mirror of https://gerrit.osmocom.org/gapk
70 lines
2.0 KiB
C
70 lines
2.0 KiB
C
/* AMR RTP Payload according to RFC4867. Only one codec frame per RTP */
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/* (C) 2017 by Harald Welte <laforge@gnumonks.org> */
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/*
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* This file is part of gapk (GSM Audio Pocket Knife).
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*
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* gapk is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* gapk is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with gapk. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <stdint.h>
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#include <string.h>
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#include <osmocom/codec/codec.h>
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#include <osmocom/gapk/codecs.h>
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#include <osmocom/gapk/formats.h>
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#include <osmocom/gapk/utils.h>
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/* AMR SID frame is according to TS 126 101 4.2.3 */
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static const uint8_t SILENCE[] = {0x80, 0x44, 0x00, 0x00, 0x00, 0x00, 0x00};
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/* conversion function: RTP payload -> canonical format */
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static int
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rtp_amr_from_canon(uint8_t *dst, const uint8_t *src, unsigned int src_len)
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{
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/* add Payload Header according to RFC4867 4.4.1 */
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dst[0] = 0xf0; /* no request */
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memcpy(dst+1, src, src_len);
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return src_len+1;
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}
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/* conversion function: canonical format -> RTP payload */
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static int
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rtp_amr_to_canon(uint8_t *dst, const uint8_t *src, unsigned int src_len)
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{
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/* Detect severely damaged frames according to RFC4867 4.3.2 */
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if ((src[1] & 0x04) == 0) {
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src = SILENCE;
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src_len = sizeof(SILENCE);
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}
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/* skip Payload Header according to RFC4867 4.4.1 */
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memcpy(dst, src+1, src_len-1);
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return src_len-1;
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}
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const struct osmo_gapk_format_desc fmt_rtp_amr = {
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.type = FMT_RTP_AMR,
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.codec_type = CODEC_AMR,
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.name = "rtp-amr",
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.description = "RTP payload for AMR according to RFC4867",
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.frame_len = 0,
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.conv_from_canon = rtp_amr_from_canon,
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.conv_to_canon = rtp_amr_to_canon,
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};
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