Adding "Stereo Mixer" to Windows 7 with Conexant sound card

This procedure worked for my laptop (Thinkpad E530) with a Conexant 20671 sound card, but I suspect it will work for other sound cards in the Conexant family.

I was playing with CamStudio to do a video capture of a Flash-based cartoon so that I can put it on the WDTV media player and play it on the big screen in the living room for my kids. The video capture worked brilliantly, but to do a sound capture, I needed to do some hacking.

Apparently, there was this recording device called "Stereo Mixer" that was pretty standard in the Windows XP days. This allowed you to capture whatever was played to the speaker in all its digital glory. Then under pressure from various organizations on the dark side of the force, Microsoft and soundcard makers starting disabling this wonderful feature from Windows Vista onwards.

So after much Googling around, I found out that for most sound cards, the hardware feature is still there, just not enabled on the software side. Unfortunately, to enable the "Stereo Mixer" feature is not as simple as ticking a checkbox. The procedure is frequently complicated and is different for various soundcard chipset families.

Luckily, for the Conexant sound card on my laptop, the procedure to enable the stereo mixer feature was comparatively straightforward.

First, right-click on the "Sound" icon in the system tray and select "Recording devices":

 

Then right-click on the whitespace and select "Show Disabled Devices":

Make sure you don't see a "Stereo Mix" device that was previously hidden.

Now, you need to add some entries to the registry. Create a ".reg" file with a text editor with the following content:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E96C-E325-11CE-BFC1-08002BE10318}\0000\Settings\EPattributes\EpSettings\StereoMixEnable]
"Enable"=hex:01
"MixAssocSeq"=hex:e0,e0
"MuteGainSettings"=hex:00,00

Double-click on the .reg file and enter it into the registry. Verify by firing up "regedit".

This enters the "StereoMixEnable" values under "HKLM\System\CurrentControlSet". You also need to enter this into all "ControlSet00x" subtrees under "HKLM\System". So for example, since I have "ControlSet001" and "ControlSet002" under "HKLM\System" on my machine, I edit the .reg file to:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Class\{4D36E96C-E325-11CE-BFC1-08002BE10318}\0000\Settings\EPattributes\EpSettings\StereoMixEnable]
"Enable"=hex:01
"MixAssocSeq"=hex:e0,e0
"MuteGainSettings"=hex:00,00

and double-click to enter it into the registry. I repeat for "ControlSet002".

Now reboot the machine. Then follow the previous steps to bring up the recording devices. If all goes well, you should now see a new, disabled "Stereo Mix" device in the list.

Right-click on the device and select "Enable":

Then set it to the default device by highlighting it, and selecting "Set Default".

Now, under CamStudio, I select "Options, Record audio from microphone". Since the default recording device is now "Stereo Mix", anything that is played through the speaker is now piped through to CamStudio for recording.

Mission accomplished!