Apparently not clipped mp4 shows extreme clipping after import

Audacity 3 Help Forum Windows
1

Happens with audacity on MacOS as Windows.

I record on the WindowsPC with OBS as .mkv (band, music, with two stereo-tracks) with QuickSync H.264-Encoder, audio-encoder set to FFmpeg PCM (16bit), should be WAV 16bit, at 48000Hz. It is then automatically remuxed, until the last OBS-update into a .mov-file, yesterday i updated OBS from 29.1.3 to 30.1.2 and one thing changed, the remux-result shows now as .mp4 - file.

Since this change, i cannot more import the file correctly to audacity. Although anything in the import-procedure seems to be identic, the track content is terribly amplified and it is not music, but a sort of white noise.

I can import this same mp4 - file in i-movie (mac), and the audio shows no clipping, anything is ok and i hear the music-record with much headroom (the same as always). I can import the file in the VLC-player, i hear the music, nor does it sound clipped nor does the “visualisation” there show any exeeded volume or even clipping – as always, there is more or less 11db headroom.

Now, importing the same file into audacity (Windows as MacOS), the track is completely amplified, one big, from the start to the end clipping audio-track. It´s not the music but only like loud white or pink noise.

When i work this file in i-movie (contrast, etc) and store then the result (too as mp4) and import that in audacity (Windows as MacOS), then the audio is normal (around -11db). Alas i-movie is mixing the 2 stereotracks to one, so it is not what i want to work with. However, it shows that the original mp4-file has not the audio-tracks with too much volume and clipped, it is audacity that is amplifying and changing the track while importing. I tried too to simply rename the .mp4 to .mov, i can load that to audacity, but the audio keeps ultraclipping and white noise.

I tried to find a setting for imports that i could change, but i found no setting that helped.

What is wrong with that file, or with audacity? Or what do i wrong?

Edit (01): When i import the original .mkv, the audio is as it should be – at least a workaround for the future. Alas, i erased the mkv of the mattering record, which is important to me, thus i have it only as mp4 remux (by OBS-30.1.2.).

Thus, still hoping somebody can help me: When loading this file into i-movie or the VLC-player, the audio is fully ok, but when loading into audacity, it´s completely amplified and clipping, and it is not more music, but white or pink noise.

2

For some reason, Audacity is not recognizing the audio format so it’s not getting decoded correctly. The audio in an MP4 container doesn’t have to be MP4.

VLC should be able to extract the audio so you can open it in Audacity.

extract the audio

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Hello DVDdoug. The link is onto extract an audio from DVD, not from mp4.

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It should work. Maybe the instructions aren’t good. …You know it can correctly decode and play the audio, and I know it can extract the audio so that’s why I suggested it.

I’ve only done it once or twice and I’ve never used the command line.

It’s probably going to convert the file (i.e. to WAV) not just extract it.

Media
Convert and Save
File → Add
Convert and Save
Convert
Profile - Click the drop-down arrow to select the audio format you want. “Audio CD” will give you a WAV file.
Click the wrench-tool and then Audio Codec to select change the format/parameters. (Some of the settings don’t make sense, like “bitrate” for WAV/CD but they should be ignored.)
Select your Destination, and Start.

Or, Kabuu Audio Converter may be able to extract the audio.

Or, XMedia Recode is a powerful tool that can do all kinds of things.

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Ok, thanks. With the XMedia-app, i could successfully extract both tracks from this mp4 as two wav-files, as wished, and they are ok, i could import them into audacity.

Since for the future, i can use the original mkv-file from OBS for to import the audio-tracks in audacity, this workaround with XMedia for those three records which i only have as remuxed mp4-files is sufficient.

However, if somebody from audacity can look at that strange effect and implements a solution for this problem, would be great.

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