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10th December 2001, 21:44 | #1 | Link |
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Stereo vs. Joint Stereo **again**
I'm sure this has been raised before on this board or other audio boards but I was wanting to hear what you movie/audio phreaks thought.
So is there ever a wrong time to use Joint Stereo? Maybe it's my ears but to me, when I encode with Joint stereo the voices seem more dominant out of my left speaker. I've noticed if I use --r3mix in LAME that it almost always encodes with J-Stereo. Then again on some other boards, I've seen people say they always use stereo. Any thoughts? |
10th December 2001, 23:23 | #3 | Link | |
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10th December 2001, 23:27 | #4 | Link |
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Can you can disable "processing" on your receiver? I can tell mine to play it as plain stereo, as opposed to trying process it as dolby pro logic/dd/dts.
If the balance changes then that might be a sign that the pro logic info is wrong. Do you use --r3mix all by itself? I have actually gotten good results with it. |
10th December 2001, 23:45 | #5 | Link | |
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11th December 2001, 00:13 | #6 | Link |
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LAME does Joint stereo perfectly (unlike some encoders, audiocatalyst to name one) and if you want to make absolutely sure use the ns safejoint flag when you encode. JS will save bits and in CBR files it will actually have better quality than a stereo encoded file because of the wasted bits in stereo files.
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11th December 2001, 11:16 | #7 | Link |
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Joint Stereo can sometimes cause a very slight "slurring" (not the right word - but you can probably guess what I mean) - But this is only everso slight, so Stereo should only be used when the bitrate is very high...else Stereo will lower the quality significantly.
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11th December 2001, 22:41 | #8 | Link | |
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12th December 2001, 08:30 | #9 | Link |
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Check your bitrate, if you are using --r3mix default with joint, and the bitrate is dipping too low(my own meaning of low bitrate), around 130ish, it might cause the error you described. Most people can't hear that tho. Anyhow, basically, joint stereo is just a combination of stereo and mid/side stereo, chosen on a frame-by-frame basis by the encoder.
So enable r3mix with --nssafejoint, now the encoder should be MORE conservative in picking M/S vs Stereo. I would suggest you do 3 test. Encode 1) r3mix 2) r3mix --nssafejoint 3) do a stereo encoding 4) optional, pick your own switches to fit the sound material of the movie. Then pick one from there. |
12th December 2001, 16:24 | #12 | Link | |
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12th December 2001, 16:26 | #13 | Link |
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My understanding of dolby surround is it "works" with any audio signal. You will always get sound out of your center and surrounds, given any signal, even if no extra work went into encoding the signal.
Please correct me. |
12th December 2001, 16:32 | #14 | Link |
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1. AC3 -> 16-bit WAV using Azid, no changes made to sampling rate (48KHz)
2. 16-bit WAV -> MP3 using Lame 3.89 --r3mix (which uses joint stereo) 3. Muxed with an .avi 4. Watched .avi in PowerDVD 4.0 XP, with it's Dolby Pro Logic II decoder enabled 5. The correct "rear channel" sound effects were being sent to the rear speakers of my 4.1 sound system (compared with DVD) For reference, here is my system: Windows XP Turtle Beach Santa Cruz in 4-speaker mode Using 4112 WDM drivers for Santa Cruz PowerDVD XP 4.0 Altec Lansing ACS-56 4.1 speakers in analog multichannel mode An AthlonXP CPU on a mobo using the KT266A chipset |
12th December 2001, 16:33 | #15 | Link |
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LAME preserves dolby surround information in joint stereo. The reason some people prefer to use full stereo instead of JS is that JS occasionally causes JS artifacts.
Using -ms is not the best solution against the JS artifacts. Using -mj with --nssafejoint is better, because JS stereo frames are still used, but stricter so that they will not be used when using a JS frame will cause bad artifacts. --ns-msfix can be used to alter the JS threshold level. It's really a trade off thing. If you use -ms, you won't get the JS artifacts but you lose quality overall because there are less bits overall to encode with. For ABR encoding, I would just go with the lame --dm-presets which have the --nssafejoint and --ns-msfix value tuned to the particular bitrate. |
12th December 2001, 16:36 | #16 | Link | |
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you need to perform a correct Dolby Surround downmix, so that Dolby Pro Logic decoders will correctly extract the channel information from the phase information that is matrixed into a 2-channel stream. Azid and dvd2avi perform correct DS downmixes. Maybe if you enable DPL or DPL 2 on a standard Stereo soundtrack you get "surroundish" effects, but those are not right or intended to be there... it just happens. Those of you so concernced about maintaining Dolby Surround... WHY DONT YOU JUST TEST IT... if you can't test it, then it seems like you probably don't have any surround equipment. in that case, WHY DO YOU CARE? stuff like divx is time-limited, and within the span of 2 years you will (probably) find another codec which puts divx311a and divx4 to shame, so why are you even bothering trying to "futureproof" your rips by making sure the sound is surround even when you are just using a pair of $5 labtecs. not to mention that "futureproofing" using an ancient technology such as dolby surround is downright ridiculous! |
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12th December 2001, 16:44 | #17 | Link | |
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All I know is I encode using --r3mix and it sounds fine to me (w/o dolby surround downmixing from ac3->wav). |
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12th December 2001, 16:48 | #18 | Link | |
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Celeron 733 256MB RAM 80GB 7200RPM Drive 52x Creative CDROM Nightingale 5.1 Pro6 with Optical Sony 675 DD/DTS Reciever Sony 140 Watt FL & FR Speakers Klipsh 70 Watt Center Kenwood 50 Watt RL & RR Surr Speakers So...I'm definitely not working with $5 speakers here. Currently all my encodes sound great on the system but I've downmixed them to stereo. What I'm really looking to do is what you suggested with DPII using PowerDVD4. Thanks again for all the info guys! |
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12th December 2001, 16:49 | #19 | Link |
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how do you know what works?
err... try this. get a dvd that has a DS 2.0 192kbps AC3 audio stream *and* a DD 5.1 384-448kbps AC3 stream. Go to a scene with surroundish effects. compare how the 2.0 channel sounds, to how the 5.1 channel sounds. assuming your recieveer is only Pro Logic, and your dvd player "knows that" (i.e. since you only plugged in the rca left and right jacks) your dvd player should downmix the 5.1 stream to dolby surround. they should sound somewhat similar. and the DPL light on your reciever should be on (or maybe you'd have to turn it on manually...) |
12th December 2001, 16:52 | #20 | Link | |
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i tend to only resort to MP3 tracks for 1cd rips and 2cd rips "taken to the limit" (i.e. 160minute fast action movie lots of daylight scenes 1.85:1 A.R. blahblahblah). obviously FP ratio is helpful in indicating whether to go for MP3 or keep AC3 in those situations. |
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