Reduce background noise and optimize the speech from an audio clip using ffmpeg












21















I extract audio clips from a video file for speech recognition. These videos come from mobile/other handmade devices and hence contain a lot of noise. I want to reduce the background noise of the audio so that the speech that I relay to my speech recognition engine is clear. I am using ffmpeg to do all of this stuff, but am stuck at the noise reduction phase.



Till now I have tried following filters:



ffmpeg-20140324-git-63dbba6-win64-staticbin>ffmpeg -i i nput.wav -filter_complex "highpass=f=400,lowpass=f=1800" out2.wav

ffmpeg -i i nput.wav -af "equalizer=f=1000:width_type=h:width=900:g=-10" output.wav

ffmpeg -i i nput.wav -af "bandreject=f=1200:width_type=h:width=900:g=-10" output.wav


But the results are very disappointing. My reasoning was that since speech comes under 300-3000 hz range I can filter out all other frequencies to suppress any background noise. What am I missing?



Also, I read about weiner filters that could be used for speech enhancements and found this but am not sure how to use it.










share|improve this question





























    21















    I extract audio clips from a video file for speech recognition. These videos come from mobile/other handmade devices and hence contain a lot of noise. I want to reduce the background noise of the audio so that the speech that I relay to my speech recognition engine is clear. I am using ffmpeg to do all of this stuff, but am stuck at the noise reduction phase.



    Till now I have tried following filters:



    ffmpeg-20140324-git-63dbba6-win64-staticbin>ffmpeg -i i nput.wav -filter_complex "highpass=f=400,lowpass=f=1800" out2.wav

    ffmpeg -i i nput.wav -af "equalizer=f=1000:width_type=h:width=900:g=-10" output.wav

    ffmpeg -i i nput.wav -af "bandreject=f=1200:width_type=h:width=900:g=-10" output.wav


    But the results are very disappointing. My reasoning was that since speech comes under 300-3000 hz range I can filter out all other frequencies to suppress any background noise. What am I missing?



    Also, I read about weiner filters that could be used for speech enhancements and found this but am not sure how to use it.










    share|improve this question



























      21












      21








      21


      11






      I extract audio clips from a video file for speech recognition. These videos come from mobile/other handmade devices and hence contain a lot of noise. I want to reduce the background noise of the audio so that the speech that I relay to my speech recognition engine is clear. I am using ffmpeg to do all of this stuff, but am stuck at the noise reduction phase.



      Till now I have tried following filters:



      ffmpeg-20140324-git-63dbba6-win64-staticbin>ffmpeg -i i nput.wav -filter_complex "highpass=f=400,lowpass=f=1800" out2.wav

      ffmpeg -i i nput.wav -af "equalizer=f=1000:width_type=h:width=900:g=-10" output.wav

      ffmpeg -i i nput.wav -af "bandreject=f=1200:width_type=h:width=900:g=-10" output.wav


      But the results are very disappointing. My reasoning was that since speech comes under 300-3000 hz range I can filter out all other frequencies to suppress any background noise. What am I missing?



      Also, I read about weiner filters that could be used for speech enhancements and found this but am not sure how to use it.










      share|improve this question
















      I extract audio clips from a video file for speech recognition. These videos come from mobile/other handmade devices and hence contain a lot of noise. I want to reduce the background noise of the audio so that the speech that I relay to my speech recognition engine is clear. I am using ffmpeg to do all of this stuff, but am stuck at the noise reduction phase.



      Till now I have tried following filters:



      ffmpeg-20140324-git-63dbba6-win64-staticbin>ffmpeg -i i nput.wav -filter_complex "highpass=f=400,lowpass=f=1800" out2.wav

      ffmpeg -i i nput.wav -af "equalizer=f=1000:width_type=h:width=900:g=-10" output.wav

      ffmpeg -i i nput.wav -af "bandreject=f=1200:width_type=h:width=900:g=-10" output.wav


      But the results are very disappointing. My reasoning was that since speech comes under 300-3000 hz range I can filter out all other frequencies to suppress any background noise. What am I missing?



