[FFmpeg-user] How can I convert mpeg2 5.1 audio to ac3?

Andy Furniss adf.lists at gmail.com
Tue Nov 11 13:29:09 CET 2014

Carl Eugen Hoyos wrote:

> Where I live all movies are broadcast PLII.

Ahh, I didn't realise it was still so popular.

> As said MythTV contains a PLII decoder (filter).

So it does, I couldn't find it when I first looked.

Doesn't seem very much compared to the quite complicated looking
descriptions of what a "real" decoder supposedly does.

float lt      = *samples++;
float rt      = *samples++;
bufs->l[ic]   = lt;
bufs->lfe[ic] = bufs->c[ic] = (lt+rt) * m3db;
bufs->r[ic]   = rt;
// surround channels receive out-of-phase
bufs->ls[ic]  = (rt-lt) * 0.5;
bufs->rs[ic]  = (lt-rt) * 0.5;

I don't pretend to know what should happen - but it's obvious that that
leaves the S in the fronts - but then you said your receiver did
too. I wonder if all receivers would.

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