--- a/doc/TFO-transform	Mon Mar 16 20:36:42 2026 +0000
+++ b/doc/TFO-transform	Thu Mar 19 04:13:45 2026 +0000
@@ -4,8 +4,8 @@
 "TFO transform" is the term adopted by Themyscira Wireless for the non-trivial
 transform on GSM codec frames called for by the TFO spec, 3GPP TS 28.062
 section C.3.2.1.1.  We have a goal of implementing TFO transform for all 3
-classic GSM codecs (FR, HR and EFR) in our Themyscira codec libraries; in the
-present release, only GSM-FR version has been implemented.
+classic GSM codecs (FR, HR and EFR) in our Themyscira codec libraries; at the
+present time, only GSM-FR and GSM-HR versions have been implemented so far.
 
 The input to this transform is the stream of received uplink frames from call
 leg A, possibly containing BFI frame gaps and SID frames if call leg A uses
@@ -95,3 +95,25 @@
 and radio interference reduction.  However, if the input to the transform is
 all good speech frames without DTX pauses, the transform does not attempt to
 apply VAD and make its own DTXd.
+
+TFO transform for HRv1
+======================
+
+This transform is implemented in libgsmhr1 in both DTXd=0 and DTXd=1
+configurations.  This feat has been achieved by factoring the Rx front end out
+of ETSI reference speech decoder, producing a common RxFE block that is then
+shared by full speech decoder and TFO transform services provided by the
+library.
+
+The following articles provide further details:
+
+HR-codec-Rx-logic	Algorithmic logic of ThemWi Rx DTX handler for GSM-HR,
+			shared between the regular speech decoder and our TFO
+			transform.
+
+HR-codec-library	This article describes the API to Themyscira libgsmhr1,
+			the library that implements the present TFO transform
+			along with other GSM-HR codec functions.
+
+HR-codec-utils		gsmhr-tfo-xfrm and gsmhr-tfo-xfrm-dc utilities will be
+			documented here.