My soruce is an old vhs-tape with very low audio level, so I normalized it to hear the speaking persons better, but now I have terrible audio noise. is there an audio-filter to remove the noise?

Never done this in Kdenlive, but I assume there is an effect for this, just check the audio effects list.

If not, you might want to try running the audio through Audacity, I know their noise removal filter is quite good. You could then join the audio and video back up in Kdenlive

How can audio be run through Audacity or Ardouzr direclty?

You can't, moorsey didn't mean it that way, just extract your audio from the video to an uncompressed format, run it through Audacity, and drop it back into kdenlive as a second audio track?

Thanks that's the way I am doing it. THis means you have to cut before and at the end you export and import the audio. Bad luck, if you forgot something to cut, than the audio export and import starts again.

sorry I don't quite follow you, currently do you use kdenlive to extract audio from the edit? It's simple to do the audio extract from the source video files with ffmpeg or similar on the CLI or batch script outside of kdenlive, process that in Audacity and then import the 'cleaned' audio into kdenlive complete as a source clip, to sync with the unedited video stream?

But have you also investigated the LADSPA plugins, there may well be suitable filters already available within kdenlive to do the job.

Audio edit from the source isn't that easy. I have hundreds of small source clips, which have been cut automatically be scene-detection.

it depends what kind of noise you are trying to remove, often 'noise' is at a few frequency ranges and those can be removed with a parametric equalizer or something similar. do spectrum analysis on the audio first to identify the frequency bands to reject.

http://en.wikipedia.org/wiki/Audio_filter

the other alternatice is to use ffmpeg with multiple outputs ( to demutex and then mutex the video files with something like sox run on the audio inbetween demutexing and mutexing to remove the noise.

ffmpeg -i my.file -vcodec copy my_video.file -acodec copy - | sox .....)

the - outputs the audio to stdout which can then be read by sox... you'll need to have a sample of the 'noise' for sox to do it's job.


sox can also do bandreject and other types of audio processing and the ffmpeg/sox solution is easy to batch or even do inline whilst recording in the first place.

I guess Pinguin's noise is mostly claasic tape noise. Original VHS used longitudinal audio recording at a ridiculous speed of cca 2cm/sec, so noise was high. Tape noise is quasi-white, so pure frequency domain filtering wont help much.

What could help is DNR (dynamic noise reduction), which uses signal amplitude as a filtering criterion. A frequency dependent version would be best.

However, among the zillion audio filters available in my incarnation of Kdenlive, search for "Dynamic" only returns a "Dynamic sledgehammer" :-) Not sure what that is, not too optimistic...

@oliverthered, at this point you've been a forum member for 10 hours and already dug up a dead thread from a year and a half ago, what's the point in that. Not a good start. :-)

I had a similar problem but managed to improve the audio quality by using a low pass filter since the noise was high frequency.

So, if anyone finds this post and has a similar noise (a water fountain created mine), definitely try this.