Selasa, 09 Desember 2008


Viewers hate if when the loudness level suddenly changes when they switch channels or commercial comes on. John Couling, professional product manager of Dolby Laboratories Inc. tells us why this occurs and how to solve the problem.

TV viewers have found the variances in loudness between different programmers and channels to be annoying for many years. Many broadcasters say that it is the single largest cause for complaint to their stations.

Now, with the transition from analogue for digital broadcasting, various effects – such as the wider dynamic range and quality of the digital programming – seem to be compounding the problem.

A study by Dolby Laboratories of the loudness of programm at a major UK cable and satellite play out facility show difference of up to 17dBLeqA. This short of variation can be attributed to a number of causes. However, whatever the cause, it is clear that the methods currently used to align material for broadcast are not working as they should.

The growth that is currently being seen in the number of channels available to viewers, across analogue and digital transmissions, cable and satellite, makes it imperative that broadcasters take opportunities such as the move to digital production and distribution to prevent the loudness problem from getting even worse.

In practical use, a loudness meter would still be used alongside conventional [peak measurements; the formers to provide true loudness information for signal alignment, the latter to avoid clipping distortion.

Outsourced material could easily be conformed before being sent to a station and then checked in QC to confirm that it matched a broadcaster’s guidelines without any concern about operators using different metering methods or interpreting a scale differently.

Asia Image,2005,January/February
By Ghinonk

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