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Diffstat (limited to 'dabplussnoop.cpp')
| -rw-r--r-- | dabplussnoop.cpp | 180 |
1 files changed, 180 insertions, 0 deletions
diff --git a/dabplussnoop.cpp b/dabplussnoop.cpp new file mode 100644 index 0000000..83f646e --- /dev/null +++ b/dabplussnoop.cpp @@ -0,0 +1,180 @@ +/* + Copyright (C) 2014 Matthias P. Braendli (http://www.opendigitalradio.org) + + This program 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. + + 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 General Public License + along with this program. If not, see <http://www.gnu.org/licenses/>. + + dabplussnoop.cpp + Parse DAB+ frames from a ETI file + + Authors: + Matthias P. Braendli <matthias@mpb.li> +*/ + +#include <stdio.h> +#include <stdint.h> +#include <stdlib.h> +#include <string.h> +#include <string> +#include <sstream> +#include "dabplussnoop.h" +#include "firecode.h" + +#define DPS_INDENT "\t\t" +#define DPS_PREFIX "DABPLUS:" + +using namespace std; + +void DabPlusSnoop::push(uint8_t* streamdata, size_t streamsize) +{ + size_t original_size = m_data.size(); + m_data.resize(original_size + streamsize); + + memcpy(&m_data[original_size], streamdata, streamsize); + + check(); +} + +// Idea and some code taken from Xpadxpert +int DabPlusSnoop::check() +{ + if (m_data.size() < 10) { + // Not enough data + return -1; + } + + bool crc_ok = false; + int i; + + for (i = 0; i < m_data.size() - 10; i++) { + uint8_t* b = &m_data[i]; + + // the three bytes after the firecode must not be zero + // (simple plausibility check to avoid sync in zero byte region) + if (b[3] != 0x00 || (b[4] & 0xF0) != 0x00) { + uint16_t header_firecode = (b[0] << 8) | b[1]; + uint16_t calculated_firecode = firecode_crc(b+2, 9); + + if (header_firecode == calculated_firecode) { + crc_ok = true; + break; + } + } + } + + if (crc_ok) { + fprintf(stderr, DPS_PREFIX " Found valid FireCode at %d\n", i); + + m_data.erase(m_data.begin(), m_data.begin() + i); + return decode(); + } + else { + fprintf(stderr, DPS_PREFIX " No valid FireCode found\n"); + return -1; + } +} + +int DabPlusSnoop::decode() +{ + if (m_subchannel_index && m_data.size() >= m_subchannel_index * 110) { + fprintf(stderr, DPS_PREFIX " We have %zu bytes of data\n", m_data.size()); + + uint8_t* b = &m_data[0]; + + // -- Parse he_aac_super_frame + // ---- Parse he_aac_super_frame_header + // ------ Parse firecode and audio params + uint16_t header_firecode = (b[0] << 8) | b[1]; + uint8_t audio_params = b[2]; + int rfa = (audio_params & 0x80) ? 1 : 0; + int dac_rate = (audio_params & 0x40) ? 1 : 0; + int sbr_flag = (audio_params & 0x20) ? 1 : 0; + int aac_channel_mode = (audio_params & 0x10) ? 1 : 0; + int ps_flag = (audio_params & 0x08) ? 1 : 0; + int mpeg_surround_config = (audio_params & 0x07) ? 1 : 0; + + int num_aus; + if ((dac_rate == 0) && (sbr_flag == 1)) num_aus = 2; + // AAC core sampling rate 16 kHz + else if ((dac_rate == 1) && (sbr_flag == 1)) num_aus = 3; + // AAC core sampling rate 24 kHz + else if ((dac_rate == 0) && (sbr_flag == 0)) num_aus = 4; + // AAC core sampling rate 32 kHz + else if ((dac_rate == 1) && (sbr_flag == 0)) num_aus = 6; + // AAC core sampling rate 48 kHz + + fprintf(stderr, + DPS_INDENT DPS_PREFIX "\n" + DPS_INDENT "\tfirecode 0x%x\n" + DPS_INDENT "\trfa %d\n" + DPS_INDENT "\tdac_rate %d\n" + DPS_INDENT "\tsbr_flag %d\n" + DPS_INDENT "\taac_channel_mode %d\n" + DPS_INDENT "\tps_flag %d\n" + DPS_INDENT "\tmpeg_surround_config %d\n" + DPS_INDENT "\tnum_aus %d\n", + header_firecode, rfa, dac_rate, sbr_flag, aac_channel_mode, + ps_flag, mpeg_surround_config, num_aus); + + + // ------ Parse au_start + b += 3; + + vector<uint8_t> au_start_nibbles(3*(num_aus-1)); + + size_t nib = 0; + for (int i = 0; i < (num_aus-1)*3/2; i++) { + au_start_nibbles[nib] = b[i] >> 4; + au_start_nibbles[nib+1] = 0x0F & (b[i]); + nib += 2; + fprintf(stderr, "0x%1x 0x%1x ", b[i] >> 4, 0x0F & b[i]); + } + fprintf(stderr, "\n"); + + vector<int> au_start(num_aus); + + if (num_aus == 2) + au_start[0] = 5; + else if (num_aus == 3) + au_start[0] = 6; + else if (num_aus == 4) + au_start[0] = 8; + else if (num_aus == 6) + au_start[0] = 11; + + + nib = 0; + fprintf(stderr, DPS_INDENT DPS_PREFIX " AU start\n"); + for (int au = 1; au < num_aus; au++) { + au_start[au] = au_start_nibbles[nib] << 8 | \ + au_start_nibbles[nib+1] << 4 | \ + au_start_nibbles[nib+2]; + + nib += 3; + } + + for (int au = 0; au < num_aus; au++) { + fprintf(stderr, DPS_INDENT "\tAU[%d] %d 0x%x\n", au, + au_start[au], + au_start[au]); + } + + m_data.clear(); + + return 0; + } + else { + return -1; + } +} + |