Measuring Loudness Levels § When we measure loudness levels, we need to account for frequency sensitivity § This is done by applying a weighting filter to audio § For several yeas the A-weighting filter was commonly used § Other weighting curves (B and C for example) are also defined § Additionally measurement with multi channel audio need to take how we hear audio from different directional sources (i.e. surrounds) into account. Loudness Management Strategies § “Measure and Set” § Measure content, set content with accurate metadata § “Measure and Scale” § Measure content, scale content to desired target level § “Target and Evaluate” § Select target loudness for submission – Specified in technical delivery specs § Evaluate content for compliance

1. Dolby and the double-D symbol are registered trademarks of Dolby Laboratories. All other trademarks remain the property of their respective owners. © 2010 Dolby Laboratories, Inc. All rights reserved.
CONFIDENTIAL INFORMATIONNovember 2, 2017
Loudness

2. 2
Dynamic
Range
is the ratio
between the
largest and
smallest possible
values of a
changeable
quantity

3. Dynamic Range - is dependent on receiver type
CONFIDENTIAL INFORMATION 3
Analog FM broadcasts
rarely have a dynamic
range exceeding 50
dB
DTV audio offers more than
100 dB of dynamic range

4. 4
Loudness Measurement

5. 5
Measuring Loudness Levels
§ Accurate loudness measurement must take the human ear into
account and the perception of loudness.
§ We know that tones of equal level are not perceived to be equally
loud when they are of different frequencies
§ This was first measured by Fletcher and Munson in 1933
§ Fletcher-Munson curves & ISO Equal Loudness Curves

6. 6
Measuring Loudness Levels
§ When we measure loudness levels, we need to account for
frequency sensitivity
§ This is done by applying a weighting filter to audio
§ For several yeas the A-weighting filter was commonly used
§ Other weighting curves (B and C for example) are also defined
§ Additionally measurement with multichannel audio need to take how
we hear audio from different directional sources (i.e. surrounds) into
account.

7. 7
Measuring Loudness Levels

8. 8
Measuring Loudness Levels
§ Following on from the updating of the Equal Loudness Curves (ISO
226: 2003, the ITU investigated loudness meters and developed a
new weighting curve.
§ It uses two concatenated weighting curves – A 2nd order filter to
account for the acoustic effects of the head followed by a Revised
Low-Frequency B-weighting curve.
§ ITU-R Rec. BS-1770- (1 and 2) defines this method and has
become the defacto world specification for loudness
measurement
§ ITU-R BS.1770-2 added a simple level-based gating component to
the “-1” version

9. 9
Measuring Loudness Levels
§ Both ITU 1 and 2 as well as EBU R128 use a K-Weighting filter with
different gain factors applied to the front and rear channels.
§ The result is displayed as LKFS for ITU-1 and 2 and LUFS for EBU
R 128 which correspond to K-weighted loudness relative to digital
full scale

10. Confidential Information
K-weighting
§ 2nd order pre-filter
§ RLB weighting

11. Confidential Information
K-weighting

12. 12
Measurement Modes
§ Short Term measurement mode
§ Measures using a 10 second “sliding window” method – BS 1770-1
§ Measures using a 3 second “sliding window” method – EBU R128
10s
Time
0sec 15sec
10s 10s 10s 10s
§ Measurement is updated each 10 second period
§ Infinite Term measurement mode
§ Measures continuously until reset either manually or automatically
§ Several “auto-reset” options available: 10 seconds to 10 minutes with reset

13. 13
Dolby Loudness Measurement Tools
§ Measurement with Dialog Intelligence on or off for LeqA, ITU BS 1770-1
§ Measurement with relative gating (infinite measurements) for ITU BS-1770-
2 and EBU R128
§ Provide multiple Time-Scales
§ Short-Term: 10 second “sliding window” for ITU BS 1770-1, 3 seconds for EBU
§ Long-Term: “infinite” (entire measurement period)
§ Utilize ‘Fixed’ measurement references
§ 0 dBFS is the same everywhere…
§ Provide a quantitative result (log)
Note: All measurements tools are currently not completely aligned

