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• How to apply audio equalization using NAudio

  19 mai 2021, par Raheel Khan

  I have a WPF app that does the following :

  


  

  1. Imports video files.

  


  2. Extracts audio from the using FFmpeg.

  


  3. Resamples the audio using NAudio to conform to a Speech-to-Text engine (16kHz/16bit/Mono).

  


  4. Plays back the video for users with overlayed subtitles.

  


  5. Allows users to correct mistakes that the STT engine might have made.

  


  


  Simple resampling with NAudio :

  


  using (var reader = new WaveFileReader(fileAudioTemp.FullName))
{
    var outFormat = new WaveFormat(16000, 16, 1);
    //var outFormat = WaveFormat.CreateIeeeFloatWaveFormat(16000, 1);

    using (var resampler = new MediaFoundationResampler(reader, outFormat))
    {
        resampler.ResamplerQuality = 60; // Highest Quality in MF.
        WaveFileWriter.CreateWaveFile(fileAudio.FullName, resampler);
    }
}


  


  The problem is that these videos have extremely bad audio quality. The sound is muffled, bassy, and makes it very difficult to make out names of people, places, etc. This makes it difficult and time-consuming for users to proof the text. Please do note that the STT engine has no problem with this and is surprisingly accurate considering the quality.

  


  What I would like to do is apply an equalization present to this audio. I found that the built-in SKA preset in VLC seems to make it 'slightly' easier for users to understand what is being said.

  


  

  


  Is there a way to use either FFmpeg (Xabe) or preferably NAudio to apply such a filter ? Is so how ? I have seen many examples out there about manipulation of sound buffers but was looking for an easier way such as a preset file or parameters that could be passed into the resamplers.

  


  Any pointers would be appreciated.

  


• Adding a dynamically positioned watermark to a video via ffmpeg

  16 janvier 2013, par Lena Borieva

  I'm trying to add a watermark to a video by using ffmpeg.

  But there is one requiment which makes that very difficult to me to understand how to make it, I searched over the web of cource.

  So, I need the watermark being change its position every 20 seconds randomly by 4 corners.

  My idea is to split the video into a set of files, apply watermarks randomly to each file and combine the result into one output file. But I think it's bad way.

  Could anyone help me please ?

  Thanks,
  Sergey

• Best Overall FFMPEG FLV Quality

  23 janvier 2012, par dcolumbus

  First of all, FFMPEG has the worst documentation of all time... secondly, the syntax is so trivial that it's hard to understand what some lines are doing.

  What I'm looking to accomplish is the best quality FLV with the lowest file size. After all, isn't that everyone's goal ? These video will be streamed if that makes a difference.

  Perhaps some of you have command lines that do just this... for now, my video are no wider than 320... some are widescreen and so their heights are little smaller than 240.

  As it stands, the quality of the converted FLV's are quite poor...

  -i video.mov -ar 22050 -ab 32 -f flv -s 320x240 -aspect 4:3 video.flv