diff --git a/python/ftl/ftlstream.py b/python/ftl/ftlstream.py
index c3790ac5491d2e3b5c439a7539ecbd57d5694c7c..f559ac9e9aea4092873500478d1408667a63ebf0 100644
--- a/python/ftl/ftlstream.py
+++ b/python/ftl/ftlstream.py
@@ -246,6 +246,11 @@ class FTLStreamReader:
             warn("frame expected, no image from decoded")
         
         if ftl.is_float_channel(self._sp.channel):
+            # todo: old hevc format twice the width, upper/lower in left/right
+            #       half of the image
+            #
+            #       new format, see depth_convert.cu:66
+            
             raise NotImplementedError("non-color channel decoding not available")
         
         else:
diff --git a/python/ftl/libde265.py b/python/ftl/libde265.py
index 20f2f250c0c7344bc81682e15ab6bf08965318b2..94f7f8664905ea67b2a8678c02a405e893c523de 100644
--- a/python/ftl/libde265.py
+++ b/python/ftl/libde265.py
@@ -165,6 +165,7 @@ class WaitingForInput(libde265Error):
 
 class Decoder:
     def __init__(self, size, threads=_threads):
+        # todo: remove _size
         self._size = size
         self._more = ctypes.c_int()
         self._out_stride = ctypes.c_int()
@@ -189,16 +190,19 @@ class Decoder:
             size = (libde265.de265_get_image_height(de265_image, c),
                     libde265.de265_get_image_width(de265_image, c))
             
+            # todo: 10 bits per pixel for new depth format
             bpp = libde265.de265_get_bits_per_pixel(de265_image, c)
             if bpp != 8:
                 raise NotImplementedError("unsupported bits per pixel %i" % bpp)
 
             img_ptr = libde265.de265_get_image_plane(de265_image, c, self._out_stride)
             
-			# for frombuffer() no copy assumed
+            # for frombuffer() no copy assumed
             ch = np.frombuffer(img_ptr[:size[0] * size[1]], dtype=np.uint8)
             ch.shape = size
             
+            # todo: old depth format twice the width
+            #       resize all channels to match Y channel and remove self._size
             res[:,:,c] = _resize(ch, self._size)
         
         return res