Null audio source, return unprocessed audio frames. It is mainly useful as a template and to be employed in analysis / debugging tools, or as the source for filters which ignore the input data (for example the sox synth filter).

It accepts an optional sequence of key=value pairs, separated by ":".

The description of the accepted options follows.

sample_rate, s

Specify the sample rate, and defaults to 44100.

channel_layout, cl

Specify the channel layout, and can be either an integer or a string representing a channel layout. The default value of channel_layout is "stereo".

Check the channel_layout_map definition in libavutil/channel_layout.c for the mapping between strings and channel layout values.

nb_samples, n

Set the number of samples per requested frames.

Follow some examples:

#  set the sample rate to 48000 Hz and the channel layout to AV_CH_LAYOUT_MONO.
anullsrc=r=48000:cl=4

# same as
anullsrc=r=48000:cl=mono