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Mpc Quality Settings For Dolby 2.1 Streams, Is the default --quality 5 insufficient?
atom
post Oct 28 2002, 19:03
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Not sure whether this has been addressed before. Had a look through the forums, but could not find anything at first glance.

Something I picked up quite some time ago with MP3 was that the surround channel in a Dolby 2.1 (is that the correct term?) stream contained severe artifacts even with fairly high quality settings.

I experimented with MPC, and found this to also be true to for --quality 5. --quality 6 is significantly better, but I lack the equipment and expertise to truly compare the original with varying quality settings.

My question is: is this reasonable cause for encoding albums at --quality 6 or higher? In my opinion, yes. I have seen mention of other parameters (--ms?) that could possibly provide better stereo encoding (which is where the surround channel data really lives, isn't it?).

Can anyone maybe confirm my findings and comment on whether I'm just being paranoid, or whether it is more appropriate to use other parameters for such streams, in stead of --quality 6?

Note that many albums (especially live shows) seem to have this type of surround channel information; I believe it's either intentional or a side-effect of the way 2.1 decoding interprets the audio.
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user
post Nov 30 2002, 15:19
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Adding --ms 15 in generally to --quality 5 ... 8 ?


I have encoded a test song with a lot surround informations, in different settings.
Well, it is a test song, which results to a higher bitrate than "average songs", I assume.
Here the bitrate increase is always neglectable.
As atom or somebody else told above, adding --ms 15, results to increases between 1% and max. 10%; so, for a better stereo image or surround image, people could add that switch.

So I suggest, to write this switch --ms 15 to recommended list of mpc settings (with remark about slightly increased filesizes), but only, if there are no other drawbacks, disadvantages.


The test:

CD Stereoplay Dolby Pro Logic 2 DPL2 Promo-CD
01.Pink Panther, Henry Mancini , Erich Kunzel & Cincinnati Pops Orchestra 2002
5732 samples, 2.29 min.sec
This song contains a lot surround info. Especially informations for
Logic7/DPL2 decoders. These informations are compatible to old DPL-decoders.

As Encoder I used actual recommended mppenc 1.14.

avr bitrate - filesize - setting (difference: kbit/s - Byte)

190.3 - 3,561,276 - --quality 5 --xlevel
190.9 - 3,572,708 - --quality 5 --ms 15 --xlevel (difference: + 0.6 - + 11,400)
221.5 - 4,144,888 - --quality 6 --xlevel
221.7 - 4,149,804 - --quality 6 --ms 15 --xlevel (difference: + 0.2 - + 4,900)
252.8 - 4,730,904 - --quality 7 --xlevel
252.8 - 4,732,108 - --quality 7 --ms 15 --xlevel (difference: 0 - + 1,200)
265.4 - 4,966,428 - --quality 7.5 --xlevel
265.4 - 4,967,360 - --quality 7.5 --ms 15 --xlevel (difference: 0 - + 1,000)
287.1 - 5,373,028 - --quality 8 --xlevel
287.1 - 5,373,868 - --quality 8 -ms 15 --xlevel (difference: 0 - + 0,800)
318.9 - 5,968,532 - --quality 9 --xlevel
318.9 - 5,969,068 - --quality 9 --ms 15 --xlevel (difference: 0 - + 0,500)
356.7 - 6,675,772 - --quality 10 --xlevel
356.7 - 6,675,772 - --quality 10 --ms 15 --xlevel (difference: 0 - 0) identical by bit to bit comparison.

Conclusion:

(well, I know, you should not draw conclusions based on one sample or song,
but this is "normal music" with surround-info, lasting 2.5 minutes. So it
contains different parts of music und should represent a kind of "average").

Only in q5 and q6 settings you have a minor increase of bitrates (+ 0.6
kbit/s !), comparing quality setting and same quality setting with added
switch --ms 15.
From q7 to q10 you can forget the bitrate increase at all.
q10 results to bit-identical output compared to q10 --ms 15.

So:
If --ms 15 does not have any other disadvantage regarding sound quality, I
would recommend to add --ms 15 to the quality settings, if you want more
precise stereo-image or keeping surround informations.
Because the bitrate increase is nearly neglectable, or below 10% (tested by somebody above).

Or do you have examples, where you experience worse sound quality, due to
added --ms 15 ?


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Posts in this topic
- atom   Mpc Quality Settings For Dolby 2.1 Streams   Oct 28 2002, 19:03
- - atom   Have done some more reading and testing. A fairly...   Oct 29 2002, 21:46
- - smok3   some rumble: very interesting, did you test any ot...   Oct 29 2002, 23:14
- - floyd   QUOTE (atom @ Oct 28 2002 - 12:03 PM)Note tha...   Oct 29 2002, 23:31
- - atom   A good example of an album with fairly strong surr...   Oct 30 2002, 17:37
- - Gecko   MPC is designed and tuned only for normal stereo l...   Oct 30 2002, 19:14
- - floyd   QUOTE (atom @ Oct 30 2002 - 10:37 AM)My probl...   Oct 30 2002, 22:15
- - atom   Another happy customer :-) Thanks, Gecko. Your c...   Oct 31 2002, 02:05
- - Trelane   I've been using a "poor man's surroun...   Nov 3 2002, 06:51
- - Dibrom   QUOTE (atom @ Oct 30 2002 - 06:05 PM)The funn...   Nov 3 2002, 07:01
- - CiTay   QUOTE (Dibrom @ Nov 3 2002 - 07:01 AM)Maybe s...   Nov 3 2002, 14:45
- - user   Adding --ms 15 in generally to --quality 5 ... 8 ?...   Nov 30 2002, 15:19
- - liekloo   Yes this is a very interesting topic. I do think ...   Nov 30 2002, 16:58
- - CiTay   We surely shouldn't generally append this swit...   Nov 30 2002, 17:53
- - user   I hope, my words above are not misunderstood, plea...   Nov 30 2002, 18:03
- - CiTay   Got an email from Frank Klemm (you too, user, thx)...   Nov 30 2002, 23:20
- - ssamadhi97   i don't like the term "stereo imaging...   Nov 30 2002, 23:42
- - CiTay   You are right, "surround information" th...   Nov 30 2002, 23:46
- - user   yes, you are right. I don't know, if Frank has...   Nov 30 2002, 23:47
- - user   Adding --ms 15 does not cause artefacts or worse s...   Dec 1 2002, 19:00
- - atom   Hi folks. As is implied in my earlier tests, I DI...   Dec 4 2002, 02:49
- - floyd   hmmm, i have about 15 gigs of mpcs (mostly), and n...   Dec 4 2002, 07:42
- - ProtectYaNeck36   please correct me if i am wrong but, just because ...   Dec 4 2002, 08:04
- - David Nordin   Uhm.. Dolby Surround is just 2 channels where you ...   Dec 4 2002, 08:38
- - floyd   QUOTE (ProtectYaNeck36 @ Dec 4 2002 - 01:04 A...   Dec 4 2002, 23:34
- - Mr. Superbad   I believe NIN's broken was made with DPL in mi...   Dec 5 2002, 00:04
- - atom   After considerably more searching than I anticipat...   Dec 5 2002, 02:59
- - floyd   I agree with you there. Movie soundtracks likely ...   Dec 5 2002, 03:40
- - user   QUOTE (floyd @ Dec 4 2002 - 11:34 PM)QUOTE (P...   Dec 5 2002, 09:24
- - atom   QUOTE (user @ Dec 5 2002 - 12:24 AM)hmm, have...   Dec 9 2002, 03:27


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