[MPlayer-users] [Question] Why 2 channel ac3

[Ed Fisher]

Reason to keep 2ch ac3 rather than convert it to mp3, and reason to use
2ch ac3 instead of 5.1:

2ch ac3 is usually 192kbit/s, sometimes 384.  A VBR mp3 is usually about
135-160k/s average.  The difference there is minimal, but the quality is
significant, especially with a good speaker system.

That being said, many people don't have a 5.1ch speaker system, and for
them 2ch ac3 makes sense, especially since 5.1ch is 448kbit/s.

Now consider who/what you would rather have mix your 5.1ch down to 2
channels: the sound engineers who made the dvd, or your little bit of
software on your computer.  Hell, there may be no difference between the
two, but I'd take a professionally downmixed stream to one done at home
any day.

I have no idea about your other query, but it sounds like bunk to me.
My guess is they send out the channels at different volumes to make it
seem like 5ch, but it's really hard to say.  

Anyway, if you have a 5.1 speaker system, by all means rip to 5.1, but
for 90% of the people out there, 2ch ac3 is a much better compromise,
especially given the small increase in file size over mp3.

-gleam

On Tue, Dec 24, 2002 at 06:57:17AM +0100, Anders Rune Jensen spake thus:
> [Automatic answer: RTFM (read DOCS, FAQ), also read DOCS/bugreports.html]
> hi
> 
> I've been wondering for a why some rip dvd's with only 2 channel ac3
> and not 5.1? Sure they save bandwitdth but I mean if they just want to
> save bandwidth they could have used ogg or mp3. I've heard something
> about some amplifiers been able to "convert" that two channel to 5.1,
> I think it's Dolby Pro Logic II. So does this produce as good quality
> as 5.1? I guess if there is indeed such amplifiers that must be the
> reason, since converting it back to ac3 from ogg would just be to
> lossy I think.
> 
> My amplifiers when fed with ac3 2 channels just play it as 2 channels
> even if I use dolby Pro Logic (I believe it's not Dolby Pro Logic II).
> 
> Can anyone shed some light on this?
> 
> 
> PS: marry christmas to all of you from Denmark :-)
> 
> -- 
> Anders Rune Jensen
> 
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