fix: zero Wan2.2 TI2V timesteps for fixed frames (#1604)

Author: leejet

src/stable-diffusion.cpp

@@ -1680,12 +1680,15 @@ class StableDiffusionGGML {
                                          const sd::Tensor<float>& init_latent,
                                          const sd::Tensor<float>& denoise_mask) {
         if (diffusion_model->get_desc() == "Wan2.2-TI2V-5B") {
-            auto new_timesteps = std::vector<float>(static_cast<size_t>(init_latent.shape()[2]), timesteps[0]);
-
-            if (!denoise_mask.empty()) {
-                float value = denoise_mask.dim() == 5 ? denoise_mask.index(0, 0, 0, 0, 0) : denoise_mask.index(0, 0, 0, 0);
-                if (value == 0.f) {
-                    new_timesteps[0] = 0.f;
+            int64_t frame_count = init_latent.shape()[2];
+            auto new_timesteps  = std::vector<float>(static_cast<size_t>(frame_count), timesteps[0]);
+
+            if (!denoise_mask.empty() && denoise_mask.dim() >= 4 && denoise_mask.shape()[2] == frame_count) {
+                for (int64_t frame = 0; frame < frame_count; ++frame) {
+                    float value = denoise_mask.dim() == 5 ? denoise_mask.index(0, 0, frame, 0, 0) : denoise_mask.index(0, 0, frame, 0);
+                    if (value == 0.f) {
+                        new_timesteps[static_cast<size_t>(frame)] = 0.f;
+                    }
                 }
             }
             return new_timesteps;