Wed Oct 28 11:51:02 2009

Asterisk developer's documentation


codec_lpc10.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  * The lpc10 code is from a library used by nautilus, modified to be a bit
00009  * nicer to the compiler.
00010  * See http://www.arl.wustl.edu/~jaf/ 
00011  *
00012  * See http://www.asterisk.org for more information about
00013  * the Asterisk project. Please do not directly contact
00014  * any of the maintainers of this project for assistance;
00015  * the project provides a web site, mailing lists and IRC
00016  * channels for your use.
00017  *
00018  * This program is free software, distributed under the terms of
00019  * the GNU General Public License Version 2. See the LICENSE file
00020  * at the top of the source tree.
00021  */
00022 
00023 /*! \file
00024  *
00025  * \brief Translate between signed linear and LPC10 (Linear Predictor Code)
00026  *
00027  * \ingroup codecs
00028  */
00029 
00030 #include "asterisk.h"
00031 
00032 ASTERISK_FILE_VERSION(__FILE__, "$Revision: 125386 $")
00033 
00034 #include "asterisk/translate.h"
00035 #include "asterisk/config.h"
00036 #include "asterisk/module.h"
00037 #include "asterisk/utils.h"
00038 
00039 #include "lpc10/lpc10.h"
00040 
00041 /* Sample frame data */
00042 #include "slin_lpc10_ex.h"
00043 #include "lpc10_slin_ex.h"
00044 
00045 /* We use a very strange format here...  I have no idea why...  The frames are 180
00046    samples long, which isn't even an even number of milliseconds...  Not only that
00047    but we hvae to waste two bits of each frame to keep them ending on a byte boundary
00048    because the frames are 54 bits long */
00049 
00050 #define LPC10_BYTES_IN_COMPRESSED_FRAME (LPC10_BITS_IN_COMPRESSED_FRAME + 7)/8
00051 
00052 #define  BUFFER_SAMPLES 8000
00053 
00054 struct lpc10_coder_pvt {
00055    union {
00056       struct lpc10_encoder_state *enc;
00057       struct lpc10_decoder_state *dec;
00058    } lpc10;
00059    /* Enough to store a full second */
00060    short buf[BUFFER_SAMPLES];
00061    int longer;
00062 };
00063 
00064 static int lpc10_enc_new(struct ast_trans_pvt *pvt)
00065 {
00066    struct lpc10_coder_pvt *tmp = pvt->pvt;
00067 
00068    return (tmp->lpc10.enc = create_lpc10_encoder_state()) ? 0 : -1;
00069 }
00070 
00071 static int lpc10_dec_new(struct ast_trans_pvt *pvt)
00072 {
00073    struct lpc10_coder_pvt *tmp = pvt->pvt;
00074 
00075    return (tmp->lpc10.dec = create_lpc10_decoder_state()) ? 0 : -1;
00076 }
00077 
00078 static struct ast_frame *lintolpc10_sample(void)
00079 {
00080    static struct ast_frame f;
00081    f.frametype = AST_FRAME_VOICE;
00082    f.subclass = AST_FORMAT_SLINEAR;
00083    f.datalen = sizeof(slin_lpc10_ex);
00084    /* Assume 8000 Hz */
00085    f.samples = LPC10_SAMPLES_PER_FRAME;
00086    f.mallocd = 0;
00087    f.offset = 0;
00088    f.src = __PRETTY_FUNCTION__;
00089    f.data.ptr = slin_lpc10_ex;
00090    return &f;
00091 }
00092 
00093 static struct ast_frame *lpc10tolin_sample(void)
00094 {
00095    static struct ast_frame f;
00096    f.frametype = AST_FRAME_VOICE;
00097    f.subclass = AST_FORMAT_LPC10;
00098    f.datalen = sizeof(lpc10_slin_ex);
00099    /* All frames are 22 ms long (maybe a little more -- why did he choose
00100       LPC10_SAMPLES_PER_FRAME sample frames anyway?? */
00101    f.samples = LPC10_SAMPLES_PER_FRAME;
00102    f.mallocd = 0;
00103    f.offset = 0;
00104    f.src = __PRETTY_FUNCTION__;
00105    f.data.ptr = lpc10_slin_ex;
00106    return &f;
00107 }
00108 
00109 static void extract_bits(INT32 *bits, unsigned char *c)
00110 {
00111    int x;
