PDA

View Full Version : How to properly downmix 5.1 to stereo?


Neillithan
5th January 2011, 20:39
Hi, I have pretty much declared from my own personal tests that 5.1 is pretty much useless and I can simply use stereo AAC-LC at 320kbps and it sounds identical to 5.1 when under headphones. I do have a 5.1 surround sound speaker setup, but I listen to everything in stereo x2 mode. I think this sounds a lot better than true 5.1.

However, this is only after manually downmixing 5.1 to stereo using Audacity. If I attempt to downmix 5.1 any other way, it comes out sounding like crap... probably because the additional channels are being discarded rather than downmixed.

What I did is this:

Front left, rear left = Combined
Front right, Rear right = Combined
Center: split between Left and right

I wasn't really sure what to do with the last channel (LFE) so I mixed it between both left and right channels.

I listened to the result and it turned out perfect, better than I expected.

Does anyone know of a program, or tutorial that will show me how to properly downmix a 5.1 audio stream to stereo easily?

Thanks,
-Neil

7ekno
6th January 2011, 12:52
eac3to input.ac3 output.ac3 -down2 -mixlfe

Replace input.ac3 and output.ac3 with whatever filetypes we are talking about ...

7ek

nurbs
6th January 2011, 14:28
It should be noted that eac3to uses a DPLII downmix.

LaTo
6th January 2011, 19:52
IIRC, special downmix infos are stored in each TrueHD track when mastering... It would be great to retrieve these for downmixing to stereo, because it will be better than arbitrary DPLII coefficients.

Is this possible with a program? Eac3to doesn't show these coefficients...

leeperry
7th January 2011, 14:42
Does anyone know of a program, or tutorial that will show me how to properly downmix a 5.1 audio stream to stereo easily?
Graphedit + ffdshow?

That's a 5.1>stereo downmix for headphones use I made(24/96 90 secs sample): http://www.mediafire.com/download.php?u7adu3zn3awj2jy

ffdshow allows custom mixing matrixes and 32bit VST plugins: headphones pseudo-binaural sound galore http://forum-images.hardware.fr/images/perso/alphat.gif

LaTo
11th January 2011, 10:22
IIRC, special downmix infos are stored in each TrueHD track when mastering... It would be great to retrieve these for downmixing to stereo, because it will be better than arbitrary DPLII coefficients.

Is this possible with a program? Eac3to doesn't show these coefficients...

Nobody? :confused:

Blue_MiSfit
20th January 2011, 00:22
Is the TrueHD spec public? If so, I'd imagine it's possible to parse this metadata out of the bitstream.

Derek