22
CALM DOWN!
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
