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Author Topic: Is "5.1 channels inside a 7.1 container" broken or do I have it wrong?  (Read 2448 times)

mattkhan

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I thought that this output format created a 5.1 mix target but added 2 extra blank channels. This isn't what I'm experiencing however, it seems that a 5.1 track has the SL/SR channels copied to the RL/RR channels. I do have JRSS mixing enabled. Adding a PEQ step to mute RL/RR seems to have no effect.

Any ideas?

Context is that I have added a nearfield sub so was thinking of 5.1 in 7.1 to give me a spare output channel, I could then add an appropriate filter to copy the LFE to that channel with a different (lower) low pass. Clearly this doesn't work when there's a load of surround garbage coming from behind my ears!
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mwillems

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Re: Is "5.1 channels inside a 7.1 container" broken or do I have it wrong?
« Reply #1 on: October 04, 2015, 03:13:48 pm »

I thought that this output format created a 5.1 mix target but added 2 extra blank channels. This isn't what I'm experiencing however, it seems that a 5.1 track has the SL/SR channels copied to the RL/RR channels. I do have JRSS mixing enabled. Adding a PEQ step to mute RL/RR seems to have no effect.

Any ideas?

Context is that I have added a nearfield sub so was thinking of 5.1 in 7.1 to give me a spare output channel, I could then add an appropriate filter to copy the LFE to that channel with a different (lower) low pass. Clearly this doesn't work when there's a load of surround garbage coming from behind my ears!

5.1 in a 7.1 container should create a 5.1 mixing target with 2 spare channels.  It's possible that it's bugged, but I have one suggestion.  Can you verify that there's content present on both SR/SL and RR/RL at the same time with 5.1 in a 7.1 container enabled?

One common issue that trips people up is that the channel enumeration is different in 5.1 than in 7.1.  The standard 5.1 channel enumeration is L,R,Center, LFE, SL, SR, whereas the standard 7.1 channel enumeration is L,R,Center,LFE, RL, RR, SL, SR.  So if you're moving from "5.1" to "5.1 in a 7.1 container", SL and SR were previously mapped to the 5th and 6th channels but will now be mapped to the 7th and 8th channels.  RL and RR will be mapped to the 5th and 6th channels and should be blank.

Such a channel mapping issue would also explain why muting RR and RL has no effect (because you're not actually monitoring RL and RR, but instead monitoring the newly remapped SL and SR).  Of course it's possible that there's a bug in the mixing and the 5th and 6th channel have accidental content in them too, but first make sure you're looking in the right place.
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mattkhan

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Re:
« Reply #2 on: October 04, 2015, 05:05:32 pm »

User error then :) I did not know that 7.1 moved SR/SL down to channels 7 and 8.
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