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I got a video who needs some delicate tweaks. In that video I recite several poems. My voice sounds too low, while the background noise is too high. If someone turns its sound at maximum to be able to hear and understand me, his ears will be hurt by the final applauses.

So, I really need to edit this video before I can make it public, but, as you can see, this task is very delicate and complicated. I was not able to find a proper solution for it while i was using Windows. Now, that I am a new Linux user, the task gets even harder. But I hope that with your help and your vast experience, I can find the right app for this.

I know that there is a list of video editing software on the wiki section of askubuntu site, but that list by itself, can't help me. I need an exact answer from someone who went trough the same problem and found the solution.

Please, take into consideration the fact that I am a newbie in Linux and I have a Gnome environment on my PC.

  • Kiloseven I'm afraid that I don't have the original file. Right now I have downloaded it from my youtube account by using a Firefox add-on, and the resulted video is an .mp4. I can't remember the original format. I've tried to compress the sound by using a program If I'm not wrong, its name was WavePad Sound Editor. I have extracted the sound from the video, and then, after editing it, I have tried to put the pieces back together. I mean, I have tried to recreate the video. But the image and the sound were not synchronized perfectly. Besides, the applauses remained a treat for the ears. – Cristiana Nicolae Dec 16 '13 at 22:56
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    Tube Enhancer is good for downloading videos and audio from YouTube. You could use 'Noise Removal' in Audacity as well - you can select and remove some of the background noise. There is a long wiki on it here, but you may be able to find more if you google it. If you want to edit video, as well, you may want to use Kdenlive. Kiloseven will not get the response unless you use @kiloseven by the way... – Wilf Dec 16 '13 at 23:00
  • @wilf Thank you! I'll check on the links. I'm not sure which one of the two apps should I use in my case. Audacity or Avidemux? For downloading videos from youtube I use NetVideoHunter Downloader addons.mozilla.org/en-US/firefox/addon/… I hope it does not affect the quality of the video. – Cristiana Nicolae Dec 16 '13 at 23:10
  • > Besides, the applause remained a treat for the ears. AS WELL THEY SHOULD. Your file format is now MP4. Within that there can be multiple different audio and video streams, as explained at en.wikipedia.org/wiki/MPEG-4_Part_14#Data_streams - and Avidemux is better for this purpose than Audacity, for Audacity is audio-only while Avidemux is video + audio. – K7AAY Dec 16 '13 at 23:18
  • @kiloseven Yes, I used a humoristic metaphor but it is the truth. And I am not the only one who says that. I have asked several close friends to review it, and all of them told me that I have to solve the sound problem because it breaks their tympanum, while the reciting force them to prick up their ears. – Cristiana Nicolae Dec 16 '13 at 23:26
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So the audio level needs to be 'compressed', that is, the loudest and the quietest volumes need to be brought closer together. That could be done manually by someone 'riding the gain' (manually adjusting the audio level, or Audacity does that automatically for audio).

However, you need to keep the audio synchronized with the video, and Audacity won't do video, so I suggest you register at the Avidemux forum and post your question there, for Avidemux is the most popular video-audio editor for Linux (based on frequency of http://SourceForge.net downloads).

There's also a list of other video+audio editors here on Video editing software options? and from the screenshot, PITIVI will also do what you need.

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  • Thank you for the information. It seems to me that my reply can't get to you because your nickname doesn't get linked. As i have told before, I can't be sure what should I use Avidemux or Audacity? I will check on the links. I am tempted to choose Avidemux, because it is after all, a video editor. But, just like you've said, I need a video editor who does what Audacity can do for sound files. – Cristiana Nicolae Dec 16 '13 at 23:19
  • It will get automatically linked in Answers anyway... – Wilf Dec 17 '13 at 9:40
  • TY for your detailed reply! – K7AAY Dec 17 '13 at 16:09
20

To get a good noise reduction we cannot simply rely on basic denoise filters, as these may not be much more than low or high pass filters which then may lead to a rather muffled result.

A better approach will be using a dedicated audio processor designed to have good noise reduction algorithms on the audio content of our video only.

To do so the following short tutorial uses Audacity for audio processing, and FFmpeg for audio extraction and rebuilding the video.

  1. Extract the audio from our video file
    To keep the original's audio encoding we need to find out what codec the audio of our video file uses. This will e.g. be displayed on the right click file Properties > Video/Audio tab. You e.g will find it is AAC or mp3 encoded. Then we can extract the audio of an mp4 file with the following command:

     ffmpeg -i infile.mp4 -acodec copy outfile.aac
    

The option -acodec copy says we do not resample audio

  1. Use Audacity's noise reduction filters:
  1. Merge audio and video again.

Again, to avoid resampling we need the option copy to just use the data as they are. The source video's audio track will be remapped to the denoised sample with the following command:

    ffmpeg -i infile.mp4 -i denoised-audio.m4a -vcodec copy -acodec copy -map 0:0 -map 1:0 denoised-video.mp4
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    In case of a webm video file with Vorbis Audio codec, in order to extract the audio, I had to run avconv -i infile.webm -vn -acodec copy outfile.ogg. This extracted the audio perfectly. Followed this post on Ubuntu Forums. – Aditya May 1 '14 at 14:02
  • When using avconv 9.20 I found that I needed to add the -vn (set video to null) argument to ensure that video wasn't output as per unix.stackexchange.com/a/170401/68885. – Tom Saleeba Jun 18 '17 at 11:05
  • ffmpeg, what a gem it is. – Natetronn Apr 19 '19 at 21:34
  • where should "-async 1" be inserted? – shmu Oct 16 at 9:37
  • @shmu: thanks for the notice. Option -async is deprecated by now. Sorry for the confusion. – Takkat Oct 17 at 10:54

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