Adjusting audio gain in Avidemux
 

I see plenty of information on the web that concern using Avidemux to increase the volume of a video, if it's too quiet. It usually involves increasing the Gain value under 'Audio Filters' with either the Automatic or Manual options. But I can't get it to have any effect on my videos.

None of the information I have looked at so far gives details other than using Automatic, or selecting Manual and typing in a value. But no details as to the value to enter are given. If the Automatic option adjusts to "max -3dB", surely a minus number will make the sound softer?

The Manual option seems to have a limit of "+10" and won't go beyond this. But even with +10, there is no discernible difference to the sound volume in any video I've tried with it.

Has anyone successfully increased the volume in any of their videos using this method? And if so, how did they do it?

Thank you for any help you can give.

Hi there,

maybe that's because this magic about dB figures is familiar to audio enthusiasts.

No. In automatic mode, this number is the desired maximum level. That is, Avidemux will scan the entire audio track for the loudest spot, and then apply a constant gain to the entire track so that this loudest part will reach the level you specified.
It is common in audio processing to define 0dB as the maximum level that a system can handle without distortion, and actual levels are usually negative (because the decibel is a logarithmic unit). Therefore -3dB allows for a safety margin.

In manual gain mode, Avidemux works different: It applies the gain factor you enter directly to the audio track. And hey, +10dB is a lot - it means a factor of 10 (+3dB would be a factor of 2). Negative dB numbers result in an attenuation, so -3dB would mean to reduce the amplitudes by a factor of 2.

Yes, many times.

Auto mode, and usually -3dB as the target level.

[X] Doc CPU

The fact is, I apply this auto -3dB setting to a video clip that has a low sound level. Then I listen to it again. The volume level hasn't gone up at all. Is changing this setting meant to make the volume level go up?

Hi there,

if it was very quiet before, the volume should in fact increase noticeably.

But the way you describe what you do, I'm a bit puzzled. It appears like you just open the video file in Avidemux, set these audio processing parameters, and save the video again. Then I wonder how you're able to set these parameters, because they're only available if you chose to transcode the audio track. In "copy" mode, which is the default after opening a video file, no such operation is applied.

So to help me understand what you do, please describe it precisely, step by step. I must have missed an important detail in your procedure.

[X] Doc CPU

Having opened the file in Avidemux, I change the video format to MPEG-4 ASP (Xvid), because it's currently MP4. I then change the Audio to MP3 (lame), then click on Audio "Filters".

I change the Gain mode to Automatic. Click on OK, then Save. There's a bit of a pause before saving starts (presumably, as you said, Avidemux is scanning the audio in the whole file to get a level). But the resultant file has no noticeable difference in volume levels.

I even did manual and typed in "3.000". Still no change.

Hi there,

so you're doing this as part of an actual transcoding process. Okay, that's correct - and it's exactly what I do as well, only my original video material is usually MPEG2, but that doesn't matter.
Hmm. Weird.

Yes, exactly.

Sorry, then I'm running out of ideas. Somebody else with a good one?

[X] Doc CPU

Listen the output video
 

Sorry for necroposting, registered only for this topic, maybe will useful for newbies users.

Maybe you listen the input video and not output? There was same problem — I listened inside editor and not guessed listen from video file after save. Check it.
(and now I use Avidemux on Windows :rolleyes:, there is no "icon for input\output videos" on panel, I think she as at Linux early... :scratch:)