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

Luke Davis l1 at newanswertech.com
Wed Nov 5 20:01:37 CET 2014

On Wed, 5 Nov 2014, bluesky at caramail.com wrote:

> "Moritz Barsnick" <barsnick at gmx.net> wrote:
>> This is the technicality which needs to be understood. If the source is
>> what Carl Eugen has identified, there is no digital indication that
>> this is "Dolby Surround". You will identify two channels which can be
>> played on stereo output, and will sound like a down-mix of surround
>> material on stereo. Yet in these two channels, there is a mixture of
>> four or six audio channels. If you know how to "decode" them, you can
>> separate them. Actually, you should be able to detect this surround
>> encoding if you analyze the audio waveforms, but this may mean actually
>> decoding them and checking whether the "extra" channels contain sound.
> I might actually believe I was hearing pseudo-surround in MythTV if I did not 
> have the one test recording that clearly and unambiguously states the name of 
> each channel as it plays.  Apparently, by luck or by design, the MythTV people 
> have stumbled onto a way to play these types of recordings correctly.  If they 
> have figured it out, I would think it's not an impossible thing for someone 
> who understands what they are doing.  But that said...

I know nothing about this subject at all.  However the discussion reminded me 
of something that could possibly be relevant.

Steve Harris has one or two LADSPA effects for working with Dolby Surround, 
which may be what you're talking about here if I understand the most recent 
post correctly (I have not been following the thread)
.  Perhaps talking to him about this could be informative?


Then again, maybe that's the wrong tree to be barking up entirely, but I thought 
I'd point it out just in case it was good for something.



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