Lame and surround Options

[Fr4nz]

Hi guys. I've read many past threads about Lame and encoding movies soundtracks from AC3 to Dolby Surround1/2. While many people claim that Lame preserves the phase informations thanks to its safe joint stereo mode, in this thread http://www.hydrogenaudio.org/forums/index....t=0&#entry47454 it's stated that only at very high bitrates (for e.g. --alt-preset extreme or insane(!!)) Lame can conserve surround infos in a decent way.

Anyway i've encoded lots of movie soundtracks with Lame, and the --alt-preset standard setting seems quite good to me for surround1/2 tracks.

Thanks for any answer!

Fr4nz

[2Bdecided]

I've had an email from Frank. He asked 6 sensible questions...

1. What piece of music is affected?
2. What Dolby Surround Prologic or Dolby Surround Prologic II decoder is used?
3. In the case of Dolby Surround Prologic II: Music or Movie mode?
4. Delay for the rear channels?
5. Distance difference between front and rear speakers? ||front - listener|| -
||rear - listener||
6. What type of loudspreakers are used?


I tried listening via speakers, sending the "centre" channel to a speaker infront of me, and the "surround" channel to a speaker behind me. A poor man's experimental surround system, if you like.

Despite the obvious problems present in the surround channel when auditioned on its own, I can't hear any problems with it when replayed over speakers at the same time as the centre channel.

OK - I can hear problems if I put my ear quite close to the surround speaker - but with both speakers equidistant, the distortion in the surround channel is totally inaudible.


I emailed Frank to tell him this (I'm sure he already knows!!!) but asked, since he once had a braindead profile for people who insist on judging codecs by spectral analysis (i.e. the wrong way), maybe it would be worth his time adding a switch to preserve the surround channel for people who insist of judging codecs by listening to the surround channel in isolation (i.e. the wrong way!).


In the mean time, if anyone can find a sample which gives audible artefacts using a real surround decoder and sensible speaker placement, I think Frank might be interested.

Cheers,
David.