User Manual
Multichannel Monitoring Tutorial Booklet (M2TB) rev. 3.5.2
Masataka Nakahara : SONA Corporation
©2005 YAMAHA Corporation, ©2005 SONA Corporation
30 / 74
2-5-2. Two-channel fold-down for Digital broadcasting (Japan, MPEG-2 AAC)
[ Fig. 16] Flow of a Down mixing : Digital broadcasting in Japan, MPEG-2 AAC,
ARIB STD B-21, mandatory
[Fig. 17] Flow of a Down mixing : Digital broadcasting in Japan, MPEG-2 AAC, ARIB STD B-21;
for external quasi–surround processing, option
The MPEG-2 AAC format defined by ISO/IEC is used as the audio format for digital broadcasts in Japan.
Down-mixing is done according to ARIB STD B-21 as shown in [Fig. 16] and [Fig. 17]. As in the case of
Dolby Digital (DVD-Video), the receiver is required to support two types of down-mixing; one type that
provides the attenuation values as meta-data [Fig.16] (mandatory), and one type that is surround-
compatible [Fig. 17] (optional). This differs from the Lo/Ro downmix ([Fig. 16]) of Dolby Digital (DVD-
Video) in that some of the attenuation selection parameters are different, and that -3 dB of attenuation is
applied at the final stage. In addition to the above two down-mixing methods, ARIB STD B-21 also
allows a receiver to have (within certain defined standards) its own proprietary down-mixing option for
virtual surround.
■
Att1
0.707 (-3dB)
■Att2
0.707 (-3dB), 0.500 (-6dB), 0.354 (-9.0dB) 0.000 (-∞dB)
■Att3
0.707 (-3dB)
■Default
Att1＝Att2＝Att3＝0.707 (-3dB)
L
Lo
＝
Att3
×
(L
＋
Att1
×
C
＋
Att2
×
LS)
Ro
＝
Att3
×
(R
＋
Att1
×
C
＋
Att2
×
RS)
LFE
LS
RS
R
C
Att1
Att2
Att2
-
∞
5.1ch Master
2ch Down-mix
Meta data
Att3
Att3
L
Lt
＝
0.707
×
(L
＋
0.707
×
C
−
Att
×
(LS
＋
RS)
)
Rt
＝
0.707
×
(R
＋
0.707
×
C
＋
Att
×
(LS
＋
RS))
LFE
LS
RS
R
C
-3dB
Att
Att
-
∞
5.1ch Master
2ch Down-mix
-3dB
-3dB
■
Att
∞
0.707 (-3dB), 0.500 (-6dB), 0.354 (-9.0dB) 0.000 (- dB)
Meta data