ac3 or mpa?

[N_F]

I recently encountered a movie that had two audio channels:

1. Dolby surround 448 kbps (ac3)
2. Mpeg audio 384 kbps (mpa)

My final format will be ogg and I use Besweet for the conversion. My question is: Which one should I use? I can't claim to hear a big difference when I compare them in winamp, but it'd still be nice to choose the theoretically best one.

I suspect I should use the dolby surround audio, but it'd be nice to hear it from someone who knows what he's talking about.


If you're curious: the movie is Scream. It's one of those budget DVDs I bought for 9$ a while ago when I though every DVD was the same, I really regret this now when I know better. No more 9$ DVDs for me...

Edit: Perhaps I should mention what's wrong with it. It's fullscreen so the edges been cut off...

[DJ Bobo]

The AC3 is 5.1 and the MPA is 2.0 right?

If that so, use the MPA for your conversion to ogg stereo, because the MPA track has a much higher bitrate per channel and thus much more transparent encoding.

[rjamorim]

Originally posted by DJ Bobo
The AC3 is 5.1 and the MPA is 2.0 right?

If that so, use the MPA for your conversion to ogg stereo, because the MPA track has a much higher bitrate per channel and thus much more transparent encoding.

Besides, there's another reason why MPA is better:

MPEG audio Layer 2 (MP2) is a subband coding format, while AC3 and Vorbis are transform coding formats. Converting from subband to transform is much more desirable than converting from transform to transform (two MDCTs in a row)

Regards;

Roberto.

[DSPguru]

Originally posted by rjamorim
Besides, there's another reason why MPA is better:

MPEG audio Layer 2 (MP2) is a subband coding format, while AC3 and Vorbis are transform coding formats. Converting from subband to transform is much more desirable than converting from transform to transform (two MDCTs in a row)

Regards;

Roberto. exactly what i wanted to say!
it's so fun to have roberto in here.. :D:D.

[N_F]

Originally posted by DJ Bobo
The AC3 is 5.1 and the MPA is 2.0 right?


Is this a given or could mpa be 5.1? (extremly unlikely in this case I guess, just for further reference)


Thanks to everyone. While I have no idea what "subband" and "transform", I trust you do :D

[rjamorim]

@DSPguru: ;)

Originally posted by N_F
Is this a given or could mpa be 5.1? (extremly unlikely in this case I guess, just for further reference)

Yes, it can.

There's probably some tool (?) around that reports if a mpa file is multichannel. I created a MC MP2 with Philips multichannel encoder, and all decoders I tried - Winamp, Odio Dekoda and Philips MPEG audio player itself (v1.1 and v2b) - report it as stereo.

Regards;

Roberto.

[DJ Bobo]

But it's very unlikely to have two 5.1 tracks on a DVD if the second isn't DTS ;)

[N_F]

Yeah, that's were the "extremely unlikely" came from. ;)