      Also, I read about weiner filters that could be used for speech enhancements and found this but am not sure how to use it.







      audio ffmpeg noise voice speech-recognition






      share|improve this question















      share|improve this question













      share|improve this question




      share|improve this question








      edited Apr 24 '18 at 23:43









      Twisty Impersonator

      18.4k146699




      18.4k146699










      asked Mar 24 '14 at 21:43









      SudhSudh

      213125




      213125






















          3 Answers
          3






          active

          oldest

          votes


















          26














          If you are looking to isolate audible speech try combining a lowpass filter with a high pass filter. For usable audio I have noticed that filtering out 200hz and below then filter out 3000hz and above does a pretty good job of keeping usable voice audio.



          ffmpeg -i <input_file> -af "highpass=f=200, lowpass=f=3000" <output_file>


          In this example add the high pass filter first to cut the lower frequencies then use the low pass filter to cut the higher frequencies. If needed you could run your file through this more than once to clean up higher db frequencies within the cut frequency ranges.






          share|improve this answer
























          • Sorry, but this seems to do no noticeable noise reduction for me.

            – Angad
            Oct 14 '15 at 8:03











          • This works very well to reduce low level of background noise (fans, buzzing, etc) but may compromise the audio quality slightly, though that can be mitigated somewhat by applying other filters afterwards.

            – Iain Collins
            Nov 16 '16 at 5:01






          • 2





            For my case the original audio was so bad it was almost impossible to hear the voice because of some water fall noice in the background. I used the following. It is not great quality, but 1000x better than the original. -af "highpass=f=200, lowpass=f=1000"

            – Eric
            Mar 9 '17 at 22:51











          • I get some error with the above or rather, warning from ffmpeg: [Parsed_highpass_0 @ 0x1524780] clipping 52 times. Please reduce gain.

            – shevy
            Jan 26 '18 at 14:10






          • 2





            You may preview your filter with ffplay <input file> -af lowpass=3000,highpass=200

            – Björn
            Mar 30 '18 at 20:52



















          6














          ffmpeg doesn't have any decent audio filters for noise-reduction built in. Audacity has a fairly effective NR filter, but it's designed to be used with 2-pass operation with a sample of just the noise, and then the input.



          The comments at the top of https://github.com/audacity/audacity/blob/master/src/effects/NoiseReduction.cpp explain how it works. (basically: suppress every FFT bin that's below the threshold. So it only lets signals through when they're louder than the noise floor in that frequency band. It can do amazing things without causing problem. It's like a band-pass filter that adapts to the signal. Since the energy of the noise is spread over the whole spectrum, only letting through a few narrow bands of it will reduce the total noise energy a LOT.



          See also Audio noise reduction: how does audacity compare to other options? for more details of how it works, and that thresholding FFT bins in one way or another is the basis of typical commercial noise-reduction filters, too.



          Porting that filter to ffmpeg would be a bit awkward. Maybe implementing it as a filter with 2 inputs, instead of a 2-pass filter, would work best. Since it only needs a few seconds to get a noise profile, it's not like it has to read through the whole file. And you SHOULDN'T feed it the whole audio stream as a noise sample, anyway. It needs to see a sample of JUST noise to set thresholds for each FFT bin.



          So yeah, a 2nd input, rather than 2pass, would make sense. But that makes it a lot less easy to use than most ffmpeg filters. You'd need a bunch of voodoo with stream split / time-range extract. And of course you need manual intervention, unless you have a noise sample in a separate file that will be appropriate for multiple input files. (one noise sample from the same mic / setup should be fine for all clips from that setup.)






          share|improve this answer

































            1














            FFmpeg now have 2 native filters to deal with noise background: afftdn and anlmdn.
            Also since some time one can use ladspa(look for noise-supressor) and/or lv2 (look for speech denoiser) filters with FFmpeg.






