./configure
make clean
make
make install
ldconfig

STEP 1) Download the spandsp package. You can do this from the main web site http://soft-switch.org/downloads/spandsp/. Also, you need to download 3 more files from here. They are: app_rxfax.c, app_txfax.c and apps_makefile.patch.

NOTE: For this tutorial we will use the spandsp version 0.0.2pre21

STEP 2) The installation.


STEP 3) Put the app_rxfax.c, app_txfax.c and apps_makefile.patch files in the Asterisk application directory. Usually it is /usr/src/asterisk/apps

STEP 4) Patch the Makefile. You can achieve this by typing the following command:


Remember, that you have to be in the Asterisk application directory(usually /usr/src/asterisk/apps), when you are executing the command.

STEP 5) Check your ld.so.conf file. It has to be in the /etc/ directory. If you do not have such file - make one. In the file you need to add the path to the spandsp library. By default the directory is /usr/local/lib. So if you do not have such line in your file, you have to add it manually.

STEP 6) Rebuild your Asterisk. Go to the asterisk directory (usually /usr/src/asterisk) and type the following commands:

You need a working Asterisk PBX with registered user in the sip.conf file and made extensions. Also, you need a fax machine and an ATA device.

NOTE:We will use Asterisk CVS HEAD version. Our fax machine is Brother FAX-T94. The ATA device is Grandstream HandyTone-486 - the firmware is 1.0.6.2. To learn more about the configuration of this ATA device please take a look at our tutorial

We need one registered user in the sip.conf file.

So, we have registered the user sip_fax.

Type=friend means that this user can make and receive calls. Host=dynamic means that the IP is not static but dynamic through a DHCP server. Allow=all means that the line which this user will use, could support all audio codecs. Context=test1 - this shows that this user is working with the extensions in this context of the configuration file extensions.conf.

IMPORTANT: You can send and receive faxes with spandsp only through the G.711(alaw or ulaw) codecs.

Now lets take a look at the extensions.conf file.

On the picture above you can see our extensions.conf file.

We have an extension 300. This will be the extension on which we will receive faxes. As you can see the first application is Answer. If you want to receive faxes, you have always to answer the channel by using this application. In this way the Asterisk will hear for a fax signal.

It seems that there is a problem with the hanging up after the sending of fax. So, if you try to execute the Hangup application in the extension 300 with priority 5, nothing will happen. So, the solution is to use the AbsoluteTimeout application. As argument in its brackets we have set 35, which means that after 35 seconds the execution will continue with the extension with letter T. This one will execute the Hangup application, which will hang up the channel.

Then we have the Set application. It will set the path and the name of the file, where we would like the fax to be stored. They will be set to a variable, named FAXFILE.

The name of the file is test.tif. The directory where it will be stored is /tmp/.

NOTE: Please pay attention, that you will have to allow the reading and writing in this directory.

Finally we have the extension with the RxFax application. It will allow us to send a fax from the fax machine to the Asterisk and to store it in a file. As argument in the brackets we have set only the variable ${FAXFILE}, which we have used in the Set application, to set the location and the name of the file.

Now, when somebody dials the number 300 from its fax machine and then press the start button for sending faxes. The Asterisk will answer the channel, hear the fax signal and execute the RxFax application. The fax will be stored in the file test.tif in the /tmp directory.

There are a few settings which you have to do in the ATA. Using the web interface go to the Advanced Settings.

Set the SIP Proxy Server. This is the IP address of your Asterisk Server. In our case the IP is 10.3.3.34, but in your case it could be different. For the Outbound Proxy set the same IP address (The IP address of your Asterisk).

For the SIP User ID, write the name of the user, as it is set in your sip.conf file. In our case this is sip_fax. In your case it could be different. Authenticate ID - write the same username as in the previous option. In our case again sip_fax. Authenticate Password is related with the secret setting in the sip.conf file. So here you have to write the same as you have written in the secret option for the user which you are going to use. In our example we have set for the user sip_fax, a secret=sip_fax. So for Authenticate Password, we will write again sip_fax. In your case could be different.

Do not forget, that you can send faxes through the spandsp only by using the G.711 (ulaw or alaw) codec. So, it is very important to set the preferred codecs for the Grandstream HandyTone-486 to either PCMA(alaw) or PCMU(ulaw). In our case the codecs are set to PCMU(ulaw).

The most import option which you have to set is the FaxMode. It is set to T.38(Auto Detect) by default. You have to change it to Pass-Through.

More about the configuration of the Grandstream HandyTone-486 you can learn from our tutorial

For more information about extensions.conf you can check here.
For more information about sip.conf you can check here.

This application is tested with Brother FAX-T94 fax machine and Asterisk CVS HEAD version. They are connected through Grandstream HandyTone-486 ATA (firmware 1.0.6.2).

extensions.conf
sip.conf

patching file Makefile
Hunk #1 FAILED at 55.
Hunk #2 FAILED at 93.
2 out of 2 hunks FAILED -- saving rejects to file Makefile.rej

+APPS+=$(shell if [ -f /usr/include/spandsp.h ]; then echo "app_rxfax.so app_txfax.so" ; fi)
+APPS+=$(shell if [ -f /usr/local/include/spandsp.h ]; then echo "app_rxfax.so app_txfax.so" ; fi)

and

+app_rxfax.so : app_rxfax.o
+ $(CC) $(SOLINK) -o $@ $< -lspandsp -ltiff
+
+app_txfax.so : app_txfax.o
+ $(CC) $(SOLINK) -o $@ $< -lspandsp -ltiff

The first two lines have to be added after the following line:

ifneq ($(wildcard $(CROSS_COMPILE_TARGET)/usr/local/include/osp/osp.h $(CROSS_COMPILE_TARGET)/usr/include/osp/osp.h),)
APPS+=app_osplookup.so
endif

and the next two lines after:

app_sql_odbc.so: app_sql_odbc.o
	$(CC) $(SOLINK) -o $@ $< -lodbc

[app_txfax.so]Oct 5 12:05:24 WARNING[14665]: loader.c:314 __load_resource: /usr/lib/asterisk/modules/app_txfax.so: undefined symbol: fax_set_header_info
Oct 5 12:05:24 WARNING[14665]: loader.c:543 load_modules: Loading module app_txfax.so failed!
Ouch ... error while writing audio data: : Broken pipe