CALM DOWN!

Show

-24 LKFS

3

Show

-24 LKFS

-21 LKFS

4

Show

-24 LKFS

-21 LKFS?

5

Downmix Dilemma

Su

rrou

nd

Mix

Ls

Lf

C

Rf

Rs

?L

R

6

Frequent Downmix

Producers• Stereo Deliverables

Networks• Stereo Channels & Internet Distribution

Stations• Stereo Infrastructure & Channels

Consumers• Stereo STBs & TVs (≥61%)

7

Downmix Dilemma

Su

rrou

nd

Mix

Ls

Lf

C

Rf

Rs

?L

R?

?

0 dB

8

Preserve Center

Su

rrou

nd

Mix

C

L

R

+3 dB

Near Field

Average

+6 dB

9

Preserve Center

Su

rrou

nd

Mix

Ls

Lf

C

Rf

Rs

?L

R

?

-3 dB

∑

∑

10

Preserve Rear?

Su

rrou

nd

Mix

Ls

Lf

C

Rf

Rs

L

R

-3 dB

∑

∑

Can't Hear Dialog!

11

Adjust Rear

Su

rrou

nd

Mix

Ls

Lf

C

Rf

Rs

L

R

-3 dB

∑

∑

-3 dB

-3 dB

12

Defacto Standard Downmix

Su

rrou

nd

Mix

Ls

Lf

C

Rf

Rs

L

R

-3 dB

∑

∑

-3 dB

-3 dB

13

Defacto-Compatible Surround Mix

C

C

L

R

-3 dB

∑

∑

70 dB SPL

70 dB SPL

14

Incompatible Surround Mix

C

Lf

Rf

Power Sum10*Log(3) = 4.8 dB74.8 dB SPL

Lf

C

Rf

-3 dB

∑

∑

Voltage Sum20*Log (1+.7) = 4.6 dB

L

R

Power Sum10*Log(2) = 3 dB77.6 dB SPL

2.8 dB Error!

15

Bottom LineIf two ads are mixed in surround to measure -24 LKFS…One can sound and measure 2.8 dB louder after downmixProducers can "game" the system to be louderStations and MVPD's could be deemed non-complaint

when broadcasting "compliant" content!Not a problem when content mixed to be compatibleA real problem for some Public Television music shows

See AES e-Brief 38 for measured statistics "The Effect of Downmixing on Measured Loudness"

SOLUTION

17

Customize the Downmix

C

Lf

Rf

Power Sum10*Log(3)74.8 dB SPL

Lf

C

Rf

-12 dB

∑

∑

Voltage Sum20*Log (1+.2) = 1.8 dB

L

R

Power Sum10*Log(2) = 3 dB74.8 dB SPL

18

Producer-Controlled Metadata

Su

rrou

nd

Mix

Ls

Lf

C

Rf

Rs

AC

3 E

ncod

er

AC3

Audio +Metadata

AC

3 D

ecod

er

Left

Right

Producer Consumer

AC3

Audio +Metadata

LFE

Manual Metadata

19

TV Station-Controlled Metadata

Su

rrou

nd

Mix

Ls

Lf

C

Rf

Rs AC

3 E

ncod

er

AC

3 D

ecod

er

Left

Right

Producers Consumers

AC3

Dis

trib

uti

on

Pla

nt

TV StationsNetworks

No Metadata Channel!See ATSC A/85 Chapter 7

LFE

X X X

Audio +Metadata

20

Why No Metadata Channel?Many producers lack interest and ability in setting

metadataFor a show, requires adoption by ALL distributorsWithin a network, requires adoption by EVERY stationWithin a station, requires adoption in ALL equipmentMost equipment requires obscure custom settingsSome equipment cannot carry metadataPenalty of metadata error is severe: loss of center

channel!

*I'll buy you a beer if you'll let me whine about it.

*

*

21

Proposed SolutionStandardize downmix for systems without metadata

• -3 dB for Center and Rear

Require loudness measurement of the standard downmix• Encourages producers to mix appropriate to standard downmix• Producers can use film-style mixing or shift center channel phase• Penalty of an inappropriate mix is merely a show softer in

surround

Change delivery standardsModify A/85 Ask LKFS meter vendors to include downmix measurement

DISCUSSION