14. 14
Dolby Loudness Measurement Tools
§ LM100 Broadcast Loudness Meter
§ Dolby Media Meter

15. 15
And what about my existing meters?
§ “VU”
§ Volume units
§ VU Meters
§ Measures average power of audio signals
§ Signal peaks are not measured
§ “PPM”
§ Peak Program Meter
§ Several arbitrary scales
§ Measures the peak value of the audio signal
§ NEITHER METER MEASURES LOUDNESS!!
15

16. 16
And what about my existing meters?
§ PPM and VU meters do not measure perceived loudness
§ Short response times
§ Defined to have a flat frequency response over much of the audio
frequency spectrum
§ However, when we listen we use a longer duration of audio
§ We do not perceive frequencies equally across the spectrum
§ We intelligently select what audio to judge the overall loudness on

17. 17
So why do we measure peak levels?
§ It’s important to avoid overload of equipment
§ Essential in the digital domain
§ For systems with a small maximum SNR, it is important to ensure
the level “to tape” is maximised
§ We still have to consider that broadcast content will be modulated
on to an RF carrier
§ Need to avoid excessive overmodulation
§ Available dynamic range is small
§ Can help approximate loudness matching for narrow dynamic range
content

18. 18
But peak meters don’t indicate true peaks
§ It should be remembered that peak meters don’t read true peaks
§ PPMs have ballistics to avoid fast transients
§ Digital peak meters under read due to limited number of sample points
§ ITU BS 1770-1 & 2 and EBU R128 standardized true peak meters
that use oversampling.

19. 19
Loudness Management

20. 20
When/Where to Measure
§ Live Production
§ Post Production
§ Quality Control/Ingest
§ Transmission
§ Confidence monitoring of Bitstream out from consumer devices

21. 21
Measurement in Practice
§ Short Term measurement mode
§ Used while mixing
§ Fluctuations in Short Term measurement are OK.
§ Long Term measurement mode
§ Used while mixing with a reset period
§ Used after mixing to get an accurate measurement of the entire
program
§ Used for target level

22. 22
Loudness Control
§ ATSC’s Document A/85:2011, 25 July 2011
§ www.atsc.org
§ ITU BS1770 Loudness Measurement Method
§ Metadata friendly approach
§ Leave more room for creative mixing
§ Exhaustive document, with tips for mixing and room calibration
§ EBU R128
§ http://tech.ebu.ch/loudness - a suite of documents
§ Normalize audio at -23 LUFS +/- 1 LU, measured with a
relative gate at -10 LU
§ Encourages use of Loudness Range in conjunction with LUFS
and maximum true peak
22
Two approaches, both solve the problem

23. Loudness Standards in Digital Television:
The difference between dBFS, LKFS and
LUFS
Dolby Metadata Demystified
-20 dBFS
0 dBFS
-10 dBFS
-30 dBFS
-40 dBFS
-50 dBFS
-20 LKFS
0 LKFS
-10 LKFS
-30 LKFS
-40 LKFS
-50 LKFS
-20 LUFS
0 LUFS
-10 LUFS
-30 LUFS
-40 LUFS
-50 LUFS
The scale is the
same, only the units
are different.

24. 24
Loudness Management Strategies
§ “Measure and Set”
§ Measure content, set content with accurate metadata
§ “Measure and Scale”
§ Measure content, scale content to desired target level
§ “Target and Evaluate”
§ Select target loudness for submission – Specified in technical delivery
specs
§ Evaluate content for compliance

25. 25
“Measure and Set”
§ Used for Dynamic (Agile) metadata workflows.
§ Content is measured for loudness
§ Loudness measurement inserted into content as loudness metadata
§ File-based tools can speed-up and automate process
§ Downstream systems must support audio metadata
§ Dolby E, V-ANC, RS-422/485, H-ANC, others

26. 26
“Measure and Scale”
§ Used for Static metadata workflows.
§ A target loudness value is chosen (per standard A/85 - -24LKFS or
EBU R128 - -23LUFs or broadcaster technical delivery spec.
§ Content is measured and compared to target
§ Content is scaled to meet target value
§ Can be performed realtime during live events/post production or
non-realtime in filebased workflow as a one-time gain change.
§ Transmitted dialnorm is set to match target value