            share|improve this answer























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              3 Answers
              3






              active

              oldest

              votes








              3 Answers
              3






              active

              oldest

              votes









              active

              oldest

              votes






              active

              oldest

              votes









              26














              If you are looking to isolate audible speech try combining a lowpass filter with a high pass filter. For usable audio I have noticed that filtering out 200hz and below then filter out 3000hz and above does a pretty good job of keeping usable voice audio.



              ffmpeg -i <input_file> -af "highpass=f=200, lowpass=f=3000" <output_file>


              In this example add the high pass filter first to cut the lower frequencies then use the low pass filter to cut the higher frequencies. If needed you could run your file through this more than once to clean up higher db frequencies within the cut frequency ranges.






              share|improve this answer
























              • Sorry, but this seems to do no noticeable noise reduction for me.

                – Angad
                Oct 14 '15 at 8:03











              • This works very well to reduce low level of background noise (fans, buzzing, etc) but may compromise the audio quality slightly, though that can be mitigated somewhat by applying other filters afterwards.

                – Iain Collins
                Nov 16 '16 at 5:01






              • 2





                For my case the original audio was so bad it was almost impossible to hear the voice because of some water fall noice in the background. I used the following. It is not great quality, but 1000x better than the original. -af "highpass=f=200, lowpass=f=1000"

                – Eric
                Mar 9 '17 at 22:51











              • I get some error with the above or rather, warning from ffmpeg: [Parsed_highpass_0 @ 0x1524780] clipping 52 times. Please reduce gain.

                – shevy
                Jan 26 '18 at 14:10






              • 2





                You may preview your filter with ffplay <input file> -af lowpass=3000,highpass=200

                – Björn
                Mar 30 '18 at 20:52
















              26














              If you are looking to isolate audible speech try combining a lowpass filter with a high pass filter. For usable audio I have noticed that filtering out 200hz and below then filter out 3000hz and above does a pretty good job of keeping usable voice audio.



              ffmpeg -i <input_file> -af "highpass=f=200, lowpass=f=3000" <output_file>


              In this example add the high pass filter first to cut the lower frequencies then use the low pass filter to cut the higher frequencies. If needed you could run your file through this more than once to clean up higher db frequencies within the cut frequency ranges.






              share|improve this answer
























              • Sorry, but this seems to do no noticeable noise reduction for me.

                – Angad
                Oct 14 '15 at 8:03











              • This works very well to reduce low level of background noise (fans, buzzing, etc) but may compromise the audio quality slightly, though that can be mitigated somewhat by applying other filters afterwards.

                – Iain Collins
                Nov 16 '16 at 5:01






              • 2





                For my case the original audio was so bad it was almost impossible to hear the voice because of some water fall noice in the background. I used the following. It is not great quality, but 1000x better than the original. -af "highpass=f=200, lowpass=f=1000"

                – Eric
                Mar 9 '17 at 22:51











              • I get some error with the above or rather, warning from ffmpeg: [Parsed_highpass_0 @ 0x1524780] clipping 52 times. Please reduce gain.

                – shevy
                Jan 26 '18 at 14:10






              • 2





                You may preview your filter with ffplay <input file> -af lowpass=3000,highpass=200

                – Björn
                Mar 30 '18 at 20:52














              26












              26








              26







              If you are looking to isolate audible speech try combining a lowpass filter with a high pass filter. For usable audio I have noticed that filtering out 200hz and below then filter out 3000hz and above does a pretty good job of keeping usable voice audio.



              ffmpeg -i <input_file> -af "highpass=f=200, lowpass=f=3000" <output_file>


              In this example add the high pass filter first to cut the lower frequencies then use the low pass filter to cut the higher frequencies. If needed you could run your file through this more than once to clean up higher db frequencies within the cut frequency ranges.






              share|improve this answer













              If you are looking to isolate audible speech try combining a lowpass filter with a high pass filter. For usable audio I have noticed that filtering out 200hz and below then filter out 3000hz and above does a pretty good job of keeping usable voice audio.



              ffmpeg -i <input_file> -af "highpass=f=200, lowpass=f=3000" <output_file>


              In this example add the high pass filter first to cut the lower frequencies then use the low pass filter to cut the higher frequencies. If needed you could run your file through this more than once to clean up higher db frequencies within the cut frequency ranges.







              share|improve this answer












              share|improve this answer



              share|improve this answer










              answered Nov 4 '14 at 2:34









              av8rav8r

              36133




              36133













              • Sorry, but this seems to do no noticeable noise reduction for me.

