I'd like to know more about LAME's unsafe Joint-Stereo mode. What does it do different from the safe Joint Stereo mode? What is the advantage of that mode? I mean, is it faster or does it give a better compression...there are obviously some major disadvantages that are quality concerned I guess...

thanks

AFAIK LAME has three different stereo modes:
-ms (plain simple stereo, coding L/R)
-mf (forced M/S coding on all frames)
-mj (adaptive M/S coding)

One should always choose "-mj" since it switches adaptivly between L/R Stereo and M/S stereo to get a higher quality per bit ratio.

Whereas L/R->M/S is a lossless and reversible transform:
- M=0.7*(L+R)
- S=0.7*(L-R) or 0.7*(R-L) (I'm not sure about the polarity of S)

I did not test the performance of -mj against -mf /-ms lately but one might suspect that -mf / -ms is slightly faster then -mj since LAME doesn't need to compute and decide what type of coding (L/R or M/S) might be better than the other way.

HTH,
SebastianG

edit: grammar

so I guess unsafe Joint Stereo would be '-mf (forced M/S coding on all frames)', right? However, how can LAME force Joint Stereo? Wouldn't that be a DUAL-Channel instead?

Dual channel is stereo, not joint-stereo
Forcing joint-stereo is not a good option for mp3 unless for low bitrates
Unlike newer codecs i.e. AAC, WMA, Vorbis.....They all have a better m/s coding method than mp3! That's why there is no "stereo" and "joint-stereo" options in those codec...Normally they have only one option - "stereo"

Don't think about Force joint-stereo if you would like to encode mp3 at mid to hi bitrates!

Personally, i've tested force joint-stereo....it will destroy the stereo image!
Well, it shouldn't be said as unsafe, coz you will always get a narrower stereo image compared to the original with this option unless the source is a monoish file

Not really... The difference between Dual Channel and Simple Stereo is that in Dual Channel encoding, both channels are encoded independently, meaning that no bits get reallocated between channels if one is more complex.

Read the FAQs dude.

Before this develops into just another pointless discussion about joint stereo vs. stereo , let's turn this around to the topic Jojo really wanted to know about (at least that's how I understood it): In encspot, files not encoded with the presets (or with a low VBR preset like -V5) are not reported as having "safe joint stereo". So what does safe joint stereo do as opposed to "unsafe" JS? Does it just prevent any form of stereo collapse, or does it prevent other problems of JS like dropouts or whatever? I'd like to know this too, as I encoded lots of songs with pre-preset-era Lame 3.89 in 192 JS, which is not reported as "safe" in encspot. I've noticed it uses a lot more MS frames than e.g. APS for the same song.
So, does anyone know of a HA thread where this has been discussed?

The so called "safe" and "unsafe" joint stereo modes in Encspot are some different decision modes to choose between stereo and mid/side stereo on a frame basis.
For Encspot "safe" joint stereo means the mode formerly known as "nssafejoint"

..which translates into some bad quality files!

Which is recommended for bilingual content for example.

well, when was the last time you encoded such content

I think it should be removed from popular rippers like audiograbber, which lists the stereo modes like this: "Mono", "Joint Stereo", "Stereo", "Dual Stereo". Your average newbie would think dual stereo is best and joint stereo worst. look at all the (dual) stereo files on kazaa

Strictly speaking this is wrong. The only difference is meta information. (No encoder is forced to do a 50/50 splitting of the bandwidth for Dual Channel)


SebastianG

Oh, shit. Here we go to again the same damned old argument again. "Remove everything dangerous from Lame because people are stupid and will get hurt with that"

Why don't we try to educate people rather than delivering them everything reduced to the lowest common denominator, which only helps increase ignorance?


And your argument is utterly precious. So you want people to be limited only to high quality settings so that you can obtain only high quality illegal files on peer to peer?

More on this cursed subject: http://www.hydrogenaudio.org/forums/index....showtopic=12974

I'm not saying it should be removed from LAME, but rather from easy to use gui rippers like Audiograbber. At least a big red warning sign next to obvious settings that hurt quality wouldn't hurt anyone. There's little point trying to "educate the masses" when people in general give a rats ass about what encoder to use as long as the files end with .mp3 and fit their iPods.

just my 2¢

That wasn't really my point, Kazaa is more like a mirror for how average joe's compress their music.. I never use kazaa myself.

btw, where do you think lossy audio compression would be if it weren't for p2p?

i didn't mean that ............i mean forcing "force joint-stereo" is bad
Normal "joint-stereo" is good
Less one word force will actually change the meaning of my sentence....next I'll try to check my grammar!

EDIT: English is not my main language...pls forgive me

Graphical front-ends could also choose to follow those guidelines:
http://lame.sourceforge.net/lame_ui_example.html

It would still fit nicely in my mp3 player.
And for pratical reasons, because it's far easier to click 5 times to listen music than to search for the disc, then put in the player and play it.
[edit:]bad english...

thank you for all your replies



just to make sure, I'm talking about the LameHeader which EncSpot displays if available. So if one uses mf (forced M/S coding on all frames) would EncSpot report 'Safe Joint Stereo: No' when I view the LAME header? If not, which setting would one have to use in order to make EncSpot to report unsafe Joint Stereo in the LameHeader?


that's awesome! Who made that and for long has this been up?

Wow! I wonder why the developers of frontends / rippers just ignore this guideline?
Is it the case that they even don't know about that?

I made this mockup about 1 year ago

I'd say good job Gabriel! However, maybe you could make this easier to find...it's the first time that I've even heart about that...and as it seems I'm not the only one...