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:-( MP3 destroys Surround Sound encoding
theaveng
post Dec 3 2002, 00:18
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I've been experimenting with MP3 and converting my CDs to MP3-320 compressed files. Unfortunately, I've discovered that the MP3 encoding process destroys the Rear Channel Sound. In a few cases I can still hear music in the rear, but for most songs the rear speaker just produces garbage sound... rather disappointing compared to the rich sound produced from the original CD!

I suppose MP3 considers the rear channel information to be "inaudible" which it would be in a standard 2-speaker stereo arrangement, but the addition of the rear speaker makes these types of sounds *very* audible. It's basically an echo effect that is audible when listening to the CD and places the listener *inside* the music, but sadly lacking on the MP3 rip. The stripping of that rear channel echo dramatically diminishes the experience.

Troy

P.S. I'm using CDex for ripping and LAME for encoding with the following settings: q=0;Very High Quality, Stereo, 320kbps.
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tangent
post Dec 3 2002, 04:06
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Rear channel information is not inaudible in a standard 2-speaker stereo arrangement.

Try encoding with this custom command line: --alt-preset insane
This gives you a CBR 320kbps. Yes it uses joint stereo, but I'd bet that you'll still get a better result.
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LordSyl
post Dec 3 2002, 23:14
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QUOTE (theaveng @ Dec 2 2002 - 03:18 PM)
P.S.  I'm using CDex for ripping and LAME for encoding with the following settings: q=0;Very High Quality, Stereo, 320kbps.

Wasn't q0 buggy, at least with --alt-presets?....
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kritip
post Dec 3 2002, 23:27
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Judging by your tending to high bitrate values, i preume you are not looking for hardware support. Why not try with many of the other lossy codecs, AAC, MPC et al or if u want guaranteed retention of the surround information, go with a lossy format, FLAC, Monkey Audio @ ~800KBps

Just a though,

Kristian
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_Shorty
post Dec 4 2002, 00:06
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the mp3 file itself is fine, the problem lies elsewhere, either in winamp or your Creative sound drivers (pretty much willing to bet money you have a Creative soundcard considering problem you're asking about)
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atom
post Dec 4 2002, 12:11
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Hi TheAveng

I've actually done a fair amount of testing on this. Please have a look at the post in the MPC section at http://www.hydrogenaudio.org/forums/index....=ST&f=11&t=4109.

I've done comparisons between a number of encoders at various bitrates.

I concur that MP3 (have only tested lame, but suspect this may be generally true of the MP3 model) is terrible at encoding the stereo image for samples with surround information. It only APPROACHES acceptibility at --alt-preset insane.

MPC does a great job at (--quality 6), or at (--quality 5 --ms 15). However, both AAC and Ogg Vorbis gets it right at the "standard" quality settings.

My recommendation: switch to MPC and encode surround tracks with the settings above. You can still encode your other tracks at (--quality 5) and save space (and improve quality!) over MP3.

If you are encoding movie clips, have a look in stead at Ogg Vorbis, for which I believe there exists a Windows CODEC capable of decoding Ogg Vorbis streams.

Atom
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Gabriel
post Dec 4 2002, 13:44
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Interesting thing is that on Doom9 forum, there seems to be quite some people who are happy with DPLII tracks encoded in mp3.
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kennedyb4
post Dec 4 2002, 14:04
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My DVD rips are all encoded with alt ABR 128 and the surround info is fine.
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lucpes
post Dec 4 2002, 15:19
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QUOTE (kennedyb4 @ Dec 4 2002 - 01:04 PM)
My DVD rips are all encoded with alt ABR 128 and the surround info is fine.

Take a DVD with live music performance, with a PROPERLY mastered & recorded 5.1 AC3 @448 kbps, then encode it to ABR 128 ph34r.gif

This post has been edited by lucpes: Dec 4 2002, 15:20
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Kblood
post Dec 4 2002, 15:21
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QUOTE
Take a DVD with live music performance, with a PROPERLY mastered & recorded 5.1 AC3 @448 kbps, then encode it to ABR 128


You would be quite crazy to do that...

Movies, on the other hand, come out quite fine with such a low ABR, because of the extra "breathing room" they get from the frequent silence parts... smile.gif
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kennedyb4
post Dec 4 2002, 18:30
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For a music specific video, I normally take the 2.0 stream and mux the ac3 directly.

But I have to insist that on the rips I have done, the surround info is maintained well.

