user35814: I have an MKV video file with 5.1 channel audio. I want to use the third channel (FC) as AAC Audio Track 1 (with language label Malayalam), the whole audio file copied as Audio Track 2  (also with language label Malayalam), and save the video as MKV. I don't want to reencode the video.
How can I do that?
I tried this:
ffmpeg -i "input.mkv" -filter_complex "channelsplit=channel_layout=5.1[FL][FR][FC][LFE][BL][BR]" -map '[FC]' -acodec aac -map 0 -vcodec copy "output [Background Removed].mkv"

It gave me the error:
Filter channelsplit:BR has an unconnected output


user1871: Only extract the relevant channel using channelsplit.
Use
ffmpeg -i "input.mkv" -filter_complex "channelsplit=channel_layout=5.1:channels=FC[FC]" -map '[FC]' -map 0 -c copy -c:a:0 aac "output [Background Removed].mkv"

35814: <p>I have an MKV video file with 5.1 channel audio. I want to use the third channel (FC) as AAC Audio Track 1 (with language label Malayalam), the whole audio file copied as Audio Track 2  (also with language label Malayalam), and save the video as MKV. I don't want to reencode the video.</p>
<p>How can I do that?</p>
<p>I tried this:</p>
<pre><code>ffmpeg -i &quot;input.mkv&quot; -filter_complex &quot;channelsplit=channel_layout=5.1[FL][FR][FC][LFE][BL][BR]&quot; -map '[FC]' -acodec aac -map 0 -vcodec copy &quot;output [Background Removed].mkv&quot;
</code></pre>
<p>It gave me the error:</p>
<pre><code>Filter channelsplit:BR has an unconnected output
</code></pre>
 1871: <p>Only extract the relevant channel using channelsplit.</p>
<p>Use</p>
<p><code>ffmpeg -i &quot;input.mkv&quot; -filter_complex &quot;channelsplit=channel_layout=5.1:channels=FC[FC]&quot; -map '[FC]' -map 0 -c copy -c:a:0 aac &quot;output [Background Removed].mkv&quot;</code></p>
