Generate an audio signal made of a sine wave with amplitude 1/8.
The audio signal is bit-exact.
The filter accepts the following options:
- frequency, f
-
Set the carrier frequency. Default is 440 Hz.
- beep_factor, b
-
Enable a periodic beep every second with frequency beep_factor times the carrier frequency. Default is 0, meaning the beep is disabled.
- sample_rate, r
-
Specify the sample rate, default is 44100.
- duration, d
-
Specify the duration of the generated audio stream.
- samples_per_frame
-
Set the number of samples per output frame.
The expression can contain the following constants:
- n
-
The (sequential) number of the output audio frame, starting from 0.
- pts
-
The PTS (Presentation TimeStamp) of the output audio frame, expressed in TB units.
- t
-
The PTS of the output audio frame, expressed in seconds.
- TB
-
The timebase of the output audio frames.
Default is
1024.
Examples
-
Generate a simple 440 Hz sine wave:
sine
-
Generate a 220 Hz sine wave with a 880 Hz beep each second, for 5 seconds:
sine=220:4:d=5 sine=f=220:b=4:d=5 sine=frequency=220:beep_factor=4:duration=5
-
Generate a 1 kHz sine wave following
1602,1601,1602,1601,1602NTSC pattern:sine=1000:samples_per_frame='st(0,mod(n,5)); 1602-not(not(eq(ld(0),1)+eq(ld(0),3)))'