Orban OPTIMOD 8685 - Page 226

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OPERATION ORBAN MODEL 8685
BS.1770 algorithm does not take into account the effect of the LFE channel, for
good reason. Nacross and Lavoie
8
tried to extend the BS.1770 algorithm to include
the LFE channel by summing the K-weighted LFE channel’s power into the current
BS.1770 algorithm, where the gain is weighted for the fact that LFE channel receives
a 10 dB gain boost on playback, per Dolby’s standards. This modified BS.1770 algo-
rithm failed to agree with the judgments of a subjective listening panel unless a 10
dB attenuation “fudge factor” was applied to the LFE channel prior to its power
summation with the other channels. Nacross and Lavoie concluded:
A problem exists however, should ITU-R BS.1770 be modified to simply
include an attenuated version of the LFE channel. Because the LFE chan-
nel receives a 10 dB boost on playback, the low-frequencies on this chan-
nel would contribute differently to a loudness measure if they were
moved to one of the other main channels, even though the perceived
8
Norcross, Scott G; Lavoie, Michel C., ”Investigations on the Inclusion of the LFE
Channel in the ITU-R BS.1770-1 Loudness Algorithm,” AES Convention Paper 7829,
127
th
AES Convention, New York 2009
LKFS
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BS.1770 Histogram
Integration Time = 10 sec
Uniformly Sampled every 10 Seconds
Figure 3-5: Histogram sorting BS.1770 loudness measurements into 1 dB bins