ref #10 : add "step" argument for "stream" example

Controls how often we run the inference.
By default, we run it every 3 seconds.

stream.cpp

@@ -36,6 +36,7 @@ std::string to_timestamp(int64_t t) {
 struct whisper_params {
     int32_t seed      = -1; // RNG seed, not used currently
     int32_t n_threads = std::min(4, (int32_t) std::thread::hardware_concurrency());
+    int32_t step_ms   = 3000;
 
     bool verbose              = false;
     bool translate            = false;
@@ -57,6 +58,8 @@ bool whisper_params_parse(int argc, char ** argv, whisper_params & params) {
             params.seed = std::stoi(argv[++i]);
         } else if (arg == "-t" || arg == "--threads") {
             params.n_threads = std::stoi(argv[++i]);
+        } else if (arg == "--step") {
+            params.step_ms = std::stoi(argv[++i]);
         } else if (arg == "-v" || arg == "--verbose") {
             params.verbose = true;
         } else if (arg == "--translate") {
@@ -97,6 +100,7 @@ void whisper_print_usage(int argc, char ** argv, const whisper_params & params)
     fprintf(stderr, "  -h,       --help           show this help message and exit\n");
     fprintf(stderr, "  -s SEED,  --seed SEED      RNG seed (default: -1)\n");
     fprintf(stderr, "  -t N,     --threads N      number of threads to use during computation (default: %d)\n", params.n_threads);
+    fprintf(stderr, "            --step N         audio step size in milliseconds (default: %d)\n", params.step_ms);
     fprintf(stderr, "  -v,       --verbose        verbose output\n");
     fprintf(stderr, "            --translate      translate from source language to english\n");
     fprintf(stderr, "  -ps,      --print_special  print special tokens\n");
@@ -197,6 +201,7 @@ int main(int argc, char ** argv) {
 
     struct whisper_context * ctx = whisper_init(params.model.c_str());
 
+    const int n_samples = (params.step_ms/1000.0)*WHISPER_SAMPLE_RATE;
     const int n_samples_30s = 30*WHISPER_SAMPLE_RATE;
     std::vector<float> pcmf32(n_samples_30s, 0.0f);
     std::vector<float> pcmf32_old;
@@ -212,7 +217,7 @@ int main(int argc, char ** argv) {
             }
         }
         printf("%s: processing %d samples (%.1f sec), %d threads, lang = %s, task = %s, timestamps = %d ...\n",
-                __func__, int(pcmf32.size()), float(pcmf32.size())/WHISPER_SAMPLE_RATE, params.n_threads,
+                __func__, n_samples, float(n_samples)/WHISPER_SAMPLE_RATE, params.n_threads,
                 params.language.c_str(),
                 params.translate ? "translate" : "transcribe",
                 params.no_timestamps ? 0 : 1);
@@ -238,7 +243,7 @@ int main(int argc, char ** argv) {
         }
 
         // process 3 seconds of new audio
-        while (SDL_GetQueuedAudioSize(g_dev_id_in) < 3*WHISPER_SAMPLE_RATE*sizeof(float)) {
+        while (SDL_GetQueuedAudioSize(g_dev_id_in) < n_samples*sizeof(float)) {
             SDL_Delay(1);
         }
         const int n_samples_new = SDL_GetQueuedAudioSize(g_dev_id_in)/sizeof(float);