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

[TrNSZ]

I recall having a similar discussion on the r3mix board a very long time with Dibrom after I released the first patch for tuning nsmsfix on the command line. All of Dibrom's alt-presets already have a dynamic tuned nsmsfix value set if I remember correctly.

By increasing nsmsfix to nssafejoint (nsmsfix = 1.0) more bits will be used because simply to encode frames as stereo, so you might lose some quality since those bits would surely (??) be better used encoding the signal normally with more joint frames in most places, I assume.

Just so everyone knows and doesn't get any ideas, I wouldn't recommend this as a general quality improvement to the alt-presets by any means. IMHO it has proven itself with audible transparency on most natural audio signals for the majority of the public. Leave it alone unless your tweaking a special case such as encoding artificial signals.

I guess an interesting test would be to listen to the output of the surround from aps and aps nssafejoint. If this can be ABX'd, then I think it would be smart to ABX alt-preset extreme vs. alt-preset standard + nssafejoint. The bitrates will probably be very similar; the real test is to increase the quality of the "surround" channel without degrading the rest of the signal below the level of audible transparency. Maybe someone else can define a better test methodology -- I've been up for two days now and might not be thinking straight. =)

This post has been edited by TrNSZ: Aug 6 2003, 17:59