27. 27
“Target and Evaluate”
§ Used in Quality Control/Ingest
§ Target loudness value included in standard or delivery specification
§ Content is evaluated for compliance
§ Content that does not comply with the delivery specification may be
rejected or corrected, at the discretion of the network

28. Dolby and the double-D symbol are registered trademarks of Dolby Laboratories. All other trademarks remain the property of their respective owners. © 2010 Dolby Laboratories, Inc. All rights reserved.
CONFIDENTIAL INFORMATIONNovember 2, 2017
Dolby Technologies Overview

29. 29
What are Dolby technologies?
Dolby has created a complete technology system for the conveyance of
mono through 5.1 (and more) channel Surround Sound through content
creation, distribution, transmission, and presentation in the consumers
home.
The core of the Dolby system are:
1. Bitrate reduction audio data compression schemes (codecs)
2. The use of metadata (data about the data) to provide a controllable,
predictable, and enjoyable listening experience in a variety of listening and
monitoring environments.
3. Loudness measurement specifically the use of Dialog Intelligence to
provide the tools for proper usage of key metadata parameters.
These combine to form:

30. 30
The Complete Multichannel Audio Solution for
The Broadcast Chain
Capture
Production
Post-
production
Contribution
Distribution
Transmission
Reception
RCL
RsLs
LFE
5.1
30

31. 31
Dolby Solutions For Stereo and Multichannel Broadcast
Dolby has developed two codecs for use in modern digital broadcast.
§ Both of these are perceptual codecs but differ in purpose and the
available numbers of channel they carry, datarate, and structure.
§ Both of these codecs carry metadata.
§ One of these codecs is used only for final broadcast delivery to
the consumer. This is referred to as transmission or emission
codec - Dolby Digital Plus (E-AC-3)
§ Legacy transmission codec - Dolby Digital (AC-3)
§ The other is specifically for content production and distribution
and is referred to as a contribution codec - Dolby E

32. 32
Dolby E

33. 33
Dolby Solutions For Stereo and Multichannel Broadcast
For Multichannel Production, Contribution, and Distribution:
§ Dolby E enables up to 8 channels of audio and metadata to be
carried using a conventional AES stereo channel on equipment such
as VTRs, servers, routers, etc.
• The audio channels are grouped into programs each with its own
metadata
• Dolby E operates at video frame rates to enable glitch-free editing
and switching synchronous with video of coded audio.
• The high data rate also allows for multiple decodes/encodes with no
audio degradation

34. 34
Dolby Solutions For Multichannel Broadcast
For Multichannel Production, Contribution, and Distribution:
§ Dolby E is also used for multichannel delivery on videotape or in file-
based delivery.
§ Dolby E is used for backhaul for live events i.e. concerts and
sporting events
§ Dolby E is often used for “mezzanine” level distribution in MPEG
transport streams for distribution regionally or internationally
between broadcast facilities.

35. 35
The Contribution Pipe
Dolby E provides a contribution-level audio signal that can survive
numerous encode/decode cycles without audible artifacts.
Dolby E conveys metadata to downstream devices.
24bit AES Lt/Rt 2.3Mb/s
24bit AES L/R 2.3Mb/s
24bit AES C/Lfe 2.3Mb/s
24bit AES Ls/Rs 2.3Mb/s
Metadata
1.92Mb/s data
Dolby E encoding
delay: 1 video frame

36. 36
Decoding the Dolby E data stream recovers the original
audio programs including their associated metadata
values.
The Contribution Pipe
24bit AES Lt/Rt 2.3Mb/s
24bit AES L/R 2.3Mb/s
24bit AES C/Lfe 2.3Mb/s
24bit AES Ls/Rs 2.3Mb/s
1.92Mb/s data
Metadata
Dolby E decoding
delay: 1 video frame

37. Working with Dolby E
CONFIDENTIAL INFORMATION 37

38. Dolby E Overview - Encoder Basics
CONFIDENTIAL INFORMATION 38
Video Video Video Video Video Video Video Video
Metadat
a
Metadat
a
Metadat
a
Metadat
a
DOLBY E
ENCODER
GUARD
BAND
VRef
DOLBY EAUDIO

