mtmd : support home-cooked Mistral Small Omni (#14928)

tools/mtmd/clip-impl.h

@@ -30,6 +30,7 @@
 #define KEY_LAYER_NORM_EPS      "clip.%s.attention.layer_norm_epsilon"
 
 // vision-specific
+#define KEY_VISION_PROJ_TYPE    "clip.vision.projector_type" // for models with mixed modalities
 #define KEY_IMAGE_SIZE          "clip.vision.image_size"
 #define KEY_PREPROC_IMAGE_SIZE  "clip.vision.preproc_image_size"
 #define KEY_PATCH_SIZE          "clip.vision.patch_size"
@@ -48,6 +49,7 @@
 #define KEY_MINICPMV_QUERY_NUM    "clip.minicpmv_query_num"
 
 // audio-specific
+#define KEY_AUDIO_PROJ_TYPE     "clip.audio.projector_type" // for models with mixed modalities
 #define KEY_A_NUM_MEL_BINS      "clip.audio.num_mel_bins"
 #define KEY_A_PROJ_STACK_FACTOR "clip.audio.projector.stack_factor"
 

tools/mtmd/clip.cpp

@@ -2221,15 +2221,27 @@ struct clip_model_loader {
         // projector type
         std::string proj_type;
         {
+            // default key
             get_string(KEY_PROJ_TYPE, proj_type, false);
-            if (!proj_type.empty()) {
-                model.proj_type = clip_projector_type_from_string(proj_type);
+
+            // for models with mixed modalities
+            if (proj_type.empty()) {
+                if (modality == CLIP_MODALITY_VISION) {
+                    get_string(KEY_VISION_PROJ_TYPE, proj_type, false);
+                } else if (modality == CLIP_MODALITY_AUDIO) {
+                    get_string(KEY_AUDIO_PROJ_TYPE, proj_type, false);
+                } else {
+                    GGML_ABORT("unknown modality");
+                }
             }
+
+            model.proj_type = clip_projector_type_from_string(proj_type);
+
             if (model.proj_type == PROJECTOR_TYPE_UNKNOWN) {
                 throw std::runtime_error(string_format("%s: unknown projector type: %s\n", __func__, proj_type.c_str()));
             }
 
-            // correct arch for multimodal models
+            // correct arch for multimodal models (legacy method)
             if (model.proj_type == PROJECTOR_TYPE_QWEN25O) {
                 model.proj_type = modality == CLIP_MODALITY_VISION
                                     ? PROJECTOR_TYPE_QWEN25VL