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Topic: --ms 15 setting... (Read 5321 times) previous topic - next topic
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--ms 15 setting...

Well what is the utility of the --ms 15 setting??? I saw it in some posts here in the forum and it's claimed that it is needed to correct some problems.

Thanks for any answer!

--ms 15 setting...

Reply #1 –
--ms affects the mid/side stereo threshold in mpc. The default value is 11. There have been very rare occurences where people claimed and prooved they heard a difference in stereo imaging on selected tracks when using the default. Using a higher value remedies the problem. 15 is the highest setting. Since the increase in bitrate isn't very large, most people go straight to 15 and never bother.

Most of the time it is only recommended to try this setting to isolate the problem. If --ms 15 cures it, then it was a problem with incorrect stereo imaging. A lower setting might remedy the problem just as well.

It is not recommended to add --ms 15 to your default command line.

--ms 15 setting...

Reply #2 –
mppenc --longhelp
Code: [Select]
 --ms x           Mid/Side Stereo, 0: off, 1: reduced, 2: on, 3: decoupled,
                  10: enhanced 1.5/3 dB, 11: 2/6 dB, 12: 2.5/9 dB,
                  13: 3/12 dB, 15: 3/oo dB (dflt: 11)

--ms 15 setting...

Reply #3 –
Quote
There have been very rare occurences where people claimed and prooved they heard a difference in stereo imaging on selected tracks when using the default. Using a higher value remedies the problem. [Cut...]

It is not recommended to add --ms 15 to your default command line.

I have one question: in order to hear "the very rare" mid/side stereo faults, do you have to possess extraordinary hearing qualities or anyone can ABX them?

Anyway I find the basic --quality 5 --xlevel options really enough for me. MPC is IMHO definitely the better encoder ATM. Altough I could ABX --quality 4 samples, it works very well also on ~128kbps bitrates.

--ms 15 setting...

Reply #4 –
Quote
I have one question: in order to hear "the very rare" mid/side stereo faults, do you have to possess extraordinary hearing qualities or anyone can ABX them?

You probably have to be well trained and have experience finding artifacts. If you haven't heard artifacts before in music, don't expect to notice these rare cases.

--ms 15 setting...

Reply #5 –
Quote
I have one question: in order to hear "the very rare" mid/side stereo faults, do you have to possess extraordinary hearing qualities or anyone can ABX them?

FWIW, I couldn't abx the "Farmer Boys" sample. I didn't listen to the recently reported "Smashing Pumpkins" sample. The one who reported the sample said he heard problems with stereo imaging. Others who tested that particular sample didn't encounter stereo problems iirc, but other problems which made this sample abx-able.

--quality 5 --xlevel is fine.

--ms 15 setting...

Reply #6 –
Quote
Others who tested that particular sample didn't encounter stereo problems iirc, but other problems which made this sample abx-able.

And --ms15 didn't solve them

--ms 15 setting...

Reply #7 –
Quote
mppenc --longhelp

CODE 
--ms x           Mid/Side Stereo,

0: off,
1: reduced,
2: on,
3: decoupled,
10: enhanced 1.5/3 dB,
11: 2/6 dB,
12: 2.5/9 dB,
13: 3/12 dB,
15: 3/oo dB

(default:
q 5     uses     ms 11,
q 6                 ms 12
q 7, 8, 9         ms 13,
q 10               ms 15     )       
)




My questions:

What is the meaning of --ms 3 = decoupled ?

Is it like Ogg q6, where lossless stereo coupling takes effect ?
Or does "decoupled" mean: "left & right channels are encoded independent of each other, so no bitrate saver" ?


Or is the only way to encode in mpc the stereo losslessly, by the switch --ms 0 ?

btw., is ms 0 working by encoding left & right channels independent of each other (no bitrate saver), or are channels coupled losslessly (bitrate saver) ?

--ms 15 setting...

Reply #8 –
I do not know an exact answer, but I believe it is irrelevant anyway. I just encoded a file with the default --ms 11, --ms 0 and --ms 3. They are all bit identical. I think nowadays only the advanced modes are supported.

--ms 15 setting...

Reply #9 –
I did some tests several months back after - what I believed to be - problems encoding tracks with Dolby Pro Logic information encoded in the stereo image (see this thread).

