channels/iax2/include/format_compatibility.h File Reference

Media Format Bitfield Compatibility API. More...

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Functions
uint64_t	iax2_format_compatibility_best (uint64_t formats)
	Pick the best format from the given bitfield formats. More...
int	iax2_format_compatibility_bitfield2cap (uint64_t bitfield, struct ast_format_cap *cap)
	Convert a bitfield to a format capabilities structure. More...
uint64_t	iax2_format_compatibility_cap2bitfield (const struct ast_format_cap *cap)
	Convert a format capabilities structure to a bitfield. More...

Detailed Description

Media Format Bitfield Compatibility API.

Author

Joshua Colp jcolp.nosp@m.@dig.nosp@m.ium.c.nosp@m.om

Definition in file channels/iax2/include/format_compatibility.h.

Function Documentation

iax2_format_compatibility_best()

uint64_t iax2_format_compatibility_best

(

uint64_t

formats

)

Pick the best format from the given bitfield formats.

Parameters

formats

The bitfield for the media formats

Return values

non-zero	Best format out of the given formats.
zero	No formats present or no formats considered best.

Okay, ulaw is used by all telephony equipment, so start with it

Unless of course, you're a silly European, so then prefer ALAW

G.722 is better then all below, but not as common as the above... so give ulaw and alaw priority

Okay, well, signed linear is easy to translate into other stuff

G.726 is standard ADPCM, in RFC3551 packing order

G.726 is standard ADPCM, in AAL2 packing order

ADPCM has great sound quality and is still pretty easy to translate

Okay, we're down to vocoders now, so pick GSM because it's small and easier to translate and sounds pretty good

iLBC is not too bad

Speex is free, but computationally more expensive than GSM

Opus

Ick, LPC10 sounds terrible, but at least we have code for it, if you're tacky enough to use it

G.729a is faster than 723 and slightly less expensive

Down to G.723.1 which is proprietary but at least designed for voice

Definition at line 79 of file channels/iax2/format_compatibility.c.

{
    /*
     * 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;
}

References ARRAY_LEN, AST_FORMAT_ADPCM, AST_FORMAT_ALAW, AST_FORMAT_G719, AST_FORMAT_G722, AST_FORMAT_G723, AST_FORMAT_G726, AST_FORMAT_G726_AAL2, AST_FORMAT_G729, AST_FORMAT_GSM, AST_FORMAT_ILBC, AST_FORMAT_LPC10, AST_FORMAT_OPUS, AST_FORMAT_SIREN14, AST_FORMAT_SIREN7, AST_FORMAT_SLIN, AST_FORMAT_SLIN16, AST_FORMAT_SPEEX, AST_FORMAT_SPEEX16, and AST_FORMAT_ULAW.

Referenced by iax2_codec_pref_best_bitfield2cap(), iax2_codec_pref_from_bitfield(), and socket_process_helper().

iax2_format_compatibility_bitfield2cap()

int iax2_format_compatibility_bitfield2cap	(	uint64_t	bitfield,
		struct ast_format_cap *	cap
	)

Convert a bitfield to a format capabilities structure.

Parameters

bitfield	The bitfield for the media formats
cap	Capabilities structure to place formats into

Return values

0	on success.
-1	on error.

Note

If failure occurs the capabilities structure may contain a partial set of formats

Definition at line 59 of file channels/iax2/format_compatibility.c.

{
    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;
}

References ast_format_cap_append, and ast_format_compatibility_bitfield2format().

Referenced by iax2_codec_choose(), and iax2_getformatname_multiple().

iax2_format_compatibility_cap2bitfield()

uint64_t iax2_format_compatibility_cap2bitfield

(

const struct ast_format_cap *

cap

)

Convert a format capabilities structure to a bitfield.

Parameters

cap	Capabilities structure containing formats

Return values

non-zero	success
zero	no formats present or no formats supported

Definition at line 43 of file channels/iax2/format_compatibility.c.

{
    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;
}

References ao2_ref, ast_format_cap_count(), ast_format_cap_get_format(), and ast_format_compatibility_format2bitfield().

Referenced by iax2_call(), iax2_parse_allow_disallow(), and socket_process_helper().