[hello_hello]

Originally Posted by doomleox999

So this is the log, do you see something weird?

Nothing that I can see.

-[NoImage] # detected channels: 6
-[NoImage] # detected channel positions: 3/2/0.1
-[NoImage] LoadPlugin("C:\Users\USER\MeGUI\tools\avisynth_plugin\AudioLimiter.dll")
-[NoImage] c6_stereo(ConvertAudioToFloat(last))
-[NoImage] Normalize()
-[NoImage] return last

-[NoImage] # 5.1 Channels L,R,C,LFE,SL,SR -> stereo + LFE
-[NoImage] function c6_stereo(clip a)
-[NoImage] {
-[NoImage] fl = GetChannel(a, 1)
-[NoImage] fr = GetChannel(a, 2)
-[NoImage] fc = GetChannel(a, 3)
-[NoImage] lf = GetChannel(a, 4)
-[NoImage] sl = GetChannel(a, 5)
-[NoImage] sr = GetChannel(a, 6)
-[NoImage] fl_sl = MixAudio(fl, sl, 0.2929, 0.2929)
-[NoImage] fr_sr = MixAudio(fr, sr, 0.2929, 0.2929)
-[NoImage] fc_lf = MixAudio(fc, lf, 0.2071, 0.2071)
-[NoImage] l = MixAudio(fl_sl, fc_lf, 1.0, 1.0)
-[NoImage] r = MixAudio(fr_sr, fc_lf, 1.0, 1.0)
-[NoImage] return MergeChannels(l, r)
-[NoImage] }

The first quoted section shows MeGUI is downmixing with the c6_stereo() function, followed by Normalize(), and the second quoted section shows the c6_stereo() function, which seems normal.

0.2929 means the front left and surround left channels are being downmixed with a (roughly) 10.5dB volume reduction for each. The same applies to FR and SR.
0.2071 means the centre and LFE channels are being mixed together with a (roughly) 13.5dB reduction, then they're added to left and right. The upshot is, the centre and LFE channels have their volumes reduced by 3dB relative to the other channels, which is normal.

That's a fair volume reduction, but Normalize() will increase it again until the peaks are at maximum. Sometimes they're very close to maximum anyway (hence reducing the volume so much to prevent clipping when downmixing) and Normalize() will therefore not increase the volume much.

You could try importing the downmixed audio into Auidacity to see if it can be amplified without clipping, but you shouldn't be able to.

You can also try downmixing with one of the Pro Logic stereo options. They should sound the same as normal stereo but they don't include the LFE channel, which means the rest of the channels are mixed together at a slightly higher volume, and you might find the peaks are coming from a loud LFE channel, so Normalize() will have more effect without it. I never include the LFE channel when downmixing, but unfortunately there's no option to not include it when downmixing to normal stereo with MeGUI.

Originally Posted by doomleox999

Is it possible to copy a log of ffmpeg?

Add -report to the beginning of the command line and ffmpeg should save a log file.

I think it's likely ffmpeg isn't reducing the volume to prevent possible clipping (or maybe it uses Pro Logic downmixing by default?) but I've never used it for downmixing so I don't know how much the log file will tell you about it.