firequalizer
Apply FIR Equalization using arbitrary frequency response.
The filter accepts the following option:
- gain
Set gain curve equation (in dB). The expression can contain variables:
- f
the evaluated frequency
- sr
sample rate
- ch
channel number, set to 0 when multichannels evaluation is disabled
- chid
channel id, see libavutil/channel_layout.h, set to the first channel id when multichannels evaluation is disabled
- chs
number of channels
- chlayout
channel_layout, see libavutil/channel_layout.h
and functions:
- gain_interpolate(f)
interpolate gain on frequency f based on gain_entry
- cubic_interpolate(f)
same as gain_interpolate, but smoother
This option is also available as command. Default is
gain_interpolate(f).- gain_entry
Set gain entry for gain_interpolate function. The expression can contain functions:
- entry(f, g)
store gain entry at frequency f with value g
This option is also available as command.
- delay
Set filter delay in seconds. Higher value means more accurate. Default is
0.01.- accuracy
Set filter accuracy in Hz. Lower value means more accurate. Default is
5.- wfunc
Set window function. Acceptable values are:
- rectangular
rectangular window, useful when gain curve is already smooth
- hann
hann window (default)
- hamming
hamming window
- blackman
blackman window
- nuttall3
3-terms continuous 1st derivative nuttall window
- mnuttall3
minimum 3-terms discontinuous nuttall window
- nuttall
4-terms continuous 1st derivative nuttall window
- bnuttall
minimum 4-terms discontinuous nuttall (blackman-nuttall) window
- bharris
blackman-harris window
- tukey
tukey window
- fixed
If enabled, use fixed number of audio samples. This improves speed when filtering with large delay. Default is disabled.
- multi
Enable multichannels evaluation on gain. Default is disabled.
- zero_phase
Enable zero phase mode by subtracting timestamp to compensate delay. Default is disabled.
- scale
Set scale used by gain. Acceptable values are:
- linlin
linear frequency, linear gain
- linlog
linear frequency, logarithmic (in dB) gain (default)
- loglin
logarithmic (in octave scale where 20 Hz is 0) frequency, linear gain
- loglog
logarithmic frequency, logarithmic gain
- dumpfile
Set file for dumping, suitable for gnuplot.
- dumpscale
Set scale for dumpfile. Acceptable values are same with scale option. Default is linlog.
- fft2
Enable 2-channel convolution using complex FFT. This improves speed significantly. Default is disabled.
- min_phase
Enable minimum phase impulse response. Default is disabled.
Examples
- lowpass at 1000 Hz:
firequalizer=gain='if(lt(f,1000), 0, -INF)'
- lowpass at 1000 Hz with gain_entry:
firequalizer=gain_entry='entry(1000,0); entry(1001, -INF)'
- custom equalization:
firequalizer=gain_entry='entry(100,0); entry(400, -4); entry(1000, -6); entry(2000, 0)'
- higher delay with zero phase to compensate delay:
firequalizer=delay=0.1:fixed=on:zero_phase=on
- lowpass on left channel, highpass on right channel:
firequalizer=gain='if(eq(chid,1), gain_interpolate(f), if(eq(chid,2), gain_interpolate(1e6+f), 0))' :gain_entry='entry(1000, 0); entry(1001,-INF); entry(1e6+1000,0)':multi=on