Edit snippets of audio out of a video file--simple way?

[hech54]

You will be re-encoding the audio.
The easiest way I know is to demux the audio from the video(obviously), load it into Goldwave(simply because I know EXACTLY how to do this in Goldwave), select the portion of audio and take the volume level down to zero, move on to the next section of audio and repeat.
SAVE AS.....have GoldWave output the file to exactly match the original audio, making sure you pay close attention to whether the original audio was 44.1 or 48k.
Remux the audio back to the video.....I use AviDemux.
Select COPY on both audio and video in AviDemux and output your new video.
You will need to pay close attention to what container you need(also matching the original video - Avi, MPEG-PS, etc etc).

** You can also just save the Goldwave audio output as straight 44.1 WAV audio and let Avidemux re-encode your audio
for you. I use this method VERY often, again making sure to mind the 44.1 vs. 48k part.

[gumbygum]

I want to delete small pieces of audio from my video files without having to re-encode the video, and preferably without re-encoding the audio.

Is there a utility that lets me just delete a small segment of audio, maybe 5 seconds, and replace it with silence? Without losing audio synch on the rest of the video? Or, perhaps, replace it with audio of exact same length copied from elsewhere on the video?

I stress simple because I want to do this on hundreds of videos and don't have the time for anything complicated.

But if there's no simple way, can anyone suggest the correct software (preferably freeware) to do this?

Thanks for any suggestions.

[Baldrick]

Please don't cross post...then it will look like this....

[gumbygum]

Why did my post move to the number two position in the thread? I didn't cross-post. I posted the thread in the Audio forum and then thought it might be better answered in the Editing forum, so I tried to delete the thread from Audio but couldn't delete it. Instead I edited it to say that I was moving it to the Editing forum.

So I posted it again to Editing and now I find that instead of my original post being the number one post in the forum, it is number two, and number one is a reply to my post. This will make it very difficult to get any replies. Why did this happen?

I'm sorry if I sinned by moving the thread, but still, this shouldn't be happening.

[gumbygum]

hech54, thanks for that. I wish there was a simpler way, especially since I often find Avidemux to be difficult to use. I wish I could just turn the volume down to zero on those segments without getting all complicated with demuxing and stuff...

BTW, does re-encoding audio diminish its quality, same as with re-encoding video?

[Baldrick]

I moved the reply to this thread and the posts are ordered by time/postid. Next time click on the report-link if you want a thread moved...

[smrpix]

BTW, does re-encoding audio diminish its quality, same as with re-encoding video?

Sure, but if you use hech's method above, especially outputting as wav from Goldwave (Audacity also works) and keep your final muxed bitrate slightly higher than where you started, you won't notice it.

[hech54]

hech54, thanks for that. I wish there was a simpler way

The hardest part for me in this type of situation is actually finding the portion(s) of audio that I need to change.....and I'm normally only working with ~5 minute music videos.
Demuxing and remuxing takes only seconds.

[gumbygum]

thanks. I want to work with freeware so don't want to use Goldwave. Would Audacity work?

The idea that I have to adjust the bitrate slightly when muxing the tracks back together is daunting. I don't want to have to spend laborious hours trying to get the audio to synch perfectly with the video. Since I'm not going to do anything except reduce the volume to zero on the parts I want to mute, and not change the length of the track at all, why shouldn't I be able to mux them back together perfectly without any guesswork? Don't mux/demux programs do that kind of thing automatically?

[smrpix]

Bitrate has nothing to do with timing. You may be thinking of sample rate, which can affect length if handled improperly.

[Cornucopia]

Unless I am mistaken and things have changed, there are no apps that "Smart-Render" audio (not counting mp3gain/replaygain-aware apps which use parametric playback-based adjustment), so you will HAVE to re-render your whole audio file, and if it is a compressed format you would HAVE to re-encode/re-compress.

But at least you can retain full visual quality by demuxing and remuxing.

Best to maintain ALL parameters from the original audio stream in your new stream: #channels, Samplerate, Bitdepth, (and if compressed- compression method and bitrate).

Scott

[hello_hello]

The volume of MP3s can be adjusted losslessly (without re-encoding). If the audio happened to be MP3 it'd be easy enough to open it with mp3DirectCut and mute sections of it etc. Of course you'd still need to manually extract the audio, edit it, and then remux the original file to replace the audio with the new version.

mp3DirectCut will edit AAC audio but it can't adjust the volume. However.....
It'd be more work, but you can still copy and paste when working with AAC audio, so you could (for example) find a two second section of audio you wish to mute, highlight it, delete it, then paste 2 seconds worth of silent audio in it's place. Once it's done you can re-save the AAC audio without re-encoding.
You can have multiple instances of mp3DirectCut open at a time and copy and paste from one to the other. That way one instance can open the audio you want to edit, and the second can open an encode of "silence" from which you can copy and paste into the first.

Since I'm not going to do anything except reduce the volume to zero on the parts I want to mute, and not change the length of the track at all, why shouldn't I be able to mux them back together perfectly without any guesswork? Don't mux/demux programs do that kind of thing automatically?

You'd probably need to check the original file with MediaInfo for any audio delay relative to the video, and if there is one, use the same delay when remuxing.

[gumbygum]

Bitrate has nothing to do with timing. You may be thinking of sample rate, which can affect length if handled improperly.

Thanks, I didn't know that. I don't know beans about audio.

[gumbygum]

Thanks, Cornucopia and Hello_Hello. That was very useful info.

[MaverickTse]

hech54, thanks for that. I wish there was a simpler way

The hardest part for me in this type of situation is actually finding the portion(s) of audio that I need to change.....and I'm normally only working with ~5 minute music videos.
Demuxing and remuxing takes only seconds.

Since I don't know how would you decide on which part to cut, my advice may not suit your case...
anyway,
in AviUtl, there is a "Just a sound player" (under the "Display" menu)plugin that allows you to play the next/previous few seconds of audio from the current frame, and that might helps you to work with the audio.

There is also a waveform display so that you can spot silent region.

In addition, if your source file is a typical mp4, mkv or avi, than when you D&D the file onto AviUtl's NLE panel, the audio is represented as a separated object from the image part, so saving you a manual demux step.

Then you can just split or add mid-points on the audio object and then delete/add fades/change volume/L-R balance...
When done, just export to AVI/MP4/MKV