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19th August 2019, 19:05 | #1 | Link | |||
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AviSynth Downmix Scripts
This is a question for Tebasuna:
In AVStoDVD MrC uses downmix scripts from you. For downmixing 8ch audio to 6ch the script is this one: Quote:
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I cannot really judge this script because I do not have a surround setup for audio (I'm old school - Stereo Only) Cheers manolito |
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20th August 2019, 00:31 | #2 | Link | ||
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I recommend the script used in BeHappy or MeGUI with the sur like this: sur = MixAudio(blr, slr, 1.0, 1.0).SoftClipperFromAudX(0.0) Now we don't need Normalize and the four first channels preserve the proper volume. Quote:
Any user can do the desired mix but I can't recommend that formula at all. For what, to obtain surround channels in 5.1, you need mix left and right channels? The Ls channel is a mix of Lss and Lsr, put Rsr is a mistake:
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20th August 2019, 10:06 | #3 | Link | |
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Thanks...
JuMe did some listening tests using this method, this is what he found: Quote:
Last edited by manolito; 20th August 2019 at 10:11. |
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20th August 2019, 15:07 | #4 | Link |
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Of course everybody can test anything and select their preferences.
I can understand some coeficient variations if Ls,Rs speakers aren't at -+115º, the average of Lss,Rss -+90º and Lsr,Rsr -+140º It is well know than we need only 4 speakers (FL,FR,BL,BR) to create any surround sound 2D with the appropiate mix. The 7.1 systems were created for commercial purposes, the 5.1 is more than enough for 2D surround. But include other back channels in the mix of Ls,Rs is out of my mind.
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20th August 2019, 21:23 | #5 | Link |
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There's probably some logic behind cross-mixing both the rear channels into each side to some degree. As 7.1ch rear surround speakers are behind you, you're going to hear both through each ear, and when mixed into the side speakers, if they're situated nearly to each side of you, the balance of sound you would have heard from the individual rear speakers would change.
And THX do it differently. The rear 7.1ch surround speakers are supposed to be directly behind you, virtually touching each other, more like a single speaker, so the rear surround channels would probably benefit more from cross-mixing when combining them into single surround channels. http://www.audiogurus.com/learn/spea...-placement/100 That's ignoring the fact that the sound you hear from a left rear speaker reaches you left ear sooner than the right one, but there's probably nothing to be done about that. Surround sound sucks anyway. There's nothing like a sound appearing from somewhere behind you to take you out of what you're watching and remind you that the sound is all around you but the picture isn't. Last edited by hello_hello; 21st August 2019 at 09:49. |
21st August 2019, 11:18 | #6 | Link |
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The origin of JuMe's algorithm is an official paper by the ETSI (European Telecommunications Standards Institute) about the AC-4 standard. The PDF document is here:
https://www.etsi.org/deliver/etsi_ts...01v010301p.pdf The downmix information is on page 103. So I guess it does make some sense to use this cross-mix approach for 8ch -> 6ch downmixing. I will add it to the "Downmix.avsi" which comes with AVStoDVD as an alternative to the existing 8to6 function, I will call the function "Dmix86Dpl2x". Cheers manolito //EDIT// Further research by JuMe revealed that this downmix algorithm is for a Dolby ProLogic IIx compatible downmix. On a 5.1 system he could only hear very subtle differences between the two methods. Last edited by manolito; 21st August 2019 at 13:56. |
21st August 2019, 16:29 | #7 | Link | |
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It is not to be played for a 5.1 system. Like I say before don't have sense preserve 7.1 when 5.1 can play the same 2D surround with the recommended mix. A 5.1 system can't recover the 7.1 original and your "Dmix86Dpl2x" have "very subtle differences" with the original, the "Dmix86" is exact to original.
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21st August 2019, 17:21 | #8 | Link | |
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If your reasoning was true then you would also say that the older DPL and DPL II matrices for 5.1 -> Stereo conversions are useless, right? According to your reasoning these formats were only meant for playback on 5.1 systems and not for playback on stereo systems. I believe that Dolby Labs and a lot of users would disagree... |
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21st August 2019, 20:58 | #9 | Link |
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I am very old and I remember the first Dolby Surround in VHS tapes, a stereo analogic audio matrix encoded was converted in more than 2 channels.
Until DPL II to obtain 5.0 (not 5.1) from only stereo analogic audio. You are right was usefull before digital conections (SPDIF, HDMI) or to save some space. I say than a DPL IIx to recover 7.1 from a 5.1 is useless at all, of course in my opinion.
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