                – Angad
                Oct 14 '15 at 8:03











              • This works very well to reduce low level of background noise (fans, buzzing, etc) but may compromise the audio quality slightly, though that can be mitigated somewhat by applying other filters afterwards.

                – Iain Collins
                Nov 16 '16 at 5:01






              • 2





                For my case the original audio was so bad it was almost impossible to hear the voice because of some water fall noice in the background. I used the following. It is not great quality, but 1000x better than the original. -af "highpass=f=200, lowpass=f=1000"

                – Eric
                Mar 9 '17 at 22:51











              • I get some error with the above or rather, warning from ffmpeg: [Parsed_highpass_0 @ 0x1524780] clipping 52 times. Please reduce gain.

                – shevy
                Jan 26 '18 at 14:10






              • 2





                You may preview your filter with ffplay <input file> -af lowpass=3000,highpass=200

                – Björn
                Mar 30 '18 at 20:52



















              • Sorry, but this seems to do no noticeable noise reduction for me.

                – Angad
                Oct 14 '15 at 8:03











              • This works very well to reduce low level of background noise (fans, buzzing, etc) but may compromise the audio quality slightly, though that can be mitigated somewhat by applying other filters afterwards.

                – Iain Collins
                Nov 16 '16 at 5:01






              • 2





                For my case the original audio was so bad it was almost impossible to hear the voice because of some water fall noice in the background. I used the following. It is not great quality, but 1000x better than the original. -af "highpass=f=200, lowpass=f=1000"

                – Eric
                Mar 9 '17 at 22:51











              • I get some error with the above or rather, warning from ffmpeg: [Parsed_highpass_0 @ 0x1524780] clipping 52 times. Please reduce gain.

                – shevy
                Jan 26 '18 at 14:10






              • 2





                You may preview your filter with ffplay <input file> -af lowpass=3000,highpass=200

                – Björn
                Mar 30 '18 at 20:52

















              Sorry, but this seems to do no noticeable noise reduction for me.

              – Angad
              Oct 14 '15 at 8:03





              Sorry, but this seems to do no noticeable noise reduction for me.

              – Angad
              Oct 14 '15 at 8:03













              This works very well to reduce low level of background noise (fans, buzzing, etc) but may compromise the audio quality slightly, though that can be mitigated somewhat by applying other filters afterwards.

              – Iain Collins
              Nov 16 '16 at 5:01





              This works very well to reduce low level of background noise (fans, buzzing, etc) but may compromise the audio quality slightly, though that can be mitigated somewhat by applying other filters afterwards.

              – Iain Collins
              Nov 16 '16 at 5:01




              2




              2





              For my case the original audio was so bad it was almost impossible to hear the voice because of some water fall noice in the background. I used the following. It is not great quality, but 1000x better than the original. -af "highpass=f=200, lowpass=f=1000"

              – Eric
              Mar 9 '17 at 22:51





              For my case the original audio was so bad it was almost impossible to hear the voice because of some water fall noice in the background. I used the following. It is not great quality, but 1000x better than the original. -af "highpass=f=200, lowpass=f=1000"

              – Eric
              Mar 9 '17 at 22:51













              I get some error with the above or rather, warning from ffmpeg: [Parsed_highpass_0 @ 0x1524780] clipping 52 times. Please reduce gain.

              – shevy
              Jan 26 '18 at 14:10





              I get some error with the above or rather, warning from ffmpeg: [Parsed_highpass_0 @ 0x1524780] clipping 52 times. Please reduce gain.

