diff --git a/src/nal.h b/src/nal.h
index b1ca858e..6387eef7 100644
--- a/src/nal.h
+++ b/src/nal.h
@@ -13,17 +13,58 @@
 #ifndef __NAL_H
 #define __NAL_H
 
-enum { NAL_TRAIL_N    = 0, NAL_TRAIL_R    = 1,
+/*!
+ * \brief NAL unit type codes
+ * 
+ * These are the nal_unit_type codes from Table 7-1 ITU-T H.265 v1.0.
+ * The type codes have been prefixed with "NAL_".
+ */
+enum {
+  NAL_TRAIL_N = 0,
+  NAL_TRAIL_R = 1,
+  
+  NAL_TSA_N = 2,
+  NAL_TSA_R = 3,
+  
+  NAL_STSA_N = 4,
+  NAL_STSA_R = 5,
 
-       NAL_BLA_W_LP   = 16,
+  NAL_RADL_N = 6,
+  NAL_RADL_R = 7,
 
-       NAL_IDR_W_RADL = 19, NAL_IDR_N_LP   = 10,
+  NAL_RASL_N = 8,
+  NAL_RASL_R = 9,
 
-       NAL_RSV_IRAP_VCL23 = 23,
+  // Reserved RSV_VCL_ N/R 10-15
 
-       /* Parameter sets */       
-       NAL_VID_PARAMETER_SET = 32, NAL_SEQ_PARAMETER_SET = 33, NAL_PIC_PARAMETER_SET = 34,
-       NAL_SUFFIT_SEI_NUT = 40
+  NAL_BLA_W_LP = 16,
+  NAL_BLA_W_RADL = 17,
+  NAL_BLA_N_LP = 18,
+
+  NAL_IDR_W_RADL = 19,
+  NAL_IDR_N_LP = 20,
+
+  NAL_CRA_NUT = 21,
+
+  // Reserved RSV_IRAP_VCL 22-23
+  NAL_RSV_IRAP_VCL23 = 23,
+
+  // Reserved RSV_VCL 24-31
+  
+  NAL_VID_PARAMETER_SET = 32,
+  NAL_SEQ_PARAMETER_SET = 33,
+  NAL_PIC_PARAMETER_SET = 34,
+
+  AUD_NUT = 35,
+  EOS_NUT = 36,
+  EOB_NUT = 37,
+  FD_NUT = 38,
+
+  PREFIX_SEI_NUT = 39,
+  NAL_SUFFIT_SEI_NUT = 40,
+
+  // Reserved RSV_NVCL 41-47
+  // Unspecified UNSPEC 48-63
 };
 
 void nal_write(FILE* output, uint8_t* buffer, uint32_t buffer_len, uint8_t nal_ref, uint8_t nal_type, uint8_t temporal_id);