The Live Aid license includes ALC6 (Automatic Loudness Correction Processor) delivering high-resolution, low-latency loudness control in a world full of level jumps between programs and DMix (Downmix, loudness-process and true peak limit any mono, stereo or 5.1 source) pristine loudness processing algorithms developed for 'no-compromise' live events.
ALC6 Automatic Loudness Control
Years of research and standardization work on loudness and true-peak level has enabled TC to design high-resolution, low-latency loudness measurement and control equipment such as this Automatic Loudness Correction processor, ALC6.
In broadcast, digitization is driving the number of AV channels and platforms up, while the total number of viewers remains roughly the same.
Using only a dialog-based level control principle has led to ambiguous level management, more level jumps between programs, and extra time spent on audio production and management in general.
Non-dialog based level jumps are currently creating havoc in digital TV; and ALC6 helps correct that situation. For instance by utilizing the adaptive Stridency Reduction parameter that brings overly loud content under tight control, while leaving normal content untouched.
Measuring the loudness of a 5.1 program can give significantly different results from measuring a stereo or a mono downmix of the same program. Furthermore, these differences are systematic because measuring loudness according to BS.1770 is insensitive to inter-channel phase differences, while a downmix is not (see note 2). Tight tolerances on program loudness therefore presents a dilemma when it comes to mono or stereo listeners, generally the vast majority of a station's audience.
ALC6 introduces a new way of dealing with this issue: A 5.1 program may be adjusted based on what it measures in 5.1, or on what it measures using a specific set of downmix coefficients.
ALC6 also helps getting a higher audio quality and more headroom out of AC3 data reduction. The downmix part of the decoder is prone to overload, especially when AC3 DRC is set to Off. On the other hand, enabling DRC inserts a crude processor which nobody can get rid of again. Use the new "AC3 Codec" setting with ALC6's true-peak limiter to prevent downmix clipping while preserving headroom, thereby making it safe to switch off DRC and make AC3 more transparent.
DMix Download Mix
In just one engine, DMix can downmix, loudness process and true-peak limit any mono, stereo or 5.1 source. Input formats are dealt with automatically without the need for metadata, downmix takes place at overload-proof 48 bit resolution, the loudness processing is compliant with e.g. ATSC A/85 and EBU R128 standards and transparent transcoding keeps the output perfectly conditioned for mobile TV, iPod or IPTV. Even a wide loudness range feature film is transcoded automatically on the fly at an impeccable audio quality.
DMix presets for ATSC and EBU standards may be found in theDown-conversion factory preset bank. Be sure to try the new iX presets featuring image enhancement for an extra enveloping experience when listening in headphones.