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/* EFR RTP Payload according to RFC3551. Only one codec frame per RTP */
/* (C) 2017 by Harald Welte <laforge@gnumonks.org> */
/*
* This file is part of gapk (GSM Audio Pocket Knife).
*
* gapk is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* gapk is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with gapk. If not, see <http://www.gnu.org/licenses/>.
*/
#include <stdint.h>
#include <assert.h>
#include <osmocom/codec/codec.h>
#include <gapk/codecs.h>
#include <gapk/formats.h>
#include <gapk/utils.h>
#define EFR_LEN 31
#define EFR_MAGIC 0xc
/* conversion function: RTP payload -> canonical format */
static int
rtp_efr_from_canon(uint8_t *dst, const uint8_t *src, unsigned int src_len)
{
int i;
/* according to RFC3551 4.5.9 */
assert(src_len == EFR_CANON_LEN);
dst[0] = (EFR_MAGIC << 4) | (src[0] >> 4);
for (i=1; i<EFR_LEN; i++)
dst[i] = (src[i-1] << 4) | (src[i] >> 4);
return EFR_LEN;
}
/* conversion function: canonical format -> RTP payload */
static int
rtp_efr_to_canon(uint8_t *dst, const uint8_t *src, unsigned int src_len)
{
int i;
assert(src_len == EFR_LEN);
for (i=0; i<(EFR_LEN-1); i++)
dst[i] = (src[i] << 4) | (src[i+1] >> 4);
dst[EFR_LEN-1] = src[EFR_LEN-1] << 4;
return EFR_CANON_LEN;
}
const struct format_desc fmt_rtp_efr = {
.type = FMT_RTP_EFR,
.codec_type = CODEC_EFR,
.name = "rtp-efr",
.description = "RTP payload for EFR according to RFC3551",
.frame_len = EFR_LEN,
.conv_from_canon = rtp_efr_from_canon,
.conv_to_canon = rtp_efr_to_canon,
};
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