feat(dmr): add receive frontend and AMBE adapter

native/dmr/CMakeLists.txt

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+cmake_minimum_required(VERSION 3.10)
+project(ewsdr_dmr C)
+
+find_path(MBELIB_INCLUDE_DIR mbelib.h REQUIRED)
+find_library(MBELIB_LIBRARY NAMES mbe REQUIRED)
+
+add_library(ewsdr_dmr SHARED ewsdr_dmr.c)
+target_compile_definitions(ewsdr_dmr PRIVATE EWSDR_DMR_BUILD)
+target_include_directories(ewsdr_dmr
+  PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}
+  PRIVATE ${MBELIB_INCLUDE_DIR})
+target_link_libraries(ewsdr_dmr PRIVATE ${MBELIB_LIBRARY})
+set_target_properties(ewsdr_dmr PROPERTIES
+  C_VISIBILITY_PRESET hidden
+  VISIBILITY_INLINES_HIDDEN YES)
+
+include(GNUInstallDirs)
+install(TARGETS ewsdr_dmr
+  LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
+  RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR})
+install(FILES ewsdr_dmr.h DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})

native/dmr/README.md

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+# EWSDR DMR native adapter
+
+This optional shared library isolates `mbelib` and the imported DMR core from
+the Lazarus application. It intentionally does not depend on PulseAudio,
+ncurses, libsndfile or the DSD-FME command-line frontend.
+
+Build on Linux:
+
+```sh
+cmake -S native/dmr -B build/dmr -DCMAKE_BUILD_TYPE=Release
+cmake --build build/dmr
+```
+
+The current ABI implements the stateful AMBE+2 vocoder boundary. The burst/FEC
+layer will feed its row-major `char[4][24]` output to this library. Keep the ABI
+versioned: the GUI and daemon must remain usable when the optional library is
+not installed.

native/dmr/ewsdr_dmr.c

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+#include "ewsdr_dmr.h"
+
+#include <mbelib.h>
+#include <stdlib.h>
+#include <string.h>
+
+struct ewsdr_dmr_mbe {
+  mbe_parms current;
+  mbe_parms previous;
+  mbe_parms previous_enhanced;
+  int uv_quality;
+};
+
+uint32_t ewsdr_dmr_abi_version(void)
+{
+  return EWSDR_DMR_ABI_VERSION;
+}
+
+void ewsdr_dmr_mbe_reset(ewsdr_dmr_mbe *decoder)
+{
+  if (decoder == NULL)
+    return;
+  mbe_initMbeParms(&decoder->current, &decoder->previous,
+                   &decoder->previous_enhanced);
+}
+
+ewsdr_dmr_mbe *ewsdr_dmr_mbe_create(int uv_quality)
+{
+  ewsdr_dmr_mbe *decoder = calloc(1, sizeof(*decoder));
+  if (decoder == NULL)
+    return NULL;
+  if (uv_quality < 1)
+    uv_quality = 1;
+  if (uv_quality > 64)
+    uv_quality = 64;
+  decoder->uv_quality = uv_quality;
+  ewsdr_dmr_mbe_reset(decoder);
+  return decoder;
+}
+
+void ewsdr_dmr_mbe_destroy(ewsdr_dmr_mbe *decoder)
+{
+  if (decoder == NULL)
+    return;
+  memset(decoder, 0, sizeof(*decoder));
+  free(decoder);
+}
+
+int ewsdr_dmr_mbe_decode(ewsdr_dmr_mbe *decoder,
+                         const uint8_t ambe_bits[EWSDR_DMR_AMBE_BITS],
+                         float pcm_out[EWSDR_DMR_PCM_SAMPLES],
+                         ewsdr_dmr_mbe_result *result)
+{
+  char frame[4][24];
+  char data[49];
+  char error_text[64];
+  int errors_c0 = 0;
+  int errors_total = 0;
+  size_t row;
+  size_t col;
+
+  if (decoder == NULL || ambe_bits == NULL || pcm_out == NULL)
+    return -1;
+
+  for (row = 0; row < 4; ++row) {
+    for (col = 0; col < 24; ++col) {
+      const uint8_t bit = ambe_bits[row * 24 + col];
+      if (bit > 1)
+        return -2;
+      frame[row][col] = (char)bit;
+    }
+  }
+
+  memset(data, 0, sizeof(data));
+  memset(error_text, 0, sizeof(error_text));
+  mbe_processAmbe3600x2450Framef(
+      pcm_out, &errors_c0, &errors_total, error_text, frame, data,
+      &decoder->current, &decoder->previous, &decoder->previous_enhanced,
+      decoder->uv_quality);
+
+  if (result != NULL) {
+    result->errors_c0 = errors_c0;
+    result->errors_total = errors_total;
+  }
+  return 0;
+}

native/dmr/ewsdr_dmr.h

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+#ifndef EWSDR_DMR_H
+#define EWSDR_DMR_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+#if defined(_WIN32)
+#  if defined(EWSDR_DMR_BUILD)
+#    define EWSDR_DMR_API __declspec(dllexport)
+#  else
+#    define EWSDR_DMR_API __declspec(dllimport)
+#  endif
+#else
+#  define EWSDR_DMR_API __attribute__((visibility("default")))
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define EWSDR_DMR_ABI_VERSION 1u
+#define EWSDR_DMR_AMBE_BITS   96u
+#define EWSDR_DMR_PCM_SAMPLES 160u
+
+typedef struct ewsdr_dmr_mbe ewsdr_dmr_mbe;
+
+typedef struct ewsdr_dmr_mbe_result {
+  int errors_c0;
+  int errors_total;
+} ewsdr_dmr_mbe_result;
+
+EWSDR_DMR_API uint32_t ewsdr_dmr_abi_version(void);
+EWSDR_DMR_API ewsdr_dmr_mbe *ewsdr_dmr_mbe_create(int uv_quality);
+EWSDR_DMR_API void ewsdr_dmr_mbe_destroy(ewsdr_dmr_mbe *decoder);
+EWSDR_DMR_API void ewsdr_dmr_mbe_reset(ewsdr_dmr_mbe *decoder);
+
+/*
+ * Decode one already deinterleaved DMR AMBE+2 frame. ambe_bits is a row-major
+ * char[4][24] matrix containing only 0/1 values. pcm_out receives 160 float
+ * samples at 8 kHz. Frame extraction/deinterleaving remains in the DMR burst
+ * layer, keeping mbelib and its state behind this stable ABI.
+ */
+EWSDR_DMR_API int ewsdr_dmr_mbe_decode(
+    ewsdr_dmr_mbe *decoder,
+    const uint8_t ambe_bits[EWSDR_DMR_AMBE_BITS],
+    float pcm_out[EWSDR_DMR_PCM_SAMPLES],
+    ewsdr_dmr_mbe_result *result);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif