1 files changed, 139 insertions, 0 deletions
diff --git a/src/audio/wav_dump_backend.cc b/src/audio/wav_dump_backend.cc
new file mode 100644
index 0000000..7418a40
--- /dev/null
+++ b/src/audio/wav_dump_backend.cc
@@ -0,0 +1,139 @@
+// This file is part of the 64k demo project.
+// Implementation of WAV dump backend for debugging.
+
+#include "wav_dump_backend.h"
+
+#if !defined(STRIP_ALL)
+
+#include "synth.h"
+#include <assert.h>
+#include <stdio.h>
+#include <string.h>
+
+WavDumpBackend::WavDumpBackend()
+    : wav_file_(nullptr),
+      samples_written_(0),
+      output_filename_("audio_dump.wav"),
+      is_active_(false) {
+  sample_buffer_.resize(kBufferSize);
+}
+
+WavDumpBackend::~WavDumpBackend() { shutdown(); }
+
+void WavDumpBackend::set_output_file(const char* filename) {
+  output_filename_ = filename;
+}
+
+void WavDumpBackend::init() {
+  // Open WAV file for writing
+  wav_file_ = fopen(output_filename_, "wb");
+  if (wav_file_ == nullptr) {
+    fprintf(stderr, "Error: Failed to open WAV file: %s\n", output_filename_);
+    return;
+  }
+
+  // Write placeholder header (we'll update it in shutdown())
+  write_wav_header(wav_file_, 0);
+
+  samples_written_ = 0;
+  printf("WAV dump backend initialized: %s\n", output_filename_);
+}
+
+void WavDumpBackend::start() {
+  is_active_ = true;
+  printf("WAV dump started, rendering audio...\n");
+
+  // Render audio in chunks until we reach desired duration
+  // For debugging, render 60 seconds max
+  const int max_duration_sec = 60;
+  const size_t total_samples = kSampleRate * max_duration_sec;
+  const size_t total_frames = total_samples / kBufferSize;
+
+  for (size_t frame = 0; frame < total_frames; ++frame) {
+    // Render audio from synth
+    synth_render(sample_buffer_.data(), kBufferSize);
+
+    // Convert float to int16 and write to WAV
+    for (int i = 0; i < kBufferSize; ++i) {
+      // Clamp to [-1, 1] and convert to 16-bit signed
+      float sample = sample_buffer_[i];
+      if (sample > 1.0f) sample = 1.0f;
+      if (sample < -1.0f) sample = -1.0f;
+
+      const int16_t sample_i16 = (int16_t)(sample * 32767.0f);
+      fwrite(&sample_i16, sizeof(int16_t), 1, wav_file_);
+    }
+
+    samples_written_ += kBufferSize;
+
+    // Progress indicator
+    if (frame % 100 == 0) {
+      const float progress_sec = (float)samples_written_ / kSampleRate;
+      printf("  Rendering: %.1fs / %ds\r", progress_sec, max_duration_sec);
+      fflush(stdout);
+    }
+
+    // Call frame rendering hook
+    on_frames_rendered(kBufferSize);
+  }
+
+  printf("\nWAV dump complete: %zu samples (%.2f seconds)\n", samples_written_,
+         (float)samples_written_ / kSampleRate);
+
+  is_active_ = false;
+}
+
+void WavDumpBackend::shutdown() {
+  if (wav_file_ != nullptr) {
+    // Update header with final sample count
+    update_wav_header();
+    fclose(wav_file_);
+    wav_file_ = nullptr;
+
+    printf("WAV file written: %s\n", output_filename_);
+  }
+}
+
+void WavDumpBackend::write_wav_header(FILE* file, uint32_t num_samples) {
+  // WAV file header structure
+  // Reference: http://soundfile.sapp.org/doc/WaveFormat/
+
+  const uint32_t num_channels = 1;  // Mono
+  const uint32_t sample_rate = kSampleRate;
+  const uint32_t bits_per_sample = 16;
+  const uint32_t byte_rate = sample_rate * num_channels * bits_per_sample / 8;
+  const uint16_t block_align = num_channels * bits_per_sample / 8;
+  const uint32_t data_size = num_samples * num_channels * bits_per_sample / 8;
+
+  // RIFF header
+  fwrite("RIFF", 1, 4, file);
+  const uint32_t chunk_size = 36 + data_size;
+  fwrite(&chunk_size, 4, 1, file);
+  fwrite("WAVE", 1, 4, file);
+
+  // fmt subchunk
+  fwrite("fmt ", 1, 4, file);
+  const uint32_t subchunk1_size = 16;
+  fwrite(&subchunk1_size, 4, 1, file);
+  const uint16_t audio_format = 1;  // PCM
+  fwrite(&audio_format, 2, 1, file);
+  fwrite(&num_channels, 2, 1, file);
+  fwrite(&sample_rate, 4, 1, file);
+  fwrite(&byte_rate, 4, 1, file);
+  fwrite(&block_align, 2, 1, file);
+  fwrite(&bits_per_sample, 2, 1, file);
+
+  // data subchunk header
+  fwrite("data", 1, 4, file);
+  fwrite(&data_size, 4, 1, file);
+}
+
+void WavDumpBackend::update_wav_header() {
+  if (wav_file_ == nullptr) return;
+
+  // Seek to beginning and rewrite header with actual sample count
+  fseek(wav_file_, 0, SEEK_SET);
+  write_wav_header(wav_file_, samples_written_);
+}
+
+#endif /* !defined(STRIP_ALL) */