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1st September 2003, 16:31 | #1 | Link |
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BUG: AC3filter 0.70b has wrong DPL2 downmix
@Valex
Please debug. The new Dolby ProLogic II downmix matrix in AC3filter 0.70b has wrong parameters. The right downmix parameters (unscaled) are Code:
L C R SL SR LFE 1 0.7071 0 -0.8660 -0.5000 0 L' 0 0 0 0 0 0 C' 0 0.7071 1 0.5000 0.8660 0 R' 0 0 0 0 0 0 SL' 0 0 0 0 0 0 SR' 0 0 0 0 0 0 LFE' To maintain the original dialogue level set the Master Gain to 6 dB. Set the DRC Power to 0 dB (= BeSweets normal compression) |
2nd September 2003, 11:54 | #2 | Link |
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AC3Filter currently has LFE * 1 -> L' & R'.
If you don't want LFE downmixed, then frank's matrix is what you want. But if you do want LFE downmixed, the usual practice is LFE * 0.7071. It's easy to switch between the two by moving the LFE gain slider between -inf (-9999) dB and -3.01 dB. So the current AC3Filter matrix is not really wrong. It just depends on how you want to downmix LFE. Also, is there a BSI downmix for LFE? I've never seen one, so what does the LFE BSI lock in AC3Filter do? I'm hoping for a more elegant solution to switch between downmixing LFE or not, but of course I can just customise the matrix to whatever Last edited by bleo; 3rd September 2003 at 06:05. |
2nd September 2003, 12:27 | #3 | Link |
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You are right with the parameters, bleo.
Downmix is a great compromise. Acoustic power of 5 channels is packed into 2 channels (+4 dB)! -> There must be a compression applied. LFE can be encoded to +10 dB above dialogue channel and has no function like a subwoofer (spreading bandwith)! It's useful in the cinema (very deep bass effects). That loudspeakers have membranes of 1-2 metre in diameter. That's why Dolby never included LFE channel into Dolby Surround downmix. (See Dolby's Downmix Manual) Consequently no DS filter expands LFE channel back from 2/0. So we don't need the LFE. Last edited by frank; 3rd September 2003 at 12:02. |
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