mirror of https://github.com/drowe67/codec2.git
99 lines
3.3 KiB
C
99 lines
3.3 KiB
C
/*---------------------------------------------------------------------------*\
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FILE........: freedv_datac1_tx.c
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AUTHOR......: David Rowe
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DATE CREATED: April 2021
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Demonstrates transmitting frames of raw data bytes using the FreeDV API datac1
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mode. The data on stdin is transmitted as a sequence of modulated bursts.
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Format of each burst: ...|preamble|data frame|postamble|silence|....
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There is just one data frame per burst in this demo.
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usage:
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cd codec2/build_linux
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head -c $((510*10)) </dev/urandom > binaryIn.bin
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cat binaryIn.bin | ./demo/freedv_datac1_tx | ./demo/freedv_datac1_rx >
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binaryOut.bin diff binaryIn.bin binaryOut.bin
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Listen to the modulated Tx signal:
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cat binaryIn.bin | ./demo/freedv_datac1_tx | aplay -f S16_LE
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\*---------------------------------------------------------------------------*/
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/*
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Copyright (C) 2021 David Rowe
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All rights reserved.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License version 2.1, as
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published by the Free Software Foundation. This program is
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distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program; if not, see <http://www.gnu.org/licenses/>.
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*/
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#include <assert.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include "freedv_api.h"
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int main(int argc, char *argv[]) {
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struct freedv *freedv;
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freedv = freedv_open(FREEDV_MODE_DATAC1);
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assert(freedv != NULL);
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size_t bytes_per_modem_frame = freedv_get_bits_per_modem_frame(freedv) / 8;
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size_t payload_bytes_per_modem_frame =
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bytes_per_modem_frame - 2; /* 16 bits used for the CRC */
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size_t n_mod_out = freedv_get_n_tx_modem_samples(freedv);
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uint8_t bytes_in[bytes_per_modem_frame];
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short mod_out_short[n_mod_out];
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for (int b = 0; b < 10; b++) {
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/* send preamble */
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int n_preamble = freedv_rawdatapreambletx(freedv, mod_out_short);
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fwrite(mod_out_short, sizeof(short), n_preamble, stdout);
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/* read our input data frame from stdin */
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size_t nread =
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fread(bytes_in, sizeof(uint8_t), payload_bytes_per_modem_frame, stdin);
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if (nread != payload_bytes_per_modem_frame) break;
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/* The raw data modes require a CRC in the last two bytes */
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uint16_t crc16 = freedv_gen_crc16(bytes_in, payload_bytes_per_modem_frame);
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bytes_in[bytes_per_modem_frame - 2] = crc16 >> 8;
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bytes_in[bytes_per_modem_frame - 1] = crc16 & 0xff;
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/* modulate and send a data frame */
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freedv_rawdatatx(freedv, mod_out_short, bytes_in);
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fwrite(mod_out_short, sizeof(short), n_mod_out, stdout);
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/* send postamble */
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int n_postamble = freedv_rawdatapostambletx(freedv, mod_out_short);
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fwrite(mod_out_short, sizeof(short), n_postamble, stdout);
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/* create some silence between bursts */
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int inter_burst_delay_ms = 200;
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int samples_delay = FREEDV_FS_8000 * inter_burst_delay_ms / 1000;
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short sil_short[samples_delay];
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for (int i = 0; i < samples_delay; i++) sil_short[i] = 0;
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fwrite(sil_short, sizeof(short), samples_delay, stdout);
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}
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freedv_close(freedv);
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return 0;
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}
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