whisper : add OpenVINO support (#1037)

* openvino: use OpenVINO encoder inference

* openvino: add python script for OpenVINO model generation

* whisper: Fix 'unused' warnings when OpenVINO isn't enabled in build

* Apply suggestions from code review

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

* whisper: Fix compilation error

* whisper: revert whisper_get_openvino_path_encoder & whisper_get_openvino_path_cache to non-const func signatures

* cmake: Add openvino-encoder as separate object target

* whisper : minor style fixes

* minor : indentation fixes

---------

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

whisper.h

@@ -110,6 +110,24 @@ extern "C" {
 
     WHISPER_API struct whisper_state * whisper_init_state(struct whisper_context * ctx);
 
+    // Given a context, enable use of OpenVINO for encode inference.
+    // model_path: Optional path to OpenVINO encoder IR model. If set to nullptr,
+    //                      the path will be generated from the ggml model path that was passed
+    //                      in to whisper_init_from_file. For example, if 'path_model' was
+    //                      "/path/to/ggml-base.en.bin", then OpenVINO IR model path will be
+    //                      assumed to be "/path/to/ggml-base.en-encoder-openvino.xml".
+    // device: OpenVINO device to run inference on ("CPU", "GPU", etc.)
+    // cache_dir: Optional cache directory that can speed up init time, especially for
+    //                     GPU, by caching compiled 'blobs' there.
+    //                     Set to nullptr if not used.
+    // Returns 1 on success. If OpenVINO is not enabled in build, this
+    // simply returns 0.
+    WHISPER_API int whisper_ctx_init_openvino_encoder(
+        struct whisper_context * ctx,
+                    const char * model_path,
+                    const char * device,
+                    const char * cache_dir);
+
     // Frees all allocated memory
     WHISPER_API void whisper_free      (struct whisper_context * ctx);
     WHISPER_API void whisper_free_state(struct whisper_state * state);