39. Bitstream Design
§ The Dolby E bitstream looks like standard stereo PCM. It
meters as full scale. Don’t worry, it is supposed to look
like that.
§ Sample rate is 48kHz
§ The Dolby E output format can be 16-bit, or 20-bit
§ 16-bit – 4 or 6 channels of audio
§ 20-bit – 4, 6, or 8 channels of audio
§ Dolby E bitstreams are carried via standard digital audio
interface (AES/EBU) as well as embedded in SDI
CONFIDENTIAL INFORMATION 39
48 kHz sample rate
Bit
depth Dolby E FrameL R L R

40. Typical Program Configurations
§ 5.1 (5.1)
§ Often used when infrastructure only allows the use of 16-bit
§ 5.1 plus second language Lt/Rt (5.1+2)
§ 5.1 plus original audio from VTR 3/4 (5.1+2)
§ 4 stereo programs (4x2)
§ Often used for multilanguage applications
§ Many others including:
§ Eight mono programs (8x1)
§ 5.1 plus two monos (5.1+2x1)
§ Three stereos (3x2), etc…
CONFIDENTIAL INFORMATION 40

41. Video Frame Synchronization
§ Synchronous audio/video
§ Editing/switching is done on video frame boundaries
§ Asynchronous audio/video frames are difficult to switch from one program
to the next
§ Synchronous framing makes switching simple
CONFIDENTIAL INFORMATION 41
video video video video
audio audio audio audio audio
Asynchronous
video video video video
audio audio audio audio
Synchronous

42. Switching Dolby Digital
CONFIDENTIAL INFORMATION 42
Video
Dolby Digital
Data Frames
5.1 5.1 5.1 5.1 5.1
Switch or edit
on video
frame
boundary
2.0 2.05.1
Corrupts two
Dolby Digital
data frames
5.1
Dolby E vs Dolby Digital

43. Switching Dolby E
CONFIDENTIAL INFORMATION 43
Dolby E
survives since
frame rate
matches
video
Video
Dolby E
Data Frames
5.1 5.15.15.1
Switch or edit
on video
frame
boundary
2.0
Dolby E vs Dolby Digital

44. Latency
§ Dolby E encoding or decoding introduces a fixed 1 frame
delay to the audio
§ That is One frame on Encode, and One frame on Decode
§ The delay was fixed at 1 frame because:
§ Video equipment often introduces delays which are integer
numbers of frames
§ A low encode/decode delay is not an advantage when multiple
encode/decode cycles may be cascaded – delays will
accumulate until noticeable
CONFIDENTIAL INFORMATION 44

45. 45
Dolby Digital Plus

46. 46
Dolby Solutions For Multichannel Broadcast
For Transmission to the home consumer:
§ Emission audio, 1 to 13.1 channels, typical 5.1 data rate of 192kbps
§ Metadata for loudness control, dynamic range control, and downmixing
§ Dolby Digital Plus and E-AC-3 (or EC3) are the same thing
§ Dolby Digital Plus is an extension of the legacy Dolby Digital codec
developed in 1992 for film and later DVD and Broadcast and yields
significantly reduced datarates
Audio is encoded as Dolby Digital Plus just prior to transmission.

47. 47
24bit AES L/R 2.3Mb/s
24bit AES C/Lfe 2.3Mb/s
24bit AES Ls/Rs 2.3Mb/s
The Transmission Pipe
Dolby Digital Plus is optimized for both high audio
quality and maximum bandwidth efficiency.
Intended for transmission, not distribution.
192kb/s data
Metadata

48. 48
Left
Right
Center
Lfe
Ls
Right Surround
5.1
program
audio
Home Theater/TV Reception
In the home, Dolby Digital Plus data is decoded and
processed appropriately for the viewer’s listening
environment using Metadata.
Left
Right5.1
program
audio,
downmixed
to stereo
Left
Right
Center
Left Surround
5.1
program
audio
Dolby Digital
Plus
Decoder
192kb/s data

