Very basic version, but works

mp4_to_mp3.sh

@@ -0,0 +1,13 @@
+#/bin/bash
+
+# Works only without spaces in the titles
+
+SUFFIX=mp3
+
+for IMG_FILE in *.mp4
+do
+	#strip .mp4 from file name
+	IMG_FILE_NAME=${IMG_FILE%.*}
+	echo "avconv -i ${IMG_FILE} ${IMG_FILE_NAME}.${SUFFIX}"
+	avconv -i ${IMG_FILE} ${IMG_FILE_NAME}.${SUFFIX}
+done