              – shevy
              Jan 26 '18 at 14:10




              2




              2





              You may preview your filter with ffplay <input file> -af lowpass=3000,highpass=200

              – Björn
              Mar 30 '18 at 20:52





              You may preview your filter with ffplay <input file> -af lowpass=3000,highpass=200

              – Björn
              Mar 30 '18 at 20:52













              6














              ffmpeg doesn't have any decent audio filters for noise-reduction built in. Audacity has a fairly effective NR filter, but it's designed to be used with 2-pass operation with a sample of just the noise, and then the input.



              The comments at the top of https://github.com/audacity/audacity/blob/master/src/effects/NoiseReduction.cpp explain how it works. (basically: suppress every FFT bin that's below the threshold. So it only lets signals through when they're louder than the noise floor in that frequency band. It can do amazing things without causing problem. It's like a band-pass filter that adapts to the signal. Since the energy of the noise is spread over the whole spectrum, only letting through a few narrow bands of it will reduce the total noise energy a LOT.



              See also Audio noise reduction: how does audacity compare to other options? for more details of how it works, and that thresholding FFT bins in one way or another is the basis of typical commercial noise-reduction filters, too.



              Porting that filter to ffmpeg would be a bit awkward. Maybe implementing it as a filter with 2 inputs, instead of a 2-pass filter, would work best. Since it only needs a few seconds to get a noise profile, it's not like it has to read through the whole file. And you SHOULDN'T feed it the whole audio stream as a noise sample, anyway. It needs to see a sample of JUST noise to set thresholds for each FFT bin.



              So yeah, a 2nd input, rather than 2pass, would make sense. But that makes it a lot less easy to use than most ffmpeg filters. You'd need a bunch of voodoo with stream split / time-range extract. And of course you need manual intervention, unless you have a noise sample in a separate file that will be appropriate for multiple input files. (one noise sample from the same mic / setup should be fine for all clips from that setup.)






              share|improve this answer






























                6














                ffmpeg doesn't have any decent audio filters for noise-reduction built in. Audacity has a fairly effective NR filter, but it's designed to be used with 2-pass operation with a sample of just the noise, and then the input.



                The comments at the top of https://github.com/audacity/audacity/blob/master/src/effects/NoiseReduction.cpp explain how it works. (basically: suppress every FFT bin that's below the threshold. So it only lets signals through when they're louder than the noise floor in that frequency band. It can do amazing things without causing problem. It's like a band-pass filter that adapts to the signal. Since the energy of the noise is spread over the whole spectrum, only letting through a few narrow bands of it will reduce the total noise energy a LOT.



                See also Audio noise reduction: how does audacity compare to other options? for more details of how it works, and that thresholding FFT bins in one way or another is the basis of typical commercial noise-reduction filters, too.



                Porting that filter to ffmpeg would be a bit awkward. Maybe implementing it as a filter with 2 inputs, instead of a 2-pass filter, would work best. Since it only needs a few seconds to get a noise profile, it's not like it has to read through the whole file. And you SHOULDN'T feed it the whole audio stream as a noise sample, anyway. It needs to see a sample of JUST noise to set thresholds for each FFT bin.



                So yeah, a 2nd input, rather than 2pass, would make sense. But that makes it a lot less easy to use than most ffmpeg filters. You'd need a bunch of voodoo with stream split / time-range extract. And of course you need manual intervention, unless you have a noise sample in a separate file that will be appropriate for multiple input files. (one noise sample from the same mic / setup should be fine for all clips from that setup.)






                share|improve this answer




























                  6












                  6








                  6







                  ffmpeg doesn't have any decent audio filters for noise-reduction built in. Audacity has a fairly effective NR filter, but it's designed to be used with 2-pass operation with a sample of just the noise, and then the input.



                  The comments at the top of https://github.com/audacity/audacity/blob/master/src/effects/NoiseReduction.cpp explain how it works. (basically: suppress every FFT bin that's below the threshold. So it only lets signals through when they're louder than the noise floor in that frequency band. It can do amazing things without causing problem. It's like a band-pass filter that adapts to the signal. Since the energy of the noise is spread over the whole spectrum, only letting through a few narrow bands of it will reduce the total noise energy a LOT.



