Use toString() instead of value() to write to std::cout. https://github.com/Exiv2/exiv2/issues/901#issuecomment-627872855

samples/xmpparse.cpp

@@ -41,7 +41,7 @@ try {
                   << std::dec << std::setw(3)
                   << std::setfill(' ') << std::right
                   << md->count() << "  "
-                  << std::dec << md->value()
+                  << std::dec << md->toString()
                   << std::endl;
     }
     Exiv2::XmpParser::terminate();

samples/xmpparser-test.cpp

@@ -43,7 +43,7 @@ try {
                   << std::dec << std::setw(3)
                   << std::setfill(' ') << std::right
                   << md->count() << "  "
-                  << std::dec << md->value()
+                  << std::dec << md->toString()
                   << std::endl;
     }
     filename += "-new";

samples/xmpprint.cpp

@@ -55,7 +55,7 @@ int main(int argc, char** argv)
                   << std::dec << std::setw(3)
                   << std::setfill(' ') << std::right
                   << md->count() << "  "
-                  << std::dec << md->value()
+                  << std::dec << md->toString()
                   << std::endl;
       }