Automatic Loudness Control (ALC)

Advanced Loudness Control Solutions Which Prevent Excessive Audio Jumps

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 Key Features 
 Specifications 
 Ordering Information 
 Product Documents 
Automatic Loudness Control (ALC) Insights & Highlights
ALC Solutions Overview
Automatic Loudness Control Using Linear Acoustic AEROMAX
ALC with Grass Valley Wideband Audio Processing
Segment-to-Segment: Active Loudness Control
Channel-to-Channel Loudness Control: ALC at Head-ends
Headend Uses Decoding, ALC Audio Processing, and Re-encoding

ALC Solutions Overview

ALC WITH LINEAR ACOUSTIC AEROMAX PROCESSING
  •  Advanced loudness control, using proven Linear Acoustic AEROMAX multiband audio processing
  • Highly flexible processing, with excellent performance with vocal tracks
  • Up to 8 channels of loudness processing per sub-module
  • Audio processing for up to 2 programs per sub-module (mono, stereo, 5.1 audio)
  • Optional 2.0 to 5.1 upmixing using Linear Acoustic technology
ALC WITH GRASS VALLEY WIDEBAND AUDIO PROCESSING
  • Lower cost, high performance wideband audio processing
  • Designed for easy configuration and control
  • Up to 16 channels of on-board loudness processing
  • Audio processing for up to 8 programs (mono, stereo, 5.1 or 7.1 audio)
  • Firmware based solution leaves the sub-module sockets on the host card free for other advanced processing functions
  • Now supporting loudness measurements and true-peak limiter according to ITU-R BS.1770-3

QUICK ALC COMPARISON TABLE
  ALC with Linear Acoustic Processing ALC with Grass Valley Proprietary Processing
Max number of programs 2 8
Max number of channels 8 16
Number of channels/pgm 1, 2 or 6 1, 2, 3, 4, 6 or 8
Audio formats PCM in / PCM out
up to 24 bits at 48 kHz
PCM in / PCM out
up to 24 bits at 48 kHz
Technology AeroMAX, multiband Wideband
Pulling range ±36 dB -31 to 18 dB
Limiter range -6 to 0 dBFS -20 to dBFS true-peak
Embedded Upmixing option Yes No
Loudness Measurement methods ITU-R BS.1770 ITU-R BS.1770-3
Profile switching (including ALC bypass)
via automation/GPI
Yes Yes
Form factor Sub-module Software option
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Automatic Loudness Control Using Linear Acoustic AEROMAX

Advanced loudness control is offered by ALC with Linear Acoustic AEROMAX audio processing. It uses a third generation audio processor to provide a simple and cost-effective solution for guarding against loudness shifts.

MULTIBAND ARCHITECTURE
The AEROMAX algorithms use a multiband approach to loudness control. These algorithms can apply multiband, multistage loudness control to the audio, resulting in audio free from
abrupt loudness or image shifts, while preserving more of the original content than previously possible.
This version of ALC can be packaged with, or without, the Linear Acoustic upMAX upmixer on the same submodule for optimal integration.

TECHNICAL SPECIFICATIONS
Architecture: 8 channel multiband (5) processing
Number of programs: 1 or 2
Program configuration: 2 and/or 6 audio channels
Loudness measurement: ITU-R BS.1770
Sampling: Up to 24 bits at 48 kHz
Processing profiles: 6
Limiter set range: -6 to 0 dBFS or ±6 dB
AGC pulling range: ±36 dB

ORDERING INFORMATION
MOD-LA-ALC-2 2-channel ALC licensed by Linear Acoustic
MOD-LA-ALC-6 6-channel ALC licensed by Linear Acoustic
MOD-LA-ALC-8 8-channel ALC licensed by Linear Acoustic
MOD-LA-ALC-2-DUP 2-channel ALC and up mix licensed by Linear Acoustic
MOD-LA-ALC-6-DUP 6-channel ALC and up mix licensed by Linear Acoustic
MOD-LA-ALC-8-DUP 8-channel ALC and up mix licensed by Linear Acoustic

ALC with Grass Valley Wideband Audio Processing

Lower cost, high performance loudness control is provided by ALC using Grass Valley’s proprietary wideband audio processing algorithms. This variant of ALC offers versatile, easily configured loudness processing, which does not adversely affect the program content.

WIDEBAND ARCHITECTURE
This ALC option uses a firmware upgrade to the hosting card. Up to eight different programs and up to 16 channels can be processed simultaneously, with independent controls and loudness meters on each program. This ALC variant leaves the sub-module sockets on the host card free for other advanced processing functions.

TECHNICAL SPECIFICATIONS
Architecture: 16 channel wideband processing
Number of programs: Up to 8
Program configuration: 1, 2, 3, 4, 6 or 8 audio channels
Loudness measurement: ITU-R BS.1770-3
Sampling: Up to 24 bits at 48 kHz
Processing profiles: 3/5
Target loudness range: -31 to -10 LKFS
Limiter set range: -20 to dBFS true-peak
AGC pulling range: -31 to +18 dB
Pre-gain stage range: -20 to 20 dB

