diff --git a/IsoLib/t35_tool/extraction/MebxMe4cExtractor.cpp b/IsoLib/t35_tool/extraction/MebxMe4cExtractor.cpp
index 3b08e73..f12800f 100644
--- a/IsoLib/t35_tool/extraction/MebxMe4cExtractor.cpp
+++ b/IsoLib/t35_tool/extraction/MebxMe4cExtractor.cpp
@@ -213,41 +213,70 @@ static MP4Err findMebxMe4cTrackReader(MP4Movie moov, const std::string &t35Prefi
 
       if(setupInfoSize > 0)
       {
-        // Parse setupInfo binary format:
-        // 1. utf8string description (null-terminated)
-        // 2. unsigned int(8) t35_identifier[] (remaining bytes)
-
-        char *setupData = (char *)*setupInfoH;
-
-        // Read null-terminated description
-        size_t descLen = 0;
-        for(size_t i = 0; i < setupInfoSize; i++)
+        // Simulate the box size and 4CC type, and the reserved and dataReferenceIndex fields
+        // to reuse ISOGetT35SampleEntryFields() and ISOGetFirstHumanReadableStreamDescription()
+        u32 it35SampleEntryHeaderSize = 4 + 4 + 6 + 2;
+        u32 it35SampleEntrySize       = it35SampleEntryHeaderSize + setupInfoSize;
+        MP4Handle it35SampleEntryH    = nullptr;
+        err                           = MP4NewHandle(it35SampleEntryHeaderSize, &it35SampleEntryH);
+        if(err)
         {
-          if(setupData[i] == '\0')
-          {
-            descLen = i;
-            break;
-          }
+          LOG_ERROR("Failed to create it35SampleEntryH handle (err={})", err);
+          MP4DisposeHandle(setupInfoH);
+          MP4DisposeHandle(read_key_value);
+          continue;
         }
-
-        std::string desc;
-        if(descLen > 0)
+        char *it35SampleEntryData = (char *)*it35SampleEntryH;
+        it35SampleEntryData[0]    = (it35SampleEntrySize >> 24) & 0xFF; // box size
+        it35SampleEntryData[1]    = (it35SampleEntrySize >> 16) & 0xFF;
+        it35SampleEntryData[2]    = (it35SampleEntrySize >> 8) & 0xFF;
+        it35SampleEntryData[3]    = (it35SampleEntrySize >> 0) & 0xFF;
+        memcpy(&it35SampleEntryData[4], keyPtr, 4);       // 'it35'
+        memset(&it35SampleEntryData[4 + 4], 0, 6);        // reserved
+        memset(&it35SampleEntryData[4 + 4 + 6], 0, 2);    // dataReferenceIndex
+        err = MP4HandleCat(it35SampleEntryH, setupInfoH); // unsigned int(8) t35_identifier_length
+                                                          // unsigned int(8) t35_identifier[]
+                                                          // Optional hrsd box
+        if(err)
         {
-          desc = std::string(setupData, descLen);
+          LOG_ERROR("Failed to write to it35SampleEntryH handle (err={})", err);
+          MP4DisposeHandle(it35SampleEntryH);
+          MP4DisposeHandle(setupInfoH);
+          MP4DisposeHandle(read_key_value);
+          continue;
         }
 
-        // Read remaining bytes as t35_identifier
-        u32 identifierStart = descLen + 1; // Skip null terminator
-        u32 identifierSize  = setupInfoSize - identifierStart;
+        u8 *identifier       = nullptr;
+        u32 identifierLength = 0;
+        char *description    = NULL;
+        MP4Err readErr =
+          ISOGetT35SampleEntryFields(it35SampleEntryH, &identifier, &identifierLength);
+        MP4Err hrsdErr = ISOGetFirstHumanReadableStreamDescription(it35SampleEntryH, &description);
+
+        MP4DisposeHandle(it35SampleEntryH);
 
         std::vector<uint8_t> identifierBytes;
-        if(identifierSize > 0 && identifierStart < setupInfoSize)
+        std::string desc;
+
+        if(readErr)
+        {
+          LOG_WARN("Could not read t35_identifier from mebx me4c it35");
+        }
+        else
         {
-          identifierBytes.assign((uint8_t *)(setupData + identifierStart),
-                                 (uint8_t *)(setupData + setupInfoSize));
+          identifierBytes.assign(identifier, identifier + identifierLength);
+          if(hrsdErr)
+          {
+            LOG_WARN("Could not read HumanReadableStreamDescription");
+          }
+          else if(description)
+          {
+            desc = description;
+          }
         }
+        free(identifier);
+        free(description);
 