49. 49
24bit AES L/R 2.3Mb/s
Dolby Digital Plus in Stereo
Dolby Digital Plus is also widely adopted for stereo
transmission.
Metadata
2 channels,
48kHz, 24bit
= 2.3Mb/s
Dolby Digital
Plus
Encoder
96kb/s data

50. 50
Right
5.1
program
audio
Home Theater/TV Reception
Same as Dolby Digital Plus in 5.1. Dolby Digital Plus in
stereo is decoded and processed appropriately for the
viewer’s listening environment using Metadata.
LeftStereo
program
audio
Dolby Digital
Plus
Decoder
96kb/s data
Analogue Output
Digital Input

51. 51
STB/iDTV
Video
DD/DD+
decode
Dolby Digital
Encode
SPDIF (Dolby Digital)
HDMI
Dolby metadata
Analog out
One stream for all devices - 100% Compatible

52. 52
Metadata

53. 53
Metadata – What is it?
• Metadata is “data about the data” and is carried along with the audio
in the digital bitstream.
• The purpose of metadata is:
§ To provide the listener with a consistent listening level
§ To provide a listening experience compatible with the type of
audio reproduction system the listener is using
§ To make sure the listener hears the appropriate balance
between channels when listening to 5.1 content on a stereo or
mono reproduction system.

54. 54
Metadata – What is it?
§ Metadata is created during the Dolby Digital Plus encode and applied in the
viewers home in the decoder in their television, set-top box or home theatre.
§ It does not alter the source audio.
§ Metadata values can alternatively be set upstream from the Dolby Digital
Plus encode in Dolby E during production or post-production and passed
along to the Dolby Digital Plus encoder.

55. 55
Metadata – What is it?
§ There are two basic approaches to the use of Metadata in broadcast
workflows: Dynamic or Static.
§ Dynamic (or agile) metadata workflow – Metadata values can change with each
program as long as set correctly. This is more appropriate when metadata is set
upstream from the Dolby Digital Plus encoder.
§ Static metadata workflow – Metadata values are constant/hardset in the Dolby
Digital Plus encoder.
Whether a workflow uses PCM or Dolby E upstream from the Dolby
Digital Plus encode, accurate loudness measurement and monitoring
are essential to ensure that metadata is set properly in a dynamic
metadata workflow OR that the audio matches how the metadata will
be set in the downstream encoder with a static metadata workflow.

56. 56
Metadata – What is it?
§ Most important Dolby metadata parameter. The 3Ds
§ Dialnorm (Dialog Normalization)
§ DRC profiles
§ Downmix
§ Common Dolby metadata parameter setting
§ Dialnorm = -23LUFS (EBU recommendation)
§ DRC profiles = Film Standard
§ Downmix = -3dB

57. 57
Metadata – Dialog Normalization
§ Loudness variations are undesirable and are a source of listener
complaints.
§ When switching TV channels
§ Between different programs
§ Between program segments (station breaks and commercials)

58. 58
Variation in Loudness of Some Typical Audio Signals
LD MOVIE VHS HI-FI DSS PPV CLASSICAL POP CD TV AUDIO WERBUNG
AVERAGE / DIALOG SIGNAL PEAKS
-27 -24 -21 -20
-10
-20
-7
-20 dBFs
Peak=0 dBFs
-10 dBFs
-30 dBFs
-40 dBFs
ACTION
FILM DRAMA SPORTS CLASSICAL NEWS ADSROCK
§The problem: Different programs are mixed with different peaks and dialog levels.
The consumer must manually adjust the playback volume when switching from one
source to another to maintain the same perceived loudness.