00112    for (x=0;x<LPC10_BITS_IN_COMPRESSED_FRAME;x++) {
00113       if (*c & (0x80 >> (x & 7)))
00114          bits[x] = 1;
00115       else
00116          bits[x] = 0;
00117       if ((x & 7) == 7)
00118          c++;
00119    }
00120 }
00121 
00122 /* XXX note lpc10_encode() produces one bit per word in bits[] */
00123 static void build_bits(unsigned char *c, INT32 *bits)
00124 {
00125    unsigned char mask=0x80;
00126    int x;
00127    *c = 0;
00128    for (x=0;x<LPC10_BITS_IN_COMPRESSED_FRAME;x++) {
00129       if (bits[x])
00130          *c |= mask;
00131       mask = mask >> 1;
00132       if ((x % 8)==7) {
00133          c++;
00134          *c = 0;
00135          mask = 0x80;
00136       }
00137    }
00138 }
00139 
00140 static int lpc10tolin_framein(struct ast_trans_pvt *pvt, struct ast_frame *f)
00141 {
00142    struct lpc10_coder_pvt *tmp = pvt->pvt;
00143    int16_t *dst = pvt->outbuf.i16;
00144    int len = 0;
00145 
00146    while (len + LPC10_BYTES_IN_COMPRESSED_FRAME <= f->datalen) {
00147       int x;
00148       float tmpbuf[LPC10_SAMPLES_PER_FRAME];
00149       INT32 bits[LPC10_BITS_IN_COMPRESSED_FRAME]; /* XXX see note */
00150       if (pvt->samples + LPC10_SAMPLES_PER_FRAME > BUFFER_SAMPLES) {
00151          ast_log(LOG_WARNING, "Out of buffer space\n");
00152          return -1;
00153       }
00154       extract_bits(bits, f->data.ptr + len);
00155       if (lpc10_decode(bits, tmpbuf, tmp->lpc10.dec)) {
00156          ast_log(LOG_WARNING, "Invalid lpc10 data\n");
00157          return -1;
00158       }
00159       for (x=0;x<LPC10_SAMPLES_PER_FRAME;x++) {
00160          /* Convert to a short between -1.0 and 1.0 */
00161          dst[pvt->samples + x] = (int16_t)(32768.0 * tmpbuf[x]);
00162       }
00163 
00164       pvt->samples += LPC10_SAMPLES_PER_FRAME;
00165       pvt->datalen += 2*LPC10_SAMPLES_PER_FRAME;
00166       len += LPC10_BYTES_IN_COMPRESSED_FRAME;
00167    }
00168    if (len != f->datalen) 
00169       printf("Decoded %d, expected %d\n", len, f->datalen);
00170    return 0;
00171 }
00172 
00173 static int lintolpc10_framein(struct ast_trans_pvt *pvt, struct ast_frame *f)
00174 {
00175    struct lpc10_coder_pvt *tmp = pvt->pvt;
00176 
00177    /* Just add the frames to our stream */
00178    if (pvt->samples + f->samples > BUFFER_SAMPLES) {
00179       ast_log(LOG_WARNING, "Out of buffer space\n");
00180       return -1;
00181    }
00182    memcpy(tmp->buf + pvt->samples, f->data.ptr, f->datalen);
00183    pvt->samples += f->samples;
00184    return 0;
00185 }
00186 
00187 static struct ast_frame *lintolpc10_frameout(struct ast_trans_pvt *pvt)
00188 {
00189    struct lpc10_coder_pvt *tmp = pvt->pvt;
00190    int x;
00191    int datalen = 0;  /* output frame */
00192    int samples = 0;  /* output samples */
00193    float tmpbuf[LPC10_SAMPLES_PER_FRAME];
00194    INT32 bits[LPC10_BITS_IN_COMPRESSED_FRAME];  /* XXX what ??? */
00195    /* We can't work on anything less than a frame in size */
00196    if (pvt->samples < LPC10_SAMPLES_PER_FRAME)
00197       return NULL;
00198    while (pvt->samples >=  LPC10_SAMPLES_PER_FRAME) {
00199       /* Encode a frame of data */
00200       for (x=0;x<LPC10_SAMPLES_PER_FRAME;x++)
00201          tmpbuf[x] = (float)tmp->buf[x + samples] / 32768.0;
00202       lpc10_encode(tmpbuf, bits, tmp->lpc10.enc);
00203       build_bits(pvt->outbuf.uc + datalen, bits);
00204       datalen += LPC10_BYTES_IN_COMPRESSED_FRAME;
00205       samples += LPC10_SAMPLES_PER_FRAME;
00206       pvt->samples -= LPC10_SAMPLES_PER_FRAME;
00207       /* Use one of the two left over bits to record if this is a 22 or 23 ms frame...
