Changes between Version 36 and Version 37 of AudioChannelManipulation

Timestamp:

Nov 26, 2023, 1:56:52 AM (2 years ago)

Author:

20kbirds

Comment:

Add example of arbitrary channel reduction

AudioChannelManipulation

@@ -288 +288 @@
 ffmpeg -i input.wav -filter_complex "channelmap=map=FL-FR|FR-FL|FC-FC|LFE-LFE|BL-BL|BR-BR:channel_layout=5.1" output.wav
 }}}
+
+= Arbitrary channel reduction & mapping =
+
+The [https://ffmpeg.org/ffmpeg-filters.html#pan pan] audio filter can be used to reduce the number of channels in a stream with an arbitrary mapping of input to output channels. For example, given a multi-channel WAV input file captured from an audio interface, to extract channels 3 and 4 into a stereo output any of the following commands would work:
+
+{{{
+ffmpeg -i in.wav -af 'pan=2c|c0=c2|c1=c3' out.wav
+ffmpeg -i in.wav -filter 'pan=2c|c0=c2|c1=c3' out.wav
+ffmpeg -i in.wav -filter_complex '[0:a] pan=2c|c0=c2|c1=c3' out.wav
+}}}
+
+Here, `2c` specifies that the output should have two channels, and `c0=c2` and `c1=c3` define the mapping of input to output channels. The channel numbers start at zero, thus we define (zero-based) output channels 0 and 1 to come from input channels 2 and 3, respectively.
+
+The `-filter_complex` version is only necessary when more than one filter is employed.
 
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