59. 59
Dialog Level (Dialnorm) Metadata Provides the Solution
§ Helps to correct volume differences
§ between program segments
§ between channels, signal sources
§ Provides the listener with a consistent level of perceived
volume while maintaining dynamic range

60. 60
What is the “dialnorm” metadata parameter?
§ Defined as the level of normal spoken dialogue with respect
to Full Scale Digital (a.k.a. 0dBFS)
§ The decoder uses this parameter to “normalize” program
volume to a consistent listening level
§ It identifies the area of normal speech within an audio program
and provides the ability to “calibrate” the listening environment
§ Dialnorm also applies to other types of program material, like
music videos and concerts

61. 61
What is the “dialnorm” metadata value?
§ Dialnorm values range between -31 (no level shift in the home
decoder) to -1 (maximum level shift in the home decoder)
§ Where did “-31” come from?
§ Movie dialog ranges from -31 to -25dBFS
§ Typical movie dialog is around -27dBFS

62. 62
Dialog Normalization (Dialnorm)
LD MOVIE VHS HI-FI DSS PPV CLASSICAL POP CD TV AUDIO WERBUNG
AVERAGE / DIALOG SIGNAL PEAKS
-27 -24 -21 -20
-10
-20
-7
-20 dBFs
Peak=0 dBFs
-10 dBFs
-30 dBFs
-40 dBFs
ACTION
FILM DRAMA SPORTS CLASSICAL NEWS ADSROCK
§The solution: Set the dialog level (dialnorm) metadata parameter to indicate the
equivalent dialog level, ranging from -1 dBFS to -31 dBFS. Or adjust the audio to a
target level that corresponds to the static dialnorm metadata parameter used in the
encoder.

63. 63
Normalized Audio Signals at the Output of the Decoder
LD MOVIE VHS HI-FI DSS PPV CLASSICAL POP CD TV AUDIO WERBUNG
ACTION
FILM DRAMA SPORTS CLASSICAL NEWS ADSROCK
-20 dBFs
Peak=0 dBFs
-10 dBFs
-30 dBFs
-40 dBFs
AVERAGE / DIALOG SIGNAL PEAKS
The solution: In the home the decoder adjusts the playback level for each
program automatically, by normalizing to a common level. All dialog now
reproduced at -31dBFS
Application of dialnorm is transparent when set correctly
All dialog now
reproduced at -31dBFS

64. 64
Original Dynamic Range
LD MOVIE VHS HI-FI DSS PPV CLASSICAL POP CD TV AUDIO WERBUNG
AVERAGE / DIALOGUE SIGNAL PEAKS
-20 dBFs
Peak=0 dBFs
-10 dBFs
-30 dBFs
-40 dBFs
ACTION
FILM DRAMA SPORTS CLASSICAL NEWS ADSROCK

65. 65
Normalized Audio Signals at the Output of the Decoder
LD MOVIE VHS HI-FI DSS PPV CLASSICAL POP CD TV AUDIO WERBUNG
ACTION
FILM DRAMA SPORTS CLASSICAL NEWS ADSROCK
-20 dBFs
Peak=0 dBFs
-10 dBFs
-30 dBFs
-40 dBFs
AVERAGE / DIALOG SIGNAL PEAKS
The solution: The original dynamic range is preserved by dialog normalization

66. 66
Agile Metadata
Program 1
Program 2
Program 3
Program 4
DialnormAdjustment
withinDolbydecoder
DialnormMatches
MeasuredLevelofSpeech
OutputLevelofSpeech
Speech level = -20
Dialnorm = -20
Speech level = -27
Dialnorm = -27
Speech level = -15
Dialnorm = -15
Speech level = -31
Dialnorm = -31
Output = -31
Output = -31
Output = -31
Output = -31

67. 67
Static Metadata
Program 1
Program 2
Program 3
Program 4
DialnormAdjustment
withinDolbydecoder
Allprogrammingmeetsthe
desireddeliveryspecification
OutputLevelofSpeech
Speech level = -24
Dialnorm = -24
Speech level = -24
Dialnorm = -24
Speech level = -24
Dialnorm = -24
Speech level = -24
Dialnorm = -24
Output = -31
Output = -31
Output = -31
Output = -31

68. 68
Metadata – Dynamic Range Control
§ Digital Television can easily deliver better than 100dB of dynamic range
§ BUT-- Not everybody has an expensive home theater system
§ product capabilities vary
§ large home theaters
§ smaller “Home Theater in a Box” units
§ small stereo or mono TVs
§ Or the listening environment may be “challenged”
§ Sensitive neighbors, kids are sleeping
§ Traffic noise, air conditioners etc. raising ambient noise levels

