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I'm looking to impose a hard limit on a movie. In particular when I have earbuds in and a reasonable volume set, loud or sudden sounds (gun shot, dramatic sound effects, gun fire, etc) are loud enough to hurt. Lowering the volume makes speech and other sounds hard to hear.

Is there a third party on-the-fly solution for this, or a plug-in for VLC that I can use?

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That would be compression rather than normalization. – Hasaan Chop Mar 21 '10 at 17:44
So it is, title updated. – Josh K Mar 21 '10 at 17:50
good question. in theory you can do this under linux with PulseAudio or JACKd or even ALSA, tho it's not a simple setup. the ideal solution would allow for arbitrary signal processing (VST or similar) before outputting. – quack quixote Mar 21 '10 at 20:39
I like the response for VST plugin's on the VLC forum. "Is it possible to use a VST plugin with VLC?" "No." – Josh K Mar 21 '10 at 20:41
up vote 1 down vote accepted

I'd look at JACK. There's a source tarball for OSX on the main project's download page, and a separate OSX-specific port project called JackOSX.

JACK is a system for handling real-time, low-latency audio (and MIDI). [...] It can connect a number of different applications to an audio device, as well as allowing them to share audio between themselves. Its clients can run in their own processes (ie. as normal applications), or can they can run within the JACK server (ie. as a "plugin").

The idea here is that you'd take your audio output from, say, VLC, then run it into a compressor plugin with JACK before sending it to your audio device.

If you want to perform a real time audio processing, you will need a third party application to perform this. I used Audio Hijack.

After installing JACK, open up Audio Hijack. Make sure that you've set it up to "Hijack" the audio for a live capture.


Next setup the audio output for VLC to JACK.


VLC's output goes to Audio Hijack's input.

VLC to Audio

Audio Hijack's output goes to the system out.

Audio to Sys out

Lastly choose your filters.


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if i knew more about how to configure JACK for this i'd write up a short tutorial. hopefully someone else will come along and enlighten us! – quack quixote Mar 21 '10 at 20:51
I was going to say I have JACK, now to find a way to run it through the appropriate plugin. – Josh K Mar 21 '10 at 21:08

Audio Hijack will run VST plugins.

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That would be awesome.... If I wanted record it. O-O. I want to play a DVD and compress the audio on the fly with VLC or a third party plug-in for VLC or a standalone application for global volume. – Josh K Mar 21 '10 at 20:33
You didn't actually try it, did you? – Hasaan Chop Mar 21 '10 at 22:21
I did but it captured a lot of internal noise and sounded quite bad. Using JACK is much better and affords more options. – Josh K Mar 22 '10 at 4:56

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