                  See also Audio noise reduction: how does audacity compare to other options? for more details of how it works, and that thresholding FFT bins in one way or another is the basis of typical commercial noise-reduction filters, too.



                  Porting that filter to ffmpeg would be a bit awkward. Maybe implementing it as a filter with 2 inputs, instead of a 2-pass filter, would work best. Since it only needs a few seconds to get a noise profile, it's not like it has to read through the whole file. And you SHOULDN'T feed it the whole audio stream as a noise sample, anyway. It needs to see a sample of JUST noise to set thresholds for each FFT bin.



                  So yeah, a 2nd input, rather than 2pass, would make sense. But that makes it a lot less easy to use than most ffmpeg filters. You'd need a bunch of voodoo with stream split / time-range extract. And of course you need manual intervention, unless you have a noise sample in a separate file that will be appropriate for multiple input files. (one noise sample from the same mic / setup should be fine for all clips from that setup.)






                  share|improve this answer















                  ffmpeg doesn't have any decent audio filters for noise-reduction built in. Audacity has a fairly effective NR filter, but it's designed to be used with 2-pass operation with a sample of just the noise, and then the input.



                  The comments at the top of https://github.com/audacity/audacity/blob/master/src/effects/NoiseReduction.cpp explain how it works. (basically: suppress every FFT bin that's below the threshold. So it only lets signals through when they're louder than the noise floor in that frequency band. It can do amazing things without causing problem. It's like a band-pass filter that adapts to the signal. Since the energy of the noise is spread over the whole spectrum, only letting through a few narrow bands of it will reduce the total noise energy a LOT.



                  See also Audio noise reduction: how does audacity compare to other options? for more details of how it works, and that thresholding FFT bins in one way or another is the basis of typical commercial noise-reduction filters, too.



                  Porting that filter to ffmpeg would be a bit awkward. Maybe implementing it as a filter with 2 inputs, instead of a 2-pass filter, would work best. Since it only needs a few seconds to get a noise profile, it's not like it has to read through the whole file. And you SHOULDN'T feed it the whole audio stream as a noise sample, anyway. It needs to see a sample of JUST noise to set thresholds for each FFT bin.



                  So yeah, a 2nd input, rather than 2pass, would make sense. But that makes it a lot less easy to use than most ffmpeg filters. You'd need a bunch of voodoo with stream split / time-range extract. And of course you need manual intervention, unless you have a noise sample in a separate file that will be appropriate for multiple input files. (one noise sample from the same mic / setup should be fine for all clips from that setup.)







                  share|improve this answer














                  share|improve this answer



                  share|improve this answer








                  edited Oct 28 '18 at 14:02

























                  answered Feb 21 '15 at 10:50









                  Peter CordesPeter Cordes

                  2,3461621




                  2,3461621























                      1














                      FFmpeg now have 2 native filters to deal with noise background: afftdn and anlmdn.
                      Also since some time one can use ladspa(look for noise-supressor) and/or lv2 (look for speech denoiser) filters with FFmpeg.






                      share|improve this answer




























                        1














                        FFmpeg now have 2 native filters to deal with noise background: afftdn and anlmdn.
                        Also since some time one can use ladspa(look for noise-supressor) and/or lv2 (look for speech denoiser) filters with FFmpeg.






                        share|improve this answer


























                          1












                          1








                          1







                          FFmpeg now have 2 native filters to deal with noise background: afftdn and anlmdn.
                          Also since some time one can use ladspa(look for noise-supressor) and/or lv2 (look for speech denoiser) filters with FFmpeg.






                          share|improve this answer













                          FFmpeg now have 2 native filters to deal with noise background: afftdn and anlmdn.
                          Also since some time one can use ladspa(look for noise-supressor) and/or lv2 (look for speech denoiser) filters with FFmpeg.







                          share|improve this answer












                          share|improve this answer



                          share|improve this answer










                          answered Jan 12 at 15:53









                          Paul B. MaholPaul B. Mahol

                          32526




                          32526






























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