How to improve the sound of a videofile I have been watching the videos from the lectures with great interest, but there seems to have been some trouble with the sound; the volume level varied a lot through the recordings.
Requirements: - Mplayer - ffmpeg - the codecs (if you already can view the movie, then you only need vorbis) - a command line terminal, preferrably a GNU one... - The video files (can be downloaded from cyberone.blip.tv by pressing the export button below the streaming movie - choose the mp4 files, not the flv ones)
Step one; extract the audio from the videofile with mplayer:
mplayer -vc null -vo null -ao pcm CyberOne01.mp4
This will create a file containing the sound only called audiofile.wav
Step two; edit the audiofile Import it with a sound editing program like Audacity where you have a graphical view of the audio. Select all the areas with low volume and use the "amplify" filter on them. Select All (Ctrl-A) and use the "normalize"-filter. When you are finished with editing the audio, export it as another wav-file.
Step three; mix together the video track with the new audio track with ffmpeg
ffmpeg -i CyberOne02.mp4 -i audiofile01_normalized.wav -map 0.0 -map 1.0 CyberNormal02b.avi