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hello_hello · 30th August 2016, 16:20

Some thoughts....

Multichannel audio might sound a bit quieter than the original after it's been downmixed to stereo, but that's probably relative. If you're listening to the original audio downmixed to stereo on playback maybe it's being downmixed differently.

MeGUI uses a standard formulae for downmixing to stereo (the volume is reduced enough to prevent clipping when the channels are combined) then if the "normalise" option is selected it's adjusted so the peaks are at maximum (assuming you have the option set to 100%).

What happens if the same multichannel audio is simply downmixed to stereo on playback though.... and there's no volume reduction to prevent clipping? It could sound louder than the downmixed version created by MeGUI, but the peaks could also be clipped. Or sometimes the downmixed version created by MeGUI might sound louder, or sometimes about the same, it'd depend on the dynamic range (how loud the peaks are compared to the average volume) and how the original is being downmixed on playback.

Also... I've found after downmixing, the volume often seems to be similar to the original on playback. Not always, but it's rarely low enough to concern me, however that's assuming the multichannel audio you're downmixing and encoding is the original audio. If it's the original AC3 or DTS multichannel, the peaks might be a fair way below maximum, so after downmixing it and normalising, the stereo version could have a similar volume, but if your source is multichannel audio that someone else normalised when they encoded it (ie if the original multichannel AC3 was normalised when it was encoded as multichannel AAC) then the AAC version is probably louder than the "original" AC3, and it's far more likely your downmixed version will sound quieter by comparison.

30th August 2016, 16:20	#8 \| Link
hello_hello Registered User Join Date: Mar 2011 Posts: 4,829	Some thoughts.... Multichannel audio might sound a bit quieter than the original after it's been downmixed to stereo, but that's probably relative. If you're listening to the original audio downmixed to stereo on playback maybe it's being downmixed differently. MeGUI uses a standard formulae for downmixing to stereo (the volume is reduced enough to prevent clipping when the channels are combined) then if the "normalise" option is selected it's adjusted so the peaks are at maximum (assuming you have the option set to 100%). What happens if the same multichannel audio is simply downmixed to stereo on playback though.... and there's no volume reduction to prevent clipping? It could sound louder than the downmixed version created by MeGUI, but the peaks could also be clipped. Or sometimes the downmixed version created by MeGUI might sound louder, or sometimes about the same, it'd depend on the dynamic range (how loud the peaks are compared to the average volume) and how the original is being downmixed on playback. Also... I've found after downmixing, the volume often seems to be similar to the original on playback. Not always, but it's rarely low enough to concern me, however that's assuming the multichannel audio you're downmixing and encoding is the original audio. If it's the original AC3 or DTS multichannel, the peaks might be a fair way below maximum, so after downmixing it and normalising, the stereo version could have a similar volume, but if your source is multichannel audio that someone else normalised when they encoded it (ie if the original multichannel AC3 was normalised when it was encoded as multichannel AAC) then the AAC version is probably louder than the "original" AC3, and it's far more likely your downmixed version will sound quieter by comparison. Last edited by hello_hello; 30th August 2016 at 16:31.