channels/iax2/format_compatibility.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2014, Digium, Inc.
 *
 * Joshua Colp <jcolp@digium.com>
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */
 
/*! \file
 *
 * \brief Media Format Bitfield Compatibility API
 *
 * \author Joshua Colp <jcolp@digium.com>
 */
 
/*** MODULEINFO
    <support_level>core</support_level>
 ***/
 
#include "asterisk.h"
 
#include "asterisk/logger.h"
#include "asterisk/astobj2.h"
#include "asterisk/codec.h"
#include "asterisk/format.h"
#include "asterisk/format_compatibility.h"
#include "asterisk/format_cache.h"
#include "asterisk/format_cap.h"
#include "asterisk/utils.h"
 
#include "include/format_compatibility.h"
 
uint64_t iax2_format_compatibility_cap2bitfield(const struct ast_format_cap *cap)
{
    uint64_t bitfield = 0;
    int x;
 
    for (x = 0; x < ast_format_cap_count(cap); x++) {
        struct ast_format *format = ast_format_cap_get_format(cap, x);
 
        bitfield |= ast_format_compatibility_format2bitfield(format);
 
        ao2_ref(format, -1);
    }
 
    return bitfield;
}
 
int iax2_format_compatibility_bitfield2cap(uint64_t bitfield, struct ast_format_cap *cap)
{
    int bit;
 
    for (bit = 0; bit < 64; ++bit) {
        uint64_t mask = (1ULL << bit);
 
        if (mask & bitfield) {
            struct ast_format *format;
 
            format = ast_format_compatibility_bitfield2format(mask);
            if (format && ast_format_cap_append(cap, format, 0)) {
                return -1;
            }
        }
    }
 
    return 0;
}
 
uint64_t iax2_format_compatibility_best(uint64_t formats)
{
    /*
     * This just our opinion, expressed in code.  We are
     * asked to choose the best codec to use, given no
     * information.
     */
    static const uint64_t best[] = {
        /*! Okay, ulaw is used by all telephony equipment, so start with it */
        AST_FORMAT_ULAW,
        /*! Unless of course, you're a silly European, so then prefer ALAW */
        AST_FORMAT_ALAW,
        AST_FORMAT_G719,
        AST_FORMAT_SIREN14,
        AST_FORMAT_SIREN7,
        /*! G.722 is better then all below, but not as common as the above... so give ulaw and alaw priority */
        AST_FORMAT_G722,
        /*! Okay, well, signed linear is easy to translate into other stuff */
        AST_FORMAT_SLIN16,
        AST_FORMAT_SLIN,
        /*! G.726 is standard ADPCM, in RFC3551 packing order */
        AST_FORMAT_G726,
        /*! G.726 is standard ADPCM, in AAL2 packing order */
        AST_FORMAT_G726_AAL2,
        /*! ADPCM has great sound quality and is still pretty easy to translate */
        AST_FORMAT_ADPCM,
        /*! Okay, we're down to vocoders now, so pick GSM because it's small and easier to
            translate and sounds pretty good */
        AST_FORMAT_GSM,
        /*! iLBC is not too bad */
        AST_FORMAT_ILBC,
        /*! Speex is free, but computationally more expensive than GSM */
        AST_FORMAT_SPEEX16,
        AST_FORMAT_SPEEX,
        /*! Opus */
        AST_FORMAT_OPUS,
        /*! Ick, LPC10 sounds terrible, but at least we have code for it, if you're tacky enough
            to use it */
        AST_FORMAT_LPC10,
        /*! G.729a is faster than 723 and slightly less expensive */
        AST_FORMAT_G729,
        /*! Down to G.723.1 which is proprietary but at least designed for voice */
        AST_FORMAT_G723,
    };
    int idx;
 
    /* Find the first preferred codec in the format given */
    for (idx = 0; idx < ARRAY_LEN(best); ++idx) {
        if (formats & best[idx]) {
            return best[idx];
        }
    }
 
    return 0;
}