--- a/doc/Calypso-TCH-downlink	Fri Oct 11 00:22:47 2024 +0000
+++ b/doc/Calypso-TCH-downlink	Fri Oct 11 01:54:00 2024 +0000
@@ -110,6 +110,15 @@
   counterpart to gsmefr-dlcap-dec - just use gsmfr-dlcap-gsmx followed by
   gsmfr-decode or gsmfr-decode-r.
 
+[Update: as of libgsmfr2 version 2.1.0, the above paragraph is no longer fully
+ correct.  The new version of our Rx DTX handler does look at bad traffic frames
+ (BFI=1) in order to catch those that should be handled as invalid SID rather
+ than unusable frame classification, and our original gsmx binary file format
+ is thus no longer sufficient to match the full capabilities of our library.
+ The new hexadecimal file format of TW-TS-005 Annex A solves this shortcoming -
+ but the present suite of Calypso TCH downlink utilities is currently a low
+ priority, hence no code updates are currently being worked on in this area.]
+
 * In addition to TCH DL capture files, gsmfr-dlcap-parse also accepts the hex
   output from fc-vm2hex, originating from TCS211 voice memo recordings,
   including fc-vm2hex output in the case of VM recordings made in DTX mode.