ORDERING INFORMATION
ALC OPTIONS FOR XVP-3901 UP/DOWN/CROSS CONVERTER HOST MODULE *
XVP-3901-OPT-ALC-2 2-channel on-board ALC option by Grass Valley
XVP-3901-OPT-ALC-6 6-channel on-board ALC option by Grass Valley
XVP-3901-OPT-ALC-8 8-channel on-board ALC option by Grass Valley
XVP-3901-OPT-ALC-16 16-channel on-board ALC option by Grass Valley
ALC OPTIONS FOR AMX-3981 EMBEDDER *
AMX-3981-OPT-ALC-2 2-channel on-board ALC option by Grass Valley
AMX-3981-OPT-ALC-6 6-channel on-board ALC option by Grass Valley
AMX-3981-OPT-ALC-8 8-channel on-board ALC option by Grass Valley
AMX-3981-OPT-ALC-16 16-channel on-board ALC option by Grass Valley
ALC OPTIONS FOR ADX-3981 DE-EMBEDDER *
ADX-3981-OPT-ALC-2 2-channel on-board ALC option by Grass Valley
ADX-3981-OPT-ALC-6 6-channel on-board ALC option by Grass Valley
ADX-3981-OPT-ALC-8 8-channel on-board ALC option by Grass Valley
ADX-3981-OPT-ALC-16 16-channel on-board ALC option by Grass Valley
ALC OPTIONS FOR FRS-3901 FRAME SYNCHRONIZER *
FRS-3901-OPT-ALC-2 2-channel on-board ALC option by Grass Valley
FRS-3901-OPT-ALC-6 6-channel on-board ALC option by Grass Valley
FRS-3901-OPT-ALC-8 8-channel on-board ALC option by Grass Valley
FRS-3901-OPT-ALC-16 16-channel on-board ALC option by Grass Valley
ALC OPTIONS FOR EAP-3901 EMBEDDED AUDIO PROCESSOR *
EAP-3901-OPT-ALC-2 2-channel on-board ALC option by Grass Valley
EAP-3901-OPT-ALC-6 6-channel on-board ALC option by Grass Valley
EAP-3901-OPT-ALC-8 8-channel on-board ALC option by Grass Valley
EAP-3901-OPT-ALC-16 16-channel on-board ALC option by Grass Valley
ALC OPTIONS FOR EAP-3101 EMBEDDED AUDIO PROCESSOR *
EAP-3101-OPT-ALC-2 2-channel on-board ALC option by Grass Valley
EAP-3101-OPT-ALC-6 6-channel on-board ALC option by Grass Valley
EAP-3101-OPT-ALC-8 8-channel on-board ALC option by Grass Valley
EAP-3101-OPT-ALC-16 16-channel on-board ALC option by Grass Valley
ALC OPTIONS FOR HCO-1822 CHANGE-OVER
HCO-1822-OPT-ALC-2 2-channel on-board ALC option by Grass Valley
HCO-1822-OPT-ALC-6 6-channel on-board ALC option by Grass Valley
HCO-1822-OPT-ALC-8 8-channel on-board ALC option by Grass Valley
HCO-1822-OPT-ALC-16 16-channel on-board ALC option by Grass Valley

* If upmixing is required, it can be done on seperate sub-module MOD-LA-DUP-701 Upmixing using Linear Acoustic Technology upMAX.

Segment-to-Segment: Active Loudness Control

Grass Valley’s ALC solutions can be operated in a ‘set-and forget’ mode, with the setting of an output Target Loudness per program. This mode can achieve excellent results, and the performance can be optimized by selecting a loudness processing profile that best matches the of the facility.
An alternative approach to loudness processing involves using playout automation to actively control the loudness processing profile, according to the type of . This can yield improved results when the facility uses a significant amount of programming with a controlled loudness level or a reliable Dialnorm value.
In the example below, a facility controls three different profiles by playout automation to create an optimal loudness processing result, with minimal impact to the original program dynamics. The three different profiles provide aggressive loudness control for commercials, light processing for a movie with an uncontrolled loudness level, and a complete bypass of the ALC processing for a program with the correct loudness level or a reliable Dialnorn value. Traditionally, the most problematic from a loudness control perspective has been commercial and promo insertions.

Active Control of ALC by Playout Automation
  Program Promo Movie
Program Segments Program with correct loudness
level or reliable Dialnorm value
Loud promo Movie with uncontrolled
loudness level
Automation Decisions ALC is bypassed ALC is engaged
with an agressive profile
ALC is engaged
with a light profile
Effects on Original Audio Audio remains intract with its original
dynamics while the program meets
station’s target loudness
Audio level matches target loudness
but compression will likely affect
original dynamics
Audio level matches target loudness
with a slight impact on the original
film audio dynamics
Playout using ‘set and forget’ mode with ALC
  • Output target loudness is maintained by ALC
  • Loudness control can be optimized by choosing an ALC profile that best matches the facility’s
Playout using active control of ALC by automation system
  • Automation triggers different ALC profiles according to the program , driven by tagging performed by the traffic team
  • By adapting the ALC profiles to the , there is minimal impact to original program dynamics
Dolby Decode/ALC at ingest
  • Densité signal processor module
  • All ingested matches the station’s target loudness level
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Channel-to-Channel Loudness Control: ALC at Head-ends

Channel-to-channel loudness inconsistencies are another key issue, especially for cable and IPTV service providers. It’s common for viewers to experience different loudness levels as they switch between channels, and this is because the channels will have different average loudness and inconsistent dialnorm values.
Often, the cause of this channel-to-channel loudness variation is the broadcaster’s use of a default -27 dB DialNorm value for the Dolby Digital encoder when there is significant variation in the average loudness of the program segments.
Fortunately, Grass Valley’s automatic loudness control solutions can be used to address the problem by decoding and processing the audio with ALC, and then re-encoding. The Densité signal processor card can re-stamp a consistent Dialnorm value to match the target loudness value used by the ALC processor.

Headend Uses Decoding, ALC Audio Processing, and Re-encoding

Can fix both channel-to-channel and segment-to-segment loudness problems.

Note: This configuration is possible if the audio compression algorithm and the bit rate in use allow for an extra generation of encoding without creating audible artifacts when decoded at final destination.