user4654: What I want as result: a video with the English stream on the front lineout of my soundcard and a German audio stream on the rear lineout of my soundcard.
So far, I extracted the streams with: 
mkvextract tracks video.mkv 1:video.h264 2:audio.ac3
...to get the single streams from an .mkv. 
Is there a way to merge the two audio streams to the video the way I want to have it?

user2836: That depends on your video file format and possibly if you have a surround encoder.  Some file formats provide multiple audio channels that can be configured for different speakers, others rely on a Dolby encoding or similar to provide the speaker information in one audio stream.
Either use a file format that supports multiple independent audio tracks per speaker or use a Dolby (or some other system like MPEG Surround) surround encoder to encode the audio in to a single Dolby (or similar) stream that can be processed by a Dolby (or similar) receiver.
The encoding option would be the best one if you want to ensure compatibility with most players.  Encoders are available in most professional quality DVD/Bluray authoring software packages as well as for some better audio software packages.  You can alternately get a stand alone Dolby encoder, but licensing fees (1 time) for the encoder apply.

4654: <p>What I want as result: a video with the English stream on the front lineout of my soundcard and a German audio stream on the rear lineout of my soundcard.</p>

<p>So far, I extracted the streams with: </p>

<p><code>mkvextract tracks video.mkv 1:video.h264 2:audio.ac3</code></p>

<p>...to get the single streams from an .mkv. </p>

<p>Is there a way to merge the two audio streams to the video the way I want to have it?</p>
 2836: <p>That depends on your video file format and possibly if you have a surround encoder.  Some file formats provide multiple audio channels that can be configured for different speakers, others rely on a Dolby encoding or similar to provide the speaker information in one audio stream.</p>

<p>Either use a file format that supports multiple independent audio tracks per speaker or use a Dolby (or some other system like MPEG Surround) surround encoder to encode the audio in to a single Dolby (or similar) stream that can be processed by a Dolby (or similar) receiver.</p>

<p>The encoding option would be the best one if you want to ensure compatibility with most players.  Encoders are available in most professional quality DVD/Bluray authoring software packages as well as for some better audio software packages.  You can alternately get a stand alone Dolby encoder, but licensing fees (1 time) for the encoder apply.</p>
