examples : move wav_writer from stream.cpp to common.h (#1317)

* Allocate class on the stack instead of on the heap

* Add class wav_writer

* fix some minor issues

* fix some minor issues

* remove potential misleading API

examples/common.h

@@ -7,6 +7,8 @@
 #include <vector>
 #include <random>
 #include <thread>
+#include <ctime>
+#include <fstream>
 
 #define COMMON_SAMPLE_RATE 16000
 
@@ -139,6 +141,104 @@ bool read_wav(
         std::vector<std::vector<float>> & pcmf32s,
         bool stereo);
 
+// Write PCM data into WAV audio file
+class wav_writer {
+private:
+    std::ofstream file;
+    uint32_t dataSize = 0;
+    std::string wav_filename;
+
+    bool write_header(const uint32_t sample_rate,
+                      const uint16_t bits_per_sample,
+                      const uint16_t channels) {
+
+        file.write("RIFF", 4);
+        file.write("\0\0\0\0", 4);    // Placeholder for file size
+        file.write("WAVE", 4);
+        file.write("fmt ", 4);
+
+        const uint32_t sub_chunk_size = 16;
+        const uint16_t audio_format = 1;      // PCM format
+        const uint32_t byte_rate = sample_rate * channels * bits_per_sample / 8;
+        const uint16_t block_align = channels * bits_per_sample / 8;
+
+        file.write(reinterpret_cast<const char *>(&sub_chunk_size), 4);
+        file.write(reinterpret_cast<const char *>(&audio_format), 2);
+        file.write(reinterpret_cast<const char *>(&channels), 2);
+        file.write(reinterpret_cast<const char *>(&sample_rate), 4);
+        file.write(reinterpret_cast<const char *>(&byte_rate), 4);
+        file.write(reinterpret_cast<const char *>(&block_align), 2);
+        file.write(reinterpret_cast<const char *>(&bits_per_sample), 2);
+        file.write("data", 4);
+        file.write("\0\0\0\0", 4);    // Placeholder for data size
+
+        return true;
+    }
+
+    // It is assumed that PCM data is normalized to a range from -1 to 1
+    bool write_audio(const float * data, size_t length) {
+        for (size_t i = 0; i < length; ++i) {
+            const auto intSample = static_cast<const int16_t>(data[i] * 32767);
+            file.write(reinterpret_cast<const char *>(&intSample), sizeof(int16_t));
+            dataSize += sizeof(int16_t);
+        }
+        if (file.is_open()) {
+            file.seekp(4, std::ios::beg);
+            uint32_t fileSize = 36 + dataSize;
+            file.write(reinterpret_cast<char *>(&fileSize), 4);
+            file.seekp(40, std::ios::beg);
+            file.write(reinterpret_cast<char *>(&dataSize), 4);
+            file.seekp(0, std::ios::end);
+        }
+        return true;
+    }
+
+    bool open_wav(const std::string & filename) {
+        if (filename != wav_filename) {
+            if (file.is_open()) {
+                file.close();
+            }
+        }
+        if (!file.is_open()) {
+            file.open(filename, std::ios::binary);
+            wav_filename = filename;
+            dataSize = 0;
+        }
+        return file.is_open();
+    }
+
+public:
+    bool open(const std::string & filename,
+              const    uint32_t   sample_rate,
+              const    uint16_t   bits_per_sample,
+              const    uint16_t   channels) {
+
+        if (open_wav(filename)) {
+            write_header(sample_rate, bits_per_sample, channels);
+        } else {
+            return false;
+        }
+
+        return true;
+    }
+
+    bool close() {
+        file.close();
+        return true;
+    }
+
+    bool write(const float * data, size_t length) {
+        return write_audio(data, length);
+    }
+
+    ~wav_writer() {
+        if (file.is_open()) {
+            file.close();
+        }
+    }
+};
+
+
 // Apply a high-pass frequency filter to PCM audio
 // Suppresses frequencies below cutoff Hz
 void high_pass_filter(

examples/stream/stream.cpp

@@ -2,7 +2,6 @@
 //
 // A very quick-n-dirty implementation serving mainly as a proof of concept.
 //
-#include <fstream>
 #include "common-sdl.h"
 #include "common.h"
 #include "whisper.h"
@@ -13,60 +12,8 @@
 #include <thread>
 #include <vector>
 #include <fstream>
-#include <ctime>
-
-class SimpleWavWriter {
-private:
-    std::ofstream file;
-    int32_t dataSize = 0;
-
-public:
-    SimpleWavWriter(const std::string &filename, int sampleRate, int bitsPerSample, int channels) {
-        file.open(filename, std::ios::binary);
-
-        file.write("RIFF", 4);
-        file.write("\0\0\0\0", 4);    // Placeholder for file size
-        file.write("WAVE", 4);
-        file.write("fmt ", 4);
-
-        int32_t subChunkSize = 16;
-        int16_t audioFormat = 1;      // PCM format
-        int32_t byteRate = sampleRate * channels * bitsPerSample / 8;
-        int16_t blockAlign = channels * bitsPerSample / 8;
-
-        file.write(reinterpret_cast<char *>(&subChunkSize), 4);
-        file.write(reinterpret_cast<char *>(&audioFormat), 2);
-        file.write(reinterpret_cast<char *>(&channels), 2);
-        file.write(reinterpret_cast<char *>(&sampleRate), 4);
-        file.write(reinterpret_cast<char *>(&byteRate), 4);
-        file.write(reinterpret_cast<char *>(&blockAlign), 2);
-        file.write(reinterpret_cast<char *>(&bitsPerSample), 2);
-        file.write("data", 4);
-        file.write("\0\0\0\0", 4);    // Placeholder for data size
-    }
 
-    void writeData(const float *data, size_t length) {
-        for (size_t i = 0; i < length; ++i) {
-            int16_t intSample = static_cast<int16_t>(data[i] * 32767);
-            file.write(reinterpret_cast<char *>(&intSample), sizeof(int16_t));
-            dataSize += sizeof(int16_t);
-        }
-        if (file.is_open()) {
-            file.seekp(4, std::ios::beg);
-            int32_t fileSize = 36 + dataSize;
-            file.write(reinterpret_cast<char *>(&fileSize), 4);
-            file.seekp(40, std::ios::beg);
-            file.write(reinterpret_cast<char *>(&dataSize), 4);
-            file.seekp(0, std::ios::end);
-        }
-    }
 
-    ~SimpleWavWriter() {
-        if (file.is_open()) {
-            file.close();
-        }
-    }
-};
 //  500 -> 00:05.000
 // 6000 -> 01:00.000
 std::string to_timestamp(int64_t t) {
@@ -266,8 +213,9 @@ int main(int argc, char ** argv) {
             return 1;
         }
     }
+
+    wav_writer wavWriter;
     // save wav file
-    SimpleWavWriter *wavWriter = nullptr;
     if (params.save_audio) {
         // Get current date/time for filename
         time_t now = time(0);
@@ -275,7 +223,7 @@ int main(int argc, char ** argv) {
         strftime(buffer, sizeof(buffer), "%Y%m%d%H%M%S", localtime(&now));
         std::string filename = std::string(buffer) + ".wav";
 
-        wavWriter = new SimpleWavWriter(filename, WHISPER_SAMPLE_RATE, 16, 1);
+        wavWriter.open(filename, WHISPER_SAMPLE_RATE, 16, 1);
     }
     printf("[Start speaking]\n");
     fflush(stdout);
@@ -285,8 +233,8 @@ int main(int argc, char ** argv) {
 
     // main audio loop
     while (is_running) {
-        if (params.save_audio && wavWriter) {
-            wavWriter->writeData(pcmf32_new.data(), pcmf32_new.size());
+        if (params.save_audio) {
+            wavWriter.write(pcmf32_new.data(), pcmf32_new.size());
         }
         // handle Ctrl + C
         is_running = sdl_poll_events();