00208          important for IAX use */
00209       tmp->longer = 1 - tmp->longer;
00210    }
00211    /* Move the data at the end of the buffer to the front */
00212    if (pvt->samples)
00213       memmove(tmp->buf, tmp->buf + samples, pvt->samples * 2);
00214    return ast_trans_frameout(pvt, datalen, samples);
00215 }
00216 
00217 
00218 static void lpc10_destroy(struct ast_trans_pvt *arg)
00219 {
00220    struct lpc10_coder_pvt *pvt = arg->pvt;
00221    /* Enc and DEC are both just allocated, so they can be freed */
00222    ast_free(pvt->lpc10.enc);
00223 }
00224 
00225 static struct ast_translator lpc10tolin = {
00226    .name = "lpc10tolin", 
00227    .srcfmt = AST_FORMAT_LPC10,
00228    .dstfmt = AST_FORMAT_SLINEAR,
00229    .newpvt = lpc10_dec_new,
00230    .framein = lpc10tolin_framein,
00231    .destroy = lpc10_destroy,
00232    .sample = lpc10tolin_sample,
00233    .desc_size = sizeof(struct lpc10_coder_pvt),
00234    .buffer_samples = BUFFER_SAMPLES,
00235    .plc_samples = LPC10_SAMPLES_PER_FRAME,
00236    .buf_size = BUFFER_SAMPLES * 2,
00237 };
00238 
00239 static struct ast_translator lintolpc10 = {
00240    .name = "lintolpc10", 
00241    .srcfmt = AST_FORMAT_SLINEAR,
00242    .dstfmt = AST_FORMAT_LPC10,
00243    .newpvt = lpc10_enc_new,
00244    .framein = lintolpc10_framein,
00245    .frameout = lintolpc10_frameout,
00246    .destroy = lpc10_destroy,
00247    .sample = lintolpc10_sample,
00248    .desc_size = sizeof(struct lpc10_coder_pvt),
00249    .buffer_samples = BUFFER_SAMPLES,
00250    .buf_size = LPC10_BYTES_IN_COMPRESSED_FRAME * (1 + BUFFER_SAMPLES / LPC10_SAMPLES_PER_FRAME),
00251 };
00252 
00253 static int parse_config(int reload)
00254 {
00255    struct ast_variable *var;
00256    struct ast_flags config_flags = { reload ? CONFIG_FLAG_FILEUNCHANGED : 0 };
00257    struct ast_config *cfg = ast_config_load("codecs.conf", config_flags);
00258    if (cfg == NULL)
00259       return 0;
00260    if (cfg == CONFIG_STATUS_FILEUNCHANGED)
00261       return 0;
00262    for (var = ast_variable_browse(cfg, "plc"); var; var = var->next) {
00263       if (!strcasecmp(var->name, "genericplc")) {
00264          lpc10tolin.useplc = ast_true(var->value) ? 1 : 0;
00265          ast_verb(3, "codec_lpc10: %susing generic PLC\n",
00266                lpc10tolin.useplc ? "" : "not ");
00267       }
00268    }
00269    ast_config_destroy(cfg);
00270    return 0;
00271 }
00272 
00273 static int reload(void)
00274 {
00275    if (parse_config(1))
00276       return AST_MODULE_LOAD_DECLINE;
00277    return AST_MODULE_LOAD_SUCCESS;
00278 }
00279 
00280 
00281 static int unload_module(void)
00282 {
00283    int res;
00284 
00285    res = ast_unregister_translator(&lintolpc10);
00286    res |= ast_unregister_translator(&lpc10tolin);
00287 
00288    return res;
00289 }
00290 
00291 static int load_module(void)
00292 {
00293    int res;
00294 
00295    if (parse_config(0))
00296       return AST_MODULE_LOAD_DECLINE;
00297    res = ast_register_translator(&lpc10tolin);
00298    if (!res) 
00299       res = ast_register_translator(&lintolpc10);
00300    else
00301       ast_unregister_translator(&lpc10tolin);
00302    if (res)
00303       return AST_MODULE_LOAD_FAILURE;
00304    return AST_MODULE_LOAD_SUCCESS;
00305 }
00306 
00307 AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_DEFAULT, "LPC10 2.4kbps Coder/Decoder",
00308       .load = load_module,
00309       .unload = unload_module,
00310       .reload = reload,
00311           );

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