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Author Topic: What is happening when MC converts 6 ch source to 4 ch?  (Read 1703 times)

thezone

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What is happening when MC converts 6 ch source to 4 ch?
« on: May 27, 2014, 12:04:17 am »

Hi,

Can anyone please advise which input channels are ascribed to which output in this conversion?

Reason being, I needed to create one file with only 4 channels but I have no idea how to do this but I do know how to create a 6 channel wav file which contains only a stereo Front R/L and a stereo Rear R/L. To play this back I set MC to convert it to a 4ch for output to the sound card. However when I monitor the playback the front L & R are there in channels 1 & 2 but only one of the Rear channels are making it to the sound card in channel 3 (no ch 4). Playback is via asio/usb to a 2i4 focusrite.

Which of the 6 channels is going to which of the 4 channels? If I know this I might be able to fiddle around when making the original 6 ch file to make this work.

Cheers
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thezone

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Re: What is happening when MC converts 6 ch source to 4 ch?
« Reply #1 on: May 28, 2014, 06:37:25 am »

bump!
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mwillems

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Re: What is happening when MC converts 6 ch source to 4 ch?
« Reply #2 on: May 28, 2014, 09:00:15 am »

bump!

Could you be more specific about the settings you're using output format?  Do you mean that you're setting output format to 4 channel and telling it to use JRSS mixing?  If you do that it doesn't just route channels, it downmixes them so depending on which channels you've used in your source file you can get really different results.

JRiver's downmixing engine assumes that a 6-channel file is 5.1, which means the channels would be ordered Left, Right, Center, Sub, Left Surround, Right Surround.  If the 6 channel file you made has the rear channel information on channels 3 and 4, you will not get the results you want because JRiver assums that those channels contain center and subwoofer info and mixes accordingly.

If you have the rear left and right on channels 5 and 6 and are still not getting sensible results, you might want to try tinkering with the channel routing settings in your audio driver, or changing the channel offset in JRiver's ASIO settings.
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thezone

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Re: What is happening when MC converts 6 ch source to 4 ch?
« Reply #3 on: May 31, 2014, 05:14:49 am »

Thanks for the reply. Unfortunately none of these things has an impact. I cant change the ASIO channel offest to anything other than 0 or it wont play at all. I even tried to swap c/lfe with sl/sr but that didnt actually change anything.

I get the stereo left and right front outputting correctly, but it seems like everything else is summed to mono when it only has 4 channels to go to?
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thezone

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Re: What is happening when MC converts 6 ch source to 4 ch?
« Reply #4 on: May 31, 2014, 07:51:25 pm »

Ok Heres what Im trying to do.

I want to use MC to play backing tracks on stage because its such a good interface that I am used and is tablet friendly and Ableton and other programs are way to fussy and complicated for stage playback. There are also a gazillion programs to do this in mono (sequence left/click right) but I want to keep in stereo. I play the drums and I need (prefer) to run stereo sequences (backing tracks) and I would ideally like to run a stereo sequence and stereo click track simultaneously.

So I discovered in cool edit pro (I know its a dinosaur but it works) that I can create a 5.1 channel wma or wav file and assign stereo or mono files to whatever channels I desire. So I created a single wma lossless file (which can be tagged) that contains the sequence (backing track) in stereo front and left and then the stereo click I assigned to the rear left and right.

For playback I am using a Focusrite Scarlet 2i4 external sound card.http://us.focusrite.com/usb-audio-interfaces/scarlett-2i4 This has 4 channels in a 2 x pair set up which means it can only accept 4 ch of pcm thru usb.

....so using MC in ASIO output mode and in the DSP studio I have Output Format checked in the left top, and in the right side Channels: is set to 4 (this is the only output setting that works (which makes sense). However, the surround left and right (click track) is being sent to the soundcard in the left only channel as mono.

As a side note I have tried changing Mixing: to JRSS but the sound is quieter than "No Upmixing or downmixing"?

Just wondered why the rears(surround L/R) are being sent as a mono file to channel 3? Actually it could be that left surround ch is being sent to ch 3 on the sound card and that right surround is being discarded.
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thezone

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Re: What is happening when MC converts 6 ch source to 4 ch?
« Reply #5 on: June 02, 2014, 05:47:26 pm »

bump!
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Matt

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Re: What is happening when MC converts 6 ch source to 4 ch?
« Reply #6 on: June 03, 2014, 09:47:13 am »

6 to 4 channel conversion uses the following logic:

The subwoofer is split between all four channels in a way that maintains the power (quarter power multiplier times each and adjusted for if the subwoofer is +10dB).

The center is mixed into the sides.
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Matt Ashland, JRiver Media Center
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