diff --git a/libertem_qd_mpx/src/background_thread.rs b/libertem_qd_mpx/src/background_thread.rs
index 3dbe577e..12bbe1cd 100644
--- a/libertem_qd_mpx/src/background_thread.rs
+++ b/libertem_qd_mpx/src/background_thread.rs
@@ -11,7 +11,7 @@ use common::{
     frame_stack::{FrameMeta, FrameStackForWriting, FrameStackWriteError, WriteGuard},
     generic_connection::AcquisitionConfig,
     tcp::{self, ReadExactError},
-    utils::{num_from_byte_slice, three_way_shift, NumParseError},
+    utils::{num_from_byte_slice, NumParseError},
 };
 use ipc_test::{slab::ShmError, SharedSlabAllocator};
 use log::{debug, error, info, trace, warn};
@@ -537,6 +537,16 @@ fn passive_acquisition(
         // hardware trigger):
         let first_frame_meta: QdFrameMeta = peek_first_frame_header(&mut stream, to_thread_r)?;
 
+        match &first_frame_meta.mq1a {
+            None => warn!("missing mq1a header, this will probably cause issues in raw mode!"),
+            Some(mq1a) => match mq1a.counter_depth {
+                1 | 6 | 12 | 24 => {}
+                _ => {
+                    warn!("unknown counter depth {}", mq1a.counter_depth);
+                }
+            },
+        }
+
         acquisition(
             to_thread_r,
             from_thread_s,
diff --git a/libertem_qd_mpx/src/base_types.rs b/libertem_qd_mpx/src/base_types.rs
index 2fe762e0..ac3457ba 100644
--- a/libertem_qd_mpx/src/base_types.rs
+++ b/libertem_qd_mpx/src/base_types.rs
@@ -415,7 +415,30 @@ impl FrameMeta for QdFrameMeta {
     }
 
     fn get_dtype_string(&self) -> String {
-        todo!()
+        let raw_dtype = if let Some(mq1a) = &self.mq1a {
+            match mq1a.counter_depth {
+                1 | 6 => "uint8",
+                12 => "uint16",
+                24 => "uint32",
+                _ => {
+                    // FIXME: unknown counter depth; can't determine raw dtype!
+                    "uint8"
+                }
+            }
+        } else {
+            // FIXME: not really correct, but we can't know the data type if the
+            // detector doesn't include the mq1a header!
+            "uint8"
+        };
+
+        match self.dtype {
+            DType::U01 | DType::U08 => "uint8",
+            DType::U16 => "uint16",
+            DType::U32 => "uint32",
+            DType::U64 => "uint64",
+            DType::R64 => raw_dtype,
+        }
+        .to_owned()
     }
 
     fn get_shape(&self) -> (u64, u64) {