diff --git a/include/aare/RawMasterFile.hpp b/include/aare/RawMasterFile.hpp
index a6c04e6..16eb1ca 100644
--- a/include/aare/RawMasterFile.hpp
+++ b/include/aare/RawMasterFile.hpp
@@ -103,6 +103,7 @@ class RawMasterFile {
     std::optional<size_t> m_digital_samples;
     std::optional<size_t> m_transceiver_samples;
     std::optional<size_t> m_number_of_rows;
+    std::optional<uint8_t> m_counter_mask;
 
     std::optional<ROI> m_roi;
 
@@ -133,6 +134,7 @@ class RawMasterFile {
     std::optional<size_t> digital_samples() const;
     std::optional<size_t> transceiver_samples() const;
     std::optional<size_t> number_of_rows() const;
+    std::optional<uint8_t> counter_mask() const;
 
     std::optional<ROI> roi() const;
 
diff --git a/src/RawFile.test.cpp b/src/RawFile.test.cpp
index c96a393..90daef4 100644
--- a/src/RawFile.test.cpp
+++ b/src/RawFile.test.cpp
@@ -320,4 +320,14 @@ TEST_CASE("Read file with unordered frames", "[.with-data]") {
     REQUIRE(std::filesystem::exists(fpath));
     File f(fpath);
     REQUIRE_THROWS((f.read_frame()));
+}
+
+TEST_CASE("Read Mythenframe", "[.with-data]") {
+    auto fpath = test_data_path() / "raw/newmythen03/run_2_master_1.json";
+    REQUIRE(std::filesystem::exists(fpath));
+    RawFile f(fpath);
+    REQUIRE(f.master().roi().value().width() == 2560);
+    REQUIRE(f.master().roi().value().height() == 1);
+    auto frame = f.read_frame();
+    REQUIRE(frame.cols() == 2560);
 }
\ No newline at end of file
diff --git a/src/RawMasterFile.cpp b/src/RawMasterFile.cpp
index d54a14d..243fd9b 100644
--- a/src/RawMasterFile.cpp
+++ b/src/RawMasterFile.cpp
@@ -143,6 +143,10 @@ std::optional<size_t> RawMasterFile::number_of_rows() const {
     return m_number_of_rows;
 }
 
+std::optional<uint8_t> RawMasterFile::counter_mask() const {
+    return m_counter_mask;
+}
+
 xy RawMasterFile::geometry() const { return m_geometry; }
 
 size_t RawMasterFile::n_modules() const {
@@ -313,15 +317,26 @@ void RawMasterFile::parse_json(const std::filesystem::path &fpath) {
         }
 
         // if any of the values are set update the roi
+        // TODO: doesnt it write garbage if one of them is not set
         if (tmp_roi.xmin != 4294967295 || tmp_roi.xmax != 4294967295 ||
             tmp_roi.ymin != 4294967295 || tmp_roi.ymax != 4294967295) {
             tmp_roi.xmax++;
+            // Handle Mythen
+            if (tmp_roi.ymin == -1 && tmp_roi.ymax == -1) {
+                tmp_roi.ymin = 0;
+                tmp_roi.ymax = 0;
+            }
             tmp_roi.ymax++;
             m_roi = tmp_roi;
         }
 
     } catch (const json::out_of_range &e) {
-        LOG(TLogLevel::logERROR) << e.what() << std::endl;
+        // leave the optional empty
+    }
+    try {
+        // TODO: what is the best format to handle
+        m_counter_mask = j.at("Counter Mask");
+    } catch (const json::out_of_range &e) {
         // leave the optional empty
     }