-        // Convert identifier bytes to hex string
         std::string hexStr = T35Prefix::bytesToHex(identifierBytes);
 
         LOG_DEBUG("  Parsed setupInfo: description='{}', identifier={} ({} bytes)",
diff --git a/IsoLib/t35_tool/injection/MebxMe4cStrategy.cpp b/IsoLib/t35_tool/injection/MebxMe4cStrategy.cpp
index 39b5afa..9dfbdb5 100644
--- a/IsoLib/t35_tool/injection/MebxMe4cStrategy.cpp
+++ b/IsoLib/t35_tool/injection/MebxMe4cStrategy.cpp
@@ -268,51 +268,41 @@ MP4Err MebxMe4cStrategy::inject(const InjectionConfig &config, const MetadataMap
   LOG_DEBUG("Created key_value handle with it35 4CC");
 
   // Build setupInfo with T.35 prefix in binary format:
-  // 1. utf8string description (null-terminated, '\0' if empty)
+  // 1. unsigned int(8) t35_identifier_length
   // 2. unsigned int(8) t35_identifier[] (binary bytes)
   MP4Handle setupInfo = nullptr;
   {
-    const std::string &desc              = prefix.description();
-    std::vector<uint8_t> identifierBytes = prefix.toBytes();
-
-    // Calculate total size: description length + null terminator + identifier bytes
-    u32 descLen   = desc.empty() ? 1 : (u32)desc.size() + 1; // '\0' if empty, or string + '\0'
-    u32 totalSize = descLen + (u32)identifierBytes.size();
-
-    err = MP4NewHandle(totalSize, &setupInfo);
+    LOG_DEBUG("Creating temporary it35 sample entry");
+    MP4T35MetadataSampleEntryPtr it35 = nullptr;
+    u32 dataReferenceIndex            = 0; // unused
+    err = ISONewT35SampleDescription(&it35, dataReferenceIndex, prefix.toString().c_str());
     if(err)
     {
-      LOG_ERROR("Failed to create setupInfo handle (err={})", err);
-      MP4DisposeHandle(key_value);
+      LOG_ERROR("Failed to create temporary it35 sample description (err={})", err);
       return err;
     }
 
-    char *buffer = *setupInfo;
-    u32 offset   = 0;
-
-    // Write description as null-terminated UTF-8 string
-    if(desc.empty())
-    {
-      buffer[offset++] = '\0'; // Just null byte if no description
-    }
-    else
+    err = MP4NewHandle(0, &setupInfo);
+    if(err)
     {
-      memcpy(buffer + offset, desc.c_str(), desc.size());
-      offset += desc.size();
-      buffer[offset++] = '\0'; // Null terminator
+      LOG_ERROR("Failed to create setupInfo handle (err={})", err);
+      MP4DisposeHandle(key_value);
+      return err;
     }
-
-    // Write t35_identifier as binary bytes
-    if(!identifierBytes.empty())
+    err = atomPtrToSampleEntryH(setupInfo, (MP4AtomPtr)it35);
+    if(err)
     {
-      memcpy(buffer + offset, identifierBytes.data(), identifierBytes.size());
-      offset += identifierBytes.size();
+      LOG_ERROR("Failed to convert temporary it35 sample entry to  (err={})", err);
+      MP4DisposeHandle(key_value);
+      MP4DisposeHandle(setupInfo);
+      return err;
     }
-
-    LOG_DEBUG("Created setupInfo handle: description='{}' ({} bytes), identifier={} bytes",
-              desc.empty() ? "(empty)" : desc, descLen, identifierBytes.size());
   }
 
+  // Skip the box size and 'it35' type, and the reserved and dataReferenceIndex fields
+  err = MP4SetHandleOffset(setupInfo, 4 + 4 + 6 + 2);
+  if(err) return err;
+
   // Add sample entry with me4c namespace
   // For me4c namespace, desired_local_key_id must match the 4CC in key_value
   u32 desired_key_id = MP4_FOUR_CHAR_CODE('i', 't', '3', '5');
@@ -324,7 +314,7 @@ MP4Err MebxMe4cStrategy::inject(const InjectionConfig &config, const MetadataMap
                                         MP4_FOUR_CHAR_CODE('m', 'e', '4', 'c'), // me4c namespace
                                         key_value,                              // 'it35' 4CC
                                         NULL,       // locale_string (not used)
-                                        setupInfo); // T.35 prefix string
+                                        setupInfo); // T.35 prefix string and optional hrsd box
 
   MP4DisposeHandle(key_value);
   MP4DisposeHandle(setupInfo);