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Downmix Tables

The downmixing equations are based on AC-3 standards. They have been designed to end up the same regardless of whether signals are downmixed directly (for example, 7.1 to stereo) or in several successive steps (for example, 7.1 to 5.1 to stereo).

How to read the downmix tables

Consider the following table, describing the downmix equations used when routing a 5.1 input to a stereo output.

Sample table: Routing 5.1 to stereo

Input Channels L R
  Exact Decimal dB Exact Decimal dB
FL 1 1.000 0.00 0 0.000 -∞
FR 0 0.000 -∞ 1 1.000 0.00
C 1/√2 0.707 -3.01 1/√2 0.707 -3.01
SL 1/√2 0.707 -3.01 0 0.000 -∞
SR 0 0.000 -∞ 1/√2 0.707 -3.01

The left and right channels of the resulting stereo signal are the weighted sum of the inputs into these equations: 

            LOUT = FL + 1/√2 * C + 1/√2 * SL
            ROUT = FR + 1/√2 * C + 1/√2 * SR

Reference Tables

Like the above formula, you can calculate the output signal for each downmixed format by adding up the totals of each output channel column in the following reference downmix tables:

To Mono

Input Channels C
  Exact Decimal dB
FL 1/√2 0.707 -3.01
FR 1/√2 0.707 -3.01
C 1 1.000 0.00
SL 1/2 0.500 -6.02
SR 1/2 0.500 -6.02
BL 1/2 0.500 -6.02
BR 1/2 0.500 -6.02
Top 1 1.000 0.00
HFL 1/2 0.500 -6.02
HFC 1/√2 0.707 -3.01
HFR 1/2 0.500 -6.02
HBL 1/(2√2) 0.354 -9.03
HBR 1/(2√2) 0.354 -9.03

To Stereo

Input Channels L R
  Exact Decimal dB Exact Decimal dB
FL 1 1.000 0.00 0 0.000 -∞
FR 0 0.000 -∞ 1 1.000 0.00
C 1/√2 0.707 -3.01 1/√2 0.707 -3.01
SL 1/√2 0.707 -3.01 0 0.000 -∞
SR 0 0.000 -∞ 1/√2 0.707 -3.01
BL 1/√2 0.707 -3.01 0 0.000 -∞
BR 0 0.000 -∞ 1/√2 0.707 -3.01
Top 1/√2 0.707 -3.01 1/√2 0.707 -3.01
HFL 1/√2 0.707 -3.01 0 0.000 -∞
HFC 1/2 0.500 -6.02 1/2 0.500 -6.02
HFR 0 0.000 -∞ 1/√2 0.707 -3.01
HBL 1/2 0.500 -6.02 0 0.000 -∞
HBR 0 0.000 -∞ 1/2 0.500 -6.02

To 3.x

Input Channels L R C
  Exact Decimal dB Exact Decimal dB Exact Decimal dB
FL 1 1.000 0.00 0 0.000 -∞ 0 0.000 -∞
FR 0 0.000 -∞ 1 1.000 0.00 0 0.000 -∞
C 0 0.000 -∞ 0 0.000 -∞ 1 1.000 0.00
SL 1/√2 0.707 -3.01 0 0.000 -∞ 0 0.000 -∞
SR 0 0.000 -∞ 1/√2 0.707 -3.01 0 0.000 -∞
BL 1/√2 0.707 -3.01 0 0.000 -∞ 0 0.000 -∞
BR 0 0.000 -∞ 1/√2 0.707 -3.01 0 0.000 -∞
Top 1/√3 0.577 -4.77 1/√3 0.577 -4.77 1/√3 0.577 -4.77
HFL 1/√2 0.707 -3.01 0 0.000 -∞ 0 0.000 -∞
HFC 0 0.000 -∞ 0 0.000 -∞ 1/√2 0.707 -3.01
HFR 0 0.000 -∞ 1/√2 0.707 -3.01 0 0.000 -∞
HBL 1/2 0.500 -6.02 0 0.000 -∞ 0 0.000 -∞
HBR 0 0.000 -∞ 1/2 0.500 -6.02 0 0.000 -∞

