vad : add initial Voice Activity Detection (VAD) support (#3065)

* vad : add initial Voice Activity Detection (VAD) support

This commit add support for Voice Activity Detection (VAD). When enabled
this feature will process the audio input and detect speech segments.
This information is then used to reduce the number of samples that need
to be processed by whisper_full.

Resolves: https://github.com/ggml-org/whisper.cpp/issues/3003

---------

Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>

include/whisper.h

@@ -189,6 +189,15 @@ extern "C" {
         uint32_t             value; // Unicode code point or rule ID
     } whisper_grammar_element;
 
+    typedef struct whisper_vad_params {
+        float threshold;               // Probability threshold to consider as speech.
+        int   min_speech_duration_ms;  // Min duration for a valid speech segment.
+        int   min_silence_duration_ms; // Min silence duration to consider speech as ended.
+        float max_speech_duration_s;   // Max duration of a speech segment before forcing a new segment.
+        int   speech_pad_ms;           // Padding added before and after speech segments.
+        float samples_overlap;         // Overlap in seconds when copying audio samples from speech segment.
+    } whisper_vad_params;
+
     // Various functions for loading a ggml whisper model.
     // Allocate (almost) all memory needed for the model.
     // Return NULL on failure
@@ -570,11 +579,18 @@ extern "C" {
         size_t                           n_grammar_rules;
         size_t                           i_start_rule;
         float                            grammar_penalty;
+
+        // Voice Activity Detection (VAD) params
+        bool         vad;                         // Enable VAD
+        const char * vad_model_path;              // Path to VAD model
+
+        whisper_vad_params vad_params;
     };
 
     // NOTE: this function allocates memory, and it is the responsibility of the caller to free the pointer - see whisper_free_context_params & whisper_free_params()
     WHISPER_API struct whisper_context_params * whisper_context_default_params_by_ref(void);
     WHISPER_API struct whisper_context_params   whisper_context_default_params       (void);
+
     WHISPER_API struct whisper_full_params * whisper_full_default_params_by_ref(enum whisper_sampling_strategy strategy);
     WHISPER_API struct whisper_full_params   whisper_full_default_params       (enum whisper_sampling_strategy strategy);
 
@@ -652,6 +668,53 @@ extern "C" {
     WHISPER_API float whisper_full_get_token_p           (struct whisper_context * ctx, int i_segment, int i_token);
     WHISPER_API float whisper_full_get_token_p_from_state(struct whisper_state * state, int i_segment, int i_token);
 
+    //
+    // Voice Activity Detection (VAD)
+    //
+
+    struct whisper_vad_context;
+
+    WHISPER_API struct whisper_vad_params whisper_vad_default_params(void);
+
+    struct whisper_vad_context_params {
+        int   n_threads;  // The number of threads to use for processing.
+        bool  use_gpu;
+        int   gpu_device; // CUDA device
+    };
+
+    WHISPER_API struct whisper_vad_context_params whisper_vad_default_context_params(void);
+
+    WHISPER_API struct whisper_vad_context * whisper_vad_init_from_file_with_params(const char * path_model,              struct whisper_vad_context_params params);
+    WHISPER_API struct whisper_vad_context * whisper_vad_init_with_params          (struct whisper_model_loader * loader, struct whisper_vad_context_params params);
+
+    WHISPER_API bool whisper_vad_detect_speech(
+            struct whisper_vad_context * vctx,
+                           const float * samples,
+                                   int   n_samples);
+
+    WHISPER_API int     whisper_vad_n_probs(struct whisper_vad_context * vctx);
+    WHISPER_API float * whisper_vad_probs  (struct whisper_vad_context * vctx);
+
+    struct whisper_vad_segments;
+
+    WHISPER_API struct whisper_vad_segments * whisper_vad_segments_from_probs(
+            struct whisper_vad_context * vctx,
+            struct whisper_vad_params    params);
+
+    WHISPER_API struct whisper_vad_segments * whisper_vad_segments_from_samples(
+            struct whisper_vad_context * vctx,
+            struct whisper_vad_params    params,
+                           const float * samples,
+                                   int   n_samples);
+
+    WHISPER_API int whisper_vad_segments_n_segments(struct whisper_vad_segments * segments);
+
+    WHISPER_API float whisper_vad_segments_get_segment_t0(struct whisper_vad_segments * segments, int i_segment);
+    WHISPER_API float whisper_vad_segments_get_segment_t1(struct whisper_vad_segments * segments, int i_segment);
+
+    WHISPER_API void whisper_vad_free_segments(struct whisper_vad_segments * segments);
+    WHISPER_API void whisper_vad_free         (struct whisper_vad_context  * ctx);
+
     ////////////////////////////////////////////////////////////////////////////
 
     // Temporary helpers needed for exposing ggml interface