MC7304 audio codec

Hi All!

Is there any AT command or method to read which codec is using an MC7304 Fw during a voice call?

We can make calls and record audio using USB, but we need to distinguish when voice call is performed using AMR-NB or AMR-WB (HD Call).

Many thanks.

you can refer AT!CUSTOM - DISSTACK command.
You can enable audio codec before the voice call.


Can you describe the procedure for moving voice audio via USB? Is there a tech doc on this somewhere?

you can look for audacity tool.


The doc about audacity tool on this website is gone. Google doesn’t show any results. Could you provide another reference?

Bump on request for this audacity doc. No longer on server.


Windows driver creates a new multimedia audio device and you can access to voice call audio channel selecting this device while audio play/rec. You can use free audacity tool (sourceforge), or other audio application to select this audio board, you can select directly in your own code too.

Audacity doc content is this:

Steps as followed at our end:

  1. Verify that the MC7304 is in the “sound, video and game controller” in Device Manager

  2. Open Audacity and select the MC7304 as mic and speaker

  3. After setting done in Audacity, provide these AT command in HyperTerminal to the MC7304 module:
    a) at!custom=“ISVOICEN”,1
    b) at!avsetprofile=1,0,0,0,5,0
    c) at!avsetvol=1,0,5
    d) AT! AVCFG=1, 3, 3

  4.  Establish voice call from Module to other Handset (Mobile) using ATDxxxxxxxxxxx;
  5.  Immediately Start Recording in Audacity
  6.  Speak from other end i.e. from handset for a while (1 or 2 mins) and simultaneously play an audio
  7.  Stop recording in Audacity but don’t disconnect the call.

8 ) Play the recorded audio in Audacity, so that you can hear sound on Handset.

Note: Audacity is a free open source digital audio editor and recording computer software application, available for Windows, Mac OS X, Linux and other operating systems.


Many thanks Alex,

I’ve done some tests and it seems that this command configures available codecs, but we cannot read which of them is used at active call.

We need detect for example when network doesnt support HD voice, in this case, AMR WB is enabled at modem but not selected during call setup.

Is there any command available to get this status?


Hi all
we are changing solution with sierra wirrelless 850/875 analog audio to last MC7304 with USB Audio.
Now we are using MC7304 trought soundcard - Windows sound mapper (Like is described in forum)


But we have to many problems:

1.) At start windows 7 64b sound card MC7304 isn’t accessible- Sound Mapper ERROR - MainBoard Gigabyte -> After at+cfun=1,1 soundcard is ready
(Older intel board this problem has not - but intel mainboard ended production). Problem is detected after each restart coputer shorter than 30 seconds.

2.)Sound card is accessible but sound first time not playing - indicator in sound devices control panel detecting sound. After I click recording tab sound starts!!!??? (I found command to activate this tab by command promt)

3.) When playing sound in windows - atdt xxxxxx; to my mobile phone, sound has each 1 second distortion “cracking” (i try few times ATDT ->ATH >ATDT… ussualy 2-3 call has clear sound wthout cracking)

4.) I tryed few times implemmented Voice Player/Recorder AT!AVAUDIO but AT commands described in reference manual not working. I dont know why…

We are counting MOS from recorded sound - for us is very important played/recorded clear sound…
Do you have any idea? Thanx

My firmware is SWI9X15E_04.05.23.00 r18872 CNSHZ-AR-BUILD
Windows 7 64bit

To be able to use USB audio you must update your FW. Several issues has been solved regarding USB audio. So ask you distributor for the latest FW. Should be or later.

Note that when you use AT!AVAUDIO command the files system path is in the file system of the module. It is not possible to access this file system externally.

I received firmware But some modules not support AT!AV____ commands with new firmware with messages NOT IMPLEMENTED or ERROR. (But with old firmware was AT!AV___ commands supported?) How I can select/ buy modules with correct firmware and correct voice commands?

I flashed for testing 3 modules from 4.5.23 to One is ok. But 2 modules not support voice at commands now with new . When I flash modules back on 4.5.23 voice commands are supported :cry:

Or exist some command for activate AT!AVxxxx commands? (AT!CUSTOM ISVOICEN=1 is allready set)

I had a similar issue to yours not long ago and managed to correct it.

Upgrade your device to the latest version 05 firmware and then execute the AT!RMARESET=OEM command (If you have modified some settings already i recommend running AT!NVBACKUP=2 first to save any modifications you made first)

The RMARESET command with reset your device to factory defaults. When you’re done that, execute AT!BOOTHOLD to put the device in boot and hold mode before upgrading to the 06 firmware.

When you’re done upgrading, the AT!AV__ commands should work now.

I find (for myself anyways) if i downgrade to the 04 firmware, it just throws my MC7354 into a reboot loop every 5 seconds for some reason