minor: use helper for frame packing

include/aare/utils/batch.hpp

@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: MPL-2.0
+#pragma once
+#include <vector>
+#include <cstring>
+#include "aare/NDArray.hpp"
+
+
+template <typename FRAME_TYPE>
+void pack_frame_batch(const std::vector<aare::NDArray<FRAME_TYPE, 2>>& frames,
+                      size_t first_frame,
+                      size_t n_frames,
+                      std::vector<FRAME_TYPE>& batch)
+{
+    if (n_frames == 0) return;
+
+    const size_t rows = frames[first_frame].shape(0);
+    const size_t cols = frames[first_frame].shape(1);
+    const size_t image_size = rows * cols;
+    const size_t total_size = n_frames * image_size;
+
+    if (batch.size() != total_size) {
+        batch.resize(total_size);
+    }
+
+    for (size_t k = 0; k < n_frames; ++k) {
+        const FRAME_TYPE* src = frames[first_frame + k].data();
+        FRAME_TYPE* dst = batch.data() + k * image_size;
+        std::memcpy(dst, src, image_size * sizeof(FRAME_TYPE));
+    }
+}