FEATURE: Add initial_prompt support for whispercpp params

src/whispercpp/api.pyi

@@ -101,6 +101,8 @@ class Params:
     prompt_num_tokens: int
     language: str
     def with_language(self, language: str) -> Params: ...
+    initial_prompt: str
+    def with_initial_prompt(self, initial_prompt: str) -> Params: ...
     suppress_blank: bool
     def with_suppress_blank(self, suppress_blank: bool) -> Params: ...
     suppress_none_speech_tokens: bool

src/whispercpp/context.h

@@ -145,6 +145,7 @@ struct Params {
   private:
     std::shared_ptr<whisper_full_params> fp;
     std::string language;
+    std::string initial_prompt;
 
     CallbackAndContext<NewSegmentCallback> new_segment_callback;
     CallbackAndContext<ProgressCallback> progress_callback;
@@ -348,6 +349,13 @@ struct Params {
         return this;
     }
 
+    // Set initial prompt
+    Params *with_initial_prompt(std::string initial_prompt) {
+        this->initial_prompt = initial_prompt;
+        fp->initial_prompt = this->initial_prompt.c_str();
+        return this;
+    }
+
     // Set suppress_blank. See
     // https://github.com/openai/whisper/blob/f82bc59f5ea234d4b97fb2860842ed38519f7e65/whisper/decoding.py#L89
     // for more information.

src/whispercpp/params.cc

@@ -604,6 +604,15 @@ void ExportParamsApi(py::module &m) {
                 WITH_DEPRECATION("language");
                 self.with_language(language);
             })
+        // NOTE set initial_prompt
+        .def("with_initial_prompt", &Params::with_initial_prompt, "initial_prompt"_a,
+             py::return_value_policy::reference)
+        .def_property(
+            "initial_prompt", [](Params &self) { return self.get()->initial_prompt; },
+            [](Params &self, const char *initial_prompt) {
+                WITH_DEPRECATION("initial_prompt");
+                self.with_initial_prompt(initial_prompt);   
+            })
         // NOTE setting suppress_blank
         .def("with_suppress_blank", &Params::with_suppress_blank,
              "suppress_blank"_a, py::return_value_policy::reference)

tests/params_export_test.py

@@ -95,3 +95,11 @@ def test_set_language():
         params_with_lang = params.with_language(lang)
         print(lang, params_with_lang.language)
         assert params_with_lang.language == lang
+
+def test_set_initial_prompt():
+    params = w.api.Params.from_enum(w.api.StrategyType.SAMPLING_GREEDY)
+    for prompt in ["This is a test initial prompt", ""]:
+        assert params.initial_prompt != ""
+        params_with_initial_prompt = params.with_initial_prompt(prompt)
+        print(prompt, params_with_initial_prompt.initial_prompt)
+        assert params_with_initial_prompt.initial_prompt == prompt