diff --git a/README.md b/README.md
index 5441ad2..66512fb 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,7 @@
 # muxsa
 
-muxsa (MUltipleXer for Slides and Audio): a collection of Linux tools for efficiently creating video files from presentation slides and background narration.
\ No newline at end of file
+muxsa (MUltipleXer for Slides and Audio): a collection of Linux tools for efficiently creating video files from presentation slides and background narration.
+
+## Documentation
+* [Demonstration video (a.k.a. the making of Network Security 2020)](https://nks-devel3.rus.uni-stuttgart.de/muxsa/making_of_netsec_2020.mp4)
+* [muxsa block diagram](doc/muxsa-blockdiagram.png)
diff --git a/bin/muxsa-al2fc b/bin/muxsa-al2fc
new file mode 100755
index 0000000..bc6805a
--- /dev/null
+++ b/bin/muxsa-al2fc
@@ -0,0 +1,108 @@
+#!/usr/bin/perl -w
+use warnings;
+use strict;
+
+# muxsa-al2fc
+#
+# part of muxsa, https://git-nks-public.tik.uni-stuttgart.de/edu/muxsa
+#
+# this script reads a "label track" that was exported by the
+# Audacity (https://www.audacityteam.org/) audio recoder/editor.
+# It assumes that the labels contain slide numbers.
+# It will output (to standard output) a sequence of statements that
+# can be read by the ffmpeg (https://ffmpeg.org/) concat multiplexer.
+#
+# MIT License
+# 
+# Copyright (c) 2023 Sebastian Kiesel <sebastian.kiesel@tik.uni-stuttgart.de>
+# 
+# Permission is hereby granted, free of charge, to any person obtaining a
+# copy of this software and associated documentation files (the "Software"),
+# to deal in the Software without restriction, including without limitation
+# the rights to use, copy, modify, merge, publish, distribute, sublicense,
+# and/or sell copies of the Software, and to permit persons to whom the
+# Software is furnished to do so, subject to the following conditions:
+# 
+# The above copyright notice and this permission notice shall be included
+# in all copies or substantial portions of the Software.
+# 
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+# THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
+# OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+# ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+# OTHER DEALINGS IN THE SOFTWARE.
+
+############################################################################
+
+
+sub printf_file {
+    my $slide_prefix = $ENV{'MUXSA_KVM2PNG_SLIDE_PREFIX'}//"";
+    if( $_[0] =~ /^[0-9]+$/ ){
+        printf("file '%s%04i.png'\n", $slide_prefix, $_[0]);
+    }
+    else {
+        printf("file '%s%s.png'\n", $slide_prefix, $_[0]);
+    }
+}
+
+sub printf_duration {
+    printf("duration %.6f\n", $_[0]);
+}
+
+############################################################################
+
+my @cur;
+my @prev;
+
+printf("# Beginning of ffmpeg concat sequence produced by muxsa-al2fc\n");
+
+while(<>) {
+    chomp();
+
+    # label start time, label end time, label text
+    @cur = /^(-?[0-9]+\.[0-9]+)\t(-?[0-9]+\.[0-9]+)\t(.*)$/ or next;
+
+    if(!@prev){ # no previous label -> this is the first label we read
+        if( $cur[0] != 0.0 ){
+            printf("# Warning: 1st label ts changed: %.6f to 0.0\n", $cur[0]);
+            $cur[0]=0.0;
+        }
+        @prev = @cur;
+        next;
+    }
+
+    my $duration = $cur[0] - $prev[0];
+    printf("# Label \"%s\" from %.6f to %.6f duration %.6f\n",
+        $prev[2], $prev[0], $cur[0], $duration);
+
+    while( $duration > 1.0 ){
+        printf_file($prev[2]);
+        printf_duration(1.0);
+        $duration-=1.0;
+    }
+    printf_file($prev[2]);
+    printf_duration($duration);
+
+    if( uc($cur[2]) eq "END" ){
+        printf("# END label at %.6f\n",$cur[0]);
+        # known bug in the demuxer:
