[FFmpeg-user] How can I convert mpeg2 5.1 audio to ac3?
Carl Eugen Hoyos
cehoyos at ag.or.at
Tue Nov 4 13:56:30 CET 2014
<bluesky <at> caramail.com> writes:
> If I play the same file in XBMC only the front
> speakers are used.
How is your computer connected to your receiver?
I can choose here between analog, hdmi and
TOSLINK (optical). If I use hdmi or the optical
input, my receiver allows me to switch the
"listen mode": As suspected, the audio uses
Dolby PLII to encode surround sound via stereo
channels. If I select "PLII" on my receiver, I
hear the surround sound (with failures because
the algorithm cannot be perfect).
If I use the analog input, I have to force the
receiver to "two-channel" input to make it
detect PLII: If I set it to 6-cable input
(which is what I normally use), I cannot choose
As said, FFmpeg does not support PLII decoding
(only encoding). Are you sure MythTV contains
an internal implementation and not does not use
your receiver's Dolby decoder?
Just to make things less confusing: Above has
nothing to do with "mpeg2": You can use any
audio codec that supports two channels and
use it to store PLII-encoded surround sound.
There is also "MPEG-2 5.1" or "MPEG-2
Multichannel". This is very rare and FFmpeg
cannot detect it (nor decode it). I don't
think your file can use both Dolby PLII and
MPEG-2 Multichannel at the same time.
Wikipedia articles for Dolby PLII, toslink and
MPEG-2 Multichannel exist.
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