Video Volume Booster

Raise or lower a video's audio by a preset or a custom decibel figure, with an optional limiter. The picture is copied through untouched. No upload.

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Only the audio needs touching

A video whose sound is too quiet is a common and irritating problem, and the obvious fear is that fixing it means re-exporting the whole thing and losing quality in the picture.

It does not. A video file holds separate video and audio streams, and they can be handled independently. This tool decodes only the audio, applies the change, re-encodes only the audio, and copies the video data across byte for byte. The picture that comes out is identical to the one that went in, and the operation runs at close to file copy speed because the expensive part was never attempted.

That is also why the output keeps the same container it arrived in rather than being standardised to MP4. There is no re-encode forcing a format decision, so there is no reason to change it.

Adjusting a file

  1. Drop an MP4, MOV, M4V or WEBM onto the box. One file at a time.
  2. Choose a Volume change preset, or select custom.
  3. If you chose custom, set the decibel figure. Negative values make it quieter.
  4. Turn on the limiter if you are boosting something already reasonably loud.
  5. Run it and download the result, named after your file with a boosted suffix.

Presets multiply, the custom field uses decibels

The two ways of specifying a change are not the same units, and mixing them up is easy.

The presets are straight multiplications of the waveform. One and a half times, twice, or half. They are intuitive and coarse.

The custom field is in decibels, which is a logarithmic scale, so equal steps correspond to equal perceived changes rather than equal arithmetic ones. Doubling the amplitude is about plus 6 decibels. That is why the useful range is small: plus 20 decibels is an enormous boost, and applying it to anything but a very quiet recording will produce distortion long before it produces clarity.

If the presets are too blunt, reach for the decibel field rather than hunting for a preset between them.

The limiter and what clipping sounds like

Digital audio has a hard ceiling. Multiply a waveform until its peaks exceed that ceiling and they are chopped flat, which is heard as harsh crackling on transients rather than as extra volume. It is the characteristic sound of a boost taken too far, and it cannot be undone afterwards.

The limiter option catches those peaks and holds them just below the ceiling, with a small margin rather than sitting exactly at full scale, because some playback chains introduce a little extra level of their own.

Crucially it runs after the volume change rather than before, so it only intervenes on peaks the boost created. Applying it first would flatten the source’s own legitimate loud moments before the boost had even happened.

Leave it off for a modest boost on quiet material, where there is plenty of headroom and it will never engage. Turn it on for anything aggressive.

When another tool is the right answer

If the audio level swings wildly between sections rather than being uniformly quiet, one fixed multiplication cannot fix it and Normalize Audio is the tool that can, since it measures loudness and adjusts accordingly.

If the file is audio rather than video, Boost MP3 Volume applies the same preset and decibel logic without any of the video handling, and it is the better starting point when you are working on a soundtrack you intend to attach to a clip later rather than on a finished video. If you want the sound gone entirely, Mute Video strips it, and if you want to replace it, Add Audio to Video does that. The rest are on the video hub.

Frequently asked questions

Does the picture get re-encoded when I change the volume?

No. The picture is copied straight through untouched, because changing the volume affects only the audio and there is no reason to pay for a video encode. That keeps the operation fast and means the visual quality is exactly what it was. Only the audio track is decoded, adjusted and re-encoded.

What does the limiter do and when should I turn it on?

It catches peaks the boost pushed past what the format can represent and holds them just below full scale, leaving a small safety margin. Turn it on whenever you are raising the volume of something that was already reasonably loud, because that is when clipping happens and clipping sounds like harsh crackling rather than like loudness. It is applied after the volume change, so it only ever touches peaks the boost itself created rather than the source's own legitimate ones.

What is the range for a custom change?

Minus 20 to plus 20 decibels, clamped rather than rejected if you exceed it. Decibels are logarithmic, so plus 6 is roughly double the perceived amplitude and plus 20 is a very large boost that will bring up every hiss and rumble alongside the thing you wanted louder. Negative values quieten the audio, which is the case people forget the tool covers.

How do the presets relate to decibels?

The three presets are straight multiplications of the waveform rather than decibel figures. Fifty percent louder multiplies by one and a half, double multiplies by two, and half multiplies by a half. Doubling the amplitude is about plus 6 decibels, so if you want finer control than the presets offer, the custom field in decibels is the more precise route.

What if my video has no audio track at all?

The file is checked before anything is done, and if there is no audio stream the video is simply copied through with no audio path attempted. That is the correct outcome for a screen recording or a silent clip, since there is nothing to boost. It also means you get a valid file back rather than an error, though obviously an unchanged one.

What container and codec comes out?

The same container you put in, with the audio re-encoded at 192 kbps in whatever codec that container requires. An MP4, M4V or MOV gets AAC audio, and a WebM gets Opus, because a WebM cannot legally carry AAC. For the MP4 family the index is also moved to the front so the result starts playing before it has fully downloaded.

Can I fix audio that is too quiet in only one part of the video?

Not here. This applies one change across the whole file. If the underlying problem is that the level swings between quiet and loud sections, a normalisation pass is the better tool because it works on measured loudness rather than a fixed multiplication.

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