diff --git a/aos/vision/blob/codec.cc b/aos/vision/blob/codec.cc
new file mode 100644
index 0000000..51ae129
--- /dev/null
+++ b/aos/vision/blob/codec.cc
@@ -0,0 +1,59 @@
+#include "aos/vision/blob/codec.h"
+
+namespace aos {
+namespace vision {
+
+size_t CalculateSize(const BlobList &blob_list) {
+  size_t count = Int16Codec::kSize;
+  for (const auto &blob : blob_list) {
+    count += 2 * Int16Codec::kSize;
+    for (int i = 0; i < static_cast<int>(blob.ranges().size()); ++i) {
+      count +=
+          Int16Codec::kSize + 2 * Int16Codec::kSize * blob.ranges()[i].size();
+    }
+  }
+  return count;
+}
+
+void SerializeBlob(const BlobList &blob_list, char *data) {
+  data = Int16Codec::Write(data, static_cast<uint16_t>(blob_list.size()));
+  for (const auto &blob : blob_list) {
+    data = Int16Codec::Write(data, static_cast<uint16_t>(blob.min_y()));
+    data = Int16Codec::Write(data, static_cast<uint16_t>(blob.ranges().size()));
+    for (int i = 0; i < (int)blob.ranges().size(); ++i) {
+      data = Int16Codec::Write(data,
+                               static_cast<uint16_t>(blob.ranges()[i].size()));
+      for (const auto &range : blob.ranges()[i]) {
+        data = Int16Codec::Write(data, static_cast<uint16_t>(range.st));
+        data = Int16Codec::Write(data, static_cast<uint16_t>(range.ed));
+      }
+    }
+  }
+}
+
+const char *ParseBlobList(BlobList *blob_list, const char *data) {
+  int num_items = Int16Codec::Read(&data);
+  blob_list->clear();
+  blob_list->reserve(num_items);
+  for (int i = 0; i < num_items; ++i) {
+    std::vector<std::vector<ImageRange>> ranges_image;
+    int min_y = Int16Codec::Read(&data);
+    int num_ranges = Int16Codec::Read(&data);
+    ranges_image.reserve(num_ranges);
+    for (int j = 0; j < num_ranges; ++j) {
+      ranges_image.emplace_back();
+      auto &ranges = ranges_image.back();
+      int num_sub_ranges = Int16Codec::Read(&data);
+      for (int k = 0; k < num_sub_ranges; ++k) {
+        int st = Int16Codec::Read(&data);
+        int ed = Int16Codec::Read(&data);
+        ranges.emplace_back(st, ed);
+      }
+    }
+    blob_list->emplace_back(min_y, std::move(ranges_image));
+  }
+  return data;
+}
+
+}  // namespace vision
+}  // namespace aos