First things first:  using --ms 0 is a bad idea.  It actually decreases sound quality.  This was claimed by several knowledgable users on the site and I managed to do my own confirmation through ABX tests.

Many people feel my ABX tests (referring to paragraph one, not paragraph two) in proving problems with ProLogic tracks were flawed, as I did not have a proper Pro Logic system to test on - I simply inverted the right channel and added it to the left channel to discover my artifacts.  I still maintain there was some validity to my tests, and will summarize my results here again:

Ogg claims to have lossless stereo coupling at Q6, but in my experience Q5 is so close to lossless coupling that it will be very, very hard indeed to perceive any difference (this is with an inverted right channel added to the left - in normal listening Q5 will be as close to lossless coupling as anything.)  This makes Ogg an excellent encoder for Prologic and Logic7 (ProLogicII) movie soundtracks and the like.  AAC achieved similar results.

MP3 (I tested LAME) sucked.  It's terrible at stereo imaging.  Even at higher quality settings.  (Note that this doesn't rule it out as a good codec for music.  It's just isn't as suited to Surround Sound encoding as some of the other encoders around.)

MPC dissapointed me to some extent.  Q5 achieved similar results to MP3 with an "alt preset extreme" profile.  Adding "--ms 15" to the command line fixed this completely - stereo imaging/surround encoding was indistinguishable from the original.  There is a debate on whether to use --ms 15 or just up the quality to Q6, though.  (Both "fixed" stereo imaging in surround tracks.)

--ms 15 achieves good results at only about 2-3kbps more on typical music.  (Some very old "almost-mono" recordings apparently behave badly and add about 50% to the bitrate.)  Q6, on average, adds quite a bit in terms of bitrate with very little other benefit.  However, it is a "cleaner" alternative and not frowned upon as a general suggestion in the forums for encoding recordings with surround information.


So in summary:
* If you're encoding a low-bitrate soundtrack for your DVD backup, you're probably best off sticking with OGG or AAC.
* If you're keen on keeping the best quality possible, simply keep the original AC3 file (preferably the 2.1 profesionally downmixed version) from the DVD
* If you're encoding a CD with surround information on it and MPC is your encoder of choice, choose Q6 for a "clean" solution or "--ms 15" if you'd like to gamble a bit.

Hope that helps anyone who plays around with surround sound stuff...

Jannie

--ms 15 setting...

Reply #10 –
If q6 cures the problems, then maybe you shouldn't jump straight to --ms 15 but try --ms 12 instead, which q6 uses. That should cut down on the bloat for monoesque music.

Did you have: orig(ignal) and enc(ode) and did this (R/L represents left and right channels of course):

s1 = orig.L - orig.R
s2 = enc.L - enc.R

and then abx between s1 and s2 (which would be mono then)? If so, you are neglecting that when listening to the whole thing properly decoded by a reciever you will be hearing the front channels as well, which will probably mask quite a bit of what you can pick up when you only listen to the surround channel.

Whenever you compare an original to an encoded signal, you need to listen to the whole thing and not just parts of it, as each part is dependant on masking of the other parts.

--ms 15 setting...

Reply #11 –
so, I am using --ms 15 regularly, because I like to listen stereo sources via Logic 7 (DPl2 comparable, not to comapre with old-fashioned dpl) decoder.

In fact, given in the other thread linked by atom, ms 15 adds less bitrate than going 1 q-level higher in mpc.

for mono-recordings:
most have "half" bitrate than compared to normal stereo music with same mpc-setting and added ms15, so all is ok.
but some mono recordings suffer by adding ms15, indeed.








about ms 0 :



I read about the experiences 1 year ago, when ms 0 worked still.

Imo, the producing of worse quality by using q 5  ms 0 compared to pure q 5,
is an mistake in setting up the mpc-encoder.

it would mean, that at that times, q5 combined with ms 0, yielded to a "target-bitrate",  and did sacrifice signal-noise ratio for the stereo.

imo, if at q5 (a given quality regarding ath etc.) the 2 channels are encoded  independently (= 'ms 0'), then there should not be artefacts introduced comapred to plain q5, but the stereo encoded losslessly.

It seems, that in ancient times, by encoding stereo losslessly, the needed bitrate was "taken away" from other "topics" of the encoded song.

Or is there really an psychoacustic effect, which reveals artefacts more clearly, if full stereo is encoded ?