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Topic: upmix to 5.1 DSP - what is the algorithm? (Read 771 times)
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## upmix to 5.1 DSP - what is the algorithm?

##### 2020-12-31 22:09:54
I use the Upmix to 5.1 DSP plugin all the time and it works great. But... what is the algorithm? I know it takes the stereo channels and mixes them using some proportions into the 5.1 channels. But what are the proportions?

How much of each stereo channel goes into each 5.1 channel?

## Re: upmix to 5.1 DSP - what is the algorithm?

##### Reply #1 – 2021-01-01 03:22:36
Stereo:
Front Left & Right = Unchanged.
Back Left & Right = Clone of the front left and right.
Center = FL + FR / 2

In Mono it sends the same thing to all channels except LFE.

In 3-Stereo (FL, FR, FC) it clones only the front left and right to the back.

In Quadrophonic it adds a center channel by combining the front left and right.

The following combos don't do anything and are left unchanged.
Mono Surround without Front Center (FL, FR, RC)
Mono Surround with Front Center (FL, FC, FR, RC)
Mono Surround with Front Center and Low Frequency Effects channel (FL, FC, FR, RC, LFE)
5.1 or higher configurations.

You can try out a few different configurations in the attached 7zip file.

## Re: upmix to 5.1 DSP - what is the algorithm?

##### Reply #2 – 2021-01-01 04:34:00
Perfect, thank you!

## Re: upmix to 5.1 DSP - what is the algorithm?

##### Reply #3 – 2021-01-04 18:24:20
Stereo:
Front Left & Right = Unchanged.
Back Left & Right = Clone of the front left and right.
Center = FL + FR / 2

In Mono it sends the same thing to all channels except LFE.

In 3-Stereo (FL, FR, FC) it clones only the front left and right to the back.

In Quadrophonic it adds a center channel by combining the front left and right.

The following combos don't do anything and are left unchanged.
Mono Surround without Front Center (FL, FR, RC)
Mono Surround with Front Center (FL, FC, FR, RC)
Mono Surround with Front Center and Low Frequency Effects channel (FL, FC, FR, RC, LFE)
5.1 or higher configurations.

You can try out a few different configurations in the attached 7zip file.

i noticed it isn't sending any data to the .1 channel. is this by design?

## Re: upmix to 5.1 DSP - what is the algorithm?

##### Reply #4 – 2021-01-06 00:17:43
Your amplifier's crossover should already be sending audio to the subwoofer without the audio signal explicitly sending anything over the LFE channel, which is usually reserved for movies and other such content.