69. 69
Dynamic Range Control Metadata Provides the solution
Dynamic Range Control metadata consists of two modes:
Line Mode and RF Mode.
§ Line mode – for most applications
§ Wider dynamic range
§ Average loudness replay level of - 31dBFS
§ RF mode – for RF modulator and analog outputs
§ Narrower dynamic range
§ Average loudness replay level of -20 dBFS
§ The source audio is unaltered. Only gain words are written into the
bitstream to be used by the decoder.
§ The viewer’s decoder implements DRC as instructed by the
consumer or as determined by the equipment’s capabilities

70. 7070
Dynamic Range Control
§ The Dolby Digital or Dolby Digital Plus Encoder offers a choice of
five different artistic compression profiles that address typical
mastering applications:
§ Film, Standard
§ Film, Light
§ Music, Standard
§ Music, Light
§ Speech
These need to be set for both Line and RF Mode

71. 71
An Example: Film Standard
§ Max boost: 6 dB (below -43 dB)
§ Boost range: -43 dB to
-31 dB (2:1 ratio)
§ Null band width: 5 dB
(-31 dB to -26 dB)
§ Early Cut Range:
–26 dB to –16 dB
(2:1 ratio)
§ Cut Range:
–16 dB to +4 dB
(20:1 ratio)
Input levelLow High
Dialogue level setting
LowHighOutputlevel
Boost
range
Null
band
Early
cut
range
Cut
range
Centered at
the dialogue
level parameter

72. 72
Dynamic Range Control
Input levelLow High
Dialogue level setting
LowHighOutputlevel
H
HM
M
L
L

73. Dialogue Normalization + DRC
§ Dialnorm ensures all audio content is output at the same reference
dialogue level
§ DRC reduces the dynamic range of the content, with the dialogue
reference level as the “null” point
§ Content below the dialogue reference level will be boosted
§ Content above the dialogue reference level will be cut
73

74. 74
Metadata – Downmixing
§ Some people who listen to multichannel audio content do so over
stereo or mono loudspeakers.
§ Automated downmixing built into every decoder constructs a stereo
downmix from a 5.1 source and a further mono downmix from the
stereo.
§ One multichannel program can feed everyone!

75. 75
Downmixing
§ There are three different types of downmixes:
§ Stereo downmix
§ Lo / Ro
§ Left only / Right only, for headphones or stereo televisions
§ Mono downmix
§ From Lo / Ro, for mono televisions
§ Surround compatible downmix
§ Lt / Rt
§ Left total / Right total, for Pro Logic or Pro Logic II
decoding

76. 76
The Downmixing process
§ Dialnorm value defines “null band” where normal speech resides
§ The “null band” is not affected by DRC
§ DRC controls peaks and prevents clipping when channels are
summed
§ The level of signals above speech are lowered in level
§ The level of signals below speech are raised in level
§ Predicted overload conditions are prevented
§ Downmix metadata defines how the center and surround
channels are summed

77. 77
Stereo Downmix Process
§ ‘Flat’ stereo downmix (within decoder) = Lo/Ro
INSIDE
DECODER
L
R
Lo
Ro
C -3dB
+
+
LS -3dB
+
+
RS
LFE ?NOT USED
-3dB

78. 78
Mono Downmix Process
§ Mono downmix (within decoder) = Lo + Ro
Mono
LFE ?NOT USED
INSIDE
DECODER
L
R
C -3dB
+
+
LS -3dB
+
+
RS -3dB
+

79. 79
Surround Compatible Downmix Process
§ Matrix downmix (within decoder) = LtRt
-3dB
-3dB INSIDE
DECODER
L
R
C
+
+
LS
+
+
RS
+
_
Lt
Rt
LFE ?NOT USED

80. 80
Metadata Control Summary
§ Dialogue normalisation, dynamic range control, and downmixing all
work together
§ An incorrect setting of dialogue normalisation could affect the quality
of the audio
§ Dialogue normalisation
§ is the threshold for dynamic range control
§ Dynamic range control and dialogue
normalisation
§ prevents overload when downmixing

81. 81
Questions?