Requirements self-explaination

Makefile

@@ -3,13 +3,13 @@ CXXFLAGS += -Wno-unused-result -Wno-stringop-overflow
 all: bin/snd2acm bin/acm2wav bin/wavc2snd bin/wavc2wav bin/acm2snd bin/wav2acm bin/snd2wavc bin/wav2wavc
 
 bin/snd2acm.bin: src/main-snd2acm.cpp src/snd2acm.cpp src/readers.cpp src/subband.cpp src/packer.cpp src/riffhdr.cpp src/bitstream.cpp src/unpacker.cpp src/decoder.cpp src/utils.cpp src/portable-utils.cpp
-	$(CXX) $(CXXFLAGS) $^ -o $@
+	$(CXX) $(CXXFLAGS) $^ -o $@ -lm
 
 bin/snd2acm: bin/snd2acm.bin
 	cp -f sh/snd2acm $@
 
 bin/acm2snd.bin: src/main-acm2snd.cpp src/acm2snd.cpp src/riffhdr.cpp src/readers.cpp src/unpacker.cpp src/decoder.cpp src/portable-utils.cpp
-	$(CXX) $(CXXFLAGS) $^ -o $@ -lvorbis -lvorbisfile -logg
+	$(CXX) $(CXXFLAGS) $^ -o $@ -lm -lvorbis -lvorbisfile -logg
 
 bin/acm2snd: bin/acm2snd.bin
 	cp -f sh/acm2snd $@

README.md

@@ -7,13 +7,20 @@ For DLTCEP info and chandes, see `readme.txt` of its
 
 ## Requirements
 
-You need to have `-lvorbis -lvorbisfile -logg` libraries available.
+To run any script that converts from `acm`, you should have `ogg`, `vorbis`
+and `vorbisfile` libraries in your system. Which you probably do in a desktop
+system.
+
+When in doubt, do you system equivalent of:
+`sudo apt install libogg0 libvorbis0a libvorbisfile3`
 
 To run any script that converts into `acm`, you should also have `ffmpeg`
 in your path.
 
 ## Building
 
+You need to have `-lvorbis -lvorbisfile -logg` libraries available.
+
 `make`
 
 Then you should get a set of scripts and links in `bin` that you can copy

sh/snd2acm

@@ -2,6 +2,11 @@
 
 SCRIPT_NAME="${BASH_SOURCE[0]}"
 
+if [ -z "$(which "ffmpeg")" ]; then
+    echo "Error: ffmpeg command not found."
+    exit 1
+fi
+
 if [ "${#}" != "2" ]; then
     echo "Usage: ${SCRIPT_NAME} infile outfile."
     exit 1