Are we discussing bitrate failure, or a problem in encoding the out of phase info?
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atom
post Dec 5 2002, 15:52
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The surround info is usually maintained to some degree, but with some severe distortion at lower bitrates. Take a closer listen to the rear speakers - in all likelyhood you will hear some severe flanging on cymbals and explosions.
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plonk420
post Dec 5 2002, 16:26
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QUOTE (kennedyb4 @ Dec 4 2002 - 06:04 AM)
My DVD rips are all encoded with alt ABR 128 and the surround info is fine.


ew! ew! ew!

192ABR/CBR (stereo) is a BARE MINIMUM... holy crap! blink.gif even APS -M S (stereo) sounds a bit odd. 224 to 256 seems to be the sweet spot for the music i've been experimenting with recently (like 99% eurodance, electronica, etc) .. i need to try some hard rock, tho; i have the Guano Apes sitting right here begging to be re-ripped ever since i discovered how APS (in its defaulting to Joint Stereo) utterly destroys the soundfield.

for the rest of you tweakers, the most buttugly example i can find of stereo being jacked up is Crazytown's Darkside .. *shudders* ... sounds pretty cool when played as a WAV/APE or high, high quality MP3...

This post has been edited by plonk420: Dec 5 2002, 16:27
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Benjamin Lebsanf...
post Dec 5 2002, 17:03
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you don't need -ms for surround, mj is just fine! MS Stereo can losslessly recreate the normal stereo information IIRC!

FYI:
http://www.hydrogenaudio.org/forums/index....t=ST&f=15&t=995

This post has been edited by Benjamin Lebsanft: Dec 5 2002, 17:07
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post Dec 17 2002, 11:11
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QUOTE (Benjamin Lebsanft @ Dec 5 2002 - 08:03 AM)
you don't need -ms for surround, mj is just fine!

Hi Benjamin

Um... not exactly sure what you're on about, but if you're referring to my use of the --ms switch above, please re-read my post carefully.

The switch is used with MPC to adjust the accuracy of MPC's equivalent of joint stereo encoding. It was merely a suggested as an alternative to MP3 (Lame), which seems to have a hard time encoding surround information properly.
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Mgz
post Dec 19 2002, 03:24
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I thinks it's a hardware problem.....


MP3 is 2 channel (stereo) and only way to get sound from rear spker is emuate it virtually


If you have a creative spk/sndcrd,it's called CMSS ...

In Philips soudncard,it's called QMSS

you can find more info @ http://www.3dsoundsurge.com


--------------------
still LAME 3.96.1 --preset extreme -q 0 -V 0 -m s at least until 2005.
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atom
post Dec 20 2002, 03:36
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Hi Mgz

This is (unfortunately) not a hardware malfunction. Dolby Pro-logic was developed as a mechanism for encoding a front center and surround channel into a standard stereo stream (i.e. four channels from a standard two-channel stereo stream.)

The mechanism relies heavily on stereo imaging (as described here and here.)

The same effect (sound from the center and surround channels) may occur on non-DPL tracks if there are sufficiently out-of-phase stereo sounds, such as heavy reverb or recording the audience in stereo on live shows.

Lossy encoders tend to sacrifice stereo information at lower bitrates, since this leaves more bandwidth for removing more apparent artifacts. Any deviation from the original recording could result in unusual sounds from the center and surround channels.

DPL and DPL-II are discribed in-depth on the Dolby Web Site.
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Mgz
post Dec 20 2002, 05:18
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QUOTE (atom @ Dec 19 2002 - 06:36 PM)
Hi Mgz

This is (unfortunately) not a hardware malfunction.  Dolby Pro-logic was developed as a mechanism for encoding a front center and surround channel into a standard stereo stream (i.e. four channels from a standard two-channel stereo stream.)

The mechanism relies heavily on stereo imaging (as described here and here.)

The same effect (sound from the center and surround channels) may occur on non-DPL tracks if there are sufficiently out-of-phase stereo sounds, such as heavy reverb or recording the audience in stereo on live shows.

Lossy encoders tend to sacrifice stereo information at lower bitrates, since this leaves more bandwidth for removing more apparent artifacts.  Any deviation from the original recording could result in unusual sounds from the center and surround channels.

DPL and DPL-II are discribed in-depth on the Dolby Web Site.

ya,I forgot,WinDVD 4.0 can do it,2 ,QMSS and CMSS is low-level support biggrin.gif


but IMO listen Mp3 in 5.1 is REALLY SUX...just try,and you will see sad.gif sad.gif


--------------------
still LAME 3.96.1 --preset extreme -q 0 -V 0 -m s at least until 2005.
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