+        # the last slide name has to be repeated w/o duration
+        printf_file($prev[2]);
+        printf("# End of ffmpeg concat sequence produced by muxsa-al2fc\n");
+        exit(0);
+    }
+    @prev = @cur;
+}
+
+# we have reached the end of the input file without an explicit END label
+# ASSUME that the last slide should be shown for 1 sec
+printf("# EOF but no END label. ASSUMING a duration for the last slide.\n");
+printf_file($cur[2]);
+printf_duration(1.0);
+printf_file($cur[2]);
+
+printf("# End of ffmpeg concat sequence produced by muxsa-al2fc\n");
+
+############################################################################
diff --git a/bin/muxsa-kvm2png b/bin/muxsa-kvm2png
new file mode 100755
index 0000000..9916046
--- /dev/null
+++ b/bin/muxsa-kvm2png
@@ -0,0 +1,224 @@
+#!/bin/bash
+
+# muxsa-kvm2png 
+#
+# part of muxsa, https://git-nks-public.tik.uni-stuttgart.de/edu/muxsa
+#
+# this script makes a series of screenshots from a KVM virtual machine
+# and saves them as PNG files.  It will press the PgDown key after each
+# screenshot.  Intended usage: dump a presentation (e.g., Powerpoint 
+# running in a Windows VM) into a series of PNG files, for further 
+# processing with the muxsa tool chain.
+
+# MIT License
+# 
+# Copyright (c) 2023 Sebastian Kiesel <sebastian.kiesel@tik.uni-stuttgart.de>
+# 
+# Permission is hereby granted, free of charge, to any person obtaining a
+# copy of this software and associated documentation files (the "Software"),
+# to deal in the Software without restriction, including without limitation
+# the rights to use, copy, modify, merge, publish, distribute, sublicense,
+# and/or sell copies of the Software, and to permit persons to whom the
+# Software is furnished to do so, subject to the following conditions:
+# 
+# The above copyright notice and this permission notice shall be included
+# in all copies or substantial portions of the Software.
+# 
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+# THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
+# OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+# ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+# OTHER DEALINGS IN THE SOFTWARE.
+
+############################################################################
+
+echo "This is muxsa-kvm2png."
+
+# various parameters can be set as an environment variable (export XX="y z")
+# or can be set in our RC file. Otherwise we will assign default values below.
+
+if [ -r "${HOME}/.muxsarc" ] ; then
+    echo "Found ${HOME}/.muxsarc ... will source it."
+    . "${HOME}/.muxsarc"
+fi
+
+echo "Will work with these settings:"
+
+echo "MUXSA_KVM2PNG_VM_NAME=${MUXSA_KVM2PNG_VM_NAME:="win10-office"}"
+echo "MUXSA_KVM2PNG_SIZE_X=${MUXSA_KVM2PNG_SIZE_X:="1920"}"
+echo "MUXSA_KVM2PNG_SIZE_Y=${MUXSA_KVM2PNG_SIZE_Y:="1080"}"
+echo "MUXSA_KVM2PNG_EXTRA_X=${MUXSA_KVM2PNG_EXTRA_X:="0"}"
+echo "MUXSA_KVM2PNG_EXTRA_Y=${MUXSA_KVM2PNG_EXTRA_Y:="0"}"
+echo "MUXSA_KVM2PNG_SLIDE_PREFIX=${MUXSA_KVM2PNG_SLIDE_PREFIX:=""}"
+echo "MUXSA_KVM2PNG_SLIDE_NUMBER_START=${MUXSA_KVM2PNG_SLIDE_NUMBER_START:="0"}"
+echo "MUXSA_KVM2PNG_SLIDE_NUMBER_END=${MUXSA_KVM2PNG_SLIDE_NUMBER_END:="9999"}"
+echo "MUXSA_KVM2PNG_FORCE_OVERWRITE=${MUXSA_KVM2PNG_FORCE_OVERWRITE:=""}"
+echo "MUXSA_KVM2PNG_BUGFIX_SHOOT_TWICE=${MUXSA_KVM2PNG_BUGFIX_SHOOT_TWICE:=""}"
+echo "MUXSA_KVM2PNG_SLEEP=${MUXSA_KVM2PNG_SLEEP:="3"}"
+echo "MUXSA_KVM2PNG_MD5_LAST_SLIDE=${MUXSA_KVM2PNG_MD5_LAST_SLIDE:="092eb68a91b4d2a73833f00a01dc5cb0"}"
+echo
+
+############################################################################
+
+TMP_FILE="$(mktemp -t muxsa-kvm2png-XXXXXXXXXX.ppm)"
+if [ ! -w "${TMP_FILE}" ] ; then
+    echo "Error: cannot create tmp_file. abort."
