Elgato Game Capture HD 2.0 software (and above) lets you record Live Commentary as a separate audio track.
It also lets you save Game Audio and Live Commentary audio to separate files.
Please Note: This is a Windows 10 feature only.
Separate Audio Tracks
The Game Capture HD Preferences window has additional audio options.
The "Record Live Commentary in a separate audio track" checkbox decides if separate audio tracks are stored during recording.
If this checkbox is checked, then Game Audio and Live Commentary audio will independently accessible.
The default for this setting is "Record Live Commentary in a separate audio track" turned on.
Automatic Export of Recordings with Separate Audio Tracks
For automatic file export there are 2 checkboxes in the Sharing section of the Preferences window:
1) Mute Live Commentary in exported video
2) Export Live Commentary to a separate audio file
Both options are unchecked by default.
The Mute Live Commentary in exported video option will give you a MP4 video file with only Game Audio in it.
The Export Live Commentary to a separate audio file option will create a separate M4A audio file with Live Commentary in it.
These checkboxes will affect "MP4 Original", "MP4 1080p" and "Movie Maker" exports only.
Other export actions (like "YouTube", "Facebook", etc.) will always make MP4 video files that contain the mix of Game Audio and Live Commentary, with no separate tracks.
Saving a Particular Audio Track
If you have turned on the "Record Live Commentary in a separate audio track" preference, then you can easily separate each audio track from your recording.
In the Edit section of the Elgato Game Capture HD software, right click on the Timeline of a recording, and you will see two new options:
1) Save Game Audio only
2) Save Game Live Commentary only
If a recording does not contain a certain audio track, then the corresponding options in the context menu will be greyed out.
Executing "Save Game Audio only" or "Save Live Commentary only" from the context menu will extract an audio track from the recording and store it as a new M4A audio file in the video folder.
The progress of the audio export will be shown at the bottom right corner of the Edit section:
For audio only file exports, the same naming convention is used as usual, along with a suffix added at the end ("Game Audio" or "Live Commentary").
More Information about Separate Audio Tracks
All of your recordings are listed in the Edit section of the Elgato Game Capture HD software.
After you share or export a recording, a special icon will appear in the Videos section, next to that recording.
If "Export Live Commentary to a separate audio file" is checked the MP4 video file and M4A audio file will be exported separately after the recording ends: