ETISnoop search for firecode

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;
+    }
+}
+