How to adjust audio volume of mp4 movie without altering or re-encoding the video in any way?

Man, people seem to have gotten lost in the weeds on this question. I have the exact same issue, and it's a very simple question. I don't want to reencode the video; isn't there a degredation in quality every time you re-encode? My videos are fine, but I need to equalize the volume across about a dozen videos. If I adjust the volume, reencode and export, they are also gaining in file size... and going another generation in encoding. I JUST want to adjust the volume and not re-encode. THAT'S the issue. Can it be simply done?

Sorry I didn't see your question 2 years ago. Your question makes complete sense and that's why there are tools to operate on the various streams inside a container separately. For your application, download the free ffmpeg tool. If you have homebrew, you can just "brew install ffmpeg" otherwise download it.

To reduce the audio volume to 25% without re-encoding the video stream (i.e. without loss on the video side) use:

ffmpeg -i input.mov -filter:a volume=0.25 -c:v copy output.mov

This command line says: apply filter to audio track: volume set to 25%, use video codec "copy" which makes sure nothing gets re-encoded on the video side.

Cheers,

Ammo

I figured out how to do this today out of sheer desperation.

This procedure replaces the audio track. The original video file is not re-encoded.

1. Strip the audio from the MP4 file. I uploaded the original MP4 file to http://audio-extractor.net/ and extracted the original sound file. I selected WAV, but they offer many other audio file formats.

2. Once you have the original sound file, use any audio processing software to make changes. I uploaded my file to https://auphonic.com/engine/ and had them do it for me.

3. Download MKVMerge GUI by MKVToolsNIX. Windows versions are at https://www.fosshub.com/MKVToolNix.html

4. Watch this one minute video on Youtube https://www.youtube.com/watch?v=1EkhHjn3OEA It shows you how to drag and drop the original MP4 file along with the new audio file, un-check the old audio file and reassemble the MP4 by clicking the "Start Miltiplexing" button.

NOTE: Be sure to give the output file a new name or else your original file will be over-written.

Sounds like so many steps, but it was easy and painless.

Good luck all.

Tuffy

The playback volume seems to be saved as some sort of preference for the file playback in QT 7.6.4 Pro... to test I just now

1. opened a movie from the Finder
2. The volume slider looked like this
   
3. I clicked the 'middle' of the slider yielding this
   
4. COMMAND + S = VERY quick "save"
5. close the movie
6. reopen the movie
7. slider looked and sounded like #3

In QT 7 Pro, one can 'boost' or 'impede' the sound volume in the "Properties" pane, [Audio Settings] TAB that DOES completely rewrite the file when you save it.

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to clarify... both MOV and MP4 are "containers" - not "formats". Format is a term for all the codecs used for a file in either container, e.g.,

H.264 Decoder, 426 x 240, Millions

AAC, Stereo (L R), 44.100 kHz

you're correct, it seems - MOV is quick save and MP4 wants to "save" a '.mov' in QT 7.x Pro - all things are the same, so it is perplexing to me. Maybe someone that lives and breathes QT today (rather than me, who was an early adopter when it first came out) can help shed light - there MAY be some utility, but I do not know it.

If I might ask... why are you worrying about this with just one file? I could understand a drive full of video, but one movie seems like just an academic exercise.

Having had some experience with "presentation" consulting, let me then suggest that you merely leave the video itself alone and precede its presentation with a statement to the effect of

Tuffy Nicolas wrote:

This e reason it's crucial to video, preserved it unchanged, is one that it's a video of a rare natural phenomenon that was captured by chance. -- so can't be replicated. It's an "important" video and viewers will demand to see it as captured, It has not been altered in any way. The volume is VERY loud, so you may wish to turn it down some!

Still seeking an answer!

👿 I am not trying to be a smart a**, it seems that anything you do WILL alter it in some fashion, if only by merely changing the modification date of the file - so since your goal is now plain ? ? ? ? ? 😎

If "best evidence" is to be preserved, my analysis of your requirements and suggested strategy is your only option

best luck, amigo

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Then the question is this... what is more important

• audio levels of irrelevant sounds
  OR
  
• "best evidence" integrity of the file

You must judge, amigo

ÇÇÇ

Since the audio track isn't related to the video track why not just delete it from the .mp4 file?

You can do that with Quicktime Player Pro and save the file. Use the Finder to change the file extension from .mov back to .mp4.

Delete the original audio and add your own. Maybe from some of the royalty free audio tracks found in iMovie or create you own with Garageband.

That app may also be used to adjust the current audio.

I give up.