Changes between Version 31 and Version 32 of AudioChannelManipulation

Timestamp:

Feb 5, 2019, 11:58:22 PM (7 years ago)

Author:

llogan

Comment:

added some join and channelmap examples

AudioChannelManipulation

@@ -114 +114 @@
 [[Image(2mono_stereo.png, nolink)]]
 
-Create a stereo output from two mono inputs with the [https://ffmpeg.org/ffmpeg-filters.html#amerge amerge] audio filter:
+Create a stereo output from two mono inputs with the [https://ffmpeg.org/ffmpeg-filters.html#join join] audio filter:
+
+{{{
+ffmpeg -i left.mp3 -i right.mp3 -filter_complex "[0:a][1:a]join=inputs=2:channel_layout=stereo[a]" -map "[a]" output.mp3
+}}}
+
+or the [https://ffmpeg.org/ffmpeg-filters.html#amerge amerge] audio filter:
 
 {{{
@@ -124 +130 @@
 [[Image(6mono_5point1.png, nolink)]]
 
-Combine 6 mono inputs into one 5.1 (6 channel) output with the [https://ffmpeg.org/ffmpeg-filters.html#amerge amerge] audio filter:
+Combine 6 mono inputs into one 5.1 (6 channel) output with the [https://ffmpeg.org/ffmpeg-filters.html#join join] audio filter:
+
+{{{
+ffmpeg -i front_left.wav -i front_right.wav -i front_center.wav -i lfe.wav -i back_left.wav -i back_right.wav \
+-filter_complex "[0:a][1:a][2:a][3:a][4:a][5:a]join=inputs=6:channel_layout=5.1[a]" -map "[a]" output.wav
+}}}
+
+The join audio filter also allows you to manually choose the layout:
+
+{{{
+ffmpeg -i front_left.wav -i front_right.wav -i front_center.wav -i lfe.wav -i back_left.wav -i back_right.wav \
+-filter_complex "[0:a][1:a][2:a][3:a][4:a][5:a]join=inputs=6:channel_layout=5.1:map=0.0-FL|1.0-FR|2.0-FC|3.0-LFE|4.0-BL|5.0-BR[a]" -map "[a]" output.wav
+}}}
+
+Another method using the [https://ffmpeg.org/ffmpeg-filters.html#amerge amerge] audio filter which is somewhat less flexible than the join filter shown above:
 
 {{{
@@ -131 +151 @@
 }}}
 
-All inputs must have the same sample rate and format. If inputs do not have the same duration the output will stop with the shortest.
+With amerge all inputs must have the same sample rate and format. If inputs do not have the same duration the output will stop with the shortest.
 
 = 5.1 → 6 × mono =
@@ -150 +170 @@
 }}}
 
-
 = 5.1 → stereo =
 
@@ -228 +247 @@
 [[Image(switch_stereo_channels.png, nolink)]]
 
-Switch left channel to right and right channel to left with the [https://ffmpeg.org/ffmpeg-filters.html#pan pan] audio filer:
+Switch left channel to right and right channel to left with the [https://ffmpeg.org/ffmpeg-filters.html#channelmap channelmap] audio filter:
+
+{{{
+ffmpeg -i stereo.mp3 -filter_complex "channelmap=map=FL-FR|FR-FL:channel_layout=stereo" output.mp3
+}}}
+
+Or with the [https://ffmpeg.org/ffmpeg-filters.html#pan pan] audio filer:
 
 {{{
@@ -240 +265 @@
 }}}
 
-----
-
 = Mute a channel =
 
@@ -256 +279 @@
 {{{
 ffmpeg -i stereo.wav -map_channel -1 -map_channel 0.0.1 output.wav
+}}}
+
+= Remap channels =
+
+The [https://ffmpeg.org/ffmpeg-filters.html#channelmap channelmap] audio filter can re-arrange the channel layout. For example, to switch the FL and FR channels in a 5.1 input:
+
+{{{
+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
 }}}