_size = BUF_SIZE + AST_FRIENDLY_OFFSET,
00430 #ifdef REALTIME_WRITE
00431    .open = pcma_open,
00432    .rewrite = pcma_rewrite,
00433    .desc_size = sizeof(struct pcm_desc),
00434 #endif
00435 };
00436 
00437 static const struct ast_format pcm_f = {
00438    .name = "pcm",
00439    .exts = "pcm|ulaw|ul|mu|ulw",
00440    .format = AST_FORMAT_ULAW,
00441    .write = pcm_write,
00442    .seek = pcm_seek,
00443    .trunc = pcm_trunc,
00444    .tell = pcm_tell,
00445    .read = pcm_read,
00446    .buf_size = BUF_SIZE + AST_FRIENDLY_OFFSET,
00447 };
00448 
00449 static const struct ast_format g722_f = {
00450    .name = "g722",
00451    .exts = "g722",
00452    .format = AST_FORMAT_G722,
00453    .write = pcm_write,
00454    .seek = pcm_seek,
00455    .trunc = pcm_trunc,
00456    .tell = pcm_tell,
00457    .read = pcm_read,
00458    .buf_size = (BUF_SIZE * 2) + AST_FRIENDLY_OFFSET,
00459 };
00460 
00461 static const struct ast_format au_f = {
00462    .name = "au",
00463    .exts = "au",
00464    .format = AST_FORMAT_ULAW,
00465    .open = au_open,
00466    .rewrite = au_rewrite,
00467    .write = pcm_write,
00468    .seek = au_seek,
00469    .trunc = au_trunc,
00470    .tell = au_tell,
00471    .read = pcm_read,
00472    .buf_size = BUF_SIZE + AST_FRIENDLY_OFFSET,  /* this many shorts */
00473 };
00474 
00475 static int load_module(void)
00476 {
00477    int i;
00478 
00479    /* XXX better init ? */
00480    for (i = 0; i < ARRAY_LEN(ulaw_silence); i++)
00481       ulaw_silence[i] = AST_LIN2MU(0);
00482    for (i = 0; i < ARRAY_LEN(alaw_silence); i++)
00483       alaw_silence[i] = AST_LIN2A(0);
00484 
00485    if ( ast_format_register(&pcm_f)
00486       || ast_format_register(&alaw_f)
00487       || ast_format_register(&au_f)
00488       || ast_format_register(&g722_f) )
00489       return AST_MODULE_LOAD_FAILURE;
00490    return AST_MODULE_LOAD_SUCCESS;
00491 }
00492 
00493 static int unload_module(void)
00494 {
00495    return ast_format_unregister(pcm_f.name)
00496       || ast_format_unregister(alaw_f.name)
00497       || ast_format_unregister(au_f.name)
00498       || ast_format_unregister(g722_f.name);
00499 }
00500 
00501 AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_LOAD_ORDER, "Raw/Sun uLaw/ALaw 8KHz (PCM,PCMA,AU), G.722 16Khz",
00502    .load = load_module,
00503    .unload = unload_module,
00504    .load_pri = AST_MODPRI_APP_DEPEND
00505 );

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