To 4.x

Input Channels L R SL SR
  Exact Decimal dB Exact Decimal dB Exact Decimal dB Exact Decimal dB
FL 1 1.000 0.00 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞
FR 0 0.000 -∞ 1 1.000 0.00 0 0.000 -∞ 0 0.000 -∞
C 1/√2 0.707 -3.01 1/√2 0.707 -3.01 0 0.000 -∞ 0 0.000 -∞
SL 0 0.000 -∞ 0 0.000 -∞ 1 1.000 0.00 0 0.000 -∞
SR 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 1 1.000 0.00
BL 0 0.000 -∞ 0 0.000 -∞ 1 1.000 0.00 0 0.000 -∞
BR 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 1 1.000 0.00
Top 1/√4 0.500 -6.02 1/√4 0.500 -6.02 1/√4 0.500 -6.02 1/√4 0.500 -6.02
HFL 1/√2 0.707 -3.01 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞
HFC 1/2 0.500 -6.02 1/2 0.500 -6.02 0 0.000 -∞ 0 0.000 -∞
HFR 0 0.000 -∞ 1/√2 0.707 -3.01 0 0.000 -∞ 0 0.000 -∞
HBL 0 0.000 -∞ 0 0.000 -∞ 1/√2 0.707 -3.01 0 0.000 -∞
HBR 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 1/√2 0.707 -3.01

To 5.x

Input Channels L R C SL SR
  Exact Decimal dB Exact Decimal dB Exact Decimal dB Exact Decimal dB Exact Decimal dB
FL 1 1.000 0.00 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞
FR 0 0.000 -∞ 1 1.000 0.00 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞
C 0 0.000 -∞ 0 0.000 -∞ 1 1.000 0.00 0 0.000 -∞ 0 0.000 -∞
SL 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 1 1.000 0.00 0 0.000 -∞
SR 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 1 1.000 0.00
BL 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 1 1.000 0.00 0 0.000 -∞
BR 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 1 1.000 0.00
Top 1/√5 0.447 -6.99 1/√5 0.447 -6.99 1/√5 0.447 -6.99 1/√5 0.447 -6.99 1/√5 0.447 -6.99
HFL 1/√2 0.707 -3.01 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞
HFC 0 0.000 -∞ 0 0.000 -∞ 1/√2 0.707 -3.01 0 0.000 -∞ 0 0.000 -∞
HFR 0 0.000 -∞ 1/√2 0.707 -3.01 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞
HBL 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 1/√2 0.707 -3.01 0 0.000 -∞
HBR 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 1/√2 0.707 -3.01

To 6.x

Input Channels L R SL SR BL BR
  Exact Decimal dB Exact Decimal dB Exact Decimal dB Exact Decimal dB Exact Decimal dB Exact Decimal dB
FL 1 1.000 0.00 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞
FR 0 0.000 -∞ 1 1.000 0.00 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞
C 1/√2 0.707 -3.01 1/√2 0.707 -3.01 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞
SL 0 0.000 -∞ 0 0.000 -∞ 1 1.000 0.00 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞
SR 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 1 1.000 0.00 0 0.000 -∞ 0 0.000 -∞
BL 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 1 1.000 0.00 0 0.000 -∞
BR 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 1 1.000 0.00
Top 1/√6 0.408 -7.78 1/√6 0.408 -7.78 1/√6 0.408 -7.78 1/√6 0.408 -7.78 1/√6 0.408 -7.78 1/√6 0.408 -7.78
HFL 1/√2 0.707 -3.01 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞
HFC 1/2 0.500 -6.02 1/2 0.500 -6.02 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞
HFR 0 0.000 -∞ 1/√2 0.707 -3.01 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞
HBL 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 1/√2 0.707 -3.01 0 0.000 -∞
HBR 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 1/√2 0.707 -3.01

To 7.x

Input Channels L R C SL SR BL BR
  Exact Decimal dB Exact Decimal dB Exact Decimal dB Exact Decimal dB Exact Decimal dB Exact Decimal dB Exact Decimal dB
FL 1 1.000 0.00 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞
FR 0 0.000 -∞ 1 1.000 0.00 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞
C 0 0.000 -∞ 0 0.000 -∞ 1 1.000 0.00 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞
SL 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 1 1.000 0.00 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞
SR 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 1 1.000 0.00 0 0.000 -∞ 0 0.000 -∞
BL 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 1 1.000 0.00 0 0.000 -∞
BR 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 1 1.000 0.00
Top 1/√7 0.378 -8.45 1/√7 0.378 -8.45 1/√7 0.378 -8.45 1/√7 0.378 -8.45 1/√7 0.378 -8.45 1/√7 0.378 -8.45 1/√7 0.378 -8.45
HFL 1/√2 0.707 -3.01 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞
HFC 0 0.000 -∞ 0 0.000 -∞ 1/√2 0.707 -3.01 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞
HFR 0 0.000 -∞ 1/√2 0.707 -3.01 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞
HBL 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 1/√2 0.707 -3.01 0 0.000 -∞
HBR 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 0 0.000 -∞ 1/√2 0.707 -3.01

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