+    exit 1
+fi
+trap 'rm -f -- "${TMP_FILE}"' EXIT
+
+############################################################################
+
+muxsa-kvm2png-screenshot-to-tmp () {
+    echo "muxsa-kvm2png: screenshot ${MUXSA_KVM2PNG_VM_NAME} ${TMP_FILE}"
+    virsh -c qemu:///system "screenshot ${MUXSA_KVM2PNG_VM_NAME} ${TMP_FILE}"
+    if [ $? -ne 0 ] ; then
+        echo "muxsa-kvm2png: screenshot failed. abort."
+        exit 1
+    fi
+
+    # the first sceenshot after a resolution change is sometimes garbled
+    # workaround: save it twice
+    if [ "${MUXSA_KVM2PNG_BUGFIX_SHOOT_TWICE}" ] ; then
+        virsh -c qemu:///system \
+            "screenshot ${MUXSA_KVM2PNG_VM_NAME} ${TMP_FILE}"
+        if [ $? -ne 0 ] ; then
+            echo "muxsa-kvm2png: screenshot failed. abort."
+            exit 1
+        fi
+    fi
+
+    # get the size in pixels of the screenshot we have taken
+    # (needs identify from imagemagick), and ...
+    TMP_SZ_X=$(identify -format "%w" "${TMP_FILE}")
+    TMP_SZ_Y=$(identify -format "%h" "${TMP_FILE}")
+
+    # ... compare to desired size
+    if  [ ${TMP_SZ_X} -eq ${MUXSA_KVM2PNG_SIZE_X} -a \
+          ${TMP_SZ_Y} -eq ${MUXSA_KVM2PNG_SIZE_Y} ] ; then
+        echo "Screenshot is ${TMP_SZ_X} x ${TMP_SZ_Y} - as desired. good."
+        TMP_SZ_OK=1
+    else
+        echo "Warning: Screenshot is ${TMP_SZ_X} x ${TMP_SZ_Y} but desired"\
+            "size is ${MUXSA_KVM2PNG_SIZE_X} x ${MUXSA_KVM2PNG_SIZE_Y} ."
+        TMP_SZ_OK=""
+    fi
+}
+
+############################################################################
+
+echo "Performing a test screenshot to check image size."
+muxsa-kvm2png-screenshot-to-tmp
+if [ ! "${TMP_SZ_OK}" ] ; then
+    echo "We will try to adjust the size of the spicy window."
+    case "$(read -p "Press q [return] to abort or [return] to continue: ")" in
+        n|N|q|Q)
+            echo "muxsa-kvm2png aborted."
+            exit 1;
+            ;;
+    esac
+    xdotool search --class spicy windowsize %@ \
+        $(( ${MUXSA_KVM2PNG_SIZE_X} + ${MUXSA_KVM2PNG_EXTRA_X} )) \
+        $(( ${MUXSA_KVM2PNG_SIZE_Y} + ${MUXSA_KVM2PNG_EXTRA_Y} ))
+    sleep 5
+    echo "Performing another test screenshot to check image size."
+    muxsa-kvm2png-screenshot-to-tmp
+    if [ ! "${TMP_SZ_OK}" ] ; then
+        echo "Screenshot still does not have the desired size in pixels."
+        echo "Maybe, resizing the spicy window has failed."
+        echo "Or maybe, you need to adjust MUXSA_KVM2PNG_EXTRA_X / _Y"
+        # extra size accounts for menus of the spicy window.
+        # if the desired size is larger than the actual size, that
+        # difference has to be added to the current extra size
+        echo "Current MUXSA_KVM2PNG_EXTRA_X value: ${MUXSA_KVM2PNG_EXTRA_X}"
+        echo "Try: $(( ${MUXSA_KVM2PNG_SIZE_X} - ${TMP_SZ_X} + \
+                ${MUXSA_KVM2PNG_EXTRA_X} ))"
+        echo "Current MUXSA_KVM2PNG_EXTRA_Y value: ${MUXSA_KVM2PNG_EXTRA_Y}"
+        echo "Try: $(( ${MUXSA_KVM2PNG_SIZE_Y} - ${TMP_SZ_Y} + \
+                ${MUXSA_KVM2PNG_EXTRA_Y} ))"
+        echo "You can set these as environment variables or in ~/.muxsarc"
+        echo "muxsa-kvm2png aborted."
+        exit 1;
+    fi
+fi
+echo "Successfully took test screenshot with the right size."
+
+############################################################################
+
+cat <<EOF
+
+This is muxsa-kvm2png.
+
+Name of the virtual machine: ${MUXSA_KVM2PNG_VM_NAME}
+Screenshot size ${MUXSA_KVM2PNG_SIZE_X}x${MUXSA_KVM2PNG_SIZE_Y} verified.
+
+Please press ... and return:
+
+    q   to abort
+    y   to start taking screenshots
+    f   to send F5 to the virtual machine and start taking screenshots
+
+EOF
+
+case "$(read -t 10 -p "Answer: ")" in
+    n|N|q|Q)
+        echo "muxsa-kvm2png aborted."
+        exit 1;
+        ;;
+    y|Y)
+        ;;
+    *)
+        echo "Sending F5 to ${MUXSA_KVM2PNG_VM_NAME}"
+        virsh -c qemu:///system "send-key ${MUXSA_KVM2PNG_VM_NAME} KEY_F5"
+        sleep 3
+        ;;
+esac
+
+############################################################################
+
+SLIDE_NUMBER="${MUXSA_KVM2PNG_SLIDE_NUMBER_START:-0}"
+while true ; do
+
+    muxsa-kvm2png-screenshot-to-tmp
+    if [ ! "${TMP_SZ_OK}" ] ; then
+        echo "muxsa-kvm2png: screenshot failed. abort."
+        exit 1
+    fi
+
+    OUTFILE=$(printf "${MUXSA_KVM2PNG_SLIDE_PREFIX}%04i.png" ${SLIDE_NUMBER})
+    SLIDE_NUMBER=$(($SLIDE_NUMBER+1))
+    if [ -f "${OUTFILE}" -a ! "${MUXSA_KVM2PNG_FORCE_OVERWRITE}" ] ; then
+        echo "Outfile ${OUTFILE} exists and overwriting not allowed. abort."
+        exit 1
+    fi
+    echo "Converting and saving screenshot to ${OUTFILE}"
+    pnmtopng -force "${TMP_FILE}" > "$OUTFILE"
+    if [ $? -ne 0 ] ; then
+        echo "Converting and saving screenshot failed. abort."
+        exit 1
+    fi
+
+    if [ "${MUXSA_KVM2PNG_MD5_LAST_SLIDE}" ] ; then
+        if md5sum "${OUTFILE}" | \
+            grep -q "^${MUXSA_KVM2PNG_MD5_LAST_SLIDE}" ; then
+
+            echo "Screenshot's md5sum = MUXSA_KVM2PNG_MD5_LAST_SLIDE. end."
+            break
+        fi
+    fi
+
+    if [ "${SLIDE_NUMBER}" -gt "${MUXSA_KVM2PNG_SLIDE_NUMBER_END}" ] ; then
+        echo "Maximum slide number reached. abort."
+        exit 1
+    fi
+
+    echo "Sending PgDown and sleeping briefly"
+    virsh -c qemu:///system "send-key ${MUXSA_KVM2PNG_VM_NAME} KEY_PAGEDOWN"
+    sleep "${MUXSA_KVM2PNG_SLEEP}"
+
+done
+echo "muxsa-kvm2png finished successfully!"
+
+############################################################################
diff --git a/bin/muxsa-pngaac2mp4 b/bin/muxsa-pngaac2mp4
new file mode 100755
index 0000000..e4cb2cc
--- /dev/null
+++ b/bin/muxsa-pngaac2mp4
@@ -0,0 +1,78 @@
+#!/bin/bash
+
+# muxsa-pngaac2mp4 
+#
+# part of muxsa, https://git-nks-public.tik.uni-stuttgart.de/edu/muxsa
+#
+# this script tells ffmpeg (https://ffmpeg.org/) to read
+# a series of slides in png file format (created with muxsa-kvm2png),
+# a soundtrack.aac (recorded with audacity), and
+# a ffmpeg concat multiplexer sequence file (created with muxsa-al2fc)
+# and multiplex everything together 
+# into a mp4 video of the slideshow with background narration
+
+# MIT License
+# 
+# Copyright (c) 2023 Sebastian Kiesel <sebastian.kiesel@tik.uni-stuttgart.de>
+# 
+# Permission is hereby granted, free of charge, to any person obtaining a
+# copy of this software and associated documentation files (the "Software"),
+# to deal in the Software without restriction, including without limitation
+# the rights to use, copy, modify, merge, publish, distribute, sublicense,
+# and/or sell copies of the Software, and to permit persons to whom the
+# Software is furnished to do so, subject to the following conditions:
+# 
+# The above copyright notice and this permission notice shall be included
+# in all copies or substantial portions of the Software.
+# 
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+# THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
+# OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+# ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+# OTHER DEALINGS IN THE SOFTWARE.
+
+############################################################################
+# see https://trac.ffmpeg.org/wiki/Slideshow
+
+echo "This is muxsa-pngaac2mp4." 
+
+OUTFILE="out.mp4"
+if [ "$1" ] ; then
+    OUTFILE="$1"
+    # make sure that file ends on .mp4
+    OUTFILE="${OUTFILE%%.mp4}.mp4"
+fi
+
+if [ ! -f slides.concat ] ; then
+    echo "error: file slides.concat missing. abort."
+    echo "consider using muxsa-al2fc for creating one."
+    exit 1
+fi
+
+if [ -f soundtrack.m4a ] ; then
+    AUDIOFILE="-i soundtrack.m4a"
+    AUDIOOPTS="-c:a copy"
+else
+    if [ -f soundtrack.wav ] ; then
+        AUDIOFILE="-i soundtrack.wav"
+        AUDIOOPTS="-c:a aac -b:a 128k"
+    else
+        if [ -f audio.concat ] ; then
+            AUDIOFILE="-f concat -i audio.concat"
+            AUDIOOPTS="-c:a aac -b:a 128k"
+        else
+            echo "neither soundtrack.m4a, .wav, nor audio.concat found. abort."
+            exit 1
+        fi
+    fi
+fi
+
+ffmpeg -f concat -i slides.concat ${AUDIOFILE} \
+    -vsync cfr -vf fps=25 \
+    -c:v libx264 -preset slow -tune stillimage -crf 23 -pix_fmt yuv420p \
+    ${AUDIOOPTS} \
+    -movflags +faststart -brand mp42 "${OUTFILE}"
+
+############################################################################
diff --git a/doc/muxsa-blockdiagram.png b/doc/muxsa-blockdiagram.png
new file mode 100644
index 0000000..25af68d
Binary files /dev/null and b/doc/muxsa-blockdiagram.png differ