Generate an audio signal specified by an expression.

This source accepts in input one or more expressions (one for each channel), which are evaluated and used to generate a corresponding audio signal.

It accepts the syntax: exprs[::options]. exprs is a list of expressions separated by ":", one for each separate channel. In case the channel_layout is not specified, the selected channel layout depends on the number of provided expressions.

options is an optional sequence of key=value pairs, separated by ":".

The description of the accepted options follows.

channel_layout, c

Set the channel layout. The number of channels in the specified layout must be equal to the number of specified expressions.

duration, d

Set the minimum duration of the sourced audio. See the function av_parse_time() for the accepted format. Note that the resulting duration may be greater than the specified duration, as the generated audio is always cut at the end of a complete frame.

If not specified, or the expressed duration is negative, the audio is supposed to be generated forever.

nb_samples, n

Set the number of samples per channel per each output frame, default to 1024.

sample_rate, s

Specify the sample rate, default to 44100.

Each expression in exprs can contain the following constants:

n

number of the evaluated sample, starting from 0

t

time of the evaluated sample expressed in seconds, starting from 0

s

sample rate