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

Andy Furniss adf.lists at gmail.com
Tue Nov 11 14:46:26 CET 2014

Moritz Barsnick wrote:
> On Tue, Nov 11, 2014 at 12:29:09 +0000, Andy Furniss wrote:
>> Carl Eugen Hoyos wrote:
>>> Where I live all movies are broadcast PLII.
>> Ahh, I didn't realise it was still so popular.
> Where I live - Germany - the "minor" stations try to use less bandwidth
> on the satellite transponders / in their bouquets, and transmit only
> one AC-3 audio stream with two channels. Nevertheless, I get quite
> proper surround sound from my sound system during many movies. So my
> conclusion is that they use the PLII "down-mix".
> (Unless that statement was a misunderstanding and we're talking about
> something totally different.)
>>> As said MythTV contains a PLII decoder (filter).
>> 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;
> That looks different from what we were looking at earlier in the thread
> (and far too simple). Carl Eugen had pointed out this file:
> https://github.com/MythTV/mythtv/blob/master/mythtv/libs/libmythfreesurround/el_processor.cpp

Agh, thanks for that - the code I posted is from myth, but obviously I 
don't know if it's ever used.

For some reason this thread has split into two for me and I didn't see 
the other bit.

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