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/* AMR support for OsmoBTS-TRX */
/* (C) 2013 by Andreas Eversberg <jolly@eversberg.eu>
*
* All Rights Reserved
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation; either version 3 of the License, or
* (at your option) any later version.
*
* This program 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 Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <stdint.h>
static int amr_len_by_ft[16] = {
12, 13, 15, 17, 19, 20, 26, 31,
0, 0, 0, 0, 0, 0, 0, 0
};
int amr_decompose_payload(uint8_t *payload, int payload_len, uint8_t *_cmr,
uint8_t *_ft, uint8_t *_bfi)
{
uint8_t cmr, f, ft, q;
if (payload_len < 2)
return -EINVAL;
cmr = payload[0] >> 4;
if (_cmr)
*_cmr = cmr;
f = payload[1] >> 7;
ft = (payload[1] >> 3) & 0xf;
if (_ft)
*_ft = ft;
q = (payload[1] >> 2) & 0x1;
if (_bfi)
*_bfi = !q;
if (f) {
fprintf(stderr, "%s: multiple payloads not supported\n",
__func__);
return -ENOTSUP;
}
if (payload_len - 2 < amr_len_by_ft[ft])
return -EINVAL;
return 2 + amr_len_by_ft[ft];
}
int amr_compose_payload(uint8_t *payload, uint8_t cmr, uint8_t ft, uint8_t bfi)
{
if (cmr >= 16)
return -EINVAL;
if (ft >= 16)
return -EINVAL;
payload[0] = cmr << 4;
payload[1] = (ft << 3) | ((!bfi) << 2); /* F = 0 */
return 2 + amr_len_by_ft[ft];
}
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