I have some MKV movie files that have loud background music, effects, action and low voices that I'm constantly adjusting the volume. I wanna know how can I fix it. I'm open to suggestions, thanks. I have to say that the audio in spanish is very good, is only whith the english track for all movies.
ID : 2
Format : AAC
Format/Info : Advanced Audio Codec
Format profile : HE-AAC / LC
Codec ID : A_AAC
Duration : 2 h 50 min
Channel(s) : 2 channels
Channel positions : Front: L R
Sampling rate : 48.0 kHz / 24.0 kHz
Frame rate : 23.438 FPS (1024 spf)
Compression mode : Lossy
Language : English
Default : Yes
Forced : No
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I used to use the method I mentioned in post #22. I often found it to be a good place to start,
and often, that was all it needed. A small touch up in an audio editor was occasionally still required.
I've had this experience with more than a few mkv files -- dialog barely audible compared to everything else going on onscreen -- and I went the "hardware solution" route myself: You can get a pretty cheap USB multi-channel audio device that'll output both digital audio (for an SPDIF connection) and analog audio outputs that let you plug your headphones or speakers into the center/front channel. Makes for a much better audio experience.
I'm not sure if it's cool posting direct links, but you can search on Amazon or Ebay for "USB 5.1 audio" and you'll find a bunch of boxes that cost $15-$20 including shipping (USA) -- they pretty much all use a C-Media CM6206 chip, easy to install, good support from C-Media. I've got several of these I use for various projects at home and at work, makes for *much* improved audio. Hope this helps!
EDIT: This won't help if your audio tracks have already been muxed down into (bad) stereo from their original source, but if you're getting a bunch of mkv files with mixed-down audio tracks, I'd check with my source to see where the mess is coming from in the first place.
Last edited by ozymango; 9th Jun 2017 at 18:10.
Handbrake, for instance, there is a gain option in the audio section. When I create a portable format file (ie Blu-ray to 404p MKV) and downmix from 5.1 to 2.0 I have to make use of gain. For my personal use and preference a gain of 8 usually works out perfectly. There are rare issues where it doesn't but that's dependent on the source and some other factors. You'll need to experiment for yourself. You need to do this from the beginning, obviously, trying to fix what's broken isn't worth it.
If it's been downmixed to a AAC or MP3 aint much you can do. if you have the original audio in AC3 or DTS (like makemkv gives) then you can use eac3to to do the downmixing for you to a 2 channel file with good results. I chose this over the MEGUI or handbrake method for the very same reason. the script I use goes like such:
eac3to.exe "file.mkv" 2: "file-out.ac3" -192 -48000 -down2 -down16 -normalize
2: is the stream number it is so change it if it's a different order. if you have a ac3 or DTS file demuxed already just omit it and do like so:
eac3to.exe "file.ac3" "file-out.ac3" -192 -48000 -down2 -down16 -normalize
i use 192k as it goes all the way to 18Khz but you can change to 224k 256k etc if you want.if all else fails read the manual
FL' = FL + 0.7071 x FC + BL
FR' = FR + 0.7071 x FC + BR
I can't speak for Handbrake but if you check the script MeGUI creates for downmixing you'll see this (5.1ch):
# 5.1 Channels L,R,C,LFE,SL,SR -> stereo + LFE
function c6_stereo(clip a)
fl = GetChannel(a, 1)
fr = GetChannel(a, 2)
fc = GetChannel(a, 3)
lf = GetChannel(a, 4)
sl = GetChannel(a, 5)
sr = GetChannel(a, 6)
fl_sl = MixAudio(fl, sl, 0.2929, 0.2929)
fr_sr = MixAudio(fr, sr, 0.2929, 0.2929)
fc_lf = MixAudio(fc, lf, 0.2071, 0.2071)
l = MixAudio(fl_sl, fc_lf, 1.0, 1.0)
r = MixAudio(fr_sr, fc_lf, 1.0, 1.0)
return MergeChannels(l, r)
If you convert the percentages to decibels, it means eac3to mixes all the channels together at the same volume, except for the centre channel which is reduced by 3dB (0.7071%), but if it detects clipping it runs a second pass and reduces the volume of each channel to prevent it. MeGUI applies an additional reduction to each channel first to prevent clipping (0.2929 = -10.67dB & 0.2071= -13.67dB), but the relative levels are the same and after normalising the result shouldn't be any different. Well aside from the fact MeGUI includes the LFE channel by default, whereas eac3to doesn't, but both programs reduce it by 3